Found the culprit, pushrod replacement question

So pulled the head off my 750 today, the bike had been sitting since the early 90's and when i got it running the right side wasn't running well at all, smoke from tail pipe, but compression okay. When i took the head off today i found this

The bottom had come off the right side exhaust pushrod (thinking this was our problem!) so my question is, is there any reason, including the fact that one has failed, to replace all 4 pushrods rather than just this one?

If the others not involved so ends still on snugly then just one to buy or beg. What will ya do with the bad one? I don't want it just curious about lettings go or collecting.

Did ya find/fix the cause of this? Ends are not on that tight to begine with and don't really need to be once trapped with correct lash set, so I'd suspect running w/o it seated which would give lack of lash of course.

The question is, where is the missing end? Maybe sitting on the lifters? I would shine a big light down there to make sure it didn't damage the cup in the lifter.

kevbo82 said:

So pulled the head off my 750 today, the bike had been sitting since the early 90's and when i got it running the right side wasn't running well at all, smoke from tail pipe, but compression okay. When i took the head off today i found this

The bottom had come off the right side exhaust pushrod (thinking this was our problem!) so my question is, is there any reason, including the fact that one has failed, to replace all 4 pushrods rather than just this one?

Click to expand...

That is a pretty common problem that doesn't seem to hurt anything except the end of the pusrod will slowly wear causing the valve lash to increase. I have repaired many of them by lightly knurling the end of the pushrod and pushing the end back on with a bit of red locktite or JB weld. You can knurl the end of the pushrod by putting three or four rings around the end with a tubing cutter or use a knurling tool. Jim

RennieK said:

The question is, where is the missing end? Maybe sitting on the lifters? I would shine a big light down there to make sure it didn't damage the cup in the lifter.

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it was just laying there right on top of the tappets, i fished it out with a pick and looked in with a flashlight, all seems well, i don't see any signs of carnage, and even the loose end doesn't have a scratch on it. The fact that the motor has 21k miles on it, was running so bad on that side, but with good compression, and had been sitting so long, made me decide to take the bike down to the frame and rebuild the motor. I figured it was a valve problem considering 125psi on each side WOT. but i guess i've come this far i should just rebuild the damn thing! I'm going to take the barrels off tonight and have a closer look make sure nothings harmed.

comnoz said:

kevbo82 said:

So pulled the head off my 750 today, the bike had been sitting since the early 90's and when i got it running the right side wasn't running well at all, smoke from tail pipe, but compression okay. When i took the head off today i found this

The bottom had come off the right side exhaust pushrod (thinking this was our problem!) so my question is, is there any reason, including the fact that one has failed, to replace all 4 pushrods rather than just this one?

Click to expand...

That is a pretty common problem that doesn't seem to hurt anything except the end of the pusrod will slowly wear causing the valve lash to increase. I have repaired many of them by lightly knurling the end of the pushrod and pushing the end back on with a bit of red locktite or JB weld. You can knurl the end of the pushrod by putting three or four rings around the end with a tubing cutter or use a knurling tool. Jim

Click to expand...

Jim,
your saying just a few rings around the bottom with something like a copper pipe cutter? can't hurt to try, then give an earthquake test before putting it back in

comnoz said:

That is a pretty common problem that doesn't seem to hurt anything except the end of the pusrod will slowly wear causing the valve lash to increase. I have repaired many of them by lightly knurling the end of the pushrod and pushing the end back on with a bit of red locktite or JB weld. You can knurl the end of the pushrod by putting three or four rings around the end with a tubing cutter or use a knurling tool. Jim

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Jim, my question would be how did it manage to come off? I don't see how you could get enough clearance in the engine to let it slide off. What am I missing here?

Ken

lcrken said:

comnoz said:

That is a pretty common problem that doesn't seem to hurt anything except the end of the pusrod will slowly wear causing the valve lash to increase. I have repaired many of them by lightly knurling the end of the pushrod and pushing the end back on with a bit of red locktite or JB weld. You can knurl the end of the pushrod by putting three or four rings around the end with a tubing cutter or use a knurling tool. Jim

Click to expand...

Jim, my question would be how did it manage to come off? I don't see how you could get enough clearance in the engine to let it slide off. What am I missing here?

Ken

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I would say it had to come off as he disassembled the engine. Likely was working fine until then. Jim

i as just thinking the same thing, maybe when it tried to come off with the head the end popped off. which would mean thats not my sick motors problem...

kevbo82 said:

i as just thinking the same thing, maybe when it tried to come off with the head the end popped off. which would mean thats not my sick motors problem...

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Agreed, you need to look further. Of coarse if the compression was good it may have been caused by carburetor or ignition problems. They can sure cause smoke also. But since you have the head off I would go ahead and pull the barrels and check or replace the pistons or rings and have a look at the camshaft. Jim

Suspect flattened cam lobe once barrel removed and beat up lifter bottom.

hobot said:

Suspect flattened cam lobe once barrel removed and beat up lifter bottom.

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they look okay to my untrained eye, a difference in color on the tips of the lobes, but i would assume thats to be expected?

They have a bit of wear but not enough to affect how it runs. They have some miles left on them but if I were rebuilding the engine I would put a new cam in it. Jim

You could measure the cam lift with a Harbor Freight 0-1" dial gauge and magnetic stand - about $20. Then you will know exactly how much wear.

I have a pushrod or two for ya, no charge.

That being said, those lifters will gring up flat with no issue.
Not knowing what you have for a cam there, you could offer it up to Jim Schmidt and see what he can talk you into.

But as Comnoz says, You could slap the head back on and head on down the road for a season or two. Save up some C-notes and wait for the weather to go to hell and have at it.

PM me if I can help you out with a pushrod. No big whoop.

Lucked out as cam lobes and lifter still servicable so I guess the push rod just never got seated in lifter socket is all. My last rebuild had scored lifter bottoms from rod bolt let go and some nicks below lobe surface. Comos surfaced the lifters and I dressed the lobes - then got to check them d/t ring job at 7000 miles wide scope of usage to be very pleased surfaces even better burnish finished and no rocker-stem dimples just burnished smoother in centers. I rev right up over 2000 on each start and don't start unless can warm fully up before shut down.

hobot said:

Lucked out as cam lobes and lifter still servicable so I guess the push rod just never got seated in lifter socket is all. My last rebuild had scored lifter bottoms from rod bolt let go and some nicks below lobe surface. Comos surfaced the lifters and I dressed the lobes - then got to check them d/t ring job at 7000 miles wide scope of usage to be very pleased surfaces even better burnish finished and no rocker-stem dimples just burnished smoother in centers. I rev right up over 2000 on each start and don't start unless can warm fully up before shut down.

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are those cams a serviceable item or does it just need to be replaced?

Huh, ya asking me? Best I can go by is examples shown here that Jim C. has evaluated as adequate or ruined. Only way I know to fix is buy new or have core welded and reground. But there's at least a few 1000 examples of soft cams with flattened lobes running adequately a long time, just not at peak performance, so seems some slack on what we can get away with a good while. Ms Peel ran 2000 miles with flattened exhaust lobe after over rev event that disappeared the tach needle bouncing off its stop and slammed back again. Only thing noticed was no more power to fly out from under me if not in full dragster lock down and would not pull over 110 mph/5000 rpm with huge wind screen on climbing steeps. Only reason I took Peel apart instead of just riding around like normal folks was Ducati came out with 1098 and realized I needed bigger engine to run down current bait fish evolution. That's when i discovered the real reason for loss of spunk - the Rick and Mary cam tensor was wiped out of the picture so valve and ignition timing shot to shit. I was dull founded how well Peel started, idled and ran above go to jail speed, just not spank 600 sports bike level any more.

My reasoning is if the lifters flat and the cam scars below surface then oil wedge surfs over the imperfections as long as rpm kept up. Also seems there is not much risk of show stopping engine damage and cam pores should just hold more oil to ski over. If splitting cases might consider cyro temper and nitride coat and polish on cam for a longer run.