gearing question

Discussion in 'Performance Mods' started by feelinright, Jan 29, 2008.

  1. feelinright

    feelinright New Member

    Man I'm excited. For 30 years I have been riding bikes competitively but mostly just for fun,bmx freestyle jumping, flatland,road etc. and for all those years I wanted small engine on my bike. I just ordered a kit and then lot's of stuff to make it work good.

    I'm getting a 47 cc engine kit. I can see I would'nt like the whole bolt the huge steel sprocket to the spokes hub flange thing so I got a stanton LHD hub. I never ride bikes unless the are sealed cartride bearing so I got a front hub to match.:grin:

    I realized that now this thing won't start with both sides of the hubs freewheeling so I found a recoil starter and saw a 36 tooth sprocket there that threads onto a LHD threaded freewheel. Perfect, less rotating mass and more speed. I also did'nt like the chain tensioner so I'm getting a 1 speed kit so I can rig the springed arm with a metal chain pulley with sealed cartridge bearing in it.

    Thanks to this forum I picked up alot of ideas to get this thing running smooth. Now I just have to get the bike to put it on. I think I am going to get a hardtail Iron Horse(a cheap $200 one) because I am way over budget on this one.

    Anyways I weigh 145lbs. and my bike is will probably be 45lbs. gassed up with the kit on it. Is 36 a good gear or should I figure out the how to attach the 44 or 48t to a freewheel?????

    All my life I rode bikes fast downhill but never uphill!! I can't wait to get this project running.

  2. azbill

    azbill Active Member

    please post an intro
    it's forum policy
  3. feelinright

    feelinright New Member

    Sir yes sir!!!:shock:

    Posted an intro and got the Iron Horse mountain bike today for this project. As an amatuer framebuilder/wheelbuilder/bicycle builder/rider I am happy that two hundred bucks buys alot of bicycle thanks to our hard working friends in China. Man, here in America I could'nt even buy a good aluminum tubeset for $200. let alone make a fairly decent complete bike.
  4. feelinright

    feelinright New Member

    Got the 36tooh freewheel/sprocket today. It seems odd and I think it will work. The freewheel is threaded inside and out. Hoping it mates up with the stanton hub I ordered for lhd. Check out the pics I painted the sprocket with color shifting paint so it looks good!!
    Is it green purple or blue??? or all the above. I am going to do the hubs and maybe some other stuff this color(s)

    Attached Files:

  5. azbill

    azbill Active Member

    the paint does look cool :D
    with this kind of attention to detail, I can't wait to see the finished ride !!!:D:D:D
  6. feelinright

    feelinright New Member

    Oh yeah finally got this thing running. The build goes like this. I got an Iron Horse hardtail mtb. I installed the starfire 2k 47cc kit on it. I changed the rear hub to a stanton lhd/rhd drive. I used a 36tooth freewheel/sprocket combo and put together a custom chain spring loaded tensioner with aluminum gear with sealed bearing. I changed the front hub to a poverty sealed bearing hub. While I had the wheels apart for relacing I painted the rim, hubs and 36t sprocket with color shifting paint. I filed the engine drive gear to use a bmx 1/2 link chain. I made the front crank sprocket single gear, those small sprockets are useless anyway and used the shifter for the clutch which is easy to get to. I mounted the gas tank to the rear with a Schwinn rack. I painted the engine etc. high temp black to not atract the wrong kind of attention(5 oh). I put a champion plug in it and auto grade fuel line. I had to make a custom front engine mount which I bronze brazed a t shaped braket and steel bars and bolted it to the water bosses.

    It's been alot of work but it finally paid off today. Rode for 4 miles at 25mph and can't wipe this grin off my face. I can't seem to rev out the gear yet. Thinking about an upgraded carb to tune the high end unless someone figures out how to mount a mini turbo on one of these!!! As for the gears I do have a 16 tooth left hand freewheel sitting around but I think it would bog too much unless I get more power!! any Ideas?? I want to keep it under 50cc's for legal reasons.

    Thank guys for all the ideas!!!

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  7. cooltoy

    cooltoy Member

    Great looking bike. Thats how I have my tank but it's in a little zippered pouch for driving under the radar. Also ,love the way you mounted your ignition.
    Other than that I did not understand one word of your post (ha ha ha ). Just goes to show that I should spend more time reading, looking at the pics here and going to real bike shops instead of "Canadian Tire"!
    Sounds like you know your stuff and look forward to more pics from you. I have so many issues with my rear tire. Ball bearings, grease washing out and today, my peddles would not "lock". In other words, I can't peddle my bike to start it, it just spins. Boy, it may have been the coldest day yet and am thinking it froze up on me.
  8. Alaskavan

    Alaskavan Guest

    From what I read, I understand the HT's gain power after break-in. So you might not want to get into too many modifications untill you get a couple hundred on it.
    Oh yeah, good looking build. With my habit of running into bumps I'd be a little nervous about the tank hanging out back there. But maybe you're a better driver than me.
  9. I LOVE that tensioner. That really cleans up the whole bike. It's a sprocket too!

    When you get a chance,could you post the other side? I liked too how you cleared the pedals.

    Nice build,man.
  10. feelinright

    feelinright New Member

    Sure thing. Here is the other side and a close up of the tensioner I put together. Luckily the chain stretched a bit today, just enough to take out a 1/2 link and take the tensioner off. The bike is much dirtier now I've been test riding it in the slushy messed up roads here in Spokane.If there was more light you could see the color shifting parts I painted. I clear the cranks fine and they are standard length 170mm.

    I just ordered a boost bottle, hopefully get some low/mid power from it. I passed on the nitrous. Looking back I should have got the 80/70cc engine as that seems to be the best power upgrade available. I don't understand why pocketbike motor have the same cc and way more power from what I read.

    Live and learn, no replacement for displacement, unless someone made a wankel engine this size!!

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  11. Alaskavan

    Alaskavan Guest

    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.
  12. SirJakesus

    SirJakesus Guest

    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 :)
  13. mickey

    mickey Guest

    Very nice. I also like the tensioner. Did you just drill a hole in the sprocket cover and bolt it through?
  14. feelinright

    feelinright New Member

    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.
  15. feelinright

    feelinright New Member

    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.
    Last edited: Feb 22, 2008
  16. loquin

    loquin Active Member

    Nice setup.

    Where did you find the larger sprocket that fits the Stanton freewheeler?
  17. feelinright

    feelinright New Member

    Ebay of coarse. 2 different guys there are selling the 36tooth with freewheel.
  18. gone_fishin

    gone_fishin Guest

    the best of all worlds..."man & machine" is my favorite aspect of motoredbiking :)

    groovy build, feelinright...and a kick-butt presentation :cool:
  19. feelinright

    feelinright New Member

    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!!
    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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  20. feelinright

    feelinright New Member


    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.:grin:

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