I don't have any internal mods to justify installing the 40mm carb but for all the external mods installed (larger intake/exhaust), I was curious if changing the stock 34mm carb to a mikuni 36mm carb (which looks the same) would be of any benefit in added performance?

I think a slightly larger carb might be of benefit, but as far as I know the only Mikuni CV carbs are the 34 and 40. They do make a 36mm pumper carb, but it's constructed similarly to the HS40 I put on mine some time back and it didn't work out. Do you have a model number?

The only 36mm cv carb I could find was a kehlin which I don't think will match up, an'05 honda rubicon 500 uses one.

Not for nothing, I have an 02 700 with a tmx 40mm that I got from Aaen In the stage 2 kit that (seems) to me to have given the single most noticeable difference with my quad. But....... I am have problems with the slide hanging up at high idle and Aaen says that I need to keep sanding the slide untill it seats itself. My point in all this is that there has to be some larger carb out there that would make a bigger diff. than stock because with these breathing mods on the carbed models were increasing air flow everywhere but the carb.

Keihin makes a 37mm FCR carb that I keep looking to see if I can pick up cheap on ebay. I haven't found one yet.

Desert, are you more impressed with the throttle response or is there an improvement in top end (overall power)? The throttle response on my 700 with the stock carb is pretty good. 10x better than the one on my old 500 (same carb). I didn't notice significant improvements in power with the two 40mm carbs I tried.

Cajun I just lost my reply to you, have to start over

Cajun, I have not reinstalled the stock carb since I dialed in the other mods so I dont have a good comparrision but Im happy with the throtle respose and the 0-50 ( to scared to go any faster) but theres throtle left to go at 50. I notice less gas milege , of course. I think the carb would be perfect for me if I could get the slide to seat and come back down to idle, thats the thing I dont get about it

quote:

Originally posted by desertsp700:
Cajun I just lost my reply to you, have to start over

I hate when that happens, especially a long response.

That sounds dangerous. Can you tell what's hanging up? I had a TM-36 on my 500, which is very similar in design. I didn't have any slide problems with it. I've heard the TMX, as delivered, uses too much gas. It may help mask the problem with bogging without an accelerator pump.

It is dangerous. When the motor is off the thumb throtle moves the slide as smooth as silk but if you start the motor the vacuum of the motor sucks the slide in and it hangs up in the carb body. Aaen says that this is something that happens on some and that the remedy is to sand the slide where there are wear marks untill it doesnt do it anymore but I havent got to that place yet. there is a slight bog if you were to hit the throtle hard in nuetral but if you start off from a stop on pavment either the rear wheels will spin or the front comes off the ground. I think if I could get the bug work out I would be happy even if it was alittle more thirsty then stock. Cajun what 2 40mm have you tried?

I have tried the Mikuni BST 40mm cv carb that comes stock on the 500 HO and a Mikuni HS40 (TM-40) which is the predecessor of the HSR series of carbs for Harley Davidson motorcycles. The HS40 has an accelrator pump and a steel slide. The throttle spring, even on it's lowest setting, would be extremely uncomfortable to drive for an extended period. This would probably be fine for a twist grip throttle, assuming you could find a semi-rigid way to mount it. That carb really is overkill for a 683cc engine. Mikuni makes a 36mm version of the same carb, but I've never laid eyes on one.

The 40mm from the 500 has potential. It's similar to the stock carb and can be mounted to a modifed bracket and the choke and throttle cable present no real problems. I purchased a 500 throttle cable because it's a much better fit. The main problem I had with the carb was that the slide was lifting way too soon causing a rich mixture at cruise. Since I was running out of time before hunting season, I put the stock carb back on and tuned it like I needed. I obviously need a stronger slide spring and may find some time this summer to try tuning it again. I'd probably purchase several different slide springs to experiment with before I do that.

thats interesting, It sounds like the intake vacuum is causing your slide to open and my slide not to close possibly.... like everyone I wish I had the money and time to try a variation to get mpg and power combo I could live with but Im going hunting again & am going to have to leave it as it is for now. Ps at 7000' I was getting around 90m to a tank , not to bad w/stock carb , getting 50m at sea level w/40mm

Cajun, when you get around to installing the 40mm carb, keep us informed on the progress.

I will, if I do experiment with it. If I do it's going to be months away from now.