Primary clutch modification

[racerone3]

I was needing a 1 1/8 clutch for my coot project, and after a few too many beers decided to modify a one-inch clutch I had laying around. (Comet 780) While studying on the project i saw a few things that make me think it started life as a 2 stroke clutch.

Anyway... Chucked it in the lathe and bored the ID out to the size I needed, then broached a new key way. Now that it is installed and in use, I am quite sure that it was a two stroke. My plan is to add some weight to the clutch arms, to lower its engagement speed. Does anyone on here have any experience doing this sort of thing. Any advice or warnings would be appreciated

[Surfer Dude]

Maybe i'm wrong but if it was a 2 stroke clutch wouldn't it of been a tapered shaft clutch? In any case. here is the website I found a while back on clutch weights and engagements rates. If you have never done one of these clutches they are super easy. remove the top 3 bolts by bending the tab out of the way and simply unscrewing the bolts. there is no constant spring pressure on a 780 so no need to worry about the top flying off or anything. once you pull them top three bolts out just remove that bell and inspect for any "deep" grooves where the weights ride. you need to figure out what weights antd spring you currently have. The max factory used Blue weights/blue side cones and purple springs from 1998 and up. which according to the site i've linked would be an engagement of 1,850 rpms. let me know if you need anymore info than that. Don't know how much you were looking for.

http://forums.bajasae.net/forum/uploads/78/QDS-09BajaSAECatalog.pdf

[Joe H]

Hey Race, I gave hydromike some weights for a salsbury a while back that I believe are for a four stroke maybe there is a part # on them. If not try searching for old golf cart parts, I am thinking Yamaha used a salsbury for a while.

[hydromike]

That's the first thing I thought of Joe. I offered him up the weights, but Race is a staunch DIY guy and is only going to take charity if he fails miserably at every other option. Birds of a feather, ay?

[racerone3]

Maybe i'm wrong but if it was a 2 stroke clutch wouldn't it of been a tapered shaft clutch? In any case. here is the website I found a while back on clutch weights and engagements rates. If you have never done one of these clutches they are super easy. remove the top 3 bolts by bending the tab out of the way and simply unscrewing the bolts. there is no constant spring pressure on a 780 so no need to worry about the top flying off or anything. once you pull them top three bolts out just remove that bell and inspect for any "deep" grooves where the weights ride. you need to figure out what weights antd spring you currently have. The max factory used Blue weights/blue side cones and purple springs from 1998 and up. which according to the site i've linked would be an engagement of 1,850 rpms. let me know if you need anymore info than that. Don't know how much you were looking for.

http://forums.bajasae.net/forum/uplo...SAECatalog.pdf

Signs that it had been a tapered shaft were what had me thinking 2 stroke. Thanks for the link. It at least gives me some idea where to start

Hey Race, I gave hydromike some weights for a salsbury a while back that I believe are for a four stroke maybe there is a part # on them. If not try searching for old golf cart parts, I am thinking Yamaha used a salsbury for a while.

Mike already offered me a set. And as he mentioned... I gotta try it myself first.

That's the first thing I thought of Joe. I offered him up the weights, but Race is a staunch DIY guy and is only going to take charity if he fails miserably at every other option. Birds of a feather, ay?

Pretty well sums it up.



Today I made my own set of rollers. More than three times the weight of the ones that were in it, and saw absolutely no change in Performance. Hydromike is sending me a set of true 4-stroke parts to try. I truly believe that adding that much weight should have made some difference. It may be time for me to get educated about speed-sensitive secondary clutches. Perhaps the problem lies there

[Joe H]

I understand the wanting to do it himself perfectly !! There is a whole array of springs for the salsbury and the shape of the dust cover also affects shift... just a little food for thought.

[ARGOJIM]

Brian, are the face angles the same as one of your 4 strokes?

[racerone3]

Brian, are the face angles the same as one of your 4 strokes?

Not a clue! I've had great luck for years just winging it on clutches, and therefore never been forced to learn about them. The Wild wolf is still running the secondary that came on it from the factory with the2 stroke spring. I will look at the face angles on a few other machines and report back.

[ARGOJIM]

Never mind that , watching the tv and typing, Joe is onto something. What I think also was seen is that the driven, in one picture looked to have been a 7/8" or 1" belt similar to the early Attex machines, did you widen it with spacers changing the spring rate? Belt alignment looks off in the pic, but may just be pic.

[racerone3]

Belt alignment is off. I need to space the clutch out from the trany a bit. The belt is 1 3/16 wide, and I didn't change anything on the clutches to accept it. Lubed up both clutches with dry graphite last night, then found that the belt is chunked, so I didn't try it. New belt ordered

[racerone3]

After a week or so of tinkering, and lifting the engine in and out 37 times ( with that much practice I've gotten to where I can unhook it remove it make a clutch adjustment put it back in and have it hooked back up and running in under 20 minutes) I am starting to make progress. Today in the mail I received a new belt and some true 4 stroke arms from Hydromike. Sadly despite the fact that it is the same part number, the new belt is slightly longer than the old one. I removed the engine and tore into the clutch intent on swaping out the arms. Then I took a left turn. Unhooked 1 spring from eaçh arm and put it all back together. This time I was met with some success. Primary clutch closes about two thirds of the way, and the machine has significantly more speed. It is faster in low gear now than it was in high gear previously. High gear at WOT is faster than my arms can keep up with to steer the thing. A few more weeks of tinkering around with things and then I will tear the machine down and send the tubs to the sand blaster

[Noel Woods]

Playing devil's advocate here: why not just get a 4 stroke clutch? Once the clutch is on, you can get Quality Drives to provide the belt, as a matter of fact they have clutches too.

There's enough room (just) in the engine bay to make a slider mount to allow for loosening or tightening of the belt.

[racerone3]

Quick reply is because I'm cheap and had this one laying around. Once i get going on an experiment, I tend to be unable to quit. I will buy proper clutches when I put the machine together for good. The strange thing on the belt is that the one I had fit well, but was a little worn. I didn't expect a new one of the same part number to fit more loosely. I can see where there would be with the Vanguard, but no room for adjustment with the Kohler. shroud is against the rotor on one side, and valve cover is rubbing the tub on the other (and tub had to be notched). I plan to add a link and adjuster to the drive chain, then build belt adjustment into the transmission mount. This will require moving the battery to the rear tub, but I'm fine with that

[Noel Woods]

I think you are on to something with shifting items such as the battery to the rear. The Coot has a weight bias to the front, an easy fix is to put a passenger in the back, but when one isn't available you note the frontal weight. I am thinking about moving the battery and fuel tank to the back.

Another thing I did with my Coot was to elevate the front seat 2.25" by adding wooden blocks to the preexisting seat brace, this gave more space around the engine and allowed it to breathe better, it still puts out plenty of heat up front, but it felt like a heating pad on the butt previously. For the folks up North the stock seating position is probably fine to deal with cold weather, where I live we contend with mostly warm and hot weather.