Bogging issue, clutch or carbs?

A

aaroncarp

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Joined
Jan 2, 2019
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14
Location
Bozeman MT
Hi all.
I just got a 2002 Mountain Max 700 from my grandparents, and was able to take it out for the first time over the holiday. It hadn't been run in a couple years and I noticed a few issues I am struggling to diagnose. Here is the background...

When I fire it up, it idles fine (around 1800) but after driving it around and coming back to idle, it wants to idle at 3500 and doesn't settle back down unless I kill the machine and start the process over again.

Then if I ease into the throttle (on flat ground) it seems to move right along normally, however, if I punch it, or if I was climbing/in deep snow it seems to just bog down badly and wont give me any power.

I looked at the belt, and it was sitting about 1/8" under the edge of the primary and seemed pretty loose. I couldn't figure out how to adjust the deflection in the field so I swapped to my spare belt and it seemed a bit tighter. The issues were "better" but not "fixed". I also noticed it was revving really high (8500 at 40mph).

Today I picked up new bolts and 6 shims and pulled the secondary. When I pulled the old bolts, there were no shims, and the ends had been worn completely down to the threads (about "1/16"). When I installed the new bolts with the shims, the belt fit looser than it did before. So I installed the larger shim with the old bolts. It seemed a little tighter. I took it for a spin here and when I punched it, it still seemed like it was bogging down. I couldn't go anywhere with deep snow tonight so I really cant tell if the issue is fixed there. It was still idling really high so I just adjusted the idle screw to get it down to 1500. At idle the track doesn't spin freely, so I think I need to tighten the secondary some more.

Now for my questions:
Is there another way to adjust the belt deflection on the secondary other than new bolts and adding/subtracting shims? I noticed if you turn the sheaves opposite of eachother they start to cam over a little, is that a way to adjust the spring tension? maybe the spring is going bad?

Could the ends of the adjustment bolts be sheared off in the other outside sheave? or is that wear normal?

The bogging down I feel like could just as easily be a fuel issue as a clutching issue. I plan to pull the carbs and give them a good cleaning this week. Is there anything else I should do there?

Does anyone have any idea why I am seeing such high revs? I've been riding for a long time and haven't ever experienced 8500rpm at 40mph, and I've spent a lot of time on this sled when the sled was still my grandparents'. I know if the clutching is screwed up, it can have an effect on that.

Sorry for the lengthy post, I just wanted to be as detailed as possible. I appreciate any help you're willing to give.
 
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welcome!

sounds like the carbs need a total tear down and cleaning for starters. the primary and secondary clutch as well for sticking parts. new primary spring might not hurt too. i would also replace the fuel filter. all pretty standard stuff for getting a sled back out on the snow.

might want to check the bearing behind the secondary and the one down on the drive axle as the grease will dry out over time in them and the wheels too.


check the belt width as they might be at min spec or below.

rpms sound right where they should be for top end but bearings could be robbing the speed.

the helix unbolts so you can adjust the secondary spring tension.

you might want to ask what elevation your grand parents clutched the sled for.
 
Thanks for the quick reply. The sled has been run in Island Park for about 10 years. I would assume it was adjusted to run at 7500ft. I was running it at around 5000ft this last weekend. I downloaded the service manual for it so I can make sure the dimensions are all within spec and that the secondary spring tension is set to factory spec. I plan to take the carbs off and deep clean them this week. I also found a good deal on a new belt so I might pick one up just to have a brand new one.

Would you recommend a full disassembly of the primary and secondary clutches for cleaning? It looks like I might need a lot of specialty tools to tear down the primary? Or can cleaning and spring replacement be done without it? I know a strap can be used to unbolt a Polaris primary to do a basic cleaning and spring replacement, but I don't have experience with the Yamahas.

Do those bearings have grease zirks? or would I need to replace them if they are dried out?

Also, I am not sure that was the "top end" of my rpms. On the flat groomed trail, I backed off at 8500 rpm. I'm sure it would have climbed much further had I stayed on it. I just didn't want to redline the engine.
 
Another question, I'm sure I can find the answer in the service manual too. The secondary seems to be floating on the jackshaft, probably about 1/8-3/16", is this okay? I know some sleds are designed with a floating secondary and others are not
 
Yes you should disassemble both your clutches and give them a good inspection and cleaning.

No special tools are needed to disassemble the primary for cleaning unless you need to change the movable sheave bushing, witch does require special tools to remove the spider assembly from the stationary sheave.

Yes the secondary is designed to float on the Jackshaft.
 
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Thanks,
The manual suggests the Y-W-Y primary spring for my elevation range. So I will get one of those, should I replace the spring in the secondary? Any specialty tools to disassemble the secondary?
 
Sounds great. Thanks for all the help. I'll update here if I am experiencing more issues after going through this stuff.
 
I just removed, disassembled, cleaned , inspected, and reinstalled my brother's clutches in about an hour.
 

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another famous issue with the carbs is the plastic enrichener or choke screw at the carbs will crack and not let the plunger go all the way to the off position---- hope that makes sense-- you will find out when you clean the carbs---but you can easily see this under the hood too....Tod
 
Thanks for all the help. I tried removing the carbs last week. I was working on the sled outside and it was pretty cold so the fuel lines were too stiff and contracted to take off. I am limited on garage space right now, but I'm going to get it inside this week. Hopefully that will help to get the fuel lines off. If not, I'll cut them off and replace them.

I have a new belt, new primary and secondary clutch springs, and new spark plugs purchased, hopefully this little tune up will get the thing ripping again.
 
Does anyone have a trick to getting this primary off? I took the spring seat off and cleaned the clutch with it on the sled. Then sheared one of the spring seat bolts off as I was putting it back on. Unfortunately I cant fit a drill in there to use an easy-out. I either need to pull all the plastics, cut a large hole, or get the primary off. I tried the water/teflon trick 4 times with no luck. I need some guidance. Thank you.
 
aaroncarp said:
Does anyone have a trick to getting this primary off? I took the spring seat off and cleaned the clutch with it on the sled. Then sheared one of the spring seat bolts off as I was putting it back on. Unfortunately I cant fit a drill in there to use an easy-out. I either need to pull all the plastics, cut a large hole, or get the primary off. I tried the water/teflon trick 4 times with no luck. I need some guidance. Thank you.
Click to expand...

https://www.richmotorsports.com/store/yamaha-clutch-puller.html

You need a proper clutch puller.
 
had to do one with a broken clutch puller water and teflon tape. took 48 hours for it to pop the clutch off after we put the sled outside at -40. it was the first time the clutch had ever been off on this sled and it would not come the normal way as it broke the puller when we tried to do it the normal way.
 
Yikes, you're having fun now.
I would buy a clutch puller. It may still be difficult to get the clutch to pop off the tapered shaft even with a puller if it hasn't been taken off in a long time. One trick is to apply as much pressure as you dare with the puller (you'll see what I mean when you get one) and then throw a bag of frozen corn or peas onto the primary shaft between the sheaves. Then just wait. I've never done this, but many say that doing this a lot of times results in their hearing the clutch "pop" off the shaft after 10-30 minutes have passed with the frozen peas trick.
Another method is to use a rattle gun on the clutch puller...but many have concerns about this causing damage to the crank shaft bearing. With that warning being said, I've talked with several folks that have said they've always removed their primary that way and never had an issue. Decision whether or not to do so is up to you. I've pulled mine this way once when it was being stubborn.
Another option is to try to drill out the broken bolt with a right angle drill and then use an easy out. A left handed drill bit can be a big help.
I've also gotten broken bolts out by using an awl and a hammer and tapping on the edge of them with the awl at an angle so that the bolt gets unthreaded out eventually.
Loading the sled up and taking it to a machine shop business is also an option. Machine shop folks have removed a lot of broken bolts and are pretty experienced at it.

I personally would get a puller and try to get the primary off first, and then deal with the broken bolt. A puller is something that you'll use at least yearly to do clutch maintenance and possibly performance upgrades here and there too, I feel they are well worth the investment in getting one.
 
mod-it said:
Yikes, you're having fun now.
I would buy a clutch puller. It may still be difficult to get the clutch to pop off the tapered shaft even with a puller if it hasn't been taken off in a long time. One trick is to apply as much pressure as you dare with the puller (you'll see what I mean when you get one) and then throw a bag of frozen corn or peas onto the primary shaft between the sheaves. Then just wait. I've never done this, but many say that doing this a lot of times results in their hearing the clutch "pop" off the shaft after 10-30 minutes have passed with the frozen peas trick.
Another method is to use a rattle gun on the clutch puller...but many have concerns about this causing damage to the crank shaft bearing. With that warning being said, I've talked with several folks that have said they've always removed their primary that way and never had an issue. Decision whether or not to do so is up to you. I've pulled mine this way once when it was being stubborn.
Another option is to try to drill out the broken bolt with a right angle drill and then use an easy out. A left handed drill bit can be a big help.
I've also gotten broken bolts out by using an awl and a hammer and tapping on the edge of them with the awl at an angle so that the bolt gets unthreaded out eventually.
Loading the sled up and taking it to a machine shop business is also an option. Machine shop folks have removed a lot of broken bolts and are pretty experienced at it.

I personally would get a puller and try to get the primary off first, and then deal with the broken bolt. A puller is something that you'll use at least yearly to do clutch maintenance and possibly performance upgrades here and there too, I feel they are well worth the investment in getting one.
Click to expand...

All great suggestions from mod-it. I would only add that I don't use an impact on the puller any longer because I rattled a magnet loose on the flywheel of a customer's Ski-Doo the last time I tried (after using it hundreds of times without issue).

I would suggest investing in a quality puller.
 
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