GXH50 heavy duty centrifugal clutch simple solution

hondabicycle

New Member
Aug 14, 2011
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Greeley, CO
I have a stage 3 tranny and gxh50 motor on a SBP platform.
I've been looking real hard for some clutch ideas on how and were to get heavy duty springs and how some other ideas include lightening the shoe with a drill by drilling weight out of the shoe.
So after finding that my issue is a little more severe then others due to the 80cc carb and low end torque causing a jerking clutch chatter.
So I am just going to get some washers that will fit under the springs while still allowing the screw to go through. This will cause more tension on the spring creating a solution.
Hope it also works for you. It might work on the G4 tranny also but I don't own one.

So with the added tension the clutch will engage like a 3000rpm heavy duty clutch and allow stopping at stop signs or warm up with the jerking clutch chatter that stalls engines.
 

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The_Aleman

Active Member
Jul 31, 2008
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el People's Republik de Kalifornistan
The stock springs are somewhere under 50lbs/inch. I had problems with early engagement on my stock springs, then another member gave me some 57lb/inch springs he bought from Century Spring, and they did the trick. He likes the 60lb/inch, and I'll prolly switch to them, too. If you google the forums you can probably find more info.
 

hondabicycle

New Member
Aug 14, 2011
63
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Greeley, CO
The stock springs are somewhere under 50lbs/inch. I had problems with early engagement on my stock springs, then another member gave me some 57lb/inch springs he bought from Century Spring, and they did the trick. He likes the 60lb/inch, and I'll prolly switch to them, too. If you google the forums you can probably find more info.
That just does'nt add up after doing some research on the 60lbs/inch J37 part number the wire diameter is .067 which is 1.7mm and the wire diameter from bicycle-engines is 1.8mm diameter.
I also found out that bicycle-engines recommends using washers to increase the clutch release rpm speed.

http://www.bicycle-engines.com/images/honda-cc.pdf

Im not trying to be a know it all but if your counting on number of coils to reach a higher compression well compression is compression as adding washers is adding compression.

I attached the file from century spring.
 

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BE-tech

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Sep 14, 2011
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Bozeman
Hey hondabicycle,

The clutch shown in the link provided is the newer clutch that comes with the 4g kits. This is a different clutch than what comes with the stage III kits.

Stage III kits: Have a "rubber tire tread" looking clutch pad material. They have much softer springs. One can easily pull the shoes away from the clutch hub by hand. I have one here, but I don't have vernier calipers, just a micrometer and I cant get a perfect measurement on it. Looks to be: .056 - .061 inches diameter, which would be 1.4 - 1.5mm.

4G kits: Have a red colored (ceramic?) clutch pad material. They have heavier springs. It is hard to pull the shoes away from the clutch hub by hand. These springs are 1.8mm diameter.

Here are a couple pics, stage III on the left, 4g on the right.

Hope this helps,
Rob
 

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hondabicycle

New Member
Aug 14, 2011
63
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Greeley, CO
Hey hondabicycle,

The clutch shown in the link provided is the newer clutch that comes with the 4g kits. This is a different clutch than what comes with the stage III kits.

Stage III kits: Have a "rubber tire tread" looking clutch pad material. They have much softer springs. One can easily pull the shoes away from the clutch hub by hand. I have one here, but I don't have vernier calipers, just a micrometer and I cant get a perfect measurement on it. Looks to be: .056 - .061 inches diameter, which would be 1.4 - 1.5mm.

4G kits: Have a red colored (ceramic?) clutch pad material. They have heavier springs. It is hard to pull the shoes away from the clutch hub by hand. These springs are 1.8mm diameter.

Here are a couple pics, stage III on the left, 4g on the right.

Hope this helps,
Rob
Yeh thanks Rob,
I was reading this thread which is titled with the words Stage 3 so after going back and double checking I found that OCSCULLY is using a G4. Hes not the OP but the source of info on the Century Spring connection.

http://motorbicycling.com/f37/grubee-gen-iii-gearbox-25359-3.html

So I have a see through ruler and the clutch on the right of your picture and just purchased the Stage 3 a few months ago as I got took for the 4G I bought from heliobikes they never sent it.
So I measure the spring and its about 18mm I cant get a 14 or 15mm mesurement, maybe they upgraded the springs at bicycle-engines as there still selling stage 3.
I did a huge upgrade on my engine so there's alot of torque were as before I didnt have any clutch problem at all with the stock carb and cheaply modified exhaust.
I want to add that the clutch problem I now have is severe it a chainbreaking jerking so I stretched my chains to much and am also replacing them.
So I'll contact bicycle-engine.com and see what they say. If they agree with me that the stage 3 is upgraded springs then I'll need much higher then 60lbs/inch
Thanks you guys for helping me staighten this out. For all I know is the stage 3 is still in production and might have to contact grubee. I contacted grubee before there real cool about sharing info. So I'll let you guys know whats going on.
Thanks Again
 
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The_Aleman

Active Member
Jul 31, 2008
2,655
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38
el People's Republik de Kalifornistan
I bought my 4G from bicycle-engines.com last year in July and it came with the older clutch. Ocscully had the same style clutch.

Mine is nowhere near being worn out (3500 miles), and last time I talked to ocscully, he was on orig clutch, too (over 15k).

The clutch appears to be the same as the Stage III. I have a grenaded Stage III in my toolbox with a clutch.
 

hondabicycle

New Member
Aug 14, 2011
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Greeley, CO
I added a picture of my spring and we can all see that it is the spring like the 4g.
Well bicycle-engines confirmed that the stage 3 comes with the 18mm springs like the 4G.
So I guess I'll go with the wet clutch option. So the stage 3 fits the bill as the g4 dont have the wet clutch option.
 

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Barnfresh

Member
Sep 5, 2011
203
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Nor-Cal
Has anyone else noticed how much this clutch looks like the Martin & Slater aftermarket one they make for the Morini? Looks like the hub is straight bored and broached for the keyway and is missing the racheting teeth for the kicker. Even the pics of the old style and new style shoes show an uncanny similarity.

Martin & Slater :: Welcome!
.
 

hondabicycle

New Member
Aug 14, 2011
63
0
0
Greeley, CO
I looked at there method of adjustment and its a whole new way of setting up a clutch.

Martin & Slater :: Clutch Information

They use spring washers instead of springs. And its for racing bikes.

Real cool stuff.
Thanks Barnfresh

Heres some ebay adds with the stuff way cheaper. I was thinking if I need a clutch later I could get one or spring washers. The top add has the clutch diameter size.
200660788231 KTM50 clutch
370545514758 ktm50 clutch
280779131327 ktm50 spring washers

I already have my bike assembled so I'll measure after next tests. If its the same I could just swap shoes.
 
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