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  1. #1
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    Default 79 Ironhead popping and banging!

    Hi all...

    hope someone can help here, a second brain thinking is better than just one.

    I've never worked on ironheads but can't be that much different than my shovels and pan really..
    So a friend turned up today and I could hear him a mile away popping and banging...
    asked me to have a look. straight away I thought, probably timing.. weights pin broke or seized.

    I went through it.
    points gap at 0.019
    front pot on compression stroke
    got the single dot just coming up the window (from what I read the irons is 2 dots BTDC and 1 dot TDC, correct?)
    turn plate till test light just lights up.

    all good. weights at the back are nice and free.
    Even put a new points plate and points.

    No luck.. still popping and banging.

    When he got here front plug was black, rear plug white.
    He's running Champion H10C plugs
    and a CV carb. no idea what jets it has... I run Super Es on mine. Who's idea was to put the idle mixture screw on the bottom of a CV carb? insane!
    from what I read should have a 48 pilot and 175 main? that's a good base?

    I reckon there might be an intake leak too.
    and need to adjust pushrods - didn't have time for that....

    anything thing else I might have not thought?

    kinda of want to get him sorted as he's a good guy, but not having much time to work on other stuff other than mine, so looking for ideas and input so I can go straight into it once he gets back to mine this weekend or next week.

    thanks
    JP

  2. #2

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    First, a fouled or partially fouled plug will make any Harley pop and miss. Also, a vacuum leak is a good possibility. Inspect and/ or replace the intake bands as a maintenance item. Check carb mounting and that it has a brace of some sort. '79 advanced timing mark should be a line, if I'm not mistaken. Valve adjustment, they ain't gonna adjust themselves.

    Jim

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    Quote Originally Posted by JBinNC View Post
    Valve adjustment, they ain't gonna adjust themselves.

    Jim
    I know.. didn't have time for that today and bike needs to be cold. he has to leave it here with me.. :/
    same stuff as shovels with hydros I guess? slack off and turn out 3 turns? can't remember... I use solids these days... :/

    i did notice there was no brace on the carb - something I'll have to make. need to have a proper look for mounting point. noticed there's no bolt in between jugs like shovels to put a bracket on
    the plugs he had were brand new, that's not to say they could be bad...

  4. #4

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    Ironheads have solid tappets, so proceed as you are familiar.
    The carb brace can go to the screw at the front intake tappet guide. When the factory did this, the screw had a stud above the hex for the bracket. If the '79 heads have the threaded bosses below the rocker boxes, that's where the stock air cleaner mounted.

    Jim

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    went through it.
    points gap at 0.019
    front pot on compression stroke
    got the single dot just coming up the window (from what I read the irons is 2 dots BTDC and 1 dot TDC, correct?)
    turn plate till test light just lights up.
    all good. weights at the back are nice and free.
    Even put a new points plate and points.
    Just read that on a '79 Ironhead, double dots is advanced timing for rear cylinder:

    "If you are running the stock ignition the two plugs fire at the same time so the two dots for the rear and the line for the front will appear at the same time.

    But, if your single dot, TDC mark is in the middle of the timing hole at idle, it means your auto advance unit is worn and you are getting too much retard at idle. It should be runnign with that mark at 10 degrees BTDC at idle. but if the bike idles and starts ok, don't worry about it. If however you ever start to get carb farts and erratic idle, be suspicious of that auto advance unit."
    http://xlforum.net/forums/showthread.php?t=523362

    You said you changed the points - what about the condenser? Did you see excessive arcing at the points? A faulty condenser will get an engine fartin' and break up under load.

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    Here is a link to a manual for reference; see images 28.2a and 28.2b for timing marks. Note 28.2a 'A' (two lines) refers to the front cylinder advance mark for late '79 to early '80 and front cylinder TDC timing mark (late '80 on):
    https://lookaside.fbsbx.com/file/197..._Q_Xe8EVHgmhVQ

    this may help; Sportster Super-Tune, by Superbikes:
    https://lookaside.fbsbx.com/file/Spo...qqaioRM8WLTALg

    I just tried those links, I see you need to log into facebook; got them from the files of Ironhead Sportster Garage...
    Last edited by TriNortchopz; 06-17-2019 at 10:49 PM.

  7. #7
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    For some reason it doesnt open for me.


    When I get on the compression stroke, I get 2 dots first, then a line, then single dot. Single dot is definitely TDC. so line must be BTDC

    You mention to put the single dot on the middle of the window? I only use middle of window if i'm stating timing of the BTDC marking and hold the cam on the advance position.
    if I time off the TDC mark then I have it just coming up on the window.

    unless irons are different than shovels? i doubt though?

    Bear in mind I dont use timing guns, I always done and do static timing and then adjust to sound if needed, most times is spot on though.

    She idles alright..kinda. but even static, just revving, she pops and bangs.

    I know of the advance unit, I have had one seize on a shovel before, symptoms of that is exactly what this little iron is doing, but weights are all good, free and not broken.

    yes sorry should have been more explicit, I replaced the whole timing, new plate, points and condenser.

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    This is from a post by Dragstwes in 2016:
    Click image for larger version. 

Name:	Ironhead flywheel timing marks.jpg 
Views:	84 
Size:	36.8 KB 
ID:	94912
    Thread: Ironhead timing question
    "The blue circle is the advance mark....
    Two dots in front of the advance mark with the lighting bolt is...for the...Rear Cylinder Advance...
    The heart dot is the TDC for the front cylinder...."
    http://www.chopcult.com/forum/showthread.php?t=47003

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    Yep it sounds like an intake leak to me..... Can you post a pic of your plugs????

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    I can't as he's taken the bike back home.. I will eventually get it back at my place, maybe next week.

    But the front one was black, proper black, the rear was white, very white, not even close to the beautiful coffee colour...

    I also don't have a clue about the CV carbs, idle mixture is a pain to adjust as it's under the carb, what a ridiculous design.
    also, don't get it how to adjust.. manual says 1 3/4 turns out then turn it till speed drops and then adjust idle. and keep doing that till speed dont drop anymore? got that right?
    need to read better on it I guess.

  11. #11

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    For CVs I find 2 1/2 to 3 turns out from lightly seated is usually the range. Factory CVs on evo XLs typically have the idle screw 2 1/2 turns or more out, and sealed from the factory.
    You want to use the idle mix screw to trim the off-idle response. You will find actual idle mix is not affected very much by that screw. On an ironhead, you are going to have to fatten the low speed a lot, usually with a 48 - 50 intermediate jet.

    Jim

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    yes, from what I read on different threads here seems like the consensus is a 48 pilot with a 175 main.

    Again, not a clue what's in there, I need to take that apart once I have the bike here. I sure will update this with my findings as in the long run it might help someone else chasing the same gremlins.

  13. #13

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    Sounds a lot like what I experienced when I put a cv on my shovel, the popping and banging.
    I needed to plug the outlet on the top at the back of the carb that is supposed to go to a voes-switch.
    That did the trick for me.
    Last edited by Vyvyan; 06-18-2019 at 12:35 PM.

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    Click image for larger version. 

Name:	IMG_2251.JPG 
Views:	2 
Size:	81.6 KB 
ID:	94926

    This. Not my carb, just a picture from internet.

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    well, interesting you say that.

    My friend when he got here said he took the plug off and thought the bike ran better. but then he called the previous owner and he said to plug it and that the plug had always been there.
    I checked and that was definitely plugged.

    but thanks for that tip

  16. #16

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    Quote Originally Posted by xJPx View Post
    Hi all...

    hope someone can help here, a second brain thinking is better than just one.

    I've never worked on ironheads but can't be that much different than my shovels and pan really..
    So a friend turned up today and I could hear him a mile away popping and banging...
    asked me to have a look. straight away I thought, probably timing.. weights pin broke or seized.

    I went through it.
    points gap at 0.019
    front pot on compression stroke
    got the single dot just coming up the window (from what I read the irons is 2 dots BTDC and 1 dot TDC, correct?)
    turn plate till test light just lights up.

    all good. weights at the back are nice and free.
    Even put a new points plate and points.

    No luck.. still popping and banging.

    When he got here front plug was black, rear plug white.
    He's running Champion H10C plugs
    and a CV carb. no idea what jets it has... I run Super Es on mine. Who's idea was to put the idle mixture screw on the bottom of a CV carb? insane!
    from what I read should have a 48 pilot and 175 main? that's a good base?

    I reckon there might be an intake leak too.
    and need to adjust pushrods - didn't have time for that....

    anything thing else I might have not thought?

    kinda of want to get him sorted as he's a good guy, but not having much time to work on other stuff other than mine, so looking for ideas and input so I can go straight into it once he gets back to mine this weekend or next week.

    thanks
    JP
    JP - if this is my old 79 XLH now owned by Shaun, there should be no issue with the Carb. it has ran the same jets since I first got it 10 years ago and they are fine for the bike. Points were gapped and timing set correctly before he picked it up too and I ran it around the block with no issues. If he or someone else has played with the timing or had the points out, it will need reset. Gap at 0.18"and get it on front cylinder 40degree advance which is the line not the dot. You can actually run the bike perfectly well by putting the timing cover stantion posts bang in the middle of the slots but to be 100% you can time it with the light. I usually ran it right in the middle as the bike seemed to like that position best. Heres a link to timing the ironhead correctly -
    https://www.youtube.com/watch?v=mKVh4pbyh2A

    Also check the weights behind the points back plate to make sure a spring hasn't broke or the small pin that keeps them in place hasn't disintegrated and the weights are moving about. This happened to me once when a set of points failed a few years back.

    Unless the bike has had the carb or intake off it shouldn't have leaks as its a CV performance built carb specifically for the Ironhead with the upgraded bolt on flange rather than the press-in fit like on stock Evo's with the CV so no need for a "carb brace" as its rigidly bolted on to the manifold. It has a 185 or 180 main although I never had any issues with fueling from the carb so never messed with the jets.

    the pushrods shouldn't need adjusting either but might be worth checking to make sure one hasn't tightened up.

    I did ask Shaun if he had removed the black plug that covers the VOSE tube on the back of the carb as removing this could cause misfire problems. But he told me it wasn't on it when he got the bike?? I told him it was 100% on it but you say he told you did actually remove it so not sure what else has maybe gone on there.

    the idle mix should be approx. 2 full turns out from lightly seated.

    It would be useful to know exactly what was changed on the bike once it got there as he did mention "a friend worked on it". I know that bike inside out since I owned it 10 years but given the distance he lives from me its difficult to diagnose in WhatsApp.

    It could also be something as simple as a condenser on the points going bad. Had that happen with a brand new set in my Evo

    - Edited as I see you put new points in and checked the weights. Shaun mentioned he had a fuel leak not long after he got the bike. Did he have the carb fuel bowl off and maybe move the float level by accident??
    Last edited by Sugarcubes; 06-19-2019 at 8:44 AM.

  17. #17
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    Always perform a compression test first to get an idea of top end health. I put the backing plate in the middle position then make SMALL movements timing it by ear. When the engine runs right, timing is right.
    If it backfires out the intake, it's too advanced. Out the exhausts, too retarded. If the last intake seal swapout time is unknown I replace them and ensure the carb has a brace. Intake leaks are common.

  18. #18

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    exactly how i used to time it. Carb is rigid mounted to the manifold with two bolts. it doesn't need a brace. Might be worth checking manifold seals to heads though to be 100%.

  19. #19

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    Quote Originally Posted by Sugarcubes View Post
    exactly how i used to time it. Carb is rigid mounted to the manifold with two bolts. it doesn't need a brace. Might be worth checking manifold seals to heads though to be 100%.
    Any manifold mounted with the bands (which this motor may or may not have) needs a carb bracket, or you WILL have a vacuum leak eventually. If it has a well mounted o-ring manifold, you can get away with no bracket, but it's still good practice to fit one.

    Jim

  20. #20

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    Quote Originally Posted by JBinNC View Post
    Any manifold mounted with the bands (which this motor may or may not have) needs a carb bracket, or you WILL have a vacuum leak eventually. If it has a well mounted o-ring manifold, you can get away with no bracket, but it's still good practice to fit one.

    Jim
    I put new intake seals and the heavyduty clamps on the intake approx 2-3 year ago and the intake manifold wasnt removed since. I rode that bike nearly every day in that trim without a carb bracket for the best part of 10 years never had an issue with leaks. far as i know the new owner just rode the bike from uk to belgium and back with no issues either so unless something has randomly changed or gone kaput in last few miles i wouldnt think an intake leak would be causing it. Both plugs ran tan when i owned it so if it was intake id expect one plug to be similar to normal colour and the leaking side to be white but this sounds like one is majorly fouled and the other super lean

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