BIKEMOTORPARTS.COM...Anyone Using?

[5-7HEAVEN]

This is only specific to the BMP kit as that is what I am using but it would probably be the same for other kits that are similar.

What if I replaced my rear 26" wheel with a 20" wheel? I know the speeds would be the same. I think I see some advantages of doing this.

Lower center of gravity as the rider and the engine will be 3" lower. If the spokes on the 20" wheel are the same thickness as my 26" wheel, would they not be stronger as they do not span as long a distance as on the 26"? Also, although I have not totally checked this out, would not tires be a little cheaper and, I have seen some wide slick type tires available in 20". Not that it matters much but the smaller wheel would be a bit lighter as well.

The BMP modifications would be very minimal. Just drill 2 holes a little further up the side supports (3") and there you go.

So, anyone try this already and have there been any problems I did not consider? At first, I thought it might look funny but, I now think it would give a little rake and angle similar to a chopper that has a smaller diameter wheel in the back. And, the seat height would be 3" lower.

What do you all think?

Bill

Bill, because most friction drive housings are short in height, you will only be able to drill 1.25" above the original holes and 1.5" below the holes. A much simpler solution is to shorten the rear struts three inches at the bottom. Drill the new struts BEFORE cutting them. If you ever go back to 26" wheels, just install new struts that BMP sells for $16.95/pair.

HOWEVER, before you cut the struts install the rim and tire you'll be using. When mounting a smaller-diameter rear 26" tire, I've had the quick-release skewer bottom out on the tire while making roller engage adjustments.

With the struts removed, lower the drive housing onto the tire. Push down hard on the housing to engage the roller. Does the quick-release bottom out on the tire? If so, measure how much clearance you need and drill the housing holes that amount above the existing holes.

Sooo, if you drill new holes .5" above the existing holes, you will need to shorten the struts 2.5", not 3".

While you have the struts off, ya might want to cut their tops off. That way, when you loosen the quick-release you can raise the engine housing to clear the struts. You will then be able to pivot the entire drive assembly more than 90 degrees to better access the four engine mounting bolts.

FWIW, Deacon the friction drive fabricator at www.motorbicycling.com uses 20" rear tires. He likes the rake, and it's easier to swing the leg over to hop onto his bike.

Hope that helped.

 

[Pirate88179]

5-7Heaven:

Thanks for your reply. I do not understand what you mean about not being able to just drill mounting hole 3" higher than the original locations on the struts. I have plenty of clearance the only difference would be, the struts would hang down past the mount to the fender mounting holes by some 3". Then, with no other modifications, I can re-install a 26" wheel and be good to go.

I do understand what you mean about cutting the top of the struts off and I think that is a great idea. No need to remove the lock-down bolt assembly, just flip up the channel 90 degrees for cleaning or servicing. Excellent idea!

I just re-read your reply and I think you thought I meant drilling lower holes in the channel. I was proposing to just drill 2 holes in the bottom section of the support struts 3" higher to compensate for the 6" smaller diameter tire. I just looked again and the extra section of the support struts will just go down 3" lower past the mounting holes. No problems, that I can see.

Good to know someone else is running a 20" rear tire. I am 5' 10" and have to raise the seat pretty high for regular pedaling but I always lower it (quick release) as low as it will go for MBing. Being 3" lower to the ground might not make it much more stable, but it might make me feel like it is more stable when buzzing along.

Thanks again for your reply. you should write to James at BMP with your suggested mod to the top of the support struts as I think that is a very good one.

Bill

 

[5-7HEAVEN]

Bill, I reread your posts and see how you intended to drill the supports, not the channel.

 

[5-7HEAVEN]

FWIW, I installed a new BMP housing, since I'm now using a stock muffler. The disc brake interferes with the left strut, so I'm using two Staton single-action rear struts. The right-side strut, I substituted and L-bracket with longer allthread and locking nuts. Also using the quick-release skewer for rigidity.

http://www.staton-inc.com/Details.asp?ProductID=2675


Unfortunately, the GP460 engine is too powerful and rips up the rear tires in less than a month. It even tears up the BMP 1.5" hard rubber friction roller.

Moving on to a Mitsubishi engine. The 460 engine will relocate to another bike with midframe Scooterguy mount.

 

[Pirate88179]

So the GP460 engine has too much power? It is too bad we can't come up with a way to make a better connection between the tire and the drive roller. Were you running 2 of these engines? I would love to do a twin engine set-up like i have seen in your videos. I love redundancy. Let me repeat that, I love redundancy, ha ha.

Bill

 

[5-7HEAVEN]

Bill, I think it's when this engine's powerband kicks in at midrange that the roller REALLY begins to dig into the rear tire. Because the 1.25" BMP roller has a smoother and less agressive contact surface, I'm gonna try that roller again. I used the 1.25" BMP roller briefly but the engine was noisier and really screamed.

As soon as my Scooterguy mounting system is installed, I'll cross over to that system with the 460 engine.


I considered using twin 460 engines, but a single 460 had enough power. Besides, it's MUCH easier to carry a 56lb bike upstairs than my 99lb twin engined cruiser.

With the lighter bike and engine, the twin-engined 460 setup might've weighed 75lbs. However, with TWO finicky carbs, it'd be a double nightmare. With my twin Mits engines, they were so dependable that I never had to mess with them. Roller adjustments and tire changes were all I ever did.

Twin 460's would've come in handy when one engine conks out on the highway, travelling at 35mph and surrounded by cars in rush hour traffic.

Ask me how I know that.