I have an Arctic Cat 90 4 stroke. It goes pretty good but my son wants a little more out of it. Instead of buying a bigger machine, is there anything that I can do to this 90 4 stroke to make it faster? Thanks

 

Pipe, air filter with more intake air ports. Also maby some clutch mods. It does have the cvt trans, right? Also rejet the carb if you pipe it and add more air.

 

Yes, it does have cvt trans. Are there any restricters in the exhaust or intake?

 

I don't know about the 4 stroke. But on our 2 stroke there were a bunch. There was one in the pipe. Where the pipes hooks into the top end. There was a brass restricter in the top of the carb which restricted the slide to open all the way up.Also in the clutch system, there was a little spacer which was placed in the middle of the 2 variator halves . The variator is the front pully in your clutch system. Easy to remove. The spacer kept the pully halves from going closer together which kept the belt from going higher up on the pullys which would make it go faster. Also it had a limiter on the cdi. What rear sprocket does it have ours had a 50 tooth rear sprocket which was another restricter. We have 3 sprockets. 30,32,35. It all depends on the track and conditions which 1 I run. The Arctic Cat quads are the most restricted quads on the Market. After I removed them all It ran like a totaly different machine.

 

Yes your 4 stroke has the front variator/clutch restrictor looks like a steel wedding band between the 2 halves.Removal is good for about 5-8 mph topend.

 

Where did you get your sprockets from.

 

I have to check my sprocket. If it is a 50 and I go with a 30 or 32, What will this actually do? Increase top end or bottom end?

 

I got my sprockets from Hetrickracing.com. That is the only place I get my parts from. Does the quad have a rev limiter on it. When you have the throttle wide open when it reaches it's maxed speed does it sounds like it starts to miss. If it does it has a limiter on the cdi. i would check into that. I put a no rev cdi on his quad and it made a really big difference.Now it will really rev up and hit max HP. If you have a 50 tooth sprocket I would junk it. If you go to the 35t rear you will gain alot of top end. The 32 works great on our modded 70 but the clutch is working perfect. I use the 30 sometimes in Nationals because they have alot of field sections. But the 19/32 is a good combination on hilly tracks . But this is all on a very moded 70 2 stroke. It will be different with 4 stroke power. But I would say a 19/35 would work great.

 

Sprocket specialists,rebel gears sells the sprockets too a little cheaper than Hetrick. BLUETICK you aren't using the stock front variator are you? If you are you, are missing out on a heck of a lot of performance from your cat 50. that var. has really bad ramp/face angles cause of having to fit that spacer/restrictor if you use a perf var. It'll run a heck of a lot better costs about $80 and makes a big difference off the line thru topend and the belt will last about twice as long.You can tell the difference the second you ride it. Just my $.02 FastestDad

 

Fastestdad,

Yes I'm useing the stock variator.I also still have the stock belt. I was thinking the next time I do a mod for more speed I was going to look into a Performance variator. This quad is plenty fast for my just turned 7 yr old son. It has the 70 Airsal head, Hetrick power up kit C. 20mm Kiehin carb with Koso intake and Boysen twin petel reeds,Works shocks,Malossi cdi,malossi clutch. Then all the good springs and rollers that come with the Hetrick kit. My son keeps it pinned right now and his mom hates to watch him race the way it runs now. I don't want to get him hurt. If I give him more power then he will use it. But thanks for the info I will keep it in mind. When the time is right I will work some more on the front variator. THANKS again. Mike.