50cc valero (jl50qt_6a) stroker install issues

[bigfifty]

whts up people well let me tell ya that if you are doing a stroker crank install ya might be like me with a head scratch or two. i have a 50cc scoot tht ive installed a 50mm complete big bore kit. then ive bought a 44mm stroker crankshaft from scrappy dog scooters( all measurements checked out for direct bolt on). it bolts right in after i kept it in the freezer over night. now the problem i have is that my piston is 1.5mm further out and i need to find a spacer or something to compensate the difference. at first a doubled up on the gaskets that are close to .50mm giving me a full milli, but im still short .50mm. so is their anyone tht would know or have done a stroker install on a 50 to give me some pointers? i got all the bells and whistles for this scooter on it but this stroker is a headache. everyone in my town tht does motor work will not touch a gy6. so ive been stuck at this point for a few months

[Rebel]

We have had a poster that the piston did not go all the way to the top of the bore too. You did the first suggestion with doubling up on the base gasket, a thin piece of sheet metal might be used for making a shim. Might try to do the same with a head gasket, or if you put the head on does it have valve clearance, if head piston does not hit the valves it would give you more compression. Next thing if it does hit the valves is to have the piston shaved down.

Jmkjr72 might have a better suggestion.

[jmkjr72]

Typically I use washers as spacers to figure things out
Then after that I mea use the thickness of the washers get a piece of Al or even go to a machine shop and use a base gasket for a template to make a spacer in fact some places hove some thickness in Stock for two strokes I don't know about 4 strokes

[bigfifty]

Well guys at my shop i found a piece of sheet metal at my shop tht was within the .47mm-.50mm spec i needed to shim my cylinder head. When i seen my piston at TDC i jumpped for joy lol...today imma reinstall the motor to the bike and fine tune my carb. Ive read tht my compression should be at 110 to 120...my roomate says otherwise, at 150 for any gy6 engine. Granted he rides a bored out 180. So wht compression would i need to be at? Imma be at 87.39cc. As far as big bore engone break in i hear soo many way to do so for 150s but nothing for 50s

[Rebel]

A stock 50 should be at that 120 range. They will run under that. Remember that unless you put a head with a bigger chamber on it, the compression will be going up, how far I do not know.

[bigfifty]

Ok. Yeah i rtht with an 50mm bore and stock stroke to puts me at 81.29cc and the correct compression range is 155-175psi. my 44mm stroker will up my compression even more to my test of 185psi(from last night). In all im maxed out at 86.39cc with a compression of 185psi. Im putting this lil cc to the test lol. Imma do my homework and see if my motor can handle tht kinda psi. I will keep ya posted

[Rebel]

With that kind of pressure don't even think about running a low or mid grade octane.

[bigfifty]

So would ya say 93octane or better? Ive always used 93grade with a lil bit of booster in it as well

[Rebel]

I'd let the motor tell me what it wants, you might need some good octane booster. If it pings you may be needing something that will bring the compression down. Perhaps another cylinder spacer, a lower compression piston.

[jmkjr72]

Or try a colder plug

I do it all the time on two strokes

The problem is unless it's a pump dedicated to 93 you are getting about a gallon of what ever the last guy pumped

After changing parts on pumps I'll give you an idea
Normal to bleed the air after just changing the nozzle is .15 gallons
If you have to change the hose or the break away at the end of the hose you are at .5 to .65 gallons depend s upon the length of the hose
Now mind you that the equipment that mixes or shifts between unl plus and prem are at the Base Of The dispenser
So that puts right around a gallon of what ever the last guy pumped in the line

[bigfifty]

So I have everything put together and fired her up. Needless to say it didn't fire up, the starter barely turned over. After reading up on it I went out and bought a high torque starter.even tht was not turning over strong. So I tried kickstarting it. Now with the compression test with the highest torque starter barely doing anything I was at 185. Kickstart would add to tht and when I did the lever slapped my foot back so I'm guessing my compression is just way too high.

[Rebel]

you are about 50-60 psi above normal

[craisin]

Jan 21, 2014 19:18:10 GMT -5 jmkjr72 said:

Typically I use washers as spacers to figure things out
Then after that I mea use the thickness of the washers get a piece of Al or even go to a machine shop and use a base gasket for a template to make a spacer in fact some places hove some thickness in Stock for two strokes I don't know about 4 strokes

this is a good idea but a bit harder to do on a four strokes
you could get some machine shop to make a thicker head gasket out of copper plate take the gasket to use as a template

[Rebel]

A metal spacer for the cylinder is not impossible to do as a home project.

[bigfifty]

so I had her running at idle around 180 psi With several gasketsbut the stress on timing chain cost my timing chain to break I did homework and met a guy that builds race scooters and he told me that I could run up to 210 psi granted I did have it run at 220psi. I know wht to do now to get her right . UT the thing tht gets me is tht when I kick start it sometimes it will kick back at my foot hard as hell I don't know what causes this let alone if this is something that will cause damage so that's the question I have now