Losing rpm

Empire087 · Jan 27, 2017

Ok, so Ive been riding my sled and noticed something is acting up. When I punch it from a stop the rpm will shoot straight to 8000-8100, then it will dive down to about 7300 then finally continue to pull lazily up to around 7900ish. Any ideas why? Belt has about 1300 miles on it looks good.

about 1950 miles, low elevation weights and secondary helix.

Checked power valves, cables, secondary spring, rollers, helix. Everything looks good.

ranger12 · Jan 27, 2017

What year sled?

Are they still the factory springs in the primary and secondary? I would start by replacing the secondary spring first and go from there. The spring might look good but is probably sacked out. Make sure your weights move freely in the primary with the cover off.

WyoBoy1000 · Jan 27, 2017

It's the secondary, they suck. Get it fixed

Empire087 · Jan 27, 2017

ranger12 said:
What year sled?

Are they still the factory springs in the primary and secondary? I would start by replacing the secondary spring first and go from there. The spring might look good but is probably sacked out. Make sure your weights move freely in the primary with the cover off.

15 high country

WyoBoy1000 said:
It's the secondary, they suck. Get it fixed

what do i have to do to get it fixed?

TRUEBLUEMAX · Jan 27, 2017

Empire087 said:
15 high country

what do i have to do to get it fixed?

Most likely the spring is bad the way you describe it but it would be a good idea to have the rollers checked and make sure the bushings aren't bad either

Empire087 · Jan 27, 2017

TRUEBLUEMAX said:
Most likely the spring is bad the way you describe it but it would be a good idea to have the rollers checked and make sure the bushings aren't bad either

it seems like the secondary is shifting out too fast, like under heavy loads such as doing a wheelie it wants to almost bog or drop rpm.

BBP · Jan 27, 2017

I think you got your money out of that belt. It's time to buy a new one!

Empire087 · Jan 27, 2017

BBP said:
I think you got your money out of that belt. It's time to buy a new one!

Would the belt be causing this issue? It is in excellent shape, no excess wear or anything.

BBP · Jan 27, 2017

Empire087 said:
Would the belt be causing this issue? It is in excellent shape, no excess wear or anything.

1300 miles? Yes, I think so.

ranger12 · Jan 27, 2017

Do you have a new belt and a caliper?
Measure across the top of the new belt and then measure the old belt that will tell you how worn out it is. Plus your old belt is probably hard and not grabbing the sheave surfaces correctly anymore. I would say that you have more than enough miles on that belt. Keep it as a spare and install a new one. It will help with your problem but I would still look at the secondary and the secondary spring also and install a new spring. The springs don't cost much but if you install a new spring you will be able to get a good look at how everything is wearing in the secondary when you have it disassembled.

Empire087 · Jan 27, 2017

ranger12 said:
Do you have a new belt and a caliper?
Measure across the top of the new belt and then measure the old belt that will tell you how worn out it is. Plus your old belt is probably hard and not grabbing the sheave surfaces correctly anymore. I would say that you have more than enough miles on that belt. Keep it as a spare and install a new one. It will help with your problem but I would still look at the secondary and the secondary spring also and install a new spring. The springs don't cost much but if you install a new spring you will be able to get a good look at how everything is wearing in the secondary when you have it disassembled.

I did measure the existing one and its 1.40 on the dot width. I have a dayco xtx thats brand new to use, gonna give that a shot. Also gonna hop in the car and head to the dealer thats an hour or so away and grab a new spring.

WyoBoy1000 · Jan 27, 2017

Stop for f cking around. The stock secondaries are not right, ppl think they work but reality is there not running efficient.
Send it to Mountain valley motor sports in Cody, wy. And get it machined.
That is the only true fix. Everything else is a waste and you will never have what you could.

BBP · Jan 27, 2017

Empire087 said:
I did measure the existing one and its 1.40 on the dot width. I have a dayco xtx thats brand new to use, gonna give that a shot. Also gonna hop in the car and head to the dealer thats an hour or so away and grab a new spring.

a new belt has a small angle cut at the top of the cogs. Your belt will run a long time before wearing that angle off all the way to the top of the cog. If you've worn the sides of your belt all the way to the top of the cog, then your belt is shot & it will still measure close to new. If you were happy with the performance of your sled before, then clean your clutches, scrub that new Dayco with hot soapy water & go enjoy another 1300 miles. If it doesn't run right, start throwing money at it.

clutch · Jan 28, 2017

Check the rollers on your primary. Make sure the weights are still centered and the set screw isn't loose. A spring isn't going to make your rpm do what you're describing. Check belt and deflection.

ranger12 · Jan 28, 2017

clutch said:
Check the rollers on your primary. Make sure the weights are still centered and the set screw isn't loose. A spring isn't going to make your rpm do what you're describing. Check belt and deflection.

With a user name like you have, can you please describe to me how a sacked out secondary spring with 1300 miles on it would not cause his rpms to do what they are doing? I'm not saying that it is the only problem that he has either.

I cant believe I just did that! That is why I don't come on this site much. And I probably know you.

mbcat · Jan 29, 2017

Losing rpms

His primary is fine, the rpms are accurate. It's the pos secondary. You'd be wise to listen when Wyo says something

clutch · Jan 29, 2017

ranger12 said:
With a user name like you have, can you please describe to me how a sacked out secondary spring with 1300 miles on it would not cause his rpms to do what they are doing? I'm not saying that it is the only problem that he has either.

I cant believe I just did that! That is why I don't come on this site much. And I probably know you.

A worn out spring may cause it to lose 100-200 rpm from new, but it won't cause it to jump up fall off and lose 800 rpm and then slowly come back up. Either it has a roller failing or something is binding in one of the two clutches. Did it just start doing this, or did you change something and then it started?

ranger12 · Jan 29, 2017

ranger12 · Jan 29, 2017

clutch said:
A worn out spring may cause it to lose 100-200 rpm from new, but it won't cause it to jump up fall off and lose 800 rpm and then slowly come back up. Either it has a roller failing or something is binding in one of the two clutches. Did it just start doing this, or did you change something and then it started?

When I read the post I took it as everything was fine until he just hit 1300 miles. There could be several things wrong here but I was just referring to the simple things first to check that are the least amount of money to start with and he more than likely needed. One of the things that I suggested was that the secondary spring is shot, which if it doesn't have the right amount of resistance anymore will open up the sheaves too quickly and put it in too high of a gear and drop the rpms and then when everything else catches up the rpms will start to creep back up slowly. Yes the machining of the secondary is a big improvement but if he was happy with it for 1300 miles he probably doesn't have to have it done. I also started that if he changed the secondary spring he would have to take it apart to do that and then he could inspect the rest of the parts. There could also be problems in the primary as some have started.
I just reread the original post and it says 1950 miles on the machine. I must have missed that the first time. That's getting to be a lot of miles on the Cat clutches!

Betterview · Jan 30, 2017

Empire087 said:
Ok, so Ive been riding my sled and noticed something is acting up. When I punch it from a stop the rpm will shoot straight to 8000-8100, then it will dive down to about 7300 then finally continue to pull lazily up to around 7900ish. Any ideas why? Belt has about 1300 miles on it looks good.

about 1950 miles, low elevation weights and secondary helix.

Checked power valves, cables, secondary spring, rollers, helix. Everything looks good.

I agree with Wyo that your problem is most likely in the secondary.
If you get 8000 plus when you punch it tells me you are in the ball park on clutch weight. Then what is probably happening with the Chinese built two roller secondary is it is wobbling and over shifting. MVM is a good choice for a fix as long as they also have your helix too.

I have had great results with a Thunder Products Hercules Helix in a secondary that would over shift so far that the engine would eventually bog out in a long deep powder full throttle pull. Talk to Lon, get his helix and his spring (it is much softer), take about three to five grams off each motor clutch weight(I ended up taking five out of mine but was a bit heavy before the change), and you will have a runner. Have done this twice. On my sled I also did his 911 clutch cover and glide washers and my clutching is as buttery smooth as any Polaris I have ever ridden while still retaining that instant aggressive pull that I relish whenever stabbing the throttle on the 800 cat.

Losing rpm

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