Tune-Up Predator 79cc 4-Stroke

This is a "Sikk Bike UFO" (black on black). Steel frame. With disc brakes and a hub-shifter they are ~$400.

I can not recommend the hub-shifter because I just spun mine out and now need to rebuild/replace the rear-end.

This bike also has forward-facing drop-outs and that has been an issue with the torque (see other post).

Another thing, there's not as much space as it seems. I added a wide crankset so I can reach the pedals. Any wider and I couldn't turn. Still, my legs are very close to the exhaust and gears. I think a larger motor would be too wide and also unnecessary. I can pull the trailer w/ 75 lb. dog at 35 mph with no trouble and the governor attached. The rest is the gearing. I could get it up to 55, 65, whatever but I don't need that.

As you can see above, I don't even have room to get the plug out. The mounting plate I bought uses a little more space than it would need if I made it custom. Then it could sit lower and that would be better. If I were to make a custom mounting plate, I could also tap-out the other oil fill plug and then tilt the whole thing to make better use of the space. As it is, I have it sitting flat.
 
most mx guys when they change to high flow filter have to go up (richer) sometimes as much as 10 jet sizes!when I rebored my cns and put hp filter stock jet was a 68 and now runs a 82 so yes very restrictive stock form.
 
This is a "Sikk Bike UFO" (black on black). Steel frame. With disc brakes and a hub-shifter they are ~$400.

I can not recommend the hub-shifter because I just spun mine out and now need to rebuild/replace the rear-end.

This bike also has forward-facing drop-outs and that has been an issue with the torque (see other post).

Another thing, there's not as much space as it seems. I added a wide crankset so I can reach the pedals. Any wider and I couldn't turn. Still, my legs are very close to the exhaust and gears. I think a larger motor would be too wide and also unnecessary. I can pull the trailer w/ 75 lb. dog at 35 mph with no trouble and the governor attached. The rest is the gearing. I could get it up to 55, 65, whatever but I don't need that.

As you can see above, I don't even have room to get the plug out. The mounting plate I bought uses a little more space than it would need if I made it custom. Then it could sit lower and that would be better. If I were to make a custom mounting plate, I could also tap-out the other oil fill plug and then tilt the whole thing to make better use of the space. As it is, I have it sitting flat.
Width isn't too much an issue, I like it big too, just feels nice.

I wonder how hard it would be to get the frame for this bike, I have a kinda crazy idea for a larger motor, maybe give a double frame a shot and weld them up nice. Crazy maybe but not too crazy.

I think it would be a fun build, I already have a bike that needs a motor but that's not really important lol, can't fit a 4 stroke in it...
 
My bike started running poorly so I added a high-flow air filter and re-jetted the carb. Now it runs even worse.

Ideas, help, suggestions?

Here's a video:

When mine started doing that it was the stupid float. But yours has not yet started to overflow. But it is worth a look. I am going to eventually get a better carb than stock.
 

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Cozmik, I cleaned everything real good and put new gas in it and now the motor runs fine again.

However, I spun-out the freewheel on the 3-speed hub. I'm not sure how I'm going to resolve that issue. I was thinking about doing a left-side direct drive like you have. How's that working out for you? What gear ratios are you using?
 
Cozmik, I cleaned everything real good and put new gas in it and now the motor runs fine again.

However, I spun-out the freewheel on the 3-speed hub. I'm not sure how I'm going to resolve that issue. I was thinking about doing a left-side direct drive like you have. How's that working out for you? What gear ratios are you using?
Internal hub?
 
Yeah, Sturmey Archer SX-RK3

The manufacturer was less than helpful. "Our hubs don't work with motors." ...which is a ridiculous response. They should have said, "Our hubs can only tolerate the smallest amount of torque." ...or something like that because the fact that it's hooked to a motor seems irrelevant to me.

Even if I put a fixie hub won't help because that would still need a freewheel connected to the drivechain. That is why I'm thinking a left-side fixed drive might be a better idea.
 
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