New Kit Clunk, my latest problem.

[jacobn48]

I I'm using a 66cc flying horse epa certified kit from amazon prime. It's a bike berry engine with about 5 min on it. High performance carburetor. Cnc hub adapter 36t. Stock or spring tensioner. My problem this time is clinking when the engine is engaged. I'm using a 41 chain I had I've always used on other engines that I've checked is straight and its not knockling against anything. I considered it being the spring tensioner being mine is the gear version. ( Spring tensioner worked fine on my other engine)
Chain isn't isn't too loose or tight.
When I take off the bike rolls smooth when I let out the clutch it rolls ok when I get it cranked it immediately starts popping and clicking any time I engage the clutch.
The engine idles fine and seems to rev ok. It just doesn't get to speed and Cloncks when it's suppose to take off.
What do you think?

 

[LewieBike]

Did you read my response to your previous thread? Check your output sprocket's teeth, most if not all are machined wrong to mesh well with their chains. They will eventually wear in, *but* will break and wear out your chain before they become worn in, and by that time they're also worn out. Rinse, repeat.

 

[jacobn48]

Did you read my response to your previous thread? Check your output sprocket's teeth, most if not all are machined wrong to mesh well with their chains. They will eventually wear in, *but* will break and wear out your chain before they become worn in, and by that time they're also worn out. Rinse, repeat.

Yes thats a good idea. I'd hate to manually wear out the sprocket. This is a new up to date engine and the drive sprocket is sort of pointy.
Mabe I'll swap sprockets to one I know works?
What do you think about this being a compression problem?
Thi's only happens under load though.

 

[LewieBike]

Yes thats a good idea. I'd hate to manually wear out the sprocket. This is a new up to date engine and the drive sprocket is sort of pointy.
Mabe I'll swap sprockets to one I know works?
What do you think about this being a compression problem?
Thi's only happens under load though.

The engine compression doesn't have much to do with the sprocket's shape.

It's purely an improper tooth profile shape for a sprocket with an chain that wraps around it nearly 180 degrees. They are too square edged at the tip and the chain's rollers are being forced past that square edge at the tip. it helps to give them about a 20 to 30 degree chamfer, about an 1/8" down from the tip.

don't grind down the tip, Bevel each tooth so they engage the chain without having to force it's way past the tips. Also bevel gently at the sides too, so any misalignment on the chain gets ecouraged to slide down the tooth to rest smoothly on the sprocket's cusps. Keep these teeth's shape consistent.

If you have to buy a digital vernier caliper if it helps keep your measurements straight.

 

[jacobn48]

The engine compression doesn't have much to do with the sprocket's shape.

It's purely an improper tooth profile shape for a sprocket with an chain that wraps around it nearly 180 degrees. They are too square edged at the tip and the chain's rollers are being forced past that square edge at the tip. it helps to give them about a 20 to 30 degree chamfer, about an 1/8" down from the tip.

don't grind down the tip, Bevel each tooth so they engage the chain without having to force it's way past the tips. Also bevel gently at the sides too, so any misalignment on the chain gets ecouraged to slide down the tooth to rest smoothly on the sprocket's cusps. Keep these teeth's shape consistent.

If you have to buy a digital vernier caliper if it helps keep your measurements straight.

Will do

 

[jacobn48]

The problem was a combination of the stock tensioner and the drive sprocker teeth. I got a gear from my other spring tensioner and adapted it to the stock bracket. Works ok but is bad on top speed.
My spring tensioner didn't work because my chain would ping against a rear mount stud.
So I ordered a better spring tensioner that fits inside the gear plate with a extra bearing for the bucking bar.

 

[jacobn48]

b

 

[Frogslayer]

Nice bike. Looks like there's so much room for a jackshaft and gears on that!

 

[jacobn48]

Nice bike. Looks like there's so much room for a jackshaft and gears on that!

Thanks it's been through two motors. This engine is much stronger than my China kit but right now its slower because of the issue im having. Gonna post a video
Check back.

 

[jacobn48]

Does anyone know what's wrong? It jerks when you let out the clutch. And it doesn't go as fast as it should, before break in.