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Ok, first it is a China made 50cc Banshee Sho with chrome steel frame, copy of the GRC GP Italian bike w/ Polini clone engine W/C, I have one, 40mm bore x 39mm stroke, 49cc. It comes w/ Cag MT-A2 body work. Someone put a Zocchi Banshee clutch kit on it. You are right the bell is to big, 79.45 - 75.68mm is 3.77mm clearance, it should be 2mm total new. It should have a 78mm bell with that clutch. Robert Brocchi of BZM, Bi-Zeta Motors makes them clutches. I am building a BZM W/C engine right now for my avatar real GRC GP all alum frame made Italy, 690 racing cases and silver stuffed crankshaft the whole nine yards. $1,200 total in parts. My banshee came with a 78mm clutch bell and 76mm 3 shoe clutch. I have a BZM clutch on it now, with different bell housing.
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You have too much space between your clutch pads & the bell, and with them heavy springs and all that clearance might take 15,000 RPMs to fully engage and push you and the bike. That's why you don't have any power to the rear wheel. With that bell you need 78mm OD clutch or lighter clutch springs.
 

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I agree with epr, you can find a almost week working rpm app on your phone. It'll at least give you an idea.

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Discussion Starter · #8 ·
You have too much space between your clutch pads & the bell, and with them heavy springs and all that clearance might take 15,000 RPMs to fully engage and push you and the bike. That's why you don't have any power to the rear wheel. With that bell you need 78mm OD clutch or lighter clutch springs.
Since we're in the UK, these parts are not really available on eBay or Amazon, and a google search doesn't bring anything up either, even over in US or China.

What we did was build an inner ring and attach it.

https://ibb.co/hdc25v

Gap is now 1.93mm.

Hoping this will work.
Also,seems one of the clutch are was really stiff, possibly seized was hardly moving so that's had a good clean up.
Will be giving it a short run tonight to see if it's any better.
 

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Outstanding, Dude I like you already, lol. Making your own parts, that's the ticket. That should work, and yes if the clutch arm is frozen, its not going to work right. Should work a lot better, can't wait to here the results. Have you tried eBay.com/uk., online, in England on the www. try Petrol Scooters, they have a lot of China stuff, in a pinch I have ordered parts from them before and I am in California, USA. A racing clutch for the Banshee crank which has a big taper, not flat shaft like Polini, I believe is made for the stock Banshee Sho bell 78mm, that clutch has a 76mm OD, I believe. The springs lengths have to be the same, dial calipers, a 1/4 turn on the nut either way changes the clutch engage RPM about 400 RPMs, there very touchy, lol. You keep adj. till you find what we call, " The Sweet Spot " lol.
BZM makes 78, 79 and 80mm bells, for racing, you keep three clutch housings and when the new clutch wears enough they change to a 79mm bell, and so on.
 

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Did you press fit the clutch bell sleeve in?? My only concern is when the clutch bell gets hot will the sleeve stay in place, its thinner so hopefully it will expand more than the bell and stay tight.
 

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Discussion Starter · #12 ·
Did you press fit the clutch bell sleeve in?? My only concern is when the clutch bell gets hot will the sleeve stay in place, its thinner so hopefully it will expand more than the bell and stay tight.
Its cut perfectly and pressed in professionally. I didn't whack it in with a hammer. ;-). It's not going anywhere.
The only concern I had was the additional 40grams weight it added. Not sure if that's beneficial or not!?

Anyhow, took it out last night for a couple of hours.

Now it flies. First time I felt the power band. It really goes. Very very quick. :)

Basically, we are gauging the performance of it on a 100m straight and racing against a cheap Chinese bike with a rider half my weight. This is the most technical way we could do it yesterday.

The characteristics of the ride are like this. As a stupid non technical way of explaining it. Feels like there are 3 stages to the ride.

Slow-medium speed takeoff for around 50m.

Feel a jolt, and the engine changes to a different noise kinda feels like a spluttery flat spot however the bike is actually accellerating faster. Lasts for about 2seconds.

Power band actually kicks in and rockets it for around 2 seconds where it does hit full speed.

I would say 50m of slow medium, to 10metres of transitions, to 10meters of pickup allowing it to get to the full speed within 70m.

Now yesterday I played with tightening the clutch springs. I done quarter turns with the aim of getting into the power band quicker. First 8 turns shown the 100m sprint getting quicker. The following 4 turns I think didn't help.

I have a few follow up questions.

1. Does the performance characteristics seem correct?
2. I cant seem to keep up with this Chinese bike until I get into the power band, at which stage I completely blow it away. (Is it just a case of i weight 190lb, Chinese bike rider is something like 120lb?)
3. I have a tachometer. Is there a way to tune the clutch with some technical precision?
4. Is there a way to be always in this power band immediately from setting off or is there always a stage where you are waiting to get into it?

Sorry for the not so technical explanation but that's the best way I could describe it.

I am really happy with the bike now, seems like good money spent. The track we are on mostly is very small though, I would say slow sharp corners at very low speed into short sweeping bends of only up to 40meters long. Would be great to tune the bike so that it could catch the power band throughout this short course.
 

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All the power on these 2 strokes are at high RPMs 8,000 to 13,000 plus. Then there is gearing ratios and carb jetting and tuning. EDIT: How many teeth on your pinion and rear gear. If you are on a small track you need a bigger rear gear for better low end to get out of the corners, got to keep the RPMs up for power.
 

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That's a fact jack, I have a 50cc Banshee Sho, it's a steel frame copy of my GRC GP with cheap chrome, lol.
A real 50cc Polini has polini cast into all the parts even the exhaust muffler. I have a 40cc air cooled Polini I just rebuilt going in my Polini 910 Carena.
A lot of times people put a China Polini in a GRC frame cause they don't have $2,000 for a real polini or BZM engine.
 

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Pictures from this Bike??
The white one is authentic, blue is banshee. You can see the aluminum dull look on the gp and the chrome on the banshee. There is a thread of a guy scraping off the chrome and repainting it. I'll see if I can find it. The banshee is a heavy bike...


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Here >> https://www.ebay-kleinanzeigen.de/s-anzeige/pocketbike-minibike-banshee-bzm/656624213-241-17516

Its a Banshee from a friend. The Frame has Chromefinish--and its a aluminium Frame ! No one in the whole Pocketbike community in Germany has ever seen or hear anything about banshees with Steel Frame....! Be sure--we have a lot of Riders and a lot of them know the Banshee and all other Bikes where used in pocketbike sport.

I dont know what Banshees you have in america... But all Banshees where to find in the net or on Dealers sites have Aluminium frames.
 
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