I have a 95 300 2x4 and I need to know what the stock gearing should be for this bike. The owmers manual I have says it should be 13/38 gearing but my dealer says it should be 13/40. When I look at aftermarket parts books they all say the stock gearing is 12/38!!!When I first bought the bike the engine was stock and it had 12/38 gearing.I added a 13 tooth front sprocket to it before I did all the mods to it.It didn't seem to make much of a difference with the bigger front sprocket.But now that I've done all the mods I want it to accelerate faster so should I go back to the 12 tooth front?By the way this bike came with stock 24" rear tires and not 22" like the Scramblers and Tblazers.I want the fastest acceleration possible but I don't want to sacrifice top speed.I have played with gearing on standard tranny bikes before and I understand what the differences do. But with the PVT It responds different with the gearing changes because the PVT shifts because of the torque applied to it.When I do a full throttle test from a dead stop it seems to go to full rpm and then drop back below the powerband as it shifts . This is even with 18lbs of preload on the secondary clutch.Am I geared too high for these 24" tires?I also have a set of Dirt Devil tires that I want to run on it but I installed them last week and they seemed to rob alot of power so I took them back off and reinstalled the stock Goodyears for now.What should I do?

 

I think you should put 20'' or 22'' tires on. It depends on the tire though, because some have different heights even though they say they are the same size. And maybe try the 12T sprocket on front again. If that doesn't help then put a bigger sprocket on rear. Doing these things will give you better acceleration, but will have a slower top-end speed.

 

I tried a set of 22" all tracs on my Magnum instead of the 25" tires the I had been running. The diffrence was terrific lots of traction to of-set wheel spin and launching from the strart that was like a rocket. Didn't try a flat out run on the road but I could stay ahead of the competition that previously blew me away on our cross country practice track. So let it rev.

 

Well after talking to Rick Ritter today we came to the conclusion that my
white primary spring is not heavy enough to let the engine rev up to and stay in the powerband.I have ordered a yellow EPI spring which is slightly stronger than the Polaris green one.This should keep the engine"on the Pipe" so it will accelerate a lot faster without the rpm's dropping off after it shifts.I just don't know if Im going to like a 3000rpm engagement for trail riding though.Have to try it out and see what happens.I am not going to put smaller tires on the rear cause I like the ground clearance i get with the 24" tires and I don't beat the rims up either.

 

sparkys,

I have the Polaris yellow spring and 55g weights. My enegagement is at 3000rpm and my shift is 6200rpm. I am running 13/34 gearing with 22" tires.(My other mods are listed in my sig)

My acceleration is awsome. My top speed is about 60 to 65 mph. I plan on a bigger carb and a pipe from Ritter in a month or so. I hope to be able to go to a 12/30 or 13/30 ratio after that.

As for trail riding, the engagement doesn't bother me. A couple of friends say they couldn't stand it. They also don't like me always beating them in straight drags.

 

Elroy,why are you running such heavy weights? It kind of defeats the purpose of the stiffer spring.They are working against each other.After talking to Rick Ritter last night he told me to try the polaris orange spring.He said the engagement should be around 3000 but it has 70lbs of pretension on it at 2 1/2".I would think that if the yellow which is 50
lbs. of pretension,with heavier weights,engages at 3000rpm,then the orange with stock weights ( per Ricks reccomendation) will engage well above 4000rpm.This is way too high for trail riding. I want to get a decent engagement and then have the engine go straight to the shift rpm of 6500 and the give me a good straight shift from there.I am going to install a tach on the bike today and do some runs to get a baseline to start from.I don't want to spend a fortune on different springs and weights to experiment.Right now I am not getting the benefit from the pipe I just installed. The engine will rev to about 6000rpm then drop off about 600 to 800 rpm on acceleration.I am falling below the powerband of the pipe.I just read Olav Aaens clutch tuning book last night and it is very interesting o say the least.

 

sparkys,

I would like to read that clutch book. I'll have to get it someday.

The reason I am running 55g weights is actually quite simple. When you install a bigger spring, the first thing you notice is a higher engagement point. This is a good thing if it was what you were after. The second thing you notice is that the shift point is also raised. This too is good if it is what you were after. However, you have to watch how much bigger of a spring you use in the primary because it may not allow the engine to shift all the way out at top end. If the spring has too much tension in the primary, the engine will not be able to turn fast enough to pull the secondary into a full shift. If it can, it may not be pulling it hard enough to keep it there when you encounter an increased load.

Before I installed the 55g weights, I was running 50.5g weights. I still had a 3100rpm engagement and about a 6800rpm shift. What I didn't like about this was that my stock pipe doesn't work well at 6800rpms. I had to lower my shift point.

The springs are basically what sets the engagement point. At lower rpm's the weights have very little effect on the spring. Their was a 100rpm difference between the 50.5g and 55g weights at my engagement point. The weights tend to set your shift point. Thats why I noticed a 600rpm difference at my shift point.

If you want to raise both, the engagement and shift points then all you need to replace is the spring. If you only want to raise the engagement then you'll probably have to go to a heavier sping and weight to make it shift at that same rpm again. If you want to only raise your shift point then go to a smaller weight.

I want to also add to this large statement that their is a few other areas I didn't touch base on such as backshift and operation of the secondary clutch. I was just trying to describe some of the operation of the primary clutch with no reference to the secondary.

 

I still don't understand why you went with both a heavier spring and weights too. If all you wanted ways a higher engagement you should use a spring with a higher pretension and the same spring rate which would make the shift rpm's the same.You can also just shim the stock spring to get the same effect.I did this to my white spring before the pipe and I had a 3000 rpm engagement with a 6000rpm shift.I just got a piece of 2" pipe and got a machinist friend of mine to cut me a nice straight peice 3/16 of an inch long.I put this between the spider and the spring and it raised the engagement but not the shift rpm's.After I installed the pipe I lost some bottom end power( this was partially because of the larger carb too)so I needed to get the engine to rev higher to use the pipe to its full potential.I just installed an orange polaris spring tonight and my first tests seemed to yeild excellent results.I have a 3200 rpm engagement and a 6700rpm shift rpm. The thing pulls like it never did before.And backshifts a lot better too. This is with the stock 48 gram weights.According to olav Aaen's book there is about a 1000 rpm difference between the peak hp and peak torque and if the engine falls below these numbers than the backshift will be affected as well as the shift rpm's af the engine.Because the backshift if controlled by the torque excerted on the secondary clutch. He was right. I tried 10MH weights the are 50.5 grams with the orange spring and the engagement rpm was almost the same as you said but the shift rpm dropped to about 6000 and the bike doesn't backshift nearly as well too.If I drove along and pinned the throtthe the rpm will jump right back up to 6800 with the 48 gr. weights but with the 50.5 weights the engine will only hit about 5500 rpm if I hit the gas after the bike is rolling along.I suggest that anyone that wants to tune their clutch should read this book.It tought me a lot. As far as the engine having enough power to pull top rpm's I'll have to wait until the snow is gone and do some more testing then.
According to Olav basically the spring has 3 determining deminsions that affect the clutch: pretension. that determines the engagemant rpm
: full shift load. this is the fully compressed tension of the spring and the spring rate that is the difference between pretension and full load.The spring rate is the factor that affects the shift rpm the most. If you want a higher shift rpm use higher spring rate and vice versa.
The orange spring I'm using has 70 lbs pretension and 170 lbs full. This gives it a rate of 100 lbs which is just right for my engine mods.

 

I am a little confused as to why your numbers with the 50.5g weights and the orange spring are a little lower than my 55g with green spring. I am running a lighter spring with heavier weights and yet, my numbers are higher?

One thing we do have to remember here is that I am still running the stock pipe and my carb has been bored out to about a 31mm.

I do know what you mean about the way the clutch shifts at a lower rpm once under way then punched to full throttle. It only does this for a split second and goes right up to the normal 6200rpm. For my quad, it makes it a little more controlable on the trail and my pipe/carb seem to work better like this. I'm sure this will all change with a different pipe and carb.

Another reason for the new heavier weights in my quad was because I didn't like the way my engine would rev up before grabbing the belt. This was only noticable once under way and then punched. It seemed like my engine would rev up ........... then grab the belt. When I switched it to the 55g weights, this disappeared. My engine know grabs just before it hits its shift point. If I were to lighten my weights by about 2g, I could probably make it grab right at the shift point. I will probably lighten them somewhere between now and the new pipe/carb.

Lastly, I did notice a drop in my top end before going to the 55g weights. I didn't like this at all. It seemed like it was revving really good but just not the top end the revs would make you think it had. Made me feel like I was in low range, all revs but no top speed.

I also must say that I just installed a straight 40 degree helix. I was able to ride it about a whole mile before my throttle cable started unravelling. What little time I did get on it was somewhat impressive. It made the front end light real easy, when I could get enough traction.

 

Elroy, as well as running a different pipe and bigger carb with a UFO, I also have the stock size 24" rear tires and 13-38 gearing too. I'm sure if I ran smaller tires I would rev up some more because of less rolling mass.I prefer the taller tires because of the better ground clearance.I might try lowering my front sprocket one tooth because according to Olav's book, when you raise the top rpm and powerband of an engine it also changes the gearing requirements of the bike.He says it is better to lower the gear ratio to make the most of the new higher peak. According to Rick Ritter my peak should be about 6500rpm now instesd of the stock 5600 rpm.A lot of this is from the RCR pipe I installed and a little bit might be from the bigger carb too.
By the way what primary spring are you running? You said it was the yellow one but in your last reply you said it was the green one.There is a fair difference in the 2 springs.I will be glad whan all the snow is gone so I can do some testing on dry ground. Theres no way I can get it to stop spinning for long enough to get any real feel of the new clutching.When spring comes and if the bike still doesn't have enough power to satisfy my HP addiction i guess I'll have to drive my street bike more. It gives me a whole new meaning of acceleration every time I roll on it!!! I guess 0 to 60 mph in 2.8 seconds with a top speed of almost 180 mph is good enough eh?