May 2, 2011

Harley engine balancing…. Reverse engineering and the balancing process,….how I do it.

Hi Everyone

I was looking for a while for a Harley engine to balance,to show my students and the members here, how to balance a bottom end ,and  I was also looking for an engine that was vibrating bad.

Since we took care of the Sidewinder project a few months ago,my students seems to  like it a lot when were touching the mechanical stuff like that… and they are also happy when there are different things to learn on the way(for those who did not follow the thread we are talking about the machining process of a S&S sidewinder 93 shovelhead engine).

I also think that it was my turn to show you how I balance a Harley engine,but before starting this story , I had to talk with the owner of the bike.

….He told me that he had the bike for  a short period now, but had certainly the time to ride it but trying to keep up with his friends with newer bike like Evo and Twinkie was not an easy task. .

He said that he was riding a lot of his time on highway at a speed of around 70-75 miles per hour trying to keep the pace with his friends, he mentioned to me, that never mind the speed he goes ,they were always in front of him,he simply could not run with them,they were riding too fast ,and his Shovelhead was vibrating like hell break loose at that speed, so he told them all  that from now on he would still ride with them, but will probably arrive well after them, no big deal they say as long as you still ride with us……or I would say behind them.

The main reason for this, he was relay feeling «uncomfortable with his ride»,his bike a 76 Shovelhead, assembled from a mismatch of parts from a FX models with a bore of 3 5/8 inch with a stroke of 4 ½ inch ,a 93 engine with S&S flywheels in a STD case.

He told me that his arm was becoming really numb after a short ride(and he mean almost paralized to his  shoulder from what he show me,explaining it to me with sign,it seem real bad) and his ride was really showing sign of problems,like the two tank mounting tabs broken  as the carburator mounting was also found broken ,without counting the too many parts that became loose on his bike,so to me ,it seem that I found the perfect engine I was looking for,he had a real problem and to show my students how to balance a Harley V-twin engine, why not taking an engine that have a real problem and I offered him to take care of his engine,at first he was not willing due to $,but ask again ,just for the purpose to educate my students around the Harley vibrating myth,…  I think it might have help change his mind when I told him I would work for free.

So let the story begin,hope you will enjoy this as my students did….:)

First thing to do , start dissamble those flywheels,by the connecting rods side play I suspect some wear on the crankpin , here in the picture shown the two ½ inch rods that serve to lock the flywheels against the jaws of the vise ,to help taking off the nuts.(I had check the assembly on the lathe between center,dial position on the pinion shaft where rollers runs and near the remaining Timkens before dissambly and runnout was less than .001 inch so that was not the problem)


This engine was run with a set of S&S strocker wheel and stock replacement set of connecting rods,it was balanced (static) at some time in the past by the series of hole located inside the the face of both wheels.




When both flywheels were completely dissamble and clean,and ready to be check…

I noticed and write down all informations,a standard process for me when doing an engine.

First picture is the balancing sheet ,I use my own custom sheet for that.



You can see what I usually do,I note the models number,flywheels and/or case serial numbers,if the holes are made inside or outside flywheel,where holes are located on each flywheels and also total depth of holes in inches,all that for future reference.

What I decide to do is call a «reverse engineering» to see why this engine was vibrating at first,so I  weight everything, from the rotating and reciprocating parts that was installed in that engine,  my final calculation end up with a bobweight amount «X» (Bobweight is a counter weight that equal the total weigh of the rotating mass plus a % of the reciprocating mass divide by 2 if you are using the static method)

All you see in the picture are both rotating and reciprocating parts involve.



In this pictures parts that are classified as rotating mass,those would be included in the balancing process ,from crankpin nuts,the locks with screws for the nuts,crankpin with small keys included,all roller bearings with cage,and the lower part of the connecting rods,call also the «Big end»,those rotating parts count 100% in the calculation,divide by 2(for each flywheels) at the end.


Then time to weight the reciprocating mass of the engine,showed in the next two pictures below,those included upper parts of both connecting rods call also the «Small End», the two pistons , wrist pins,all rings,four teflon button in this case ,if using circlips those also need to be included , all those parts  are going to be included in the formula,as a  % of the total weight call the «balance factor»,we will discuss that matter later.


What I use to balance the rotating and reciprocating parts,is my old Ohaus «Dial-o-grams» precision scale,the degrees of precision is within (.1 grams),and I am always working within .1 grams.

I had an electronic scale before,but this one is long gone,electronic scale was faster to use, but not bullet proof,mechanical type like this one is more rugged…and last a lot longer.

First thing to do when doing a reverse enginering is weighting all the parts, write down everything,first start with the rotating portion..crankpin with nuts and the small woodruff key in the shaft and then the 2 locks with screws that serve to secure the 2 crankpin nuts.



Time to weight the two female caged and rollers, and also the male caged and rollers,those are weight individually and I note the total amount on my balancing sheet.


Then it is time to weight both connecting rods«Big End»,here is the special rod support that  I made for that purpose,both aluminums bushings were machined for either the «Small End» and «Big End» are installed on really  smooth turnning C3 bearings, for less friction, all I have to do is  take off the total weight of the platform.(you could see what is supporting the Big End on the scale in the picture,that is what I called the platform)….substracting weight of the platform something that was done faster with the« tare» option on my late electronics scale.


What I have to substract from my equation,is  minus 438.5 Grams «G stand for Grams» and «S stand for Small End » of connecting rod  and minus 572 grams «G for Grams» and «B for Big end» of connecting rods.

So when weighting a «Big End», I  substract 572 grams from the total amount,and when weighting a «Small End», I substract 438.5 grams from the total amount.

All you need to do is taking care to have it perfectly level  rods,remember when you are weighting connecting rods,the total of both the Big End and Small End should equal the total weight of the connecting rod itself,to within 6 grams, if it is not within 6 grams,you have to start all over again,weighting the connecting rods  is normally what it takes longer.

In this particular case,I end up to within( .6 grams ), ….if you have less than 6 grams at the end of the weighting session ,your ok, all you need to included in the calculation  is 2/3 of the remaining weight and add/substract it to the rotating mass and the 1/3 remaining on the reciprocating mass,

In my case so (.4 grams was add on the rotating) and (.2 grams was add on the reciprocating mass) for a total of (.6 grams).

Supporting the «Big End» for weighting the «Small End»,making sure both center are at the same height.


Part of the reciprocating «Small End » connecting rod

Both pistons with rings and wrist pins need to be included in the formula for the weithing session,I did not take off rings and wrist pin for this,user still want to run same set of rings,the top end was done last years with barely noticiable wear ,so why taking chances taking off those rings,I am not a big fan of using the same rings,but in this case customer want to save some dollars.

To finish time to weight the reciprocating mass, the small teflon buttons that serve to secure the wrist pin instead of circlips.

Here is my final calculations,  I will find out at what % of balance factor this engine was done at first,this is what I call the reverse engineering,it will show you why this engine was vibrating like hell.


I end up with 1279.7 grams on each flywheels and at 60% balance factor,(balance factor is a % of the total reciprocating weight in the calculation) and  the rotating weight is included as 100% in the calculation,

In this case I use 60% balance factor as all of my balancing job,some prefer  50% (like  pre 73 Harley engine) as all were balance from MoCo,some use 55% for heavy flywheels,some prefer 58%,some 59%,but a good rule of thumb is 60% balance factor,I balance my own 67 Generator Shovel with a 60% balance factor and I am feeling «really and I mean really comfortable» with it,and those are among the heaviest wheel you can find on a Harley…

There is a lot of arguying about the «balance factor»,normally all Harley engine need to  be balance from a certain balance factor located between 50% to almost 70%,always depending on the set up you have,early engine were balance to 50% ,with a average bobweight for all of them ,some were worst bone shaker than other,but remember if you use same bobweight for all engines you might end up with at least some slight variation in all,ending up with some that will show more vibration than other,needless to say .

Those (pre 73 ) engine was also ridden at a slower speed  than what we ride nowadays,MoCo were using a lower balance factor to make a more equal balancing ride from the vertical and horizontal plane,then decide to change that balance factor in 1973 to a higher percentage at 60%.

The higher you go on your balance factor % ,the more you move the unbalance plane to an horinzontal one ,horizontal plane make it more comfortable as your bike run in an horizontal motion , you cannot go higher than 60 % on Big twins,or the vibration will simply get worst on the horizontal plane,so it is safe to say, nothing under 50% and nothing over 60% for big twin engine .

You  could go higher with your balance factor like for example for newer Evo Sportster, those could be as high as 69%,again different engine set up ,and if you look at the rubber mount engine they seem to perform a lot better at around 54%…. remember here that whatever the factor you are using, you will only move the annoying unbalance feeling of your own motorcycle to another RPM or speed,…it is only a «compromise» when talking about balancing a Harley engine,you will never achieve a perfectly balance engine with a 45 degrees set up….again it is only a «compromise» to a certain speed and RPM range that you normally ride most of the time….and that speed is normally located between 55 and 75 miles and hour,below or higher  that speed you will encounter some slight vibrations,probably the reason why Harley came up some rubber mount handlebar and floorboard to try get rid of the numb feeling rider’s were complaining about,also probably to compete with the motorcycle import from Japan and Europe,other parts that might be taken in consideration when talking about vibrations on a Harley ,is the motor support,clutch hub,tires and wheels bearings to name a few,those parts could lend to the same result as unblance flywheels,maybe not as worst but still quite annoying.

An engine that has been balance with great care using the static method, is to my opinion as close as you can get it,dynamically balance engine is done faster ,when everything is set and ready, but the method is not necessarly better,remember the «compromise»in balancing a 45 degrees Harley engine.

Rule of thumb if the component to be balance is no more than 4 inch wide, it could be balance on a single plane,and if wider than that, it is recommended to use the dynamic method,this method could balance double or multiple plane at the same time,since each Harley wheel are not that wide they could be balance with the static method with success.

Those using the dynamic method ,have to align and true both wheels with or without connecting rods mount on the assembly (depending on the type of balancing machine they are using), then need to drill the holes on the outside face of wheels,this method have a tendency to hold much oil on the outside face of rims and that oil cannot escape easily,due to the close gap between wheels and crankcase,oil equal weigth,if this oil cannot get out easily,this will result in an unbalance engine….also that oil will have a tendency to form bubble and foam  more when force to escape via a tight space,thought that oil cannot do it’s job well,were talking about cooling and lubricate,oil will be affect,….again it is my opinion.

Normally I do not included oil in my balancing formula but some do (amount of oil count as weight in some balancing formula),it is hard to figure out how much oil will count in the balancing as every engine is different from volume and or scavenging the oil in the crankcase.

For those who want to see what a complete bobweight assembly for a dynamic balancing job, it looks like the one shown here, this kit is one that is custom made but could also be buy from special supplier.


Let continue with the story, here is my personal static balancing stand , I use for balancing a Harley flywheel, it is a custom stand made for that specific purposes, as all the special tooling I use in this thread.




Most people who balance either in shop or at home still use the knife edge stand, like those sold by S&S, shown here is my very first balancing stand look like an S&S stand, with slight improvement ,I now prefer to use my newer one, a little more precise using big roller wheels with C3 bearing  without oil to reduce friction, really take not that much to make it turn.

Those knife edge are cheaper to build as a manufacturer’s point of view  and still do the job no problem,as long as they are perfectly level,in this case a center bolt and 4 jack screws in each corner to make it easy to level.

And for those who are looking to build one for their own purpose, another stand type that could be build at home without too much equipement,this one  I made in the past to balance grinding wheels ,quite similar to the knife edge except for the two round rods ,bolted on top of the knife edge,those are bolt-on and could be change if damaged.

Back to the balancing process,after all my calculation was done and the bobweight installed on the flywheel ,I noticed a strong movement,the bobweigth drop suddenly to the bottom (remember mother earth gravity attraction),meaning I was really off balance ,so I start taking off some weight out of the bobweight,a little at a time,and this is what I took off,and then the wheels were not moving at all,meaning they were in perfect balance,wherever you stop each wheels they doesn’t move,so I weight the remaining bobweigth to see at what % balance factor that particular engine was balance at first«called the reverse engineering»,see my calculation below.

To obtain the 60%  factor I was looking for at first and to show you how much weight need to be add on the opposite side I simply use «Mactac blue adhesive»  that serve  to hold  thing on the wall.


I use small metal plugs of ½ inch in diameter as it is the same size of the hole that was drilled in before.


Noticed the position of the plugs versus the previously drilled holes,I tried to match the length of holes with similar plugs on the opposite side and the wheels are now very close to balance…at 60% factor,so what happened for that specific engine? Was there any change in connecting rods and or pistons in the past for exemple? Why those wheels were so off balance ?  I guess we would probably never know but we will correct the problem….

This is basically what need to be add to both flywheels to have them balance to 60% balance factor,they were off by  88.9 grams or slightly over 3 onces (each) if you prefer, at that diameter it make a whole lot difference,from a very unbalance engine to a smooth running engine,

To give you an idea,just imagine if you put the total amount we just found ,multiply by two for both wheels 179.8 grams  in a small bag and turn it in a very short circular motion ,at the highest speed you could ,it would give you an idea of what I mean by very unbalance,….and remember  your not turning at the normal speed of an engine.


But wait ! That’s not all about this engine….the reciprocating weight difference between  both front and rear connecting rods should be very close to each other  to have an engine that run smoother,and in this case there was a 19.7 grams difference, reciprocating weight was heavier on the front cylinder,this will end up with an engine that would be unbalance,cause both reciprocating was not equal to each others,some will neglict this portion as they say, those specific engine run on a single crankpin so you don’t have to bother about that,I do not agree with them.

Remember that every time the engine make a complete turn , if one piston assembly is heavier than the other, even if they are on the same rotating assembly,this piston assembly will create an unbalance movement as the speed of the engine goes up, more on one cylinder than the other, that will allow a noticiable vibration,you would not be able to tell from front or rear which one is the heaviest assembly,but you would still be able to feel some annoying vibration with an engine that is suppose to be balance,…  but without equalizing the reciprocating assembly.

It take more time and special care to equalize both reciprocating weight,who would be willing to pay the extra difference to have it done like that ?

In every engine combination with multiple cylinders ,all reciprocating parts should be as close to each other as possible,and also as light as possible…not only the balance factor is important ,the closer the reciprocating weight from both the front and rear assembly ,the better you will enjoy your ride at the end,in this case a difference of 19.7 gramms with the old rods.


Let’s continue with the flywheels,those holes that were previouly drilled ,now most need to be plug ,maybe not all of them,but a large part.

I am still looking to achieve what I was running for at first ,an engine with a 60% balance factor.

Those holes were drill ½ inch in size( I normally drill them 7/16 inch so I could plug them if needed to ½-20 NF thread that is common size bolt),this time I will have to use either the M14 x 1.25 bolts or 9/16-NF bolts,the only bolt I have on hands is the 9/16 NF so here we go, tapping them all with 9/16-NF thread then we will take care of the rest after.


Both wheel are ready for the final touch,already tap and ready to be plug with portion of bolts,don’t forget when doing that,always use a good cleaning agent ,use primer and Loctite to make sure those threaded bolts portion will never come off.

If for example the weight of those steel bolts were not enough to counterbalance the bobweight you can use Tungstene often call «mallory metal» the density of Tungstene is much more than regular metal or cast.

Even if I don’t need all that extra weight in my own flywheels ,I will try to explain to you,how you proceed to correct the problem, with a solid carbide end mill (you can also buy some mallory tungstene metal from special supplier), this one  I cut to length with an abrasive wheel,you press this slug in, then you need to plug  the top part of the hole ,to make sure this tungtene slug will never come off or get loose,you will take a small threaded portion out of a 9/16 NF bolt, to thread on top of the plug ,cut and face the rim on the lathe or simply grind the rest, this way I will have a heavy plug that will counter balance and it will never come off .

Machining on the lathe instead of grinding the face of the flywheel  make a much more cleaner job.


Remember to clean everything correctly then prime and loctite the bolt in place before using the hacksaw to cut them,you can see that the location of the drilled hole are not in a perfect symetry,some of them are closer to the inside of the rim and some from  the outside,I will take care of that matter later.



Time to continue with the balancing process,since connecting rods bearings and crankpin were worn out,I ask my indy to bring me new quality sets.

I just receive a new set of connecting rods to replace the old set that was worn on the loose side with new one,made in Japan replacement sets,I told him to either bring me a set of american or japanese rods assembly,I do not like those made in Taiwan or in China.

I know some would take the time to resize/lapping the male and female Big End and fit oversize rollers,change the crankpin and nuts,put some new bronze bushing on the reciprocating end and hone them,a lot of work and most of the time not worth it,considering those were fit (real nice fit by the way) with all new material,cost 240 dollars plus tax,if you buy parts separatly with time you spend doing the reconditioning,it would probably cost a lot more than that,unless you have OEM or quality aftermarket and want to stick with it.

Those previous rods were replacement also and the purpose of this article was to explain how balancing is done,not fitting rollers bearings in a Big end assembly.


Same replacement part number but brand new,will save me a lot of work,just have to complete the balancing job…….but probably a bit more work to come as you all know.






Time to take care of those new rods,to included all those parts in my new specs sheet,I have to put everything in small ziplock bag,always taking care not to touch clean rollers with bare hands,all roller bearings and bearing should not be touch with bare hands,the reason for this is acidity coming from your hands that would create microscopic rusty print that will end up with rust  on surface,all major bearing companies has been doing a lot of research about this matter and they found that high speed rollers bearings touched with bare hands ,turning at high speed  will show microscopics sparks occuring at those exact spots they were touch previously,causing premature wear,so don’t touch roller bearings or whatever kind of bearings with bare hands and if you decide to do it make sure you have oil on your hands before touching them or sometimes when I am too lazy to pick some latex glove, I clean my hands with brake cleaner ,brake cleaner make my hands white and also very clean ,not the way to go but sure get clean hands,… it is always better to use latex glove,also another thing,keep those rollers away from humidity,it is very important,to prevent surface rust .

All roller bearings male and female stock  in small separate Ziplock bags,ready to be weight.

Before weighting each bag of rollers,there is  another thing to take care,empty bag still weigh something,in this case 1.9 grams that need to be substract from total weight of each bags.



After all small bags have been weight, time to take care of both connecting rods,from the « female Big end»  and the« female Small end»  and then to the «male Big end» and the «male Small end».


The only missing parts are pistons,rings, wrist pins and the 4 teflon buttons,those total weight would not change from the first weighting session,cause we will use them again , those new reciprocating part(connecting rods) will have to be weight again and would be recalculate.

Remember when I mentioned that both reciprocating weight was important,after weighting  both front and rear reciprocating weight ,I found a difference of 16.2 grams, heavier this time on the front cylinder compare to 19.7 gramms with the old rods.

So what need to be done is call equalizing reciprocating weight,either from piston or small end of connecting rod or from both.

Why I decide to take the weigth of the connecting rod end instead of the piston,if customer want to change piston in the futureto similar he will not change the end result by much and also connecting rods are there for a longer period of time ,first thing to do when doing job like that is planning where you want to take off the material without weakening the rod itself.

The  grinding session took me about an hour in all, grinding and weighting the male small end (you don’t want to take off too much) , I end up within ( .2 grams)  difference between front and rear reciprocating weight,that was close enough for me.

Here a few pics of the process from the start to final touch up.



Now that both reciprocating ends are within (.2 grams difference),it is the time to prepare for the proper bobweight assembly.


Time to take my spec sheets out,to do the balancing with the new parts,check and install correct bobweight on flywheel,1272.16 grams for bobweigt on each wheels,small paper sheet on top to have the perfect bobweight for my application.


In theory this is what need to be add to achieve correct balancing,not dead on , but close to that,those 3 sections were screwed in a little.

Cut a slot on the face of each threads, to make it possible to screw them with a screwdriver,this is just to explain how the balancing is done,those need to be taken off again,clean properly,prime and loctite in place,then the section that is protruding need to be machine flush and final balancing could be achieve,by drilling some very light spot at the end.

To show you how close it will be before finishing the balancing ,I just add 1 little threaded portion on the opposite(end of my finger) equal the total length of the 3 protruding portion of  bolts and after I add that little portion of thread bolt  the flywheel was stopping everywhere without moving too much,those pictures are just to explain how to proceed,probably some small touch up hole need to be done to achieve perfect balancing.

Then time to take care of the final plug-in of those holes,both parts need to be clean correctly with brake or contact cleaner,then prime both parts with 7649 loctite,then some Red Loctite high strenght inside the threaded portion in the flywheels.


When all bolts section have been threaded in ,your ready to mount both flywheels on the lathe to machine the face,that make a clean finish.

At the same time I had the flywheel on the lathe I always take care of doing a circular line on the center  of the protruding portion of the flywheel,this way you will end up with a symetric series of holes for your next balancing job.




Here is what the plugged holes looks like after the machining on the lathe,see the black spot(it is cured Red loctite) inside one hole,…it is the threaded plug portion from the hole that is the closest,normally you should leave at least 1/8 inch between each hole on forged wheel and ¼ inch between each hole on cast wheels,as you can see symetry also was not taken care of,those rules were not respected,poor balancing job to me.

Now it is time to mount both flywheels on the balancing stand for the final touch up,should be very close for sure but still some fine tuning needed to finish both wheels,just to give you an idea again of what need to be drill to achieve perfect balance I took a small  9/16 NF threaded bolt about 5/16 in length for one flywheel and about 1/8 in long for the other flywheel on the opposite side ,and both wheels were not moving at all anywhere you stop them,see the «X in black» that need to be drill and on opposite small length of bolt to compensate for the hole that is not drill yet.


At the time of mounting bobweight for final balancing I noticed wear on the inside face of both flywheels,actually around where crankpin is mounted, another thing to take care before finishing the balancing process,so I order a set of steel trust washer(from early model) and will fit them on, one for each flywheel to make them as new again,on S&S wheel there is no connecting rod trust washer,the wheel are forged steel and normally doesn’t wear out fast,this set must have some mileage.


Flywheels mounted on the CNC mill and dial.

Using circular interpolation on the cnc mill make perfect grooves to adapt those news hardened trust washers.

Need to put some coolant to do the machining, first picture was made with only a air pressure hose but end up with broken end mill.



Will now take care of the final balancing ,and the balancing would be as close as you can have a Harley engine running,the owner will then be able to keep the rhythm and ride with his friends on their newer bikes,without being severely shaken.

Shown is the final balancing ,you can see what need to be drill on each flywheel to have both in perfect balance.,both wheels are balance to within .1 grams with this static method.

The balancing stand I use in this thread has been try with a small dab of mactac weighting( .1 grams ) and wheel was moving….accurate enough for any person doing a balancing job on a Harley engine.


Here is my final balancing sheets for future reference….and also for those who are curious.

Now time to reassemble those flywheels as a complete assembly,need to see torque specs from S&S,left is with stock shaft and right is with S&S shaft,I use a Jims pinion and the OEM sprocket shaft.


To do this,I am using the shop table with 2 holes drill through it to accept 2 mounting bolts and a slot to clear both shafts,very solid and easy to do for anyone.



Time to check each wheel for concentricity on the outside and on the the side,all with in .001 inch,now ready to finish the assembly.


That is what you need to complete.

Torco assembly lube is a must for any engine .


Slide both connecting rods over the bearings assembly

After mounting the flywheels on the lathe both wheels were off by .005 inch with torque at 175 ,missing only 35 pounds to get it finish,note the 2 rods that are secure with vise grip,they were machine to slide with slight drag ,that way flywheels are set up quicker.


Final assembly runs within specs at .0000 inch on sprocket shaft and at .0002 inch on pinion shaft.


Another problem occurs before closing the case,since the previous assembly was so unbalance,the inner portion of the pinion race end up with a total out of round of .0035 inch so nothing I can do ,I need to put a new race in and then line lap.

Another special tool to press the old pinion race bushing


But surprise the race do not need to be press out,only finger pressure will do,I guess another problem coming…

Bushing .001 under the bore size,only set screws was securing the race….but set screws were  not tight,I mean not touching the harden race too much,so I order an oversize race and we will fit this new race.

Guess what another problem ,when mounting the new oversize Eastern made race on a custom aluminum mandrel,I found out the race was not concentric ,interior was perfect but outside  was off by .0025 inch,so if I had measure the race and order the one next in size to fit as a shrink fit in the bore I would have a big surprise…hard to lap something that is not in centerline with the opposite Timkens bearings….I would assume the interior and exterior was concentric,but it was not,some quality control problems from most North American companies nowadays ,quality is not was is used to be.

The outside race was at 1.135(I think it was a .005 OS,I asked for at least .005 inch or more, I was expected to machine the outside to make it fit anyway) so I had enough material to remove to have the fit I was looking for at 1.1295 for a bore size of 1.127(.0025 inch as a shrink fit)

Ready to be cut with the ceramic insert.

Time to heat the case and shrink the pinion race.


I use snow to freeze the race(get to 1.129 so .0005 inch down)


Time to lap the race,I use the old Timken in their respectice race with the pilot from my lapping tool,and then lap the new race to final size at 1.7515 (starting from 1.749 inch on each end and 1.7485 in the middle after the shrink fit) ,the new pinion shaft from Jims is at 1.7502 inch so I ordered a set of .0002 os rollers at .2502 inch to have a .0009 inch tolerance.

Almost done with this engine,my indy ask me if I could check the Timkens play for him since he did not have the tools to check it,well I said yes it is a small job when you have the proper tool,but guess what, total backlash from brand new Timkens kit was at .009 inch,way too much ,Harley recommmended  between .001 to .006 max,so I took the small spacer to the surface grinder and take .006 inch off of it to end up at .100 instead of .106 inch, I end up at .0017 backlash, that is a nice backlash for a set up like that.



As you can see the total backlash is now at .0017 inch a lot better than the .009 inch we had at first,again never assume even if the company is Timkens.


This is time to call my indy telling him that he could come and pick up this project,the rest will be complete by him with a few phone call to me in the meantime….

I stop at the shop and took a couple more pictures of the flywheels now assemble in the crankcase,getting closer …


Things I forgot to mentioned,I drill a ¼-20 nc set screw to reduce the flow to the connecting rods,drill I use is a 3/32 inch,I might have drill a little smaller but at .093 inch I would be safe ,the Jims shaft come with a threaded hole of ¼-20 without any plug or reducer in the box,so the hole was at over .200 inch ,too big for a pinion hole,the pump need to build pressure.


I am sure some of you might have other method  to do a balancing job,and some  might disagree with the way I am doing things ,and I fully respect that,remember here my main goal was to show my students how a Harley bottom end was balance,I have had a few more to thing to take care along the way,more than first expected for sure, but it is part of life,you live and you learn, I expect some of you might have learn something from this also .

Hope you have enjoy this very long thread ,(saddlebagrail)


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