My daughter was riding the 90 in the snow today and it seemed a little sluggish. A few questions:

What is the stock compression rating?

How are the valves adjusted and what is the spec? I know the plug has to come out of the crankcase and I have to turn the crank until ------ shows. Please fill in the blank. I know it has to be on the compression stroke.

I believe the auto clutch is adjustable. How and what is the spec?

What is the stock gearing/

Thanks

 

I don't think the compression is very high. My guess is around 9:1. As for the valves, you shouldn't ever really have to adjust them on a 90. If they're clicking really badly, then yes but if not they are probably fine. You can find the stock gearing specs on denniskirk.com. And what you want to see is the piston when you are turning the engine over to adjust the valves.

 

I just found that the stock rear sprocket is 48 tooth. I just ordered a 50 since she never really hits top gear very often. Valves are ticking a little. I could probably leave them but will do them anyway. There should be something on the flywheel that you see through the crankcase after you remove the screw. I could probably figure that one out. Was wondering what the compression psi would be so I could check it. I remember there is a way to adjust the clutch, I just can't find it. It has Works shocks and has been piped and jetted (which helped a ton). Thinking about a 104cc kit for it, they are cheap.

Thanks for the reply

 

Compression ratio is 9.2:1. A fresh top end should have 178psi compression according to my shop manual.

 

<div class="FTQUOTE"><begin quote>Originally posted by: inthedirt

I just found that the stock rear sprocket is 48 tooth. I just ordered a 50 since she never really hits top gear very often. Valves are ticking a little. I could probably leave them but will do them anyway. There should be something on the flywheel that you see through the crankcase after you remove the screw. I could probably figure that one out. Was wondering what the compression psi would be so I could check it. I remember there is a way to adjust the clutch, I just can't find it. It has Works shocks and has been piped and jetted (which helped a ton). Thinking about a 104cc kit for it, they are cheap.



Thanks for the reply</end quote></div>

A 104 kit, larger carb and a free-flowing exhaust system would really wake that quad up. You could probably do it for around $500 too. I'm glad I could help though.

 

Wow. 178 psi is a lot. I'll have to check it out. First I'll change the gearing and check compression. I had the tires real soft too and that may have been a factor. my daughter only weights about 65lbs at 12 years old. She's a peanut. If that doesn't do it, I can do the 105 kit for about $150. Sounds like a bargain if the compression is low. I'll need to check the carb specs though witht he company selling the kit.

Thanks for all your help.

 

I thought stock gearing on all the TRX 90's was 13/50?