Flat top piston, how much of a difference?

M

mgregg85

Member
#1
#1
Long story short, my friend and I both have the same type of minibike, baja warriors with gx200 clones. We both have billet rods, AGK single stage headers, 6* spark advance and 18# springs. I've got a .265 lift modified cam in mine and my friend has a flat top piston on his. I have the TAV30 and my friend is still running an all stock jackshaft.

If we do a drag race we will stay even up until about 20 mph and then he will rapidly pull away from me, we haven't clocked his top speed yet but i'm thinking it is around 45mph or so, he is rapidly pulling away from me and I know my speed is 37mph.

So far as I can tell the only difference in the engines would be my .265 cam and his flat top piston. I know he doesn't have anymore mods because I modded the engine for him.

So my question is, is the flat top piston responsible for this speed gap? Is that increase in compression really that powerful? I figured the torque converter would give me the edge but it seems to be holding me back at this point.

Any ideas? I've got a 22mm mikuni on the way and I'm probably gonna get a 14cc head and the flat top or just get my stock 22cc head milled and get a flat top.
 
Strigoi

Strigoi

#3
#3
you need to run jack shaft vs. jack shaft. the TC makes a difference.

a flat top won't make that much of a difference (or even close to it). the cam also won't help you much with the stock carb since that one is designed for larger than stock carbs. you should have done the carb first.
 
M

mgregg85

Member
#5
#5
Strigoi said:
you need to run jack shaft vs. jack shaft. the TC makes a difference.

a flat top won't make that much of a difference (or even close to it). the cam also won't help you much with the stock carb since that one is designed for larger than stock carbs. you should have done the carb first.
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Yeah I know, I've got a VM22 on the way right now, do you think thats gonna really make that much difference? AGK's website said it could provide up to a 1.5 hp gain.


Any suggestions on where to go from here to get the most power gains? I'm thinking compression with a 14cc head but I could just get my 22cc head milled. Anyone know how far you can safely mill it without getting interference?

Other options would be 1.3 ratio rockers or a billet flywheel maybe?
 
mike75925

mike75925

New Member
#9
#9
by having the lowest setting you are short shifting. if you were using a manual tranny, you would be shifting @ 2 grand out of say 11grand. more tension equals more time in gear. so by adding tension you would be moving the shift point from 2k to 3-5k. relatively speaking of course. giving you that much more speed per 'gear'.
 
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