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Discussion Starter #1
Could someone help explain how the primary and secondary clutches work. I am having a problem with my 1991 Indy 650 RXL boging down around 50-55mph. I first thought it may be a fuel delivery problem but after browsing this site I am leaning toward a clutch problem. Thanks in advance.
 

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Ok here's a basic...
1. Engine Rpms raise causing the primary(front clutch) to spin. Spinning causes the weights to move, causing pressure on the spring which in turn closes the primary around the belt.

2. Belt starts turning causing the belt to spin the secondary. Which then spins the jackshaft and then through the gearcase spins the drive shaft... thus turning the track.

3. As the belt spins in the primary it begins climbing on the walls of the primary which in turn pulls the belt into the secondary and causes the secondary to open as the primary clutch is closing. This upshifting.

4. When you left off the gas the spring in the secondary closes the plates around the belt thus pulling the belt up higher in the secondary, which in turn pulls the belt back down in the primary. This is down shift.

This is real basic, i am not a clutch expert.
Basically you need to keep the Clutch Plate Faces, Weights, buttons, the pins holding the weights all clean and you need to make sure your springs arent sacked out. If everything is clean and the springs are fresh your clutch should be fine.

Someone will probably give a better explaination but this is the basic.
 

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first thing, what are your rpms,what are they supossed to be
is this from a stop to wfo
or cruising and letting off and accellerating[not backshifting]
 

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Discussion Starter #6
From a dead stop I will floor it and it will pull like hell all through the powerband (7500-8000rpm or so) then at 50-55mph the sled will bog down, stay out of the powerband and not go any faster. No matter how I try at this point it will not go and faster. Jim
 

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After reading this post I became curious into how to clean a cluch by not taking it apart or do you have to take it apart? Maybe this will help jturley's problem as well.
 

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The only thing I have done it to use a air hose and blow the clutch out real well with air only. I also clean the inside faces with common brake cleaner on a rag. If this is wrong or if there are better methods I too would like to know.
 

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If at 55 MPH your clutch stats shifting too fast and it drops your RPM then you can adjust your secondary spring. Each notch is about 200 RPM difference in shifting RPM. But first make sure your clutch is clean and working propery first.
 

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To clean them you really do need to take them apart. Use an Scotchbrite pad to clean everything. The clutch faces slid open and close and there is no way to clean inside without taking them apart. You didnt do anything wrong by cleaning the faces with brake cleaner, but there is more stuff inside that air just wont clean. I had to scrub my weights and roller's real good.
 

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So Darkstar, you took the primary apart and cleaned the weights and things. How often do suggest doing this? I don't think I my clutch has ever been apart. Probably not a bad idea to do this, huh?
 

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As for frequency, ever year is probably overkill but it doesnt hurt to do preventative maintenance... After learning how to do it have done mine every year.

Yep I cleaned everything inside.
 

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I'd like to get that Aaen's clutch tuning handbook, but I can't find it online. I found one at sledgear.com but they wanted almost 40 bucks with S&H. Anyone know where I can find it for 20?
 

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make sure u don't overlook the drive belt.there's an adjustment on the secondary clutch face.this should b adjusted as the belt wears, the belt should ride 1/8" above the secondary sheave.a new belt will make all the difference in the world sometimes.g'luk
 

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what color primary spring do you have, sounds like your primary spring maybe sagging. You should target 8000 rpm for max rpm, with my 650 when i had the stock pipe it ran best with 10A weights and an almond/gold primary spring= 4500 rpm engagement with max rpm of 7800-8k, 10al weights are ok as well. Remove clutch cover to replace springs, also inspect weights for wear and make sure there are no flat spots on the rollers, if the rollers are bad you'll have to remove the clutch and have a professional replace them, as you need special tools to remove and retorque the spider bolt. Problem definatley sounds like a primary clutch issue so i would focus there first.
 

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Discussion Starter #17
This is excellent advice guys thanks a bunch. I am running a Blue primary spring and it seems to engage around 4200rpm and max rpm's are around 8000. I will be working on the problem this weekend but wont know for sure till we get some snow on the ground. Thanks again.
 

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Is it dark blue or light blue? I dont know for sure but it sounds like that isnt the right spring for that sled. I have a dark blue spring in my 1990 500. I would assume you would need a little stiffer spring in a 650... Just thinking out loud again...
 

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hmmmm Scrathin Head... It sounds like an aftermarket spring... Anybody know what the stock setup is for this sled is?

Jturley, Did you get a chance to take the clutches off and clean them? Your engagment sounds to be just about right, which is what leads me to believe it isnt a setup issue, probably a cleaning/maintenance issue.
 
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