gearing question

That tensioner is cool. And they do make a rotory engine that size. There's a post here somewher of one on a go-kart. Impresive.
 
Looks like the 50cc was a perfect size on that bike though, Going 70cc would probably make the engine really tight in there. I had a kings 80 on a mtb similar to yours and it was a pain the arse to get the spark plug boot on and off. Just remember its a bicycle, you dont need tons of power as just about anything is better than pedaling all the time. I'd personally keep the tensioner on there since the chain will probably stretch a bit more over time and I personally dont like the feeling of having much slack in my chain. One of the best builds I've seen! I especially like the idea of using a staton LH freewheel and the HappyTime pullstarter. I bet that makes the ride so much more smooth than the bumpstart configuration. I always pull my clutch in when cruising down hills because the drag from the engine just doesn't feel right. Good for you man! If you ever want to be rid of it I'd be happy to take it off your hands for a reasonable price :)
 
Very nice. I also like the tensioner. Did you just drill a hole in the sprocket cover and bolt it through?
 
Yes I drilled a large hole for the mounting bolt and a small one for the spring. I am having fun with this project now that the hard work is over( I hope). I like the stanton hub and the freewheel set up. I made it up a steep hill the other day on my second try by pedaling my a** off. I like that the bike is fully functional without the motor. A bit heavy for a bike (50lbs ish) but compared to a motorcycle/moped it is very light.
 
Well I could'nt leave this thing alone so I put in an 80(70?)cc engine in it yesterday. I also got a boost bottle and a small dry shot of nitrous and am waiting for a better flowing intake and muffler. I test rode it today and the chain fell of at 30mph. Then the recoil starter broke again so this time I can't fix it and am getting a new one that is hopefully better. I am hoping once this thing is broken in and the bugs worked out maybe I'll hit 40mph. I think with the 36 gear I should be able to do it.

I was wondering if anyone knows of any hop up carbs available with a high speed screw to tune the high end?? I don't like the one size fits all carbs on these things with only an idle speed screw. Both engines I've tried seem gargled and buzy at high rpm. I say high rpm with humor really my mazda rx7 seems to be smoother and higher in rpms than these little motors and thats like 1300cc's. I think there must be alot of untapped potential here.
 
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I made it up a steep hill the other day on my second try by pedaling my a** off. I like that the bike is fully functional without the motor. A bit heavy for a bike (50lbs ish) but compared to a motorcycle/moped it is very light.
the best of all worlds..."man & machine" is my favorite aspect of motoredbiking :)

groovy build, feelinright...and a kick-butt presentation :cool:
 
Well I've been wrenching some more. First i changed the belt tensioner again this time using the stock tensioner and instead of the plastic tensioner I used a skateboard wheel and bearings. I had to groove the wheel so I used a drill like a lathe and it has turned out great. The bearings on the skateboard wheels are about the smoothest bearings on the planet and the wheel is very durable. I've also changed the muffler to dax's upgraded muffler and ported the exhast port a little.

I am also working on attaching a Warlbro HDA 49 carb for a chainsaw. The intake is going to be tricky and I'm waitng for parts(velocity stack/K&N style air filter/modified pocketbike intake for boost bottle). The carb has idle speed and high/low setting which should help tune this thing a bit.

40 mph is my goal still. I have hit 37mph downhill and peak around 32 mph on flatground so I almost there. If this carb mod does'nt work I do have a nitrous kit sitting around!!
:rolleyes:
I found a pic showing the skateboard wheel tensioner. It was fairly easy to do and fairly cheap too just need wheel/bearings/washers/nut and 7mm bolt.
 

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update

Got the warlbro chainsaw carb hooked up. I took a performance steel intake and welded a mount to it for the carb. Apparently warlbro carbs need a intake pulse for the fuel pump which was easy with a boost bottle already hooked up just had to add a 1/4"T. Also added the velocity stack and k/n type filter and believe it or not the intake is actually quiter than the stock setup.

I am happy with the carb. It can be mounted in any position and has idle speed, low and high adjustments. My initial test run today got me to 35 mph which is about 5mph better than the stock setup which is good since it was snowing at the time. The venturi size is about the same size too. I've included a pic.:D
 

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