I just put on the Edelbrock (Thumb Kit #3026) on a Yamaha Raptor ATV. I modified the kit slightly by putting a K&N air filter directly on to the carb and tossed the entire stock air box setup. First off, let me say that the carb is awesome. I have had many performance carbs on atv's over the years and this one is great. It is really fast and easy to tune.

Performance is great. My bike has a 12 tooth front sprocket, the carb, and airfilter. No exhaust yet. With the Edelbrock, I picked up 3 lengths on a stock honda 450. We used to run dead even. My other buddy has a vforce. Stock for stock, we used to run dead even. He added the muzzy exhaust and an airbox kit, I added the carb, and now he has me by 1 lenght at most. On the beach, it pulls wheelies in 4th gear now. I can't wait to add the LTE duals to really bring it alive.

Anyway, on to my tuning question. When I run it wide open for > 15 sec (or so), it begins to sputter. Like it is running out of fuel. I back off the throttle, it recovers and runs fine. If I roll off the throttle for a few seconds then go back to WOT, it will run fine then stumble again. It is not the rev limiter. The engine behaves differently when I hit it.

I have experienced this in the past with a partially plugged fuel filter where it would not fill the carb fast enough at WOT and eventually it would run out of fuel. That recovery was much slower. That is not my case here, I have excellent flow to the carb.

Could this be a poor adjustment of the float height? Any other thoughts on what it could be?

Thanks,
Courtney

 

Well I don't want to be the one to ruin your day and if you don't want to believe, thats cool, I wouldn't want someone to give me bad news either. However, I know that you like your new carb, but so far, I have heard nothing but bad news about those new ATV Edelbrock carbs. They change jetting by themselves while you're riding. They change temps and freak out. You said that when you ride for about 15 minutes, it starts sputtering. Thats because the jetting is freaking out and starts running really rich. Once it cools back off, or gets more air, it adjusts again and goes back to performing perfectly. Everyone I know that has an Edelbrock has nothing but trouble trying to jet those things. Sorry to give you the bad news.

 

The problem I was descibing earlier was not measured on minutes but in seconds. Run wide open down the beach at full throttle for 15 seconds and it starts to sputter. Back off the throttle for 5 seconds and the wide open again. It will run fine, then sputter again. Way too fast for temperature variation or any of the problems you mentioned.

I spoke with Edelbrock and they also thought that it was a float level setting.

I appreciate the brutal honesty but after my first weekend, I would have to disagree completely. The carb worked great all weekend. The jetting seemed fairly stable. Over the course of the weekend there was a lot of humidity and temperature variation and it still seemed stable. If I had a super built race motor that was really sensitive to AF, I might be singing a different tune. For now, I gotta give the edelbrock a big thumbs up.

 

Ok, thats cool. What you are saying about the float adjustment is kind of what I am trying to say though. I have heard that it changes no matter how hard you try at dialing it in. Now, if you ride in the same place all of the time, then you might be able to get the float set right for where you ride. But the float is definetly the problem.

 

I also heard nothing but bad news about the carb but decided to try it anyways. I noticed a nice difference in power and it runs great. it does run a tiny bit fat but i can live with that and not spend a week trying to perfectly jet it since i mostly ride at mx tracks. it ran perfect in little sahara and i was able to beat a few piped jetted 450s. not claiming that it is a gazillion times faster but the riders on the 450s might not have been quite as good at drag racing and the carb did make a difference.
I am very pleased with it and i must admit i was quite worried due to all the negartivity about them
But I did get the twist throttle version

also how did you like the differnce when you went to a 12 tooth up front

 

The float level should not change dramatically with temperature. Jetting maybe, but not fuel level in the float boal. I think it is just set wrong. A quick check tonight will answer that.

As for the 12 tooth front sprocket, that was the first mod for the raptor. In stock form, 2nd gear was just too fast & 1st was too slow. it didn't have a good gear for slower playing. Dropping 1 tooth up front made the slow speed stuff way more enjoyable.

It also did not pull 5th gear wide open on the dunes very well. I have 20x10x10 8-paddle extremes and it never wound out when running wide open. After the smaller sproket, I could still maintain the top speed because it let the engine rev out fully.

 

well i ordered the sprocket last night and i also ordered the 13 tooth just in case
also got a magura hydraulic clutch