Psycmike,
Had the unison desert cat out again this weekend. In the desert at 1000ft, we had no boggin down like you mention and I did up here at 7000 ft. JR cruised on the trails and we had to go thru a couple of washes that were rocking and rutting going up and out. Not long up hills, but relatively short and steep. So he was going slow and the Cat scooted right up and out. I was certain I was going to have to push him out after the experience with our first ride. I'm thinking jetting, but will try it agai at this elevation on the same trail. Maybe it was all riding skills, I am not sure. I have seem some other comments on the sprocket changes and people seem to think it does help that low end torque issue. You might want to check that spot out too.

 

For a stock machine that will most likely work, but imo it's not the way to go if you plan to add other mods. And I promise a simple gearing change won't give the low speed/take off power I have. And mine's a pretty mild engine compared to some.

 

I want the low end power for low end torque, not for quickness or speed. I do a lot of trail riding, no sand dune stuff. So, I want what is best for getting my boy up a mtn trail with at a slower speed, but higher rpms. Does that make sense? With that said, is the sproket the way to go or internal mods, i.e. rollers.?

 

Don't think you'll raise the rpms with a sprocket change. It'll help your take off but that's about it in my mind. You will raise rpms with a pipe or head and high rev cdi (forgot yours was restricted).

Power is power with a cvt. Low-end/top-end has no meaning on a constant rpm tranny. You are simply using gearing. Which you can lower, but it seems to me the tranny would offset any sprocket changes once you get going? The roller weights control the rpms. Once you hit that rpm they constantly roll out increasing your gearing on the pulley's in the cvt.

The clutch springs control the stall speed (at what rpm the clutch shoes engage).

 

Doesn't cost anything to remove a roller or two. Best advice I can give is try that and see if you think it's what you want or if you need a little more.

Oldyeller tried removing rollers on his and I think Spike may have changed the sprocket. Shoot the a PM and ask what they think. Both are great guys and would be happy to help.

 

So removing a roller (or two or more) would lower the speed, yet allow the rpms to still create the tourque needed to climb hills and negotiate rocks at a lower speed? Sorry, this is all new to me. Your patience and explainations have been appreciated.

 

Removing the rollers (or lighter rollers) forces your cvt to hold a lower gear longer.

Take mine for example. The pipe, head and carb allowed me to turn a whole lot more rpms. BUT without the mod to the cvt I had a bad lag coming off the line. It wouldn't rev high enough to hit the optimal rpm until I got up to about 6-7 mph. Then it would take off. After changing to lighter rollers, it hits the optimal rpm upon full throttle instantly. Think of it as reving your manual before letting out on the clutch.

Course I changed the torsion spring and clutch springs while I was in there. The torsion spring helps prevent belt slippage if you boost your HP.

Like I said, give it a try. It doesn't cost anything if you have the tools laying around. I have an Eton repair manual I can email you, if you want it. The cvt's are pretty much identical. Be sure you've removed the jumper in the cdi. If you do overrev the cdi may cause problems.

 

Sounds like an easy mod. I've already removed the cdi jumper, so that's not a concern now. PM me and send me the "how to on the roller removal" from the manual. That'd be helpful. I don't have the tools, but I have a friend who has a shop that he'd share. Thanks for all your help. I may bug you in the future.

 

Psycmike and others,

Just to clarify the pros / cons of sprocket changes to obtain more bottom end power, here's some details....

Sprocket changes: It's an external change that can make the engine rev to obtain the same amount of MPH ground speed. To change, one simply orders the parts, removes the old chain / sprockets and installs the different size sprockets. If bigger rear and smaller front, one usually needs to purchase a longer chain as well. To someone with my limited skills, it's a very easy change. All parts are external and it only takes standard wrenchs to do it. From a power gain perspective, one doesn't obtain power gains when going from 0 to say 8 mph. The low end power gain is nearly the same. But the power gains from say 8 mph to 24 mph is higher. Assuming mph is the new max top end ground speed. Think of a graph and in the top left corner, lower its diangle line from 30 mph to 24 mph. Sprocket changes does compress the RPMs to a much more controled engine RPM from 8 to 24 mph. For our "average trails" of 8 - 18 mph, sprocket changes was a great mod for us. It also allowed us to keep our stock pipe. Hence, we didn't end up with a very load mini for our trails.

Clutch & Roller changes: I've been told it can give you higher engine rev to 0 and all the way up to 30+ mph. Depending on the clutch & roller change, one get create a very nice "bull load" power from 0 to 8 mph. But, you get a high RPM engine as a result. And, clutch / roller changes "could be" very scary for the non-mechanical person. Just like myself.


If I had to do it again for our unique trails, I'd still go with a sprocket and "higher quality" chain upgrade for our Pred-90. Should have done a sprocket & chain upgrade from day one. On my bush trails, we want a quiet engine (stock pipe with normal RPMs) yet have a stronger / thicker chain for our heavy weight riders. For others who do mostly 0 to 15 mph over rocks, logs at a needed "bull low" ground speed, the clutch / roller changes would be a much better upgrade option for them.


Before doing any kind of low ground speed "more power"upgrade to their mini, one must consider one's technical comfort, price of customized parts, exact type of riding conditions and the target output they are striving towards. Each has their pros / cons / cost and environment noise impacts.


Hope this helps...

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