Beginner01's first build..

[chainmaker]

Looking good. Are you leaving the motor stock?

[beginner01]

Originally Posted by chainmaker

Looking good. Are you leaving the motor stock?

Yes, for now. I will port and polish it someday... just don't have much time ATM

[beginner01]

I've been busy lately, but finally got some more done on the bike.

I'm having many issues and have solved a few of them.

1. Front disc brake alignment. When assembled with the adapter on the fork (203mm) the adapter was rubbing on the brake. I took the adapter to work and milled .040" off the mounting tab points, and it seemed to fix the problem. Maybe the fork I have is junk, or the wheel builders messed up with the hub spacing... but the fit was nowhere near perfect as stock.

2. Clutch. Cut up a beat up old 2-3" Starret .001 micrometer to use for my clutch arm. The hole in the engine faceplate has threads, but I couldn't figure out what it was though I was thinking it was a 5/16-18. I went in there with a 5/16-18 tap anyway, and put a screw in.

I need a stronger spring. The belt will be tensioned as stock, and when I pull the clutch lever the cable will pull the arm away from the belt, releasing tension and allowing it to slip (I hope!)

3. Intake manifold. After hours of searching and researching for a B&S intake manifold designed to fit the 45deg angled bolts, I gave up and decided to make my own. For a short time I was thinking of getting into DIY sandcasting and making a complete part, then milling out the internals. Fortunately I found a couple of scrap parts at work with a flange, 1" OD and hole through, and modified them into two halves of an intake manifold. The japanese Honda knock-off carb I have from thebay has a 1.9" bolt pattern with .854" center hole, set horizontal, and the briggs is an approx. 1.35" bolt pattern with a .812 or so hole set at a 45deg angle. Have fun finding an intake manifold to fit that.

These two intake manifold flanges will be connected by a 1" ID rubber tube hose clamped on both. And maybe glued. I wish I could weld aluminum!

I still have multiple issues to work out.. need a stronger clutch spring, figure out the clearance in the back for gear shifting, and my front disc brake. The inner piston doesn't retract all the way back in (needs cleaning/oiling) and the line needs to be shortened. I guess other issues will arise when I get through these

[beginner01]

Well, I've got most of the bike built up and started doing some first runs this week. It sure is fun to ride around just pedaling it, with the super low sitting position. I'm sure I look funny riding around like that but it sure is fun!

I'm having trouble with practically everything on the bike, though. I solved the intake manifold issue - kept the flange for the carb side and needed a more solid way to mount it.. so I took the original carb, sawed it off about 1.5" from the intake flange.. then mounted it by the bore on a tapered shaft (.7495 to .751) and machined the end of it with a 1deg taper to fit the carb side flange I made last week. Then I put some red loctite and hammered the carb side flange onto the taper... and voila!! an intake manifold that fits perfect and still has the original carb angle and mounting flange, with the bottom screw farther away for easier mounting.


There is a problem with the belt drive. With a 33" belt, the motor will not start as there is not enough slip. A 34" belt will allow the motor to start, but when I let the clutch lever out (tension the belt) there is still too much slip. Seems I need a clutch lever with more throw and a bigger idler pulley. I'm determined to get it working as it is, but I'll do an automatic centrifugal clutch setup if I have to.

Also having some chain clearance issues. I can't use 4th, 5th, or 6th gear as the chain rubs on the inside of the chainstay. Looking for a 3-speed megarange freewheel. Do they exist?

Test running today I got a flat on the front tire... and had to walk the bike three blocks home.. man that was fun


Got some lights as well. Found a 5" 12V headlight and 2" taillight at the auto parts store for a combined $20. Seems like a good deal. Hooked up the headlight to a car battery and it is BRIGHT! Thinking of using a Tung-lin 12V bicycle generator but will have to convert it to DC if I will run an LED tail-light. Just got them today and haven't tried to mount them. More pics to come!