Engine Trouble She won't 2 stroke?

[Wildturkey]

I have a Rock Solid 70. 300kms on it now and it refuses to 2 stroke?

I have tried several diffent carby/jet/air cleaner combinations. All the adjustments I make will not let it 2 stroke up high. At times the low to mid range is impressive. Though the bloody thing will not sing up the top end?

The only way I can make it run to its potential is to turn the fuel off. Then the moment before it runs dry it goes like a stabbed rat, screaming 2 stroke the way it should. Only for a second or 2. So I guess I can not get it lean enough on the main. I have tried all sorts of jets???

I have tried a .80 jet down to the jet out of a stock 50? Running many different fuels and ratios.... no luck? Straight caster oil at 20:1 all the way through to TTS at 32:1. Still will not 2 stroke???

I have match ported the exhaust and opened up the inlet port a little while match porting to the very short inlet manifold I have made as my frame is very small. Yes the inlet tract is sealed. I am a qualified mechanic and have built 24 hour winning race cars. So I have some idea. I have worked on all sorts of engines for over 25 years and no engine has bothered me like this one.

I wanted to run a SBP expansion exhaust I have along with a shaved head I have had luck with in the past. I wanted to hear this thing run well before changing to much stuff.

What the **** is wrong with this thing???

 

[Ghost0]

The stock jet is a .70 typically. I usually recommend a .68 or a .66 to most customers.

 

[ddesens]

If you havent put the expansion chamber exhaust on yet, do so. It will help lean you out a little more.

 

[motorpsycho]

The stock jet is a .70 typically. I usually recommend a .68 or a .66 to most customers.

That's really weird because my stock jet was around .70 but it was too lean and it would bog big time on the top end.
I ended up putting a .72 jet in mine to make it run right.
but of corse, the part of the counrty that you live in will affect the air-fuel ratio, so any one certain jet will not work for everyone.
you have to try different jets and use trial and error to get your carb tuned for where you live and for your engine.
no two engines will run the same with the same jet.

 

[Big Red]

Won't 2 stroke

Hey Wildturkey,
Just a few simple things to try. I've done a lot of hard work on engines only to find out it was something simple in the first place. I'm not saying it's any of these things, But I always check the easy stuff first.
If you didn't already, get rid of the plug and wire that came with it. That plug will run it for about five minutes before going bad. The plug wire won't supply the plug with enough to spark it properly.
Check the float level, again. I like to raise it to just below, but not touching, the primer rod. In other words, All the way up. Keep the floatbowl FULL.
Check for air leaks. With a spray bottle squirt the intake fittings to see if the engine bogs. any air leaks will suck in water and bog the engine.
Check that cheap chinese gas cap for proper venting. If it only vents a little then the engine will run at low RPM's just fine. If not venting properly and it lets only a little air in, when you go for high RPM's not enough air is getting in to allow proper gas flow. When you let it run out of gas, in the end, it's getting more air and rev's up. I've had them not vent at all. Run's great for a block or two then die's. took me a minute to figure that one out.
It may be none of these things, but like I said, I like to check the easy stuff first.
Thanks,
Big Red.

 

[Wildturkey]

Cheers Big Red, I have tried most those things mate. The ignition system is all high quality. I am starting to think the angle I have on the carby is a problem now. I am chasing that out today.

Cheers

 

[Big Red]

Carb?

Hey Wildturkey,
I simply went through what everyone suggested to me. The gas cap thing I figured out myself. I also have an engine that won't 2 stroke or "rev out". I also had my carb at a steep angle and putting it level helped some. So WHEN (not IF, couse I have faith,) you get this figured out PLEASE let me know so I can finally get my bad boy on the road too.
Thanks,
Big Red.