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Old 06-26-2009, 01:24 PM   #1
sho305
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Join Date: Jun 2009
Location: West MI
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Default Cleaning your clutches for more power: How-To, long version

When you have ~10HP the clutches need to work right or you will not get it all. The engine makes the most power in a specific range of rpm and the clutch system is designed to keep it at those rpm, or you get less power. The engine should stay at roughly the same speed as the cart speeds up, until it has shifted all the way, for a stock cart that would be above the 12mph limited speed. Engine rpm will vary according to throttle below that speed.

This seems to be an issue because few of them get serviced. If your cart creeps when you start it, or climbs a hill/tows poorly, or lost its top speed then this procedure could help. This is primarily for a G2 or G9, but many things are similar on other Yamahas. I would recommend you do this before or while you mod the clutches, or after you buy a used cart. You may not have to do all of it, but at least check movement and how dirty it is and grease the bushings. I clean mine every summer if I run it a lot on the trails, and lube it a couple times minimum, but less with less miles. If I run trials I might run it up to 8 hours a weekend. If I just use it close to home then once a season as I don't put near the miles on it. In general you want it clean, then lube the grease fittings once in a while. It takes quite a while to get the inside of the primary dirty, depending on conditions.

Other issues to look for:

G2/9 have a 'tension cable' under the starter pulley that keeps the engine from pulling into the transmission, as it is on rubber mounts. Adjustment of this cable can change how the clutch reacts. It tends to pull harder from a stop with the cable tighter, and will creep at idle if too tight and will lose top speed. Loose or missing cable it may bog starting on a steep hill and will have good top speed providing rubber mounts are all good.

Ramp pucks on the secondary. If they are gone/broken it will not shift smoothly and can not even provide full range of shifting. Will also grind up the ramps.

Excessive sheave wear. The sheave is one half that the belt contacts. Most Yamaha have one steel and the other aluminum. The aluminum can wear from dust and sand so it is grooved or dished in, it should be flat from the center to outer edge of the belt contact surface. This will affect shifting and eventually the belt can wear right through the aluminum so you have holes in it.

Testing the clutches for shifting. You can take a magic marker and make a line from center to outside edge, so that the belt wears the mark off with some running around at top speed. This is an old sled trick to see if the belt goes up to the top (full shift out). When you get top speed it should do this. You can run it in neutral and rev it up a little, but the clutch senses load so it may not do the same thing pushing the cart. You can also pull the primary in/out on the engine, it should move easily and not have too much play up/down. The secondary if you have some strength you can grab the inner side and twist it up the ramps and away from the other side so the belt falls in. With a performance spring you might not. It should turn somewhat easily and smoothly, and slide in with only the spring resisting.

Cleaning and lube of the clutches:

The primary (engine) clutch typically has a cover that needs to be removed, inside you will see the weights that swing out. Newer models have rollers. If the cover has phillips screws you might need an impact driver, they are pretty cheap (the type you hit with a hammer). This is easier to see if you remove the belt, but as you pull the outer clutch in/out the weights will move. Inspect the pins they swing on, they should not have a lot of play so the weight can move sideways or bind. Of course if one is broken it must be replaced. If the clutch is dirty inside, I use brake cleaner to clean it. Then use a quality chain (bicycle, motorcycle) lube or a light oil such as gun or 3 in 1 oil to lube the pins where a weight or link moves. Check the center bushing by trying to move the outer clutch up/down. They have a little play, but if the bushing gets worn too far they move more and can get out of balance. This will cause vibration and noise. A new bushing can be pressed in or a new half sheave purchased last time I checked. Yamaha has discontinued the older model like this, but other places still had parts.

There should be a grease fitting on the outer edge of the clutch to lube the center bushing. Grease it until grease comes out of the bushing if you have the cover off, then remove any extra grease. If you have the cover on put one pump in only and not very often. Always make sure no lube gets on the belt or belt surfaces, clean it off. With the new style clutch ensure the rollers are working properly. That is about it for the clutch, put the cover back on and go to the secondary.

The secondary clutch is pretty simple, the newer ones have a grease fitting near one of the ramps (and older G2 might not); it also has a center bushing to lube. I clean the shaft inside the spring with brake clean first and check condition of the ramps and pucks. Newer style secondaries have a different type of puck also, the old ones they sit in holes and break much easier. Replace pucks if needed, I think clutch must be removed I always did but maybe not. Ensure ramps are smooth. Grease until you see some come out, again make sure none can get on the belt. You can put the brake on and twist and push in the moving sheave if you have a stock spring in there. G1 has double ramps one set for forward one for reverse.

If you have to remove the sheave, you can use a puller or the old school way. If you have to do it that way, take the nut loose and put it on a few threads. Use a steel rod maybe 3/4" by at least 1ft long. Place it between ramps (from under the bumper usually) and hit it hard with a 3lb hammer. Rotate to the next ramp and be sure you are not damaging the hub. It should pop loose this way but if it has been on a long time it will take some work. Do not damage the hub, only strike it in the thick area between the ramps closer to the shaft. If you start damaging it then use a puller. Once it pops loose you can remove it the spring will push it apart. Note the spring hole locations, can often tell by dirt and wear marks as there are three holes it can be in, or take it off really carefully holding the spring. Stock spring you put it on and preload it 120 degrees, each of the ramps is 120 degrees. A performance spring is difficult as it has much more pressure, see instructions from a seller for that, and note it does not use any holes or have preload twist. When you are done the pucks should press on the ramps except for the G1 that does not preload with twist. Note if you don't have the grease fitting, either grease the polished part of the shaft when clutch is apart, or carefully grease it through the spring.

Take a last check and make sure no oil/grease can get on the belt and you should be done. The primary clutch should fall open when you stop, so the cart does not move when you start it.

Last issue is the belt: they are 1 3/16" wide new. Factory says they are good to 1" width and that is true, but you lose take off performance. When you lift a cart or otherwise gear it up this becomes very important. When a belt is 1" on a lifted cart takeoff is poor, with stock 18" tires and gearing this is not very noticeable. If you have a tension cable you might try tightening it a little with a worn belt, but a new one works the best and they last quite a while.

G1 note: The older G1 had a different clutch that is all cast aluminum looking with no steel dished cover. This IMO is a better clutch for offroad but not as smooth on the GC. It can be adjusted kind of like a comet but I will not go into that here. Otherwise find a manual page with it, and lube the moving metal parts as you would with near any comet style clutch. Not sure if you can find parts for this clutch.

Secondary preload note: The purpose of this is to regulate low throttle rpm or shift down. If you preload the spring more the engine will stay at high rpm at part throttle. It will make it more responsive, take more gas, make more noise, but WOT rpm will stay the same. It could cool a little better due to the cooling fan runs at crankshaft speed. It is variable; if you preload a lot it runs at WOT rpm all the time and down to little preload it shifts to low rpm at low throttle. It may not work well with hardly any preload it should have around 100 degrees minimum. The belt can fall into it with too little, causing it to bog badly near stop with a big load. The three holes allow finer tuning of how much preload it has.

When the clutches are working best the engine will change rpm with the throttle not the speed of the cart, until it shifts out all the way. Then the engine will just speed up with the cart, that is top gear more or less, and the engine does not slow until you go back under that speed where it can shift again. So if you were to drag race the engine will run at WOT speed until shifted out, then rpm will gradually go higher until you hit top speed or a limiter.
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