81 RM125x No Power at Full Throttle

[PCMAX]

My '81 RM started playing up last weekend it runs great into the start of the power band but then as you hit peak power its like it is running out of fuel or spark particularly if I jam it full open.

I have done the following but the problem persists:
*Replaced the spark plug
*Replaced the plug cap
*Replaced the stator coil assembly
*Cleaned the carby & jets & needle valve & set the float level
*Tried a bigger (270) and smaller (250)main jet
*Pulled the barrel off and checked the piston, rings & reeds

Has anyone had any similar problems or does anyone have any suggestions???

[holeshot buddy]

is it flat power nothing there
or loading up

check fuel flow from tank i drill out the suzuki one
to a bigger size

[RMJJ]

Is it the instant you jam the throttle wide open or after a few seconds

[PCMAX]

Holeshot, don't think its loading up it just dies as im hitting peak power. Its perfect down low and into the first half of the power band.

RMJJ, its the instant I hit peak power (throttle full open) it just dies.

I have also posted this on the Tech Talk thread and after some suggestions there will change the ignition coil and check the exhaust for blockage/restrictions today.

[Lozza]

Sounds like fueling to me.

[Big John]

I had a this same problem with a YZ250 turned, out to be the muffler, it had broken the perforated steel insert and was obstructing full flow of exhaust gas. 

[bazza]

 Its a suzuki
No seriously,have you owned the bike for a while and this has just happened? Do they have a fuel filter built in to the tap?

[PCMAX]

Bazza, I get good flow from the fuel tap & I have an inline fuel fiter but this has been changed.

I checked the ignition coil today and found that I have 50,000 ohms resistance from the coil (black/white wire) to the plug cap. The book says I should have 10,000--11,000 ohms so I guess ths could be the problem. Unfortunately I don't have a similar coil to troubleshoot with, all the spare ones i have only have one wire and a plug lead.
Does anyone know what the other wire (white/blue) that runs from the ign coil does??

[Lozza]

You can test how much air gap the spark can jump will determine the health of the ignition. A pit bike coil will work fine.

[bazza]

Any progress finding problem?