Ironhead low compression after riding

[Macksabbath]

Just bought this thing at the end of last summer it is a 1971 xlch900, just recently replaced the top end gaskets and stuff to see what i had going on inside and fix some leaking. Rocker covers still leak but whatever. Everything looked fine. Put it all back together, didnt have great compression, (was super soft on the kicker) basically took little to no weight to kick it through, it eventually fired up and everything was great. Fast forward to today, i took it out on a 30 minute rip around town and went to a buddies coffee shop(i know, super moto hipster of me) had my drank and went out to head home and it had very low compression again, like it did when i first put it back together. It took for fucking ever but it finally caught enough to fire up. Had great compression before the ride! Im 99% the pushrods are adjusted right. My question is what the fuck is going on and where should i start. I dont want to have to kick this fucker over 500 times everywhere i go this summer. Im gonna start fucking with it but i just want some chopcult input

[Tattooo]

Did you do any test before you tore it down or did you just say this is what's wrong??

Also how far did you tear it down?? Rings, valves etc??? Way more info is needed....

Also what did you mean by {Rocker covers still leak but whatever.} You fixed it but you didn't so oh well???

[TriNortchopz]

When you say you "replaced the top end gaskets and stuff", did that include removing heads and replacing head gaskets?
What did you see when you looked inside? Did you do anything to the valves?
So it "didnt have great compression...at the end of last summer", and it didn't get any better by itself as noted today. How did it start before "went to a buddies coffee shop"?
and it starts okay when cold?
Are you sure valve clearances aren't too tight?
Do you have a manual?
If you didn't perform a compression test and leakdown test yet, now is the time...before you pull it apart again.

Here is some good info from the XLforum: http://xlforum.net/vbportal/forums/s....php?t=1046163
which includes this link:
Cylinder Compression And Leakage Tests For Your Ironhead

http://xlforum.net/vbportal/forums/s...ad.php?t=48311

Here is a good discussion on HDforums with a similar question by 75hdxlh:

https://www.hdforums.com/forum/sportster-models/796718-low-compression.html

I just did a compression test on my bike and found that the front cylinder has only 15 psi ! But the back one has 90 psi, what could be the problem?

alexl answered: worn rings/cylinder wall, valve sticking open, burnt valve seat, cam timing off. do a leak down toest to see where the problem lies. you can take an old spark plug, knock out the ceramic piece, weld on a male air tool connector and plug into an air compressor. air coming out exhaust or intake indicate valve problem, through crankcase indicate rings/cylinder wall.

with another good response from hog4U, with a link:
Sounds like a rebuild is in your future. You can get lots of help on the Ironhead forum.

https://www.hdforums.com/forum/ironhead-66

How to Do Compression and Leak Down Tests
from the Dennis Kirk blog:

http://powersports-blog.denniskirk.com/5188/powersports/how-to-do-compression-and-leak-down-tests/

If your machine just doesn’t have the snap that it use to have, you might have issues with the compression of the engine cylinders. If your bike or sled won’t even start and all your electrical is working, you almost definitely could have some compression issues. An engine needs enough compression to compress the fuel mixture, which raises the temperature enough to be combustible. A simple compression test can tell you if you need to further investigate your engine to figure out the problem before serious damage can occur.

And of course, we all know "Newtons Law of Kick Starting"...
from Jim M:
Ok, here is the true scenario that happened today and it has happened to me several times in the past. Push the knucklehead out of the garage, I am by myself, no one around. Open the fuel line, give it two soft prime kicks, turn the ignition on, check around, still no one around, starts on the FIRST kick. Ride to a friends shop. Walk around don't see anyone I know so I jump back on the warm bike. No prime, two people watching, one a nice looking girl, fails to start on the first kick, smile at the girl, starts on the THIRD kick. Feeling good, crowd gathers around to hear the old bike. Forget to disengage clutch before shifting because I am nervous being the center of attention. Bike stalls. Feel really stupid. I should have known better. Darn it. Crowd still there, some chuckling, probably 15 or so people. Kick it several times probably 15 TIMES, too tired to talk. Get off change plugs, crowd leaves, no one around, bike starts first kick...It happens to me all of the time. The number of kick starts is proportional to the number of people watching. Next time I'm going to tell everyone to leave before I try starting it again in public.
and,
from L.A.:
In my younger, DUMBER years, my ridin' buddies & I would ride to our local watering holes & meet up with other ridin' buds...mostly men...not too many women rode back then, so I had many male friends...(yowsa!)...anyway...we'd be in a bar, drinkin'...then someone would decide we'd move on to another...got to the point where any one of my buddies would holler over @ me, "Lell! Go start kickin' that damned sportster...we're headin' up the road!"
So...'bout a half hour or so before our scheduled departure, LOL, I'd go outside...I'd finally get it started & on my way...pull into the parking lot of the next place...before I even shut off my scoot, everybody'd come roarin' in!!!
They had it down to a science!
PERFECT TIMING!
and,
from HJahn:
Another time I was with some local boys who were putting together a Sporty. They got it all ready and started kicking and kicking and kicking. Somehow I knew that bike would start, but that they were kicking it wrong -- hard but wrong -- like applying the kick at slightly the wrong time and the bike didn't like that. I know that sounds nuts, but I think it's true. If kick the bike wrong, it will take offence and refuse to start. Anyway, after they were all tired out, I said: "let me try once." I acted real confident, threw a leg over it, and gave it an easy shove and I swear that it started right up on that first kick!

See more from Newtons Law of kickstarting here:

http://www.antiquemotorcycle.org/bboard/archive/index.php/t-8902.html

I forgot to add; did you get a good deal on it? If so,you will need to speak with Dragstews...

[Dragstews]

Adjust the valves, rundown the simply stuff first ...

Sometimes that "Good Deal" ain't so good ... !!



Where have I seen ^^ that before .. ??

[Macksabbath]

Did you do any test before you tore it down or did you just say this is what's wrong??

Also how far did you tear it down?? Rings, valves etc??? Way more info is needed....

Also what did you mean by {Rocker covers still leak but whatever.} You fixed it but you didn't so oh well???

I tore it down because it was leaking all levels from the rockers to the cylinder base. Tore it down to the cylinder base gasket. Put it all back together after just cleaning some carbon and puting gaskets back. Didnt see a need to do much more and i just wanted to be ready for warm weather. The rocker boxes still leak a little but nothing else does. I say oh well because Ironheads tend to leak and still be fine ya?

[Macksabbath]

When you say you "replaced the top end gaskets and stuff", did that include removing heads and replacing head gaskets?
What did you see when you looked inside? Did you do anything to the valves?
So it "didnt have great compression...at the end of last summer", and it didn't get any better by itself as noted today. How did it start before "went to a buddies coffee shop"?
and it starts okay when cold?
Are you sure valve clearances aren't too tight?
Do you have a manual?
If you didn't perform a compression test and leakdown test yet, now is the time...before you pull it

A lot of good info i’ll go through, thanks. I didnt do anything to the valves besides clean some carbon off and adjust them when i put everything back together. It had fantastic compression yesterday when i first started it. And still great compression when i turned it off and restarted it. It was when it sat amd cooled for 10-15 minutes while i was in getting coffee when it had shit compression. Other than then and when i first went to start it after regasketing did it have weak compression

[Tattooo]

Didnt see a need to do much more and i just wanted to be ready for warm weather.

Well I guess there was really a need to look further... Because now you have to tear in back down before warm weather... Buy more gaskets etc... It's much easier to do it right the first time...

Ironheads are not supposed to leak if they are put together correctly no matter what you have herd...

Now start all over and do a leak down test to try and find your problem...

[TriNortchopz]

Sounds like it could be a sticking valve - sticking in the open position.

IronMick from the HDforums says this: When a valve sticks it always sticks in the open position with the valve spring compressed, so there is no pressure in that valve train {cam, lifter, pushrod, rocker}. You hear a loud clattering noise as the pushrod bounces up and down with the loose rocker.

In my limited experience if i then shut off the engine, pull off the road and re-start, the valve frees up and i am good to go again - until the next time. Usually means that the valve guide needs to be honed...https://www.hdforums.com/forum/ironh...uck-valve.html

He also lays out this procedure: Ironhead Push Rod Adjustment, with two options for process.

Ironhead Sticky Valve fix from xlforum:
So, where do I go to buy a hone for a Harley sized guide? Anybody here have any good advise for getting my valve to be a little less "sticky"?

http://xlforum.net/vbportal/forums/archive/index.php/t-821438.html

Really strange ironhead problem that fixes itself

http://www.jockeyjournal.com/forum/showthread.php?t=88600

Ok so this is the second time my bike has done this to me and I cant figure this out. after riding when its hot out or being on the freeway for a while even in cold temps when i stop it wont start back up. it kicks over as if there is no compression, just spins very easy. after a while it will "have compression" again and fire up. last time it did this i took off the pushrod tubes to make sure they were tight and moving normally and they were.
My only guess would be a stuck intake or exhaust valve but the odds of that happening on both cylinders are not good I dont think. would it spin so easy with just one cylinder not having compression?
carbineken replied: Haven't had the experience myself but I've heard a few guys talk about tight valve guides. Valve and guide get good and hot causing the valve to stick, once it cools some everything is back to normal.
Slim55G concurred: carbineken hit the nail on the head. Had a 77CH did the same thing.

[Macksabbath]

Really strange ironhead problem that fixes itself

http://www.jockeyjournal.com/forum/showthread.php?t=88600

Ok so this is the second time my bike has done this to me and I cant figure this out. after riding when its hot out or being on the freeway for a while even in cold temps when i stop it wont start back up. it kicks over as if there is no compression, just spins very easy. after a while it will "have compression" again and fire up. last time it did this i took off the pushrod tubes to make sure they were tight and moving normally and they were.
My only guess would be a stuck intake or exhaust valve but the odds of that happening on both cylinders are not good I dont think. would it spin so easy with just one cylinder not having compression?
carbineken replied: Haven't had the experience myself but I've heard a few guys talk about tight valve guides. Valve and guide get good and hot causing the valve to stick, once it cools some everything is back to normal.
Slim55G concurred: carbineken hit the nail on the head. Had a 77CH did the same thing.

THIS! This sounds almost exactly what mine is doing. It has compression and runs fucking perfect until its time to head back home from somewhere.

[Dragstews]

Perhaps the rings are stuck to the piston lands....
A bike that old may have seen a long time sitting in storage .. ??

A leak-down test could show the problem..
Most likely yo'll be ending up doing a top end job with boring to the next size up bore, new oversize pistons, replacing valve guides etc ....
Hope it doesn't need the whole motor rebuilt, that would get into the pocket pretty deep.

[Macksabbath]

Perhaps the rings are stuck to the piston lands....
A bike that old may have seen a long time sitting in storage .. ??

A leak-down test could show the problem..
Most likely yo'll be ending up doing a top end job with boring to the next size up bore, new oversize pistons, replacing valve guides etc ....
Hope it doesn't need the whole motor rebuilt, that would get into the pocket pretty deep.

Yeah that would fuckin suck. The bottom end seems to be pretty solid. Shifts proper and stuff so i think im doing okay down there, i have a shitty feeling that if my valves are indeed still adjusted right i may be looking at least at a valve job. The ring and pistons and cylinders looked solid when i had it apart but my eyes are still pretty new to all this so who knows.

[Tattooo]

Yeah that would fuckin suck. The bottom end seems to be pretty solid. Shifts proper and stuff so i think im doing okay down there, i have a shitty feeling that if my valves are indeed still adjusted right i may be looking at least at a valve job. The ring and pistons and cylinders looked solid when i had it apart but my eyes are still pretty new to all this so who knows.

You say they look good?? What are you comparing them to??? What did you do to the bottom end when you had the cylinders off that told you it was ok??

[Macksabbath]

You say they look good?? What are you comparing them to??? What did you do to the bottom end when you had the cylinders off that told you it was ok??

Hope and prayed haha. As far as the top end I just looked for scratched up cylinder walls and pistons. The thing ran great before i opened it up so i was assuming everything was kosher. Like i said the only reason i took it apart is because the gaskets were crap. Otherwise i would have had no reason too. It never showed signs of low compression except for right after i put it back together and when i was leaving yesterday to head home. Also like i said, im still new to this old thing so cut me some slack dammit!

[Macksabbath]

I would rather not open up the bottom end can of worms unless i had absolute reason to do so. Stuff gives me a headache just thinking aboutut

[Tattooo]

Hope and prayed haha. As far as the top end I just looked for scratched up cylinder walls and pistons. The thing ran great before i opened it up so i was assuming everything was kosher. Like i said the only reason i took it apart is because the gaskets were crap. Otherwise i would have had no reason too. It never showed signs of low compression except for right after i put it back together and when i was leaving yesterday to head home. Also like i said, im still new to this old thing so cut me some slack dammit!

LOL That's you learn.... Just because your new doesn't give you a pass.... You learn from your mistakes and if someone doesn't point it out to you, you will do it again....

Now we are getting somewhere... You said it was running just fine before you tore it down to replace the gaskets right???

Your valves are to tight....