Full blown race build with a 212 4 stroke stroker motor that was on a racing go kart running on alcohol. So much compression I cant even pull start it

[DieselTech]

I think you might have missed they "why" it's hard to pull start portion of his post. It's a race motor with extremely high compression. What he needs is a compression release.

I didn't miss that at all. I've seen way too much builders going through complex procedures only to find out something simple and/or easy to fix was causing the problem.

Just like in the movie Slingblade when Billy Bob ask if the mower has gas in it. Lol Eliminate the simple/easy fix before pursuing the complex.

He is probably running diesel compression figures or close to it, since it was on alcohol. I bet it would yank your arm off with a rope. I bet the timing is on the crazy side to pull start.

 

[Sidewinder Jerry]

He is probably running diesel compression figures or close to it, since it was on alcohol. I bet it would yank your arm off with a rope. I bet the timing is on the crazy side to pull start.

It could very well be all of these things along with needing a compression release valve installed.

That being said it's very simple to check the oil level. It's also very simple to make sure you're at TDC on the combustion stroke and check valve lash clearence. If one or both are wrong, fix those issues first; they may fix the problem.

If there isn't too much oil in the crank case and/or the valves are adjusted correctly then one should consider installing the compression release valve.

What'll be so disappointing is installing a compression release valve and the problem still isn't fixed. Then discovering something similar and easy to fix was causing the problem.

 

[Chainlube]

I think you might have missed they "why" it's hard to pull start portion of his post. It's a race motor with extremely high compression. What he needs is a compression release.

Bigger pipes.

 

[Chainlube]

He is probably running diesel compression figures or close to it, since it was on alcohol. I bet it would yank your arm off with a rope. I bet the timing is on the crazy side to pull start.

He could give himself a break with a thicker head gasket.

 

[ImpulseRocket]

I didn't miss that at all. I've seen way too much builders going through complex procedures only to find out something simple and/or easy to fix was causing the problem.

Just like in the movie Slingblade when Billy Bob ask if the mower has gas in it. Lol Eliminate the simple/easy fix as the cause, before pursuing the complex.

Having built a few race spec motors, both big and small, I know how hard it gets to kick start a 250cc bike engine at 12:1. Literally stripped kick start gears and bent levers from it, and that's with aggressive cams that have a lot of overlap. The bigger the bore, the worse it gets.

 

[DieselTech]

He could give himself a break with a thicker head gasket.

Yeah I'm giddy to hear the specs. Will definitely need a jet change/ possibly the whole carb, as most alcohol carbs are not gas compatible. Yeah if it's a zero deck engine he needs to stay at a .030" or thicker head gasket.

 

[DieselTech]

Having built a few race spec motors, both big and small, I know how hard it gets to kick start a 250cc bike engine at 12:1. Literally stripped kick start gears and bent levers from it, and that's with aggressive cams that have a lot of overlap. The bigger the bore, the worse it gets.

No broken legs or cracked shins I hope. Or thrown over the handle bars.

 

[ImpulseRocket]

Yeah I'm giddy to hear the specs. Will definitely need a jet change/ possibly the whole carb, as most alcohol carbs are not gas compatible. Yeah if it's a zero deck engine he needs to stay at a .030" or thicker head gasket.

Yeah, bespoke alcohol spec carbs have huge fuel passages, among other things. Not ideal for gasoline use, unless you need all of the fuel possible for some reason.

 

[DieselTech]

Yeah, bespoke alcohol spec carbs have huge fuel passages, among other things. Not ideal for gasoline use, unless you need all of the fuel possible for some reason.

Have you seen these guys running the gx390 honda with the big super SBN mikuni pumper carb? Guy around New York area made if I remember correctly 86.6hp on a fully custom gx390. Still the a record holder in his race class I believe. I think that gx390 cost $8000 to build.

 

[Sidewinder Jerry]

Having built a few race spec motors, both big and small, I know how hard it gets to kick start a 250cc bike engine at 12:1. Literally stripped kick start gears and bent levers from it, and that's with aggressive cams that have a lot of overlap. The bigger the bore, the worse it gets.

It may be very exactly what you're talking about. Basic mechanical diagnostics procedures dictates to eliminate the simple and easy to fix as a cause, before pursuing the complex.