off road setup

hey guys, i have a heavilly upgrades Mongoose amasa comp bike (about 1500.00 invested) and recently decided on putting an engine on. I think i have made my mind up on Chris Hills kits at Bicycle Engine Kits, Motorized Bicycles, Bike Engine, Bike Motor, Bicycle Motor kit

but just want to here some opinions from others. I am not wanting to go hardcore off road, but could I still do fire roads, single track that is mostly flat ect? also I will be riding it on my grandfathers farm which is 400+ acres of beutifull montana, he has a paved road for all 400 acres which is his personal road. there is no governed speed limmit on these roads and would like to beable to go a top speed of maybe 45mph so i can cruise at 35-40 in a comfortable rpm range. What tooth sprocket do you suggest? thanks so much

chris is a great guy and think you will be very happy with him and i assume you are from canada. he rides all winter long and can best advise you the set up. if i lived in canada i would be buying my motors from him. he is a member here just go to members list on top and pm him or give him a call. can't wait to here what you go with. i think off road would be a blast with a motor. here is a link to the bike i am going to put a rack mount on. http://motorbicycling.com/f15/my-mountain-bike-67.html

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very cool bike, ya I am just thinking that I want the motor in the center of the bike, being off road you are changing your body position alot and a balanced bike is going to handle better off road, were as what your doing (engine on rear) doesnt affect driving around town.

It will be rough to have a lot of spare power AND 45 mph top speed. 35-40mph '"cruise" on a bicycle is pretty fast....really fast. Beats the bike to death.

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If it ain't broke, and you mess with it long enough, it will be.

My first attemt at a double suspension bike was with the motor on the rear just because it was easier. I never got far enough to have it all together because when I got it mounted I took it down some trails and it was awfull. To top heavy and the center of gravity was all screwed up. Just did not feel right. I'm sure for the pavement it would have been just fine. But I was trying to build a down hill racer. I'm making plans for a new one but this one I will take my time and do it right.

the bike has double track rims, not sure if your familliar with them but they are made for DownHill mountain biking and I have zero doubts on their strength. As for the bike, its all xtr components, and a manitou sherman front fork, its a very sturdy bike that can handle downhill riding, so all its gonna be doing is carrying an extra 40 pounds and going at the speeds it was ment to do so, just I wont be beating the piss out of her. I have another mt bike so im starting to think that im gonna keep this bike with some wide 2.5" street tires (maxxis hookworms) which should handle those speeds no problem. on the staight aways, i would like the bike to beable to go 40mph, I mean its an 80cc engine, i dont think thats to much to ask? but if i did gear it to go 40-45 mph, would i beable to still have decent start up, i mean, when im going up a slite hill will i need to pedal to help her get up it? i really don't know how much power this engine has.

The 80's are really 70's. However, with a 36T sprocket you may hit 40-45 mph. I can't say with full qualification how it will do up hills, since I haven't finished my build that's using the 36T. I would venture to say that it's a road gearing.

With my 44T, 200 pounds of me on the bike and no mods to the engine, I could pull up any hill around here with no pedal assist. Granted I am not in hill country and peoples definition of "hill" can be quite different.

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If it ain't broke, and you mess with it long enough, it will be.

hmmm, well Chris's kit can either come with a 48t sprocket or a 44t, i guess I will get a 44t for now, see how I like it, and purchase a 36t or a 34t sprocket for when im strictly doing street, and for when i do cross country mtbing, i will throw on a 54t sprocket,

ok guys, iv done my homework some more and have been very surprised at what i found. I wish to cruise around on my bike at 30mph, at first I though the 36t could do this no problem, but after further reading it seems that even the 36t to get to 30mph (which i could do easilly) would still be pushing a rather high rpm just at cruising at 30mph, so what does this mean? Should I go to the 34 or 32 tooth sprocket for what im trying to achieve? And please remember that im not driving this on public ways, so I don't care of the 25mph speed limmit for bikes were im from, im driving on private land and can go as fast as i want.

Just keep in mind that the smaller the rear sprocket, the less low RPM power you have.
I find that these motors have no torque/power unless they are really revving. There is no way I can get up a hill unless I have a good head start, giving the engine a chance to wind out.