pit bike

Beck · September 20, 2008, 10:06:50 PM

When I was at Speed Week I new I was hooked. I made a list of things I had to have when I came back. One item was a pit bike with power. My wife just got a new bicycle so her old cross bike was headed to the recycle center. Her last 10 speed road bike was still hanging there too. I commented at work that I wished I had an old chainsaw to put the motor on one of these. 2 days later one of the guys brings in an old rusty chain saw. It had been under his deck for about 8 years. I pulled the chain and bar off and had it running pretty quickly. There is a lot of info on the net about powering bikes so using their information about gearing I started figuring. There was no way to gear down enough without a jack shaft. I started cutting and welding. A week later the beast is about done. While test riding today I lost a jam nut for a peddle crank assembly. As soon as I find another It will be ready to really do a shake down.

I should have just gone out and bought something. I have concerns about the reliability of this one. I have been throwing the middle chain. A weeks labor in the garage would have gotten my truck project that much closer to done.

Bib_Overalls · September 20, 2008, 11:21:33 PM

Actually looks a little retro. Cool!

Sometimes a little break is just what the Doctor ordered.

You will be more focused when you get back to the truck.

Don't break your neck.

And I hope your bike does not break three miles down the long course.

Beck · September 21, 2008, 12:08:11 AM

My wife thought I should put on a white robe and go as Doc from Back to the Future.

Riding is easier than walking but...
Walking is easier than pushing your pit bike.

57larry · September 21, 2008, 08:09:57 PM

could you post some more pics. it looks like a great idea

Crosley.In.AZ · September 21, 2008, 08:39:10 PM

Interesting.....

Just today my weed wacker puked. The drive shaft - cable end twisted off at the clutch on the engine. It looks like a huge speed-O cable end that ripped off... I've used it for 5 years , guess I can not complain.

This weed whacker engine is a 4 - stroke 29cc ... not sure it would power any type of bike

Beck · September 22, 2008, 01:06:16 AM

The motor on this one is a 33 cc Poulan chain saw engine. I would guess it to be at least 10 years old. It is 2 cycle. It takes a little while for the motor to get the bike up to speed. The clutch slips quite a bit until the speed comes up. There are just to many sprockets and chains on this thing. My daughter took it for it's 2nd test ride. She fried her leg on the exhaust pipe as she was getting off. OUCH! That's gonna leave a mark!
I think I would have been better to just fix up an old mini bike. The chain saw motors have to rev pretty hard. The 4 cycle briggs style motors don't need the rpm. There is a local store that handles clutches for them. I saw the price for them was about $30. I saw 2 old chassis the other day that might be available. I would just have to find an affordable old horizontal shaft motor.
I saw a used GoPed the other day too.
What I'll do to save a buck.

DRD57 · September 22, 2008, 04:51:02 AM

Quote from: "Beck"I would just have to find an affordable old horizontal shaft motor.

I picked up a couple of 8hp horizontal shaft OHV engines at CostCo a while back for $75 a piece. I've been looking for a cheap mini bike frame ever since.

Crosley.In.AZ · September 22, 2008, 08:37:52 AM

oh . oh..... get one one of those small V-twin Honda motors. About 25 -30 hp on a mini bike... that would be fun.

Some of the Cushman scooter guys use those engines to replace the 1 lung Cushman engine.

GPster · September 22, 2008, 09:38:18 AM

George (Purple Pickup) was working on one a while back. He bought a couple of motors that were soon to be taken off the market because 2 cycles as bike motors was going to be out-lawed. Maybe he could at least give you an idea of their size (might check archives but I have no idea of the subject). There was foreign (French?) type of motorized bicycle that used a friction drive on the front wheel and the motor mounted on the handle bars. Something like this with a tall front wheel may help to off-set the RPMs of a 2 cycle motor and also eliminate the invisible burn points and all the gear re-duction. I had all these plans for my Columbia three wheel bicycle but then I started driving again. Might be cheaper in the long run. Last time I was in Bonneville someone did $1,000.00 damage to my rental car in the motel parking lot. GPster

Cword · September 22, 2008, 01:43:38 PM

Most power bike engines are in the 49 to 90 cc range.
If you look into your local laws for street use you'll often find 50cc as being the point where a "power bicycle" becomes a "moped". Crossing the 50cc marks means licensing and insurance become requirements.
So if anyone asks, my bike is a 49.
George (Purple Pickup) is using a similar kit to the ones my brother and I used on our pit bikes.
I've got some pictures of the engine installation and bike configuration online here;
http://1149.ca/bike

mike

57larry · September 22, 2008, 08:53:37 PM

very interesting. any trouble with the engine running?

Beck · September 22, 2008, 11:32:03 PM

Quote from: "57larry"very interesting. any trouble with the engine running?

I am having trouble starting the motor when it's cold. I had to roatate the motor 90 deg for the installation. When I choke the motor the fuel runs out of the carb to the ground instead of into the engine. Once I get the fuel into it it fires up.