ohh60 Flywheel Key/Valve Rocker questions

[Girl-Trapped]

Howdy, Y'all!

So we've been driving the Yerf Dog lately (when it's not raining, anyway) and I finally got around to rebuilding the carb and getting the best idle the kart's ever had. The only other issue I usually have is that my jackshaft/axle/30-series pulleys are a little off as far as alignment--it's always been wonky but I shimmed it on one side and it's also better than it's been.

All of that to say that I pulled the kart out yesterday and after a couple of training laps in my neighborhood with some friends, I pulled into my driveway, the motor went to idle, and then died with more gusto (or if you're a fan of the Breakfast Club, more RUCKUS!) than usual--not unexpected given the rain we've had and I hadn't cleaned the drive clutch up so it was a little grabby.

That's it--would NOT restart. Plus gives me a slightly noticeable kickback. Doesn't even try to start, sort of like the kill switch is on. Did some searching online and on this site regarding a sheared flywheel key and the symptoms I've read about seem to fit what's happening. The rocker on the flywheel side of the engine seems to have a lot of play in it unless it's engaging that valve, otherwise pretty floppy. The flywheel key is not sheared completely, but is it sheared enough to cause the problems I'm describing? See pics below. . .

Thanks!

 

[KartFab]

thats retarded.

literally haha! Timing is retarded slightly.

Just line up the flywheel to where you think it should go and torque it down to 65 ft lbs. I dont think the kickback was the flywheel key being damaged though as it is in about the right spot anyway. More than likely is the valve lash. The cam wont lift the valves in time to release compression when your lash is too much. Makes it really hard to start.

as for the valve train, look up the valve lash at TDC on the compression stroke, and set valve lash.

Also, check for bent valve, or bent pushrod. Loose is never good. loose comes from wear, and if its 'really' loose, it could have been one of those instantly shorter pushrod moments.

 

[Girl-Trapped]

I removed the spark plug so I could be sure the piston was at TDC, and lash clearance on the exhaust side is slightly larger than the .035 gauge I have--gap is supposed to be .004 and the feeler gauge set I have goes from .010 to .035, so I need a smaller set to get it correct.

So does a slightly retarded keyway on the flywheel and ridiculously gappy exhaust valve lash clearance give me the no-start problem I suddenly experienced, or do those problems just give me a poorly running engine and I still need to find the cause of my recent no-start problem?

 

[KartFab]

I removed the spark plug so I could be sure the piston was at TDC, and lash clearance on the exhaust side is slightly larger than the .035 gauge I have--gap is supposed to be .004 and the feeler gauge set I have goes from .010 to .035, so I need a smaller set to get it correct.

So does a slightly retarded keyway on the flywheel and ridiculously gappy exhaust valve lash clearance give me the no-start problem I suddenly experienced, or do those problems just give me a poorly running engine and I still need to find the cause of my recent no-start problem?

beats me. Pull your pushrods out and see if they are straight. If they are straight, id just set lash and get that flywheel torqued and see if it runs.

 

[firemanjim]

Piece of standard notebook paper is .004".....
And yes, retarded ignition and bad valve geometry could/would cause no start.... But not necessarily your problem. Pull the rods and see if there is any bend. If so , buy new ones.

 

[Girl-Trapped]

Piece of standard notebook paper is .004".....
And yes, retarded ignition and bad valve geometry could/would cause no start.... But not necessarily your problem. Pull the rods and see if there is any bend. If so , buy new ones.

Now googling push-rod removal tecumseh ohh60. . .

I just got the flywheel off and the key has a line along the side that follows the contour of the crankshaft, but it doesn't really appear crooked or sheared at all. I cleaned up the surfaces and put them back together.

Should I be measuring that lash clearance on a particular stroke for each valve when it's at TDC? Different strokes are giving me different readings--the intake valve is either greater than the .035 or less than the .010 I'm able to measure depending on which TDC I'm at.

---------- Post added at 04:43 PM ---------- Previous post was at 04:24 PM ----------

The more I tear into this motor, the more I wonder how it was running at all. . .

The good news is that the pushrods are nice and straight. The interesting news is that the exhaust valve rocker arm pivot/lock screw was COMPLETELY loose enough to turn by finger! Didn't even have to use either a hex wrench or 7/16 open-end to loosen them. Intake side was locked down, although, as I said a moment ago the clearance is probably way too big.

I'm gonna go grab a smaller feeler set and a fresh quart of SAE30 so that maybe I can get this puppy running tonight!

 

[Nosandwich]

Now googling push-rod removal tecumseh ohh60. . .

I just got the flywheel off and the key has a line along the side that follows the contour of the crankshaft, but it doesn't really appear crooked or sheared at all. I cleaned up the surfaces and put them back together.

Should I be measuring that lash clearance on a particular stroke for each valve when it's at TDC? Different strokes are giving me different readings--the intake valve is either greater than the .035 or less than the .010 I'm able to measure depending on which TDC I'm at.

---------- Post added at 04:43 PM ---------- Previous post was at 04:24 PM ----------

The more I tear into this motor, the more I wonder how it was running at all. . .

The good news is that the pushrods are nice and straight. The interesting news is that the exhaust valve rocker arm pivot/lock screw was COMPLETELY loose enough to turn by finger! Didn't even have to use either a hex wrench or 7/16 open-end to loosen them. Intake side was locked down, although, as I said a moment ago the clearance is probably way too big.

I'm gonna go grab a smaller feeler set and a fresh quart of SAE30 so that maybe I can get this puppy running tonight!

That don't help!!!!

 

[firemanjim]

Check valves on the up stroke of compression. Use a piece of note book paper . Its .004"..... Fold in half and you have .008".... Im a machinist by trade.

 

[Girl-Trapped]

It lives!

Check valves on the up stroke of compression. Use a piece of note book paper . Its .004"..... Fold in half and you have .008".... Im a machinist by trade.

Excellent tip--saved me a trip to the auto parts store, thanks!

After stopping by Home Depot to pickup new mounting bolts for the engine and jackshaft, I adjusted the valve lash to a piece of notebook paper and started putting everything back together and sprayed it down with some engine degreaser.

HOLY COW--it started up and sounds AMAZING!

So maybe the herky-jerky death on my last lap yesterday was somewhat of a coincidence in that there was not a violent key shearing, but instead the valves were getting progressively looser until they were so loose they couldn't keep things working at all. The only thing now is to get it mounted back onto the kart and pickup a new carb kit for a couple of the o-ring and main jet gaskets that were falling apart when I took the carb apart yesterday. Maybe once the drivetrain is hooked up, it'll idle just fine without that, so I guess I'll see tomorrow. I've read before and it makes sense that it has a tendency to idle high with no load.

Thanks for the help!