2 stroke clutch on 4 stroke motor

[zhall822]

I've searched on here for a few weeks and haven't been able to find anything on this, so if I missed something, please redirect me.

I recently acquired a 1983 Yamaha g1. I have a hf 346cc motor I want to put in it. I ordered the tapered clutch adapter and clutch puller from ccp yesterday.

Since the drive clutch is weighted and operates by centrifugal force, will it engage properly since 2 stroke motors turn higher rpm's than 4 strokes? I've heard of people drilling holes in the weights to make them lighter. Has anyone used one of these clutches on a 4 stroke?

[1989Marathon]

The clutch will still engage and shift out at the same rpm it did on the G1. The only difference will be that the 4-stroke will likely not turn as many rpms as the G1 motor can. You will also lose reverse if you run a 4-stroke on a G1 rearend.

[zhall822]

Right, but will changing the weights or the mass of the weights effect speed or acceleration since the clutch was designed for higher rpm?

I'm sure it will work ok, but I don't want this thing to be a slug.

[bronsonj]

Yes, changing the weights will affect the performance of the clutch. I think Sho305 posted about that not too long ago, but it might have been someone else.

I have not modified the springs or weights in a clutch so I can't tell you how to go about it.

[sho305]

Yes that is how they are tuned for the application. But the g1 engine turns the same rpm as a 4 stroke cart, yamaha even sold the 4 stroke clutch as a replacement for the original G1 clutch. So it should not be an issue for the clone it will be pretty close to the right rpm. However the larger problem is how good are your clutches, worn clutches don't work that well. I'm replacing mine they are shot, I rebuilt another cart it shifts way better than mine and you get more power. The G1 engine will rev much higher than 4 strokes but the powerband stock is not in that high rpm, its 3-4K like 4 strokes are. The G1 is an old sled engine they re-ported to work like it does sedately in a golf cart....one of the best carts ever IMO, but they are what they are.

What you should do is get it running with the clone and put a tach on it, even a $20 ebay one, when you hit 4-4500 rpm WOT then you are good. Mess with the clutch until it does that, if you have to.

I drilled holes in the weights in my stock g9 clutch to raise the rpm a little. It didn't do much for the stock engine but it helps the clone and it runs better now. But replacing the primary anyway it is about to wear through. The sheave is 200 give or take and 300 for a better tunable clutch so no point in fixing this one.

[zhall822]

Allright. Good info, thanks. Will I be able to tell if it's to worn by looking at? There is noticeable wear, but I don't know if it's normal or excessive. I've read reviews on clutches from CCP where people said it made a huge difference in acceleration and power. I also read on here where somebody lubed their clutch which apparently made it perform better. I'll have to go back and read that one again. I really don't wanna buy anything if I can work with what I have. Especially for $300. My goal is to get this thing functional by the end of the month.

It won't let me post pics for a few more days since I'm a newb, but I have pics of the internal clutch parts in my album on here. maybe you can tell me if it looks worn out. I'll post them in a few days.

[sho305]

The belt and dust/dirt will wear the alum sheaves, they will be dished inwards. Hold something straight like a rule from inside to outside edge to see dish. Eventually they wear through. The weights and pins they swing on can wear, the bushing the moving part slides on can also wear out and get sloppy.

[zhall822]

Thanks Sho. The outer sheave does dish in but less than approx 1/32" It doesn't feel like its close to wearing through. Hopefully there's a fair amount of life left in it.

[DOOmsman]

I have never worked on a clutch like that, but it appears the end of one arm is grinding on something, cheek the the bushings and the pivot pins.

[CharlieN]

The wear in your G1 clutch is not bad at all. The wear on the alloy sheave is less than the average that I have seen and can be machined flat on a lathe should you choose but will not have much effect on performance as is. If it were mine I would fair back the top of the sheave to flatten it.
The weights in the cover do not look bad as well. The power pulses of the engine cause the weights to rock sideways with their bores wearing on the pins first and with advanced wear of the weights wearing through the thrust washers and into the housing. Your clutch shows minimal wear to the sides and a small amount of looseness- rocking on the pins.
I wish the clutch in my G1 was anywhere near as good as yours is.
The pivot pins and the weights are still available should you chose to rebuild what you have. Pricing is around $100 and will climb if you buy additional bits.

The G1 clutch engages about 1600 Rpm and this will vary a bit. I find driving slow the engine will be around 2100 to 2400 rpm and I would expect the clutch to shift out in the 3400 range. Should be fine with the 4 stroke.
Keep in mind the G1 was developed for operating with a 9MPH top speed. The clutch is tuned for that range.
With no governor the G1 engine will rev out but the clutch in stock form will have shifted to high gear pretty early.