installed 83cc kit- no top end power?

[theo547]

ok i installed the 83cc kit and a new carb with it. im running 45 pilot jet and 90 main jet...
It has trouble starting cold. rarely will it start with the electric starter, but almost always 1 or 2 kicks. sometimes it will die with out gas other times it will stay running... once it starts running it has no problems staying that way.
valves are set to .004" on intake and exhaust. when at idle it seems and sounds fine. on the stand when i rev on it it has a slight tapping sound that i think is the valves - only when i wot.
i have taken it for a few runs and it doesnt want to go much faster 35mph. it has awesome pickup but it tapers off around 30 and it struggles to get to 35 and barley gets past that if atall. it has the cdi "green wire" rev limiter pulled. when i plug that wire back in it only goes 30. what do you guys think?

[reveeen]

ok i installed the 83cc kit and a new carb with it.

Head too?

valves are set to .004" on intake and exhaust. when at idle it seems and sounds fine. on the stand when i rev on it it has a slight tapping sound that i think is the valves

See above.

i have taken it for a few runs and it doesn't want to go much faster 35mph. it has awesome pickup but it tapers off around 30

1) compression test, perform a compression test.
2) pull the valve cover and verify cam timing (relative to the crankshaft) and chain tension. Verify TDC indicated (on crank) is TDC (piece of wire, or screwdriver in spark plug hole)
3) remove head and verify piston is not hitting head. Check for bent valve(s).

Start at top of list and work your way down it.

[theo547]

Ok got some progress updates....
The head is Scrappy's Big bore head - not the performance home
ran a compression test and i ended up with about 170psi - so thats good.
check my TDC and that lined up pretty good.. then i noticed something -- I had put my Cam in upside down

Swapped the Cam around and its running alot better now... well there is no tapping sound atleast.. still only topping out at 40mph but before i dig into that more im going to wait to get my exhaust that i have coming... sometime next week... i put some wholes in the stock exhaust, but i may have gone a bit overboard...

Just by chance if its not the exhaust what do you think could be keeping me out of the 45-50 range for speed... its still getting up to 35 pretty easy but it needs alot of road to get to 40.

[90GTVert]

Jetting could be off a tad. Maybe a CVT tuning issue.

[theo547]

well like i said i have a 45 pilot and 90 main in there... i have a pretty good idea, but tuning these GY6 engines doenst seem as obvious as my 2T... right now i have the air\fuel mixture turned out 1 full turn.

Should i still be listening for the RPM's to peak and then turn it in a little?

[90GTVert]

Yeah, it's the same basic procedure for setting the mixture screw on a 2T or 4T. Have a look at your spark plug. If it's light, try the next size up on main jet. If it's dark, go down a size. See if you get an improvement with the new jet.

[theo547]

Ok i upgraded the jet to a 95?! i drilled out a old jet to a .95mm drill bit
It starts fine, but when i give it gas at wot it will choke and backfire?! seems like it needs more air or like the exhaust is stopping flow?!im going to try putting a lower 88 jet or so in this afternoon see what that does for me.

[theo547]

I was replacing the brakes on my aerogtx and decided to grab the cdi out of that scooter and put it in the Dazon... the Dazon is having major back fire problems and the AeroGtx barley runs atall.... this is what im thinking:
The CDI that was in the Dazon is garbage and the Exhaust for the Dazon is plugged.. i have a free flow on the way so I ordered a new CDI today...
It would be pretty awesome if a bad CDI was causing the remainder of my problems

[theo547]

Updates:
New exhaust and CDI installed - Started with no problems... finally! but it was bogging really bad after throttle - found out the new exhaust i had installed's gasket was leaking.. replaced that and bogging went away.

After all of this i took it for a run... still ran like crap - great take off no top end 35mph max - went to scootdawg forums and asked around.

My 5g weights with this setup were way to low - i needed 8g+. the reason has less to do with my clutch and variator setup as i does with my cam. the stock cams on these scoots do not sometimes work in the normal power band of your scooter so you need to up the weights to counter. ?!?! or something like that. anyways i havnt taken it for a long ride - just up and down the street and it seems like its got alot more top end.

So in review - if you do a kit on these and you dont have top end try heavier weights. and not a little - Much heavier!

[90GTVert]

Glad you got it going better and thanks for the info.

[speedy1125]

weird. i use 5g to 6g in mine and it runs 55 flat out. i guess not all 139qmb engines are created equal.

[craisin]

you mention [WOT]

[Deleted]

Dec 2, 2011 21:48:05 GMT -5 craisin said:

you mention [WOT]

WOT=Wide Open Throttle

[craisin]

Wide open throttle.
The vacunm is down and the vacunm operated fuel tap is likely not to be passing enough fuel.
On my scoot I have eliminated the vacunm fuel tap and I can get 70kph on the flat 50cc.
I am over 6 foot and 130 kgs

[craisin]

I have to correct myself
The 70kmh on the flat was with the electric choke had come unscrewed from the carb and was laying on top of the crankcase.
I had to put a fatter screw in it cause the old one stripped th thread out
So now its slower