I recently installed a VDI CDI and a dynojet kit on my Brute 750. I am now noticing a sound coming from the engine that I did not have before. I dont really want to call it a knock because its not that profound, but there is definitely a different sound coming from the engine. My brother has the same 750 but his is all stock, and his does not have the sound when sitting side by side. I guess I really dont know what to expect. It runs like a raped ape and I am loving that, but I was just wondering if anyone has experienced the same. Please let me know. Thanks fellas,
hollow

 

A new CDI? I wonder if it's pre-detonating.

 

Sounds like detonation to me as well. Running too lean will make a motor run like a raped ape, but a pinging sound means you're too lean. adjust your main jets a hair richer until the sound is gone.

 

I have the VDI and the dynojet and have not noticed any difference in the engine noise. If you think you might be experiencing a problem with the VDI install the factory CDI and see if the noise is gone. If you are running the map for 91 fuel make sure yuou have 91 fuel in your beast. I have one map for 87 and one for 91. Flip your switch and see if your second map is doing the same thing.

I am running my air fuel screw at 1.25 turns out and could probably go leaner, but everything is working so good I don't want to play with it.