Need help!!

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Beavinator

New Member
I am looking to put a gas engine on my mountain bike. I want it to be super fast and be able to climb a very steep hill that i live on. Any suggestions where I can get a kit? I see those 80cc kits and they seem a little weak to me! I live in a rural area so cops arent an issue.
 
Beavinator,
You need to do some reading here before building or buying. Generally speaking you build for either high top end speed, or hill climbing ability. That is determined by the gear ratio, sprocket size, you select. In other words, "you can't have your cake and eat it to". You do have one other option which is to install a kit designed to allow use of the bicycle gears to give you the ability to gear up, or down as required. I know of two such shift kits, both available here from our sponsors. Sick Bike Parts LLC - Performance parts for your motorized bicycle FRONT_CRANK_FREEWHEEL_KITS_AND_PARTS_PAGE_1

But as I said at the beginning, read and learn what most of us have done to build reliable motorized bicycles before investing money into the project.

Tom
 
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Well from what I have found sofar, it seems like an 80cc engine from Chris Hill engines is my best bet. I really would like something bigger but there doesn't seem to be anything available.
 
Beavinator said:
Well from what I have found sofar, it seems like an 80cc engine from Chris Hill engines is my best bet. I really would like something bigger but there doesn't seem to be anything available.
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I have one Chris Hill kit and I've been very satisfied with the quality. Yes, 80cc is the biggest 2 cycle engine available for bicycle conversions. Read Chris's information regarding actual displacement of his, and all so called, 80cc engines. The Chinese who manufacture the engines use a different way to measure engine size (displacement) than everyone else. The 80cc is actually closer to 70. Good luck, keep us posted on your project.
Tom
 
If you get a jackshaft kit for it (that sends engine power thru the gears on the bike), you will have the right gears for both hill and flat road.
If you don't get the kit, you have a choice of one engine ratio for hills or a different one for flat speed.
 
Beav, If The Shift Kit Is In Your Budget, It Is Awsum. Turns Bike Into A Motor Cycle. If Installed Correctly, They Are Trouble Free. Imho, Use A 5 Or 7 Speed Cassette On Rear Wheel. The 9 Speed Chains Are Weak. ! also have the 34 tooth rear cog on rear wheel for extra power in low gear. When up shifting from lower gears, let off on the throtle for a second, they bang hard when the chain drops to a smaller sprocket if you hold full throttle. Ron .cvlt1
 
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I recommend the 4cycle greyhorse engine at Harbor Freight .I bought one at sale price, looks like a real workhorse of a engine....not sure if it will fit tho...
 
Beavinator said:
So if I get the Chris Hill engine do you think it will have no problem climbing a steep hill? I am 220 lbs
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Beav,
Think of your bike as an automobile with a manual transmission that can't be shifted. The rear sprocket size (tooth count) determines what gear ratio you are in. The larger the rear sprocket, the lower the gear. The lower the gear, the better hill climbing ability you will have but on the flats the engine will rev high and not be able to pull you as fast. Decreasing the rear sprocket size will give you all round performance but might be too high for a steep hill at your weight. A motorized bicycle not equipped with the shift kits mentioned above is restricted to one gear and that is the sprocket size you select. Generally speaking the 41 and 44 tooth sprockets are standard in most kits and will give you center-of-the-road performance. Increasing or decreasing the tooth count will allow for higher top end speeds on the flats or better hill climbing. If you buy from Chris Hill talk to him about your options. He is always willing to discuss a customer's concerns.
Tom
 
You might need to consider whether hill climbing or speed is the more important to you. As the guys have already mentioned with a shifter kit you have a wider range of performance available to you. With a fixed rear sprocket as used on most kits you need to select the rear sprocket for one area of performance. One thing you might also consider is how fast you want to ride a bicycle. To me the major limiting factor is brakes. Bicycle brakes were never designed to stopl a heavy, fast moving vehicle. My two stroke build will top out just about 30mph and still climbs hills reasonably well. Of course in summer with hot weather I'll have to be careful climbing long hills to prevent over heating the engine.
 
i don't see why you're making it so hard on yourself. you could just get a slower bike, and ride it down hills...
 
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