Cylinder head designs for the 80cc / 66cc 2-stroke Chinese bicycle engine

[butre]

PHEW! Thanks for that info, Butre. I hope this is the norm and the slant heads that Fabian has seen are the exception. I really didn't like the idea of having to mess around with that!

I think mine may be the exception, everything I've seen has shown that slant heads should be high compression. high compression isn't as big a deal as some of the guys here make it out to be though, as long as it's below 130-ish psi you're all good.

 

[Fabian]

I think mine may be the exception,

Can you please take a high resolution photo of your low compression slant cylinder head; both the combustion chamber and the top surface showing the height of the cooling fins.

I am curious to see if the low compression design makes it a taller cylinder head.

 

[butre]

Can you please take a high resolution photo of your low compression slant cylinder head; both the combustion chamber and the top surface showing the height of the cooling fins.

I am curious to see if the low compression design makes it a taller cylinder head.

I would if I could, all I've got is an old and blurry camera phone. I'll get you what I can when I get home but I can't promise it won't be grainy and 2 megapixel.

 

[FurryOnTheInside]

I think mine may be the exception, everything I've seen has shown that slant heads should be high compression. high compression isn't as big a deal as some of the guys here make it out to be though, as long as it's below 130-ish psi you're all good.

Oh drat!
Yeah I'm not too worried about that specifically. But the freaky shape of the combustion chamber on Fabian's slant head worries me. Lots of things worry me, I'm easily worried, lol! I've been advised to look into fitting a compression release valve too, for ease of starting (even with moderate compression) using unusual (huge reduction in RPMs from engine to pedals) shift kit gearing so a normal dome would maybe give more room or simplify that modification, or just worry me less.

Some good reading here for newbies like me lol. http://justyamahard350.com/articles/dale_1.htm

 

[Fabian]

I'm easily worried, lol!

If you are easily worried, you should forget the idea of sharing a joint bank account with a woman. That's the stuff of nightmares; filled with images of your wallet lying helplessly on the ground in a dark room; hemorrhaging profusely and barely breathing; with blood soaked walls at every corner, and the weapon of choice being a credit card.

 

[FurryOnTheInside]

LOL thanks for the advice.. tbh it's never been an option lol, no one would share a bank account with me. I have just been out and put a deposit on a new bike, to settle up and collect on Thursday. So now I have six complete bicycles! (and I'm really excited!) It's another Carrera Subway 2, exactly like my old one but all original parts and no salt damage which is amazing for a seaside town, and only costing me £65.
Means the MAB project is going to take even longer to get the parts for lol; but I'm still kind of on track to get the frame, engine and drivetrain sorted over the course of this summer. I could even use parts off this new bike as temporary eqpt for the MAB until the next January sales. I'm a very happy chappy today.
I'm so happy, I'm not even worried about clearance for a compression release valve!

 

[Majicfingers@1]

I could see how lower rpm's could cause oer heating as the gas oil mix also cools the engine and lower rpm increases burn time. I run my mix at 18:1 to help lubricate the engine more I ride through some steep hills here.

I've always ran 32:1 mix in all of my 2 strokes never a problem and I beat the s h i t outta my 2strokes lol

 

[Deleted member 12676]

fuel/oil ratios are meaningless without the context of the oils viscosity and flash point temperature. Oils with high viscosity and high flash point can be used at high fuel/oil ratios.
see http://www.dragonfly75.com/motorbike/oil.html

 

[Deleted member 12676]

No, that's how the oil manufacturers determine fuel/oil ratios for their different oils.

ps- USA is quickly becoming a 3rd world country. It is rated 17th in the world in economic freedom and is going down the ladder. http://www.heritage.org/index/ranking
Chile, a "3rd world country" is rated 10th. The only thing the USA is best at is their military strength and the high percentage of citizens in prison.