77 LF, Kiortz Rebuild, Yamaha Clutch Removal

[gmsnowman906]

Hello All,

This is a clutch sheave stuck issue. I'll get to that after a Brief introduction and lengthy background - It's been about 10 years since I've posted on this site, and it looks like my last post was as "UPbeck". I'm now, newly retired and able to spend only a little more energy on fun stuff. so....

Nov, 2019 (5 years ago): my 77 LF SORT of DIED on me while under a pretty heavy workload - After about an hour (2 miles) of breaking trail to deer camp in the UP. 18 inches of wet snow that was really slowing down our trucks. Lots of fun.

"Sort of Died" means that I felt or maybe heard a shutter and it seemed that it was at 60% power. I continued another mile to camp, under reduced power, mostly following the other sled that I had brought for that need.

I did use it the next day or two until being aware that it was struggling a little. Then it totally died (stopped and would not start) after hitting a small bump on my way back for lunch. I was a half mile away from camp so I walked the rest of the way, got the camp jeep and then towed my sled back to camp.

Back at home, 5 years ago, I began troubleshooting. This time it actually started but would not idle/run. I replaced plugs (both were wet and one was fouled; however, I believe that fouling/wet plugs had always been a problem), checked compression (both sides were 125 psi), rebuild carbs, eval's reed valves, flushed out the gas including the tank, checked the fuel pump, air intake, exhaust (black gas dripping at the coupler and out of the tail pipe), clutch, belt and all the moving parts downstream of the motor.

I decided to replace the original CDI with an aftermarket one. That did improve behavior but only a little. The motor would start and idle but was at 20% power.... I'd have to push it to get it going. Top speed was 10 MPH.

I had replaced the dead magneto with a used one back when I had first bought it back in 2001. Then, its top speed was about 55 MPH. Thinking through this today, I should have gone back to the "used" magneto as the root cause. Oops.

Instead, I decided to rebuild the motor even though the compression wasn't terrible and the motor would start and idle as normal but with no real power.

Lots of fun but, here I am... an average skilled troubleshooter and mechanic stuck in the middle of a motor tear down hoping that I am not in some rabbit hole. I am not the original owner and don't know the maintenance records so, I am assuming that a rebuild was due anyway. This would be my first rebuild on a sled.

I have the kit for the top end including rings but I had also wanted to replace the seals on the crank. So about that clutch (inner sheave?).

So, my clutch removal issue - I am aware of the hydraulic trick and the special removal tool (I can't find one online). I have tried the hydraulic trick and have failed on each attempt.

My notes say that my clutch is the preferred Yamaha and that LF's sometimes have the less desired Comet. I'll attach a pic of the "stuck" sheave and the trail breaking day in 20219 - the snow on the hood is from blowing that snow. I'm looking for any help on what to do/try next and, of course any thoughts on root cause.

[nick80lf]

Here's my comments.

- I'm not a yamaha guy but a coworker told me his SRV had a comet clutch but it had M16 threads for the puller instead of 3/4. Only reason I mention this is because of your puller comment. New Breed Parts has the 3/4 comet puller but I,m wondering if you're dealing with metric puller threads.

- Your photo shows you doing the hydraulic trick so I'm not sure if this would work. The worst clutch I delt with, I was using a comet puller. In the end, time an some gentle heat did the trick. During my struggles I applied all sorts of different sauces to try to help loosen the clutch. I basically tightened the puller as tight as I could and left it set over night. The next day I would use a heat gun and heat up the area of the clutch where the crank taper is. Then would try to tighten the puller again. It took me about a week of doing this every day. When the clutch finally came off, I was glad the engine was in the sled and I did not have my hand in the way. It came off the crank like a rocket.

[gmsnowman906]

Thanks for the reply, Nick... and the warning about buying something that does not match. I am hesitating to ask, but how can an SAE/Comet and a metric/Yamaha clutch be interchangeable? I did surf a few forum conversations just to refresh my memory and looked at my drive clutch - it has "Yamaha" stamped on it. My notes from 2019 say that my bolt is a 3/4, 16 pitch. Maybe my clutch is a Frankenstein. So, trying to keep my blinders on ..... My plan is to revisit the gentle heat method and be a little more patient. Thanks, again.

[nick80lf]

Many clutches have a 30mm tapered bore that mates with the tapered crankshaft. Same concept as Morse taper drill bits. The big thing with clucthes is different manufacturers used different counter bore depth. It sticks in my mind that yamaha's bore depth was pretty close to what Deere used. As long as the clutch mates with the crank, doesnt interfere with some other part of the sled, you have the ability to shim the secondary to line up two sheaves, the primary is setup for the same width belt, it would have the potential to work. Different thread types for the puller becomes sort of insignificant.

[SS440-80]

Yes, Yamaha use millimeter (like everyone except US, Liberia and Myanmar) so a puller with the M16 fine thread will work.

I have had som clutches stuck like yours nick80lf, and my guess is that when the clutches where mounted, the came from a warm and nice workbench in a garage to a deepfreeze cold snowmobile outside.
And with the warm metal in the clutch expanded, and the crank much colder, the clutch slips on the taper much longer then if everything would have had the same temperature.

[gmsnowman906]

Thanks for the input SS440. I assume that your removal method used either a traditional puller or used the "oil" and heat method that I am about to re-try.

Nick - Sorry for the delay - I was away for a week - some work and some play. Thanks for the tapered shaft in-sight. I plan to revisit this soon - Sticking with my bolt sealed with pipe tape and the counter bore of the shaft filled with oil + heat. But I'm also thinking about a "plan B" (buying a puller) if this doesn't work. So, I'm not clear about your "...sort of insignificant" comment above but it seems like a "Yamaha" puller might not have the correct length to contact the end of the crank shaft. Is that what you were referring to?

[SS440-80]

I used a bolt with teflon tape and transmission oil when I removed the hard stuck Yamaha clutch. But water will also work just fine, and is less messy.
And using a impact wrench, pneumatic or electric with high torque will help a lot.

I think that oil or water tric is much better than a puller. If the clutch is stuck like yours, the tip of the puller gonna bend like a spaghetti.

[gmsnowman906]

Hi SS440 - I think that you are exactly right on all points.... based on my foggy memory from my first attempts almost five years ago. Back then, I had tried both the (homemade) puller and the oil method but suspected that my impact wrench was/is under-powered. So, last night, I re-tried my homemade puller and big Cresent wrench and my impact wrench again.... and failed... again. My next step is to borrow or buy that high torque wrench.... and create a landing spot for that projectile. I'm starting to get a good feeling about this.

[SS440-80]

My next step is to borrow or buy that high torque wrench.... and create a landing spot for that projectile. I'm starting to get a good feeling about this.

Let us know how far it went

[gmsnowman906]

So, I do have an old but never really used "high power" (?) impact wrench. It is suppose to reach around 250 ft-lbs. I have never been able to get much power out of it but I did add 10 drops of oil and tried last night with a short 3/8 hose and larg-ish compressor/tank with the regulator at it's max (117 psi). I used the easy, less messy traditional puller setup just to confirm that my wrench is too weak for the job. My attempt did fail but not in the way that I had expected - My bolt spun and stripped the first 1/2 inch (7 threads) of the bolt. So, now, I need to understand what went wrong..... I bought the bolt five years ago.... I think that it was from Fastenal. I'm sure that it's not hardened. My Mitutoyo calipers show that the bolt is 0.7465 inches/18.96 mm across the outer threads... on the remaining good threads. My bolt matches the 16 tpi scale on my (printed-on-paper) thread size chart. My guesses: bolt hardness, clutch hole taper or is causing this problem and/or that my bolt's first 6 or 7 threads was not match for my very questionable "250 ft-lb" wrench. I'd appreciate some advice before I wonder off in the wrong direction. Thanks!

[SS440-80]

You write about inches... but the Yamaha clutch have mm threads
And as far as I can understand, you used a traditional puller, and not a bolt and liquid?

One thing I have noticed with pullers, regardless if they are for snowmobiles, cars or mopeds, is that the threads on the pullers are very sharp. I think that they are machined at high speed and just in one momentum. So the threads are "high" and sharp, and above that painted, so they don't really match the threads where they are suppost to fit.
They are often very hard to screw in to the object (clutch for you) even if you lube the threads. So the pullers often destroy the threads in a aluminium object.
I have learned from my own misstakes, to massage the threads with a "thread file" (sorry for direct translation) to smooth the threads on the puller before use.
But If I have the possibility, I always use a bolt and the oil/water tric.