1975 XLH Ironhead Sportster. Bored +.040, otherwise pretty much stock? I use Valvoline 50 wt raceing oil.

Had heads reworked by local bike shop, got 2 new exhaust valves, guides, and seals. Also I put on a new S+S super "E" shorty carb.
After careful push rod adjustments, and double checked everything it ran about 1.5 miles and front exh valve hung open.
No piston damage. Remove head, bike shop fixed, took off again went 15 miles, and front exhaust stuck open. CRAP!!
($#%@*=Towtruck home was $90.00) OUCH.
Have good oil flow through rocker boxes. Push rods are NOT too tight.
I'm tired of taking the top end apart, (I Wana Ride!)
What could be causing this malfunction. I am not beating the bike (too much).
Please advise,
Thanks, Reffixer.

 

Sounds like the valve is getting bent, I don't know of anything else that would stick one on a new rebuild that quick, for sure somethings not right, you said there was no damage to the piston the first time was there any marks at all on the piston? Only other other thing I can thing of would be valve warpage due to heat or the valve guide valve clearance is way too tight. Did the shop that rebuilt the heads have any suggestions on what they think happened did they inspect to see if the valve was warped or bent or seized to the valve guide?

 

No John, there were no marks at all on the first piston, and that valve hung open farther than this second one did. You could see the valve throught the empty spark plug hole. This time as it started to hang up, the motor would start farting out the exhaust pipe, loose power, then regain itself. That's when I tried headded for home. While on a freeway off ramp it stuck for open good. I parked, let motor cool down, tried restart, but no good. That's when I called for a tow. The bike shop had no difinitive answer for the first hang up, although the first exh valve I am sure was a tiny bit longer than the original, seeing as how I had a hard time getting the push rod into the lifter.
All (4) push rods are the same leingth.
Maybe it's getting too hot seeing as I am breaking in the new +.040 Wiseco pistons. There is around 17 miles total on motor so far
Hope this helps, thanks again,
Reffixer.

 

Sumpin' ain't right. But you already know that. [8D]

You should not have had any problem getting the pushrod installed. As you said, they're all the same length on an Ironhead. While it could be several other things, the first couple things I'd suspect is they fitted the wrong valve, the guide is installed wrong (canted), or the clearances are too tight. If your shop just unstuck the valve without checking anything out, they need to strip the head and check the valve & guide thoroughly.

 

Would breaking in the new +.040 Wiseco pistons create enough heat to cause the valve to stick?
What if I remove one of the exhaust push rod covers, then with spark plugs removed turn engine over to check oil flow?
I'm tired of wrenchin, I wana ride.
thanks
Reffixer.

 

If the pistons & rings were properly fitted and assembled, breaking them in should not create enough heat to stick a valve. Won't hurt to check for oil flow as you describe, but if you weren't getting oil to the top end, you'd probably hear the rocker arms squealing in the bushings. I'd still want to pull the head and have a competent mech look at everything.

 

It will be done in the morning.
This head job is getting scary.........., the good thing is, I can get this engine apart and back together in just a few hours, when this time last year I had never opened one.!
Thank You abunch for your input.
Reffixer.

 

Many times if you have the valve guide changed when they ream them you can get a tight spot once it starts to run it will gall and bind up. I bought a hone kit for guides that makes reaming them look like you are using a stone axe lol The hone does a much better job and is more accurate. Takes a bit longer but well worth it. Check to make sure valve is straight a set of vee block and a dial indicator will work there, or roll it on a flat surface.