Dang, that was odd

[EVOL Tweety Bird]

So we head up to Road Atlanta to race, along with the EVO, I took Evol Tweety Bird and Pure Evol to cruise the pits.
Unload and get ready to cruise around the place. Tweety who has run like a champ for what 2 years now, normally starts on the first pull. Not now, like she's gone bonkers, rips the pull start out of my hand, no matter where in the rotation I try and start her. Block the wheel get her to fire with the throttle open and as soon as you release the throttle she dies.

Just for info, 212 Hemi, billet flywheel/rod, no governor, rejetted, reported/ polished, Mod 2 cam, 22 pound springs, oil sensor delete, 3 angle valve job, custom header and air filter, dual breathers. VALVE LASH SET TO ZERO (0), both valves, cold.

What the heck! Pull the plug, and it's slightly rich like normal, but even with the plug out, it pulls hard. Aw crap!
Thinking maybe it sheared the key I disassemble her between rounds. Nope just fine. What the hello is going on?

Just in case, I drain the oil to check for metal, thinking maybe the compression release or spring had broken. No joy there, not a spec of steel or aluminum in it.

Finally pull the valve cover off and check the lash. Well that's odd, the exhaust is at 2 thos. Really? Could that be?
Well, checked the adjuster, it's tight, not moving. Okay, loosen it up and reset the lash to zero (0).
Put the cover back on, and she fires up on the first easy pull and sits there and idles like the little Harley she sounds like.

Really? That was it? REALLY? 2 stinking thousandth of an inch of valve lash made it do that? Seems so... ut:
I guess 2 years of running had loosened up things and opened up the lash enough to not hit the compression release. :facepalm:

 

[2SlickNick]

Bas ass bike!
Good old valve lash -LOL

 

[SAS289]

Sounds pretty odd to me. Especially zero lash cold.

I thought I would have some fun and look up the specs in an old HF Greyhound engine owners manual. Says after each year or 300 hours the lash should be adjusted to .15mm intake and .2mm exhaust cold. That's about .006" and .008"! After reading what others do including zero lash it makes me wonder how the engine with these specs would even run set that way?

The 2 Greyhounds I run are just low hour utility engines. I don't remember what I set them to when new and have never adjusted them since. It's been at least 8 or 9 years.

If I had your issue I would have set it back to .002" just to verify that was the root cause.

 

[TheDullCarbide]

Pulls hard with the plug out? WTF?

Yes Greyhounds call for 0.006"/0.008" lash but that all goes out the window with a race cam and rockers. At 0.002" you should be fine.

I would have said it was the compression release hanging up but what really screws me over is pulling the plug didn't make a difference. Something was binding/breaking/seizing...

 

[EVOL Tweety Bird]

Got me. I've started it a half dozen times since and it's acting normal.

As for hard pull with the plug out, it wasn't snapping the cord out of my hand, but more like it was not allowing the exhaust valve to open up on the exhaust stroke, so there was no where for the air to go, except out the plug hole. Who knows, that's the only thing I did, was tighten up the exhaust lash to zero again.

As for something coming apart, well it is a Predator, I haven't ridden the bike since, just tried starting it and reving it up, like said around half a dozen times. If it blows I'll just buy another, got 2 good years out of it.

 

[DeadPixel]

That's a long time to not check the lash.

 

[EVOL Tweety Bird]

Just a follow up, have ridden the bike a few times, and she's still running/starting normal. Single pull to start with the choke on. Flip off the choke and she rumbles like a little Harley. Did have a small scare on the first run. Blasting down the street and all of a sudden it was like the engine was coming apart, vibrating the whole bike. Back to the shop turn in, and nearly dumped her as the rear tire was flat. Dang roofing nail in the tire. Gotta love two piece wheels, made the tire removal a snap. Tube patched and she's back to her normal self.