400ex cdi

[kaptainkx]

Just checking to see if anyone out there runs an aftermarket cdi. I just bought one for my 400ex and was wondering what the limitations are as far as compression. It ran fine before but now with the new cdi the engine makes some rattleing noises. I have 11:1 compression and am just hoping my fuel octane is too low, or maybe its just not a good idea to run advance on higher compression, I dont know. Any input would help.

Its an 03 bored .5 mm with wiseco 11:1 piston, carb jetted with dynojet kit with 170 main, ehs air box lid, and T4 pipe. And know an AMR stage 2 cdi which I'm not sure of as being a wise investment. Thanks guys.

[416exfreak]

Advanced timing would detonate the fuel sooner. You may need tog o up in octane to helop the fuel detonate slower.

Try that. If it doesnt help, your problem is obviously elsewhere.:(

[kaptainkx]

thanks, that was my first and most obvious thought, I know it cant be anything internal or anything aside from the cdi, because i can run it with the new one and have odd noises, but put the stocker back on and its fine. Do you or anyone know if there is a limitation on compression for timing advancements. thanks again

[416exfreak]

Yes, if you advance the timing to much and have to much compression, you will get valve-train noises.

Its not good for your engine, thats for sure. Id put the stock CDI back in it.I had an aftermarket CDI, it didnt produce enough of a gain for me to risk tearing up my engine.