Looking to build a bike for the backcountry

[Steve Best]

If you are smarter than average, go 2 stroke. The Grubee 66cc motor is easier to install, 10 lbs lighter and only a little more work to keep alive. What ever the design you pick, this assures it will be 10 lbs lighter and at least 50% more power, and $175 cheaper.

Single speed is simpler and I'd recommend it. Far less complication for the build and for driving it. It is more durable as well. With your stated goals - not looking for speed, just want a trail bike without the heavy pedaling - go for a 56 tooth sprocket mounted with a rag joint on a cheap hard tailed mountain bike with 2" to 2.5" tires. Look the Kijiji ads over well and you can build this bike for less than $300 with a brand new motor.

This bike will do 40-50kph top speed, roll any paved or gravel hill and handle sand if you are rolling at least 10 kph or so. You can build this bike in an afternoon. It will be easy to start (some mid drives can be hard) and easy to maintain. All parts are readily available and cheap. It will also be light enough to lift over a fence. You can upgrade things as you need to as there is no welding or frame modifications. Lightweight, it will roll over sand and trails well. The 56 tooth sprocket gives a power advantage to hills, sand and rough trails, while still giving a decent top speed.

Try it, you'll like it.

 

[brendan714]

Thanks for the input.

Quick question - do 2 stroke engines overheat if they're run for an hour or two straight? I've heard that they run hot and that this could be a problem if you're riding for a while.

 

[Street Ryderz]

Thanks for the input.

Quick question - do 2 stroke engines overheat if they're run for an hour or two straight? I've heard that they run hot and that this could be a problem if you're riding for a while.

They do tend to run hot during prolonged use especaily if at high rpm,That is mostly due to the stock componants not complimenting each other very well and can be fixed pretty easily with not much added expence,The first thing is alot of folks using the stock carb run it lean to get the performance and throttle responce they think it should have and that causes heat,next the stock head could have been thicker more surface area to aid in wicking away the heat and less prone to warpage but since it's not an after market head cures that then set up properly you can ride for an hour or so straight no problem it's still best to moniter it and let it cool down now and then.

 

[Steve Best]

Thanks for the input.

Quick question - do 2 stroke engines overheat if they're run for an hour or two straight? I've heard that they run hot and that this could be a problem if you're riding for a while.

My bike in the photo has a 44 t sprocket on it and would run 40mph (due to mods). On a summer evenings I would often take it on an after supper run that see me travel 100 miles in 3-4 hours. I have not found the Grubee 2 stroke prone to overheating at all. Jetting and timing are important, but even completely stock I found they will run for hours.

If they are overheating it is the sign of a problem. Lean jetting, timing off, not enough air flow, plugged exhaust, who knows? Not experienced it.

 

[Street Ryderz]

My bike in the photo has a 44 t sprocket on it and would run 40mph (due to mods). On a summer evenings I would often take it on an after supper run that see me travel 100 miles in 3-4 hours. I have not found the Grubee 2 stroke prone to overheating at all. Jetting and timing are important, but even completely stock I found they will run for hours.

If they are overheating it is the sign of a problem. Lean jetting, timing off, not enough air flow, plugged exhaust, who knows? Not experienced it.

Steve I dont know if you got lucky and received the rounded end stock pipe in your kit or if you got it after wards but that and your rechambered head and knowing how to jet it properly makes a huge difference.Alot of folks run lean with a stock engine trying to get all they can out of it and hold sustained high rpm,the stock pipes comming with kits right now suck(very restrictive) and just make it worse.And in my experience of late the Grubee (Skyhawk) with the epa pipe is the worst of them all it a shame because their still one of the best engine kits out there.So it does not suprise me when people say its running hot I here it all the time I used to think there must be a air leak or something they dont know about or how to identify but have seen to many where thats just not the case.

 

[Steve Best]

Steve I dont know if you got lucky and received the rounded end stock pipe in your kit or if you got it after wards but that and your rechambered head and knowing how to jet it properly makes a huge difference.Alot of folks run lean with a stock engine trying to get all they can out of it and hold sustained high rpm,the stock pipes comming with kits right now suck(very restrictive) and just make it worse.And in my experience of late the Grubee (Skyhawk) with the epa pipe is the worst of them all it a shame because their still one of the best engine kits out there.So it does not suprise me when people say its running hot I here it all the time I used to think there must be a air leak or something they dont know about or how to identify but have seen to many where thats just not the case.

ST, you are right on all accounts. I did find the stock black EPA catalyst muffler was a power killer and swapped it out for the $20 chrome "accessory" muffler shown in the picture, which works very well. The EPA muffler would add to engine heat, as would any air leak. I leaned down slightly, but not too much, and my largest mileages were done with the stock head rechambered with increased squish area for improved performance. All these things are well documented here and simple enough for a backyard mechanic. Even so, a stock engine will survive long mileages with 32:1 of good good oil and good care.

 

[Deleted member 25783]

I'm looking to build something that I can go on backcountry / offroad trails that I can easily store at home and transport with my bike rack. So a motorized bicycle comes to mind.

I know that I need a great bike to start with, so let's assume I have that.

I'm looking for something that can handle some bumpy / muddy roads and hills. I'm definitely looking for torque over speed.

My question - is a cheap 2 stroke China motor good enough if I upgrade parts? Or is the extra dough for a 4 stroke a no-brainer?

Is the 4 stroke more reliable (important if I'm in the backcountry)? Does it require less maintenance? Can it get up hills in a 4 stroke as easily as a similar cc 2 stroke? Would I still need to upgrade a bunch of parts on the 4 stroke?

Being from Canada (where the exchange rate, shipping and duty from anywhere the USA kills me), the only reasonable 4 stroke engine I found was here: http://www.motorizedbicycle.ca/bicy...lt-drive-complete-gas-powered-engine-kit.html

So the standard junk 66cc 2 stroke kits run $200 - $220 here in Canada, and the 49cc 4 stroke kit runs $375. I wouldn't really want to spend a whole lot more than the $375 plus maybe some minor upgrades (bolts, etc).

Thanks a bunch for any help!

Honda 90 trail is what you are looking for.

 

[brendan714]

Honda 90 trail is what you are looking for.

Is that a motor model or a motorcycle model?
If it's a motorcycle, I have nowhere to store it and no ability to transport it.
A quick google search came up with motorcycles?

 

[Deleted member 25783]

https://en.wikipedia.org/wiki/Honda_CT90

 

[panmines]

4 stroke is the way to go for off-road. more reliable and doesn't scare the deer as bad.

look into electric hub motors to. last I checked conversion kits were like $400

Ah, But you won't deter the bears either.