Carb main jet?

[ccdhowell]

My daughter runs in a 90cc stock class in a local XC series. I can't do much to the quad, but I did get permission to change the stock air canister to an UNI slip-on filter due to terrible used oil analysis on her engine. That stock filter was letting it way too much dirt into the engine. Anyway, I took the carb off wanting to increase the main jet a step or two and couldn't believe how tiny the main jet was. Anybody know where to get those tiny little main jets? How about pilot jets too? Thanks

[guenther]

Most motorcycle and ATV shops that carry little ATVs and motorcycles will have them. Even scooter dealers (they are the same jets as the Honda Rukus). I just changed the pilot jet yesterday on ours to a 38 (from stock 32) and now it starts like a champ with no backfiring on deceleration. I think the main that I put in was an 88 but not 100% sure since it was a couple months ago.

[mbellaver]

What carburators do your typhoon 90's have? Mine came with a Kehin copy. The dealer stated that all the other 90's he has seen come with a genuine Mikuni. I ended up putting a pilot from a trx 90 (kehin size 40) in and it idles much better. It came with a 32 and I could hardly get it to run. I'd also like to bump up the main as well. It came with a 78 and I think it needs more. Anyone got any suggestions? The largest main you can buy for a trx 90 is an 82. Thoughts?

[guenther]

Mine is a Keihin copy as well. Other than the having to get the jetting right it's working just fine. I think the main I have must be an 85. I know it is bigger than an 82 because the stock was 78 and I made sure I bumped it up almost 10%.

[mbellaver]

Do you know where I can order an 84 0r 86 or cross reference with another model that uses a similar carb?

Thanks

[guenther]

I don't, sorry. My local cycle shop had it in their stash of jets. Send a PM to Hondo121, he might be able to help you. Or try www.jetsrus.com and eBay.

[ccdhowell]

JetsRUs...kinda funny. I checked them out, they don't list pilot jets.

My carb is not a brand I recognize so it's a copy of something, don't know what. So the jets are the same a TRX90? Main and pilot? If so I should be able to take them to a Honda dealer and get new jets, right? Thanks

[guenther]

Should be able to.

[mbellaver]

If it is a keihin copy it should be the same. I just went to the dealer and had them order a size 40 pilot from like a 2000 model trx 90. This is what my carb looks like.....

[ccdhowell]

Yep, that's my carb. Thanks for the picture. Now I can get the right jets.

[mbellaver]

No problem. I struggled with this a little too since the dealer thought they all came with Mikuni carbs. Not sure why they would put such a small size pilot jet in them from the factory. The main is much closer in size to a trx 90, but the pilot is way small! I'm still going to bump up my main, but not sure what to go to yet.... Jets-R-Us has the KEIHIN ROUND MAIN JETS (SMALL)
99101-116. I think those are the ones we need for the main if you are going to use one larger than you can get for a trx 90 from the dealership. Anyway, put the trx 90 size 40 pilot in, adust the air screw and it will at least idle!

[mbellaver]

Also, does your air screw have a slot in it so you can turn it with a screwdriver? Mine didn't have one! I had to take a hacksaw blade and very gently cut a groove in mine so I could adjust it.

[guenther]

That's mine as well. Instead of taking a hack saw, just take your Dremel and cut a little slot with it on the bike. A lot easier, unless you don't have a Dremel that is.

[mbellaver]

yeah, that would have been much easier!

[mbellaver]

Ok, I just put the 85 main jet in that I got from Jets-R-Us. For some reason it now starts without the choke. I thought that only the pilot jet effects the idle? Anway, it stars easier now, and idles fine. Seems to have more power, but it still hesitates a little if you go from 0 to full throttle very quickly. Do it too quickly and it sometimes dies. It is better now though. Thoughts anyone? Should I go up on the main again?

[guenther]

Ours will do that until it's warmed up good. Try adjusting the mixture screw after it's warmed up.

[ccdhowell]

Alright guys, I have the jets I needed for my carb. It is the same Keihin copy that is pictured earlier in this thread. I did a little research and ran down the Keihin jet numbers:

Main: #99101-116
Pilot: #N424-74C


I started with an 85 main and 35 pilot. Cold and raining right now, I'll test it when I can warm it up and run it some. I started it and it sounded fine. Made a few adjustments on the air screw and the throttle response is not what I would like, but it may be the cold temps and not warming it up fully.

Hope this helps.

[mbellaver]

Thanks for the update. I put the 85 main in ours and 40 pilot. It came with a 38 and would barely idle no matter what I did with the mixture screw. It now idles, but bogs on the takeoff backfires on deceleration. The mixture screw is only a 1/4 turn out. Any further out makes no difference. I think I need to bump up the pilot a little more, but it is only 18-20 degrees out!

Mark

[mbellaver]

UPDATE, mine is now running nearly perfect with a 85 main and a 42 pilot...