The clutch is slipping sometimes and also has a slight vibration, but not all the time. ? It has only done 4500klm. {Darryl, Tasmania, Australia 2001 Suzuki LT250 Quad Runner 2wd Quad}

The clutch slip and off and on vibration can be caused by quite a few things. The good news is that they are all under the clutch cover, so you can check for all possibilities in a short amount of time.

I do not believe that the fact that you have only put 4500 km on the ATV really matters. It is more the roughness of the terrain, heat and riding style that will wear out clutch components.

Refer to the parts diagram below. All of the numbers in parentheses { } reference items in the parts diagram. I will work from just under the cover, towards the engine. If the first or second item on the list seems to fit the bill, do not stop, keep working your way down the list. It could be a combination of things.

Be aware of the orientation of the parts you remove. You will need to replace them in the same way. Focus on what you are doing and limit distractions. It may be helpful to use a Sharpie or other permanent marker to put a small dot at the 12 o’clock position of all parts or take a digital photo to help jog your memory during reassembly. It may sound silly now, but if you need to order a part it could be a week or more before you are able to install it. Are you sure that you will remember how it goes?

Some possible causes for your problems are:

• The nut {12} in the center of the clutch can become loose. This can cause both slip and vibration.
  
• The clutch plates {14} may be worn and in need of replacement. The first sign of wear is usually slippage, chattering and/or vibration. Your quad has seven drive plates, Suzuki Part number 21441-22A01. You can also purchase them from aftermarket suppliers like EBC and Barnett.
  
• The aluminum basket or primary gear assembly {8} is riveted to the steel gear. The differences in heat absorption and dissipation as well as just normal engine vibration can cause the rivets to become loose or break. When the basket rocks on loose rivets this causes vibration also.
  
• Check the nut {5} under the basket, it can become loose. This can cause both slip and vibration.
  
• Next is the one way clutch assembly {4}. This is a centrifugal clutch. You will see that the clutch basket has teeth on it. Those teeth drive the one way clutch assembly. It has small springs and weights on it. The springs lose tension over time, with lots of use and heat. The hotter the springs get, the softer they get, causing slippage when the engine is hot. The weights are similar to brake shoes. When they are worn, they slip.
  Other manufacturers sell the springs and weights separately, and you can rebuild the centrifugal clutch. Suzuki calls theirs a one way clutch assembly and sells it as a unit, part number 21500-19B21.
  
• Also check the inner race {2} and one way clutch {3} for wear. Although it is less likely that these are causing your trouble, if the one way clutch assembly {4} is badly worn, it could have damaged 2 and 3.
  

We see this problem very often in the Honda Rancher, not so much in the Quad Runner. But then again, I have never worked on a bike from Tasmania.

I hope it turns out to be nothing more than a loose nut. Good luck and do not forget to order a Clutch Cover Gasket, Suzuki part number 11482-19B12.