has anyone here done this mod?

 

Ya, I did. Never got the jetting right and it was a pain in the rear to get it to fit on the stock boot and exhaust tube. I eventually had to use a different style of clamp to get it to fit and stay put. If it sit more than 2 weeks it was a pain to start. I'm sure that had to do with the jetting.
With that said I noticed a small difference on the top end power and a loss on bottom but, then again I never got the jetting right.

 

i have been thinking about trying it. i am going to cam my 400 this wknd and bought a carb on ebay for 38 bucks. found a guy in minnesota that makes adapters to fit the carb in the boots. read alot about it on exriders.com but was wondering if anyone here has done it.

 

Ya, if you could get the jetting right it'd probably be nice. The 450R's is a slide carb and the EX is the butterfly style. Slide carbs are suppose to be more responsive. I sold mine before I got it tuned in.

38 bucks is a good deal for the carb. I'm sure the idle jet should be a notch or 2 down sized because mine would absolutely refuse to start in the cold or if it sit long. Not sure what the main should be. Have you read any on that?

 

yeah i have. on ex riders there is a lot of info on this mod. most of them have been pretty high on there mains. with a stock motor my main is 178 now, and that was still to lean with the air box lid off. there is another guy here in mn that has this mod so i will be talking to him to see how his jetting went.

 

Koopa,
when you tried this mod did you just force the 450 carb into the 400ex stock intake boot? they guy that has the adapters wants more then what i paid for the carb and you still have to grind down the ridge on the carb. im not into doing that.

 

Ya, the intake side was the easy part. I just worked with it until it went in. The exhaust side on the other hand was tricky, it's not a rubber boot that will stretch like the intake side. Use some spray lubricant to help it slide. Like I said before I had to use different clamps after i got it on because it did not seat in the same spot as the EX carb did and the stock clamp wanted to pinch it off. On top of that the 450 carb seems a tad bit more narrow so, you'll have to be patient to make this mod work. You'll have to work it a bit to get it all to go together properly. I do not remember if I filed down the lip on it or not. It may help.

 

well i got my cam today so i will get that in first thing this wknd while i have my stock carb on yet. then i will try the 450 carb. i really dont want to have to file or make to many mods to the boots, that way if i dont like it i can always throw the stock carb back on and resell the 450r carb. i hope it works out tho

 

i also read that ppl have put the 450r carb on there yfz's and that made a huge difference too. but dont the yfz's come with a top of the line fcr carb?

 

Hmm. Haven't heard of that. It is a slide style Keihin carb and I don't think the 450r carb is much larger if at all.

I'm not touching the carb on my yfz. I feel I have the jetting nailed and don't want to risk messing it up. I've been thinking about doing the cam mod but thats as far as I'm going on this beast. It's got plenty of go power for me.