RPM Drop at WOT Hot?

[race24x]

As already stated, I think the rpm drop is culmination of several factors, IAT, clutch/belt temps, conditions associated with warmer temps, safety features in the engine etc.

Left yesterday morning and sled was spinning 9150. In the afternoon outside temps hit 30f. Trail riding showed IAT consistently in the 50s and a quick pull would raise it to 107-110 degrees. By mid afternoon rpms down to 8750.

By evening things cooled off and rpms up to 8900-8950, but still low. I figured something was amiss so checked things when I got home a found another set of rollers have bitten the dust. Grrrrr

Checked rollers a week ago and looked new. Did lots of long pulls yesterday on the rr bed. Rode with several aquaintences running big iron all of whom took their turn attacking my Winder. The Winder fought valiantly and puts its skis to the front everytime like a loyal stallion. Unfortunately, I digested a set of rollers in the process...... still worth it.

I once thought it was the heavy weights ruining rollers. Yesterday, I knew it would be hot/mealy so put a setup with only 75 gram weights in the primary. I ate a set of rollers anyway. Cant figure out what causes this

Hey Fleecer,
How do you check your rollers? I have inspected mine every other ride, but never taken them out. From your picture it looks like the inside bushing is gone and you would have to actually take them out of the clutch to inspect?

 

[kviper]

Where do I get at the mid pipe clamp to check them? I had plenty of other things loose so I wouldn't be surprised if they were loose.

 

[Fleecer]

Hey Fleecer,
How do you check your rollers? I have inspected mine every other ride, but never taken them out. From your picture it looks like the inside bushing is gone and you would have to actually take them out of the clutch to inspect?

Great question...I simply pushed the bushing out for the pic to show the bushing wear. When the bushing is shot like mine were, the roller wont turn anymore. It also wont be centered on the pin and/or between the plastic washers on each side. The roller will appear counter sunk on the pin due to the botched bushing inside.

When I check them, I just take the tip of my finger and give each a good spin. If they dont spin/turn you have issues. Hope this helps!

 

[race24x]

Thank you it does. That is exactly how I checked mine. I want sure if I was checking them wrong. They all spin good still.

 

[snowbeast]

No boost drop

Ya,same here,when my IAT,s get hot,my rpms drop,but not my boost.

 

[See n blue]

Where do I get at the mid pipe clamp to check them? I had plenty of other things loose so I wouldn't be surprised if they were loose.

You’ll have to pull your heat shields off your exhaust and you will see the 2 clamps. The lower could be a pain to get to but mine was visible

 

[Fleecer]

I think I've found the largest contributing factor responsible for roller wear. Based on my experiences, I've come to the conclusion that rollers take a beating when sled is held WOT and speed stays the same. Let me explain my thoughts here.

Thus far, conditions this winter have been hard, cold and fast. When holding sled wot it picks up speed until I let off. Hence, rollers have looked new all winter.

Yesterday, conditions were warm, soft and mealy. It would take everything to get to 120mph. Sometimes I held it there at 120 an extra 1/2 mile waiting to see 121. I think what was happening was once at 120, clutches hit a wall due to conditions and would not shift anymore. Due to the dynamics/vibrant frequencies this engine puts out, holding it wide open with clutches stuck in position caused the weights to hammer the rollers. This in turn ruins the internal bushings and the rollers are trashed.

Let's say for example a guy has a high horsepower winder and only races 1000ft on ice. Sled leaves the line, shifts out to 140mph, and then gets shut down. In this example, the rollers will last forever because they are always moving, shift up and then down.

Now take a guy with a stock winder who gets on a lake with 14 inches of slush and has to travel 5 miles on it. And lets say this guy can only go 90mph due to temperature and resistance caused by the slush, but he holds it wot for the full 5 miles. Hence, because the clutches only shifted to 90mph, and because this guy held it there, the rollers cant help but get hammered by the weights. In this scenario, I would be willing to bet that at the end of the lake his rollers would be finished due to reasons stated above.

Thoughts?????

 

[snowbeast]

Ya fleecer,that sure does sound correct,whenever I have blown a belt on a procross sled,either 998 or 1100 it was when I was attempting to hold on to long in harsh conditions,when it was already topped out for those conditions. The only belt I have blown on my 998 came after a real hard run down its 86 from oxbow to Houlton,when my belt was already hot from hammering it down 86,once it hit its83 south RR bed,i noticed the conditions were warmer and very mealy,i bet I hardly got to 110 speedo,and Bam it exsploded,into a million pieces. Oh ya,stock 8jp belt.

 

[kviper]

You’ll have to pull your heat shields off your exhaust and you will see the 2 clamps. The lower could be a pain to get to but mine was visible

Yup, I got to them. I got about 1 or 1.25 turns on the one closest to the tank and only about .25 turn on the one by the turbo. I haven’t run it yet but I doubt that was the problem. How loose were yours?

 

[See n blue]

Yup, I got to them. I got about 1 or 1.25 turns on the one closest to the tank and only about .25 turn on the one by the turbo. I haven’t run it yet but I doubt that was the problem. How loose were yours?

I probably had an easy 4-5 full turns on both clamps.

 

[kviper]

I probably had an easy 4-5 full turns on both clamps.

Yah yours were loose! I was hoping mine were looser that way my problem would be solved. Oh well I’ll find the problem eventually. Thanks for your time

 

[STAIN]

I think I've found the largest contributing factor responsible for roller wear. Based on my experiences, I've come to the conclusion that rollers take a beating when sled is held WOT and speed stays the same. Let me explain my thoughts here.

Thus far, conditions this winter have been hard, cold and fast. When holding sled wot it picks up speed until I let off. Hence, rollers have looked new all winter.

Yesterday, conditions were warm, soft and mealy. It would take everything to get to 120mph. Sometimes I held it there at 120 an extra 1/2 mile waiting to see 121. I think what was happening was once at 120, clutches hit a wall due to conditions and would not shift anymore. Due to the dynamics/vibrant frequencies this engine puts out, holding it wide open with clutches stuck in position caused the weights to hammer the rollers. This in turn ruins the internal bushings and the rollers are trashed.

Let's say for example a guy has a high horsepower winder and only races 1000ft on ice. Sled leaves the line, shifts out to 140mph, and then gets shut down. In this example, the rollers will last forever because they are always moving, shift up and then down.

Now take a guy with a stock winder who gets on a lake with 14 inches of slush and has to travel 5 miles on it. And lets say this guy can only go 90mph due to temperature and resistance caused by the slush, but he holds it wot for the full 5 miles. Hence, because the clutches only shifted to 90mph, and because this guy held it there, the rollers cant help but get hammered by the weights. In this scenario, I would be willing to bet that at the end of the lake his rollers would be finished due to reasons stated above.

Thoughts?????

I think you are 100% correct. That's why you see some guys on here running the big trails in Canada, places you can cruise at high speed all day, destroying rollers in no time. Ask Byam how quick he goes through rollers. He rolls 600 miles in a weekend. I cant do that here. My trails are on/off throttle all the time, with few places to ride sustained speeds of 70mph plus. That's probably why I have been having good luck with my rollers.
Hopefully I cured my worries that with my purchase of the TAPP primary....

 

[1nc 2000]

Two things.

1. These machines have protections built in that when the IAT's get too high the power levels drop. The old 1100 did not have these protections.

2. When its warm out the clutches and mostly the belts get warm and stick harder in the sheaves dropping RPM. When its happening, put on a cool belt and try it and see what happens, the RPM comes back up, but only until that belts gets warm or hot again.

It's going to happen and RPM will not stay up. Don't get too overexcited. When it gets cold again it will all return. In cold weather I run 83.4G, warm weather I'm down to 78 and its still too low in RPM. All the Sidewinders the other day when it was 30F were down major RPM's.

Spot on with the same results I am seeing.
Get away from the 8jp belt was the best improvement I did for clutching.

 

[kviper]

My sled lost rpm's (400-500) in stock form. Intake temps were the same as when I still had my rpm's.

Sled acts the same with a tune. It does not show any knock or any codes when this happens.

Big_Phil,
Do you have any information from Yamaha explaining on how the ecu pulls timing and fuel and at what temperature does this occur at? I would like to see that publication.

1nc 2000, my 2018 ltx is dropping 3-400 rpm on longer pulls also and has done it since day one when it was bone stock. Did you ever get to the bottom this or find a cure?

 

[1nc 2000]

1nc 2000, my 2018 ltx is dropping 3-400 rpm on longer pulls also and has done it since day one when it was bone stock. Did you ever get to the bottom this or find a cure?

I switched to the timkin xs 825 belt and its more consistent. The belt change will require the primary weights to be lightened up some due to the belt gripping better.