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Thread: Harley XA heat problem

  1. #1

    Harley XA heat problem


    My Harley XA is nearly ready restored. The engine runs.

    Idle sounds ok. It starts on the first or second kick.


    I have a heat problem. The right cylinder/header pipe has after two minutes running a temperature from around 200°C. The paint smokes and I stopped the engine. The left header has in the same time around 60°C and the cylinder head feels only a little bit warm.

    The feeling is, that the left cylinder runs only in 1/2 power and the right one works double.

    I have double checked the valve tappets. Inlet 0,004-0,006 (015) and outlet 0,014 (030) like the manual says.

    First I thought that it could be a coil problem. But I changed the spark plug caps and cables from the right to the left and from the left to the right. Same problem with the right cylinder.

    To double check that I changed the complete coil. Same problem. Right cylinder much to hot.

    Spark plugs I used in the first go modern ones. After that I fixed original Harley no. 4 inside the heads.

    Distributor: Is there a way to mount this the wrong way? Manual says: Flywheel marking on the point, fixing screws for the distributor have to be 90° to the driving direction. I have that. Cam mark is around 10-11 o'clock in driving direction. And I say it again. It starts perfect and it has idle like that in the videos.

    Carburetors: Original M17 R - M17 L

    Main jet 63 in both carbs. Short needle tight inside.

    Low speed needle. I started the engine with only one spark plug cap. Turned the needle inside click for click to that point where the engine makes another noise. I turned the needle five clicks back. Done that on both sides in the same way.

    Bowl level. The bowl valve closed when the petrol is around 7-8 mm under the edge.

    I have nearly now no idea what I make wrong or where the problem is.

    Have you guys a idea for my problem?

    I have no fuel leaks....really strange for me.


  2. Re: Harley XA heat problem

    Only your right cylinder is working, the left is getting a free ride.
    Remove your spark plug wire from the left cylinder while the engine is running .. I believe it will continue to run at the same speed.

    You have checked your timing, spark plugs, carburetor settings and double-checked the valve clearances.
    I believe you are not getting compression on the left cylinder .. perhaps a crack or poor seating of the valves.

  3. #3

    Re: Harley XA heat problem

    Valve seats are new machined/fixed with NOS valves. I have full compression on both cylinders. Valve clearances I have double checked. Valves are working, too. No sticky valve.
    Plugs, I have used now 8 different plugs. All the same.

    Left cylinder works, when I take the right spark plug cap off. I know that, because I fixed on that way the left low speed needle. But you are right, when I take the left cap off, the engine runs only on the right in the same sound. It is like the left cylinder works only 1/3 and the right works double.... :-) I can't understand that, too.

    Is it possible to make a 180° mistake with the distributor?

  4. #4

    Re: Harley XA heat problem

    Once it starts will it run on just the left cylinder if you pull off the right spark plug, and if yes does it run the same doing the same test the other way around? With the the heat differences I’d say it’s possibly electrical and a miss fire on the left side. What ever the fault is I’m sure it’s nothing much and you will fix it. I’d just like to say it’s been a fantastic build thread and I’ve enjoyed seeing and reading everything that you have done to this bike, well done.

  5. #5

    Re: Harley XA heat problem

    On any opposed cylinder machine I have worked on 180 out is going to fire the same because the cylinders are 180 degrees apart.
    Not like a v twin.
    Do you have the same continuity on both plug wires?
    or is one bad connection?
    fuel to both carbs?

  6. Re: Harley XA heat problem

    OK - good compression on both cylinders.
    I suggest you remove your left muffler.

    You assembled the machine from very old parts .. even if NOS they have rested for many years.
    I have seen Mickey Mouse make air-tight homes inside mufflers and engines.
    If the left exhaust is plugged, you will get no power.

  7. #7

    Re: Harley XA heat problem

    Micky Mouse....hahaha.... ;-)

    Assembled from many very old parts. Right. But, the complete technique parts are NOS or in perfect condition like new. Every gear...

    The mufflers are NOS and complete free. When I stand behind the bike the air comes out of both mufflers.

    But you are right, the left side doesn't fire as the right side. More air as heat like that one on the right side.

    "Do you have the same continuity on both plug wires?
    or is one bad connection?
    fuel to both carbs"

    Yes, all good. To double check I have changed the complete coil with cables and spark plug caps and plugs today. Same problem. Fuel to both carbs? Yes, both bowls getting fuel easily.

    "Once it starts will it run on just the left cylinder if you pull off the right spark plug, and if yes does it run the same doing the same test the other way around?"
    I will check this again tomorrow.

    The only parts where I have no way to change them is the distributor and the carbs.

    I can't see a problem with the distributor. Could be that I'm blind but is it possible to make a mistake to fix it right inside the housing? And when there would be a mistake would it start then so good as you can see it in the video?

    At the carbs I can't change very much. Is it possible that I have a low speed needle problem? Not enough fuel? To much fuel?

    Thanks for all your help,
    Best, ziro

  8. Re: Harley XA heat problem

    You mention switching wires, plugs and coils, but I did not see mention of having spark at both plugs. If you do not have spark at both plugs I would watch the relationship between the points and the distributor cam. Do the points only open on one of the lobes? If the points open, you should have spark, unless you have a wiring issue. Got spark? Only leaves compression which you have or fuel. If its running on one cylinder the timing has to be close enough not to make much difference.

  9. Re: Harley XA heat problem

    I do not own an XA but from your pictures, I believe they have a cross-over pipe between the exhaust pipes.
    "When I stand behind the bike the air comes out of both mufflers."
    I would expect this.
    You are seeing a portion of the right cylinder exhaust coming out the left muffler.

  10. #10

    Re: Harley XA heat problem

    Ziro I don't own an XA and I am not an expert mechanic. But I did find an NOS XA operators manual and parts manual (together with some interesting papers) in the bottom of a box of manuals I bought and sold them for a heck of a LOT of money (I have a 42WLA)!!! Now back to your XA. At the end of your last post you said "At the carbs I can't change very much. Is it possible that I have a low speed needle problem? Not enough fuel? To much fuel?" Does not seem like those questions have been answered. So with regard to that and if all else fails you may want to FIRST check to see that both carbs are freely getting fuel - pull the lines off and check both for that. THEN: switch the carbs - if possible? - and see if that does anything. I have worked on some old multi-carb bikes and in two different instances I had problems like yours. When I would encounter them I would ask some local mechanics for help and they would suggest all sorts of things (mainly electrical and/or lack of compression and/or vacuum leaks of some sort). But in both instances it was a carb problem (solved by a complete rebuild after thorough cleaning and blasting pressurized air through all openings in the carbs). Again, just a thought, and if all else fails. Good luck and you certainly do have a very RARE bike there!. Regards, Eric

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