'84 Yamaha YTM 200 clutch slip

[garykneisl]

I have a 1984 Yamaha YTM 200. The clutch slips a little bit when starting and slips more when going up a hill slowly. When it engages, it seems to grab fairly good and not slip aftewards. If I creep up a steep hill in first gear it sometimes starts to slip halfway up the hill and doesnt want to grab again. I have adjusted the clutch according to the manual. I have not gone into the case to see what the condition of the clutch is, because I need to use it for hunting opener shortly and need it useable. How much slippage is acceptable and normal? Should I try to put new clutches in it before I need it to prevent getting stranded? Any advice would be much appreciated. Thanks

[fabiodriven]

There are two clutches in that machine. A centrifugal clutch and a regular plate-style clutch. My guess is the centrifugal may be worn out if you adjusted the other one, but they both could need replacing. It is an old machine. Some of the Yami gurus will chime in soon I'm sure.

[El Camexican]

How much do you weigh? (you don’t have to answer that) Those clutches work a lot better with 150# than they do with say 280#. With a lighter load the engagement is fairly smooth, but once I get my daughter and I together on my 200 the engagement process becomes a brutal affair.

Basically you have the centrifugal clutch that works like the torque converter in your car and locks up at a specific RPM and then turns the basket of the pressure plate style clutch which is always in a locked position unless you are changing gears, in which case it is temporarily disengaged by the foot pedal actuated rod.

The lighter the load the lower the RPM the centrifugal clutch can lock up at. The more weight it has to move (which is intensified with things like uphill climbing, towing and low tire pressure) the harder it is for the centrifugal clutch to lock up. During this engagement period is when all the heat and wear occur on the centrifugal clutch so you want to avoid “slipping” it as much as possible. The only way to do this is to get your rpm’s up as fast as possible and get that centrifugal assembly locked up ASAP and keep the RPM range high enough that it does not disengage under load. This is done by staying in the proper gear (i.e. low) and trying to keep the revs up when climbing a hill or pulling a load.

So to answer your question, slipping is normal for this trike, especially if you are accelerating slowly and have a couple hundred pounds on the trike, but as far as excessive slipping is concerned can you tell us if say you are on a hill stopped and try to accelerate will the motor be pulled down, or does it rev out without moving the trike? If you are not sure, try this: Get the trike up to operating temp and chain it to a tree, or drive it up against a wall. Put it in 1st gear and ease into the throttle. One of two things should happen A: the engine comes up to a certain RPM, the trike wants to move and can’t, so the RPM seems to stay were it is even though you have your thumb hard into it. (the same as if you put your foot on the brake of an auto trans car and rev the engine) or B: at a certain point the engine seems to disengage from the clutch and rev up as though it is accelerating under a heavy load.

If “A” is the answer it seems like everything is normal and you either weigh a fair bit, or are driving the trike too slow. If it is “B”, then your centrifugal clutch is likely worn-out. It could be the pressure plate clutch, but because of how that clutch is designed someone would have had to be extremely abusive and manipulated the foot shifter a lot to damage it. You’ll get to see both when you open the right side cover.

If you do end up going into the centrifugal clutch keep in mind that it is likely you’ll have a damaged drum as well as the clutches, so it could get a little pricy. Ebay will be your best bet. You may also have to remove a left thread nut at some point, so keep that in mind before you start using an impact wrench on things. I don’t have a photo with the centrifugal clutch installed (What you see in the photo is the pressure plate clutch), but its basically a steel hub with some brake shoe looking pads with springs holding them in place. As the revolutions come up the springs are forced to stretch from the centrifugal forces on the spinning pads and this allows the pads to open and make contact with the metal drum and lock up.

Let us know how your test goes.