Help need it / erratically backfire and loss of power under WOT

Forum rules
Please can you post items for sale or wanted in the correct For Sale section. Items / bikes for sale here will be removed without warning. Reasons for this are in the FAQ. Thanks
Post Reply
Settled in member
Posts: 18
Joined: Mon Oct 01, 2018 5:03 pm
Bike owned: CBR 400RR / VFR 400R
Help need it / erratically backfire and loss of power under WOT

Post by goose400 » Sun May 24, 2020 6:30 am

I'm in a need of ideas and or advice to help solve this problem.
Here is the situation:
My NC30 track only bike , suddenly started to develop a back fire and loss of power when passing the 5000 RPM.
It will continue to erratically backfire and never reach more than 10.000 RPM. (either with the bike on the stand or riding)

I have read every topic regarding fuel, ignition and electrical but I still can not solve the problem.

So far I did:
-Rebuild and synchronized the carburetors. (with new boots)
-Tested with two different (good) batteries. I have good voltage reading at 5000 RPM
-Tested the coils, (primary and secondary) and Pulse generator (They are not perfect, but in range) I ordered a new set of coils, but not got them yet.
-I have good ground.
-I have spark on all the plugs. (they are new)
-I have tested with two CDI's (ignitech)
-I'm running total loss system , with no alternator (stator and rotor) and the reg/rec

I have not yet done a Valve clearance. Could this be the problem?

During all these tests, something particular happened. If I used the Ignitech CDI, (stock map) the bike will turn on and run perfectly until I rev it pass 5000 RPM. If I use the original CDI (Last time I used was working perfect), the bike will not start at all. The ignition will just go and go, but not start.
I tried another Ignitech CDI and the same problem, so I'm ruling out that could be that, but It puzzle me that the original CDI will not get the bike running.

Any help or advice will be much appreciated.

Thank you

Post Reply