Need advice on Carb selection

[kkdad]

I need advice on what size carb I should put on my son's xtreme 90cc two stroke. He does not race. He just trail rides, but likes to be heavy on the gas when he can.

Engine set up is : air cooled 54mm ported cylinder, standard stroke, hetrick pipe I think.

I bought the pipe used. The seller on ebay claimed it was a hetrick. My son really wanted a pipe on his quad. So I installed the pipe and it of course could barely move. So I discovered this forum and began reading. Luckily I bought the pipe with a complete predator engine. The clutch was already set up for the pipe. So instead of buying all new rollers and springs I just pulled the original engine out. Installed the big bore kit and removed the oil pump on the predator engine. Then installed it on the xtreme. The xtreme has an unlimited cdi I think?

I had to play with the jetting alot, but the thing really rips now. My 7 year old son loves it. My wife hates it. And my 2 year old fell asleep last night telling me that bubbi went rrrooom rrrooom. So I think he loves it too.

Last thing to change is the Carb and air filter.

What size of carb 24 or 28mm? What kind pe or pwk? Also after the carb change will I have to optimize the clutching again?

[Logan #34's Dad]

1st, welcome to the site. 2nd, be very careful about who you take advice from on here. We all have ideas and think we know everything. :devil:
With that being said, I DO know everything......:blah:
Na Seriously, you may not need to get a bigger carb. What size is on it? If she runs good then leave it alone. Until your rider is asking for/or needs more power - don't waist your money. Trust me, we all ran out and bought the newest-latest-greatest thing or part because we just thought we had to have it. As he grows and his skill level improves your wallet will get opened up enough so take your time.
If you insist your rider is ready for more power then stick to listening to the main builders/businesses that know what they are doing. Hetrick, MaximumRPM, G-Force, Hot Quads..... Once you find ONE of them you like - stick with them. These guys stay up to date one the market and will guide you the right way.
Since your just trail riding and not racing YET, You don't need to go crazy. For trail riding i'd think you'd want a snorkle type air filter to keep the carb from sucking in water and mud. I've got one you can have if you pay shipping.
There's my 8years of cvt racing........worth 2cents.
Good Luck

[kkdad]

Thanks for the welcome.

The carb is currently the 16mm stock carb with electric choke and the factory air box. It took me quite awhile to get it to run decent with the factory snorkle air box it. I am using a 32.5 pilot to with a 85 main jet. The main is a little lean still. The pilot is rich. They are equalizing each other for now, but I am concerned with the the main being lean that it will cause damage if I don't get it changed. I also need to put the single pull throttle cable on it. He only got to ride it once and now I told him I have to change it again.

Is your snorkle air filter for the 16mm carb or for something bigger? I want to protect it from water, but still give it some air flow.

Finally if he needs more speed then this, and still isn't big enough to handle a bigger quad, I will have to pick up a apex, drr or shifter. Something liquid cooled with dual arms and a wider profile. Just trying to make it one more year before I consider that kind of investment.

[desratt]

I see you are in indiana. Heath racing is also in indiana and they have been great to work with. He has several carbs. Nathan adams

[EthansDad]

Hey Kkdad,

yes, welcome. If you do plan on doing this for a while, do find a shop like Rocky mentioned, or get in touch with your local crew like others suggested. for the "fine tuning" art of things, its always best to check with others in your same area/climate/terrain, etc than what someone on the other side of the USA thinks runs well in their area.

that said, I do think a 16mm carb on a 90 is small. the motor will run better with a larger carb, say a 24 or 28mm. my $.02 -for a 7yr starting out on a 90cc - don't mess with it yet - he may not like to ride it as much if you really open the flow up to have it on a 28mm.

that 16mm is really restrictive, which makes the power predictable and overall the bike very ridable - great for yard or trails. as long as its getting enough fuel not too be lean, your OK. I do think when you are ready for more "go fast" -changing that carb should be top on your list. just know going from a 16mm to say a 28mm may take more than just a carb - new intake at the least, maybe more to have it run well on that new setup.