Hey, I just picked up my first quad, and i'm having a couple issues, possibly all related. I've got a 2000 Honda 300ex, with an FMS pipe/muffler, K&N filter, and an unspecified jet kit. Engine has a new plug in it, and he claims he adjusted the valves just before I bought it.

1. The bike will not idle when cold, even with full choke. Once its been driven for a couple minutes and is warm, it will idle fine. I was told this is a characteristic of the jet kit.

2. It runs great at full throttle and pulls up to limiter fine. When cruising at a constant throttle position, it sounds like its breaking up alot of the time.

3. When I shake it around alot, going over rough trails, or bumps it will die, usually when landing, sending my head into the handlebars. It will do nothing pushing the throttle in further, i'll have to release it, when the terrain smoothes out and then it will come back to life.

Ideas?

 

TTT

 

Monte, the 300ex is really cold blooded. One thing that helps with the cold blooded nature is to get an air tube from a 350X. This is the tube that goes from the air box to the carb.

The other problem sounds like a float problem. After all these years I wouldn't be surprised if that the little rubber tip is worn that closes the orfice on your float system.

CRR

 

Sounds like you may have a dirty carb, I would first start with a disassembly and careful cleaning, making sure all the ports and jets are blasted out with carb cleaner,then blown out with an air gun. Then you need to find where you are on jetting, do a plug test to see if you are lean anywhere, and go from there. With the mods you have, you should start at 1 size up on the pilot jet, and 2 up on the main from stock, this will help your cold starting and idle. When you say it breaks up under constant throttle, that could be a lean condition in your midrange on the carb, when it is missing, hit the kill switch and coast to a stop and pull the plug, if it is dark, you are a little rich, if it is light tan or white, you are lean and need to jet up or raise the needle to richen up the carb at that speed. Dying when bounced around sounds like fuel slosh, your float level could be too low, starving your engine for fuel because the rough movements cause the low fuel level to allow air to be sucked in the main jet and severely lean out the motor.

 

Sounds good.

Any literature online about rebuilding the carb? I can rebuild a Holley 4barrel in my sleep, but I know nothing about these carbs.

 

This is a float problem or (NEEDLE VALVE) for the stalling and cold blooded starts.

The cold blooded starting can also be

Loose exhaust causes backpressure evaporates gas too quickly.
Loose air box or dirty filter cuases backpressure, gas evaporation.
Incorrect plug for the quad

 

Exhaust is good and tight....I took care of that when I bought the quad.
Air filter could stand a cleaning, but its not horribly blocked.
I'll have to check the plug.

Thanks.