View Full Version : 90cc advice needed

07-23-2007, 08:42 AM
I am needing some advise, I have an 04 with some mods, hetrick pipe, 24mm carb, uni filter, it is a 52mm bore I just put a fresh piston and rings in it and now it will idle fine, but if you give it past 1/4 throttle it cuts out and backfires and won't hardly run, but it goes right back and idles fine. If you go straight to full throttle it bogs and dies? I've tried plug, reeds, and cleaned the stator. Anyone got any suggestions?

Nick's #1 Fan
07-23-2007, 11:56 AM
First thing I would try is checking the grounds. If they are in place add an extra one just to be sure.

We had a similar problem and added a ground wire and it seemed to solve the problem.

The not running part sounds like a fuel (Carb) problem but the back fire make me think it's electrical.

:confused: :confused: :confused:

07-23-2007, 12:37 PM
Are you are using the stock carb and airbox?

07-23-2007, 12:58 PM
No I am not using the stock carb, It's a 24mm with uni filter. It was running good befor the top end rebuild. I looked at the wireing some, I will try the add a ground and see. where exactly did you add ground?

Nick's #1 Fan
07-23-2007, 03:03 PM
I went right from the coil to one of the bolts on the clutch cover. I can't remember which side of the coil I came off of so look and see where the ground is coming off now and add another one to the same side.

Are you still running the stock wiring harness on the bike?

07-23-2007, 03:03 PM
Is the piston in correctly ?

Nick's #1 Fan
07-23-2007, 03:08 PM
Would it still idle if the piston was in upside down?

I heard that they don't run very long when they are installed upside down but don't know about idling.

07-23-2007, 05:00 PM
The wiring harness has been stripped down to the bare minimum. piston is right..lol (I checked it) I think I will get a compression tester and just see what she has, Does anyone have a number on what stock compression psi is?

07-23-2007, 05:06 PM
with a stock head around 120

07-23-2007, 11:13 PM
jetting? You did just do a fresh topend.

07-24-2007, 12:50 PM
im gona say ground.