Jet size help needed!!! **Updated**

[250r'en +TCB]

I recently put a 38mm mikuni TMX carb on my R and I love the results! The powerbands are a lot more brutal! Mike (DeePa) will back me up on that!!!

But getting rolling is the draw back. It bogs and you have to usually rev the throttle up to keep it from bogging, then jumping then stalling...... It wasn't doing this until I put the clamp on airfilter on. So obviously between getting so much air and fuel now it's a little too much..... So correct me if I'm wrong but I have to go down in jet sizes right??
I believe there is a 300 main and 50 pilot on the carb now. So what is the next size down?

As previously stated jetting is the one area that I truely lack much knowlage in, so any help and/or advice is greatly apprechiated!!!

[Dammit!]

If it was running fine before the clamp-on, odds are it's running lean now. You want to go to a bigger jet so there's more fuel to go along with the increased air flow. In theory anyway.

Plug chops and experimentation is the only way to get it nailed. First thing you gotta do is make sure your main is correct because there's a trickle down effect from the main. Only way to get the main right is wide open plug chops. After that get your needle set right (this is probably what's causing your problem more than anything). After the needle you can adjust pilot and air screw.

[jason 32]

so you are saying that it was sucking air from the clamp being too loose?
verry possible revit up check the plug
then check plug at idle and mid
if it is boggy like your sayin from not enough air
then jet down on the pilot
it depends on the type of jets that are in it,and they go in different sizes
my book says they are in incraments of 2.5
try a 45-

[250r'en +TCB]

No the filter is on fine. The machine wasn't doing this until I put the UNI filter on.....

what size jets should I get? And are all jets the same for every carb?? damn I'm clueless on this stuff!!!

[wanta86r]

you need to buy mikuni jets for you mikuni carb. as far as size goes get a couple size bigger main jets and do what dammit has suggested. i am not familiar with the mikuni jet sizes, so someone else will have to chime in. the kehien carbs generally go in incriments of 2. However, to me it sounds like its more the needle or air screw that needs adjustment.

[Dammit!]

I'm not familiar with Mikuni carbs either. Just go to the dealer and ask them for a main jet that's a couple sizes larger than a 300. You should pick up a few actually but get what you can afford. Some places charge five bucks a piece for the stupid things.

You can do some wide open plug chops before you even go buy any jets. You might not need a main but my guess is you're a little lean on top if the filter had that much of an effect.

If the main is ok, adjust your needle. To increase the fuel flow to match the increase in air allowed by the new filter, LOWER your needle CLIP. That raises the needle out of the main jet and lets more fuel out.

Do all that and get back to us.

[250r'en +TCB]

Well I got 310's for it, had to order them. I could only get them in sets of 4 for $10 though!!!!!

thanks for the needle adjustment tip, it helped a lot!!! Just still wasn't there 100%....

Hopefully those 310's are good and I don't have to get 320's...... I'll be going up to MT. Washington this friday. The summit is roughly 6,200 ft above sea level. I live where it's about 500ft..... Will my R run at the top with the 310 or will I have to re-jet up there back to the 300??? I am not going to be racing up there it just needs to start and run!!! I'll never leave second gear the whole trip I'm sure.

Thanks for all the help guys!!!

[Dammit!]

Impossible to say how it's gonna run up there. Just take the jets with you on the trip. You can change jets without pulling the carb. Do you have a jet tool? Your dealer should have one for a couple bucks.

Just make sure you do plug chops. Don't trust it by how it runs alone. It's possible to be dangerously lean and have it running fine.

[250r'en +TCB]

Well I put the 310 in and there's a differnce but not enough of one...... I knew I should have gone with the 320's or maybe even the 330's.... Oh well it should run well on the rockpile (Mt. Washington) this weekend......