Weed Whacker Bike tips

[deacon]

I am starting this thread because I am learning a lot of things as I build the Weed Whacker bike. Some of them might help others prevent my problems and if you have a tip please leave it for me.

So let me start with once you are happy with your mount use red locktite on the threads of the screws in the motor case. Be sure you satisfied with the basic mount.

My bolens whacker has two broken spots on the motor case from vibrations of the case. Actually I am considering just drilling out the next one and putting more substantial bolts and nuts on it next time. That pot alum casing isn't really strong enough to hold up under vibrations I am afraid.

[deacon]

Of all the motors I have used, I do not have one now but have trashed a few perfectly good ones because I was to stupid to understand how to use them correctly, the Ryobi 31cc and 30cc are almost perfect for this application.

They are full sized and have a 3/8 24 threaded shaft. That is the perfect size for the bmx threaded axle peg. I had an alum set that were about an inch in diameter and they were already textured.

If I have to replace the bolens, I swear I am going with one of those that I know runs. Lots of the used ones don't run for some reason mostly carb problems I expect.

I think it is almost impossible to drag start any 31cc engine that is what I didn't know when I trashed the ones I did.

[deacon]

If you are going to buy a junker bike to build to a Weed Whacker bike go with an old mountain bike.

Since you don't need the gears for a motor bike, you can use the controls for your engine and save a bunch of money.

I personally am looking for a rear coaster wheel for the bike so I can have one more brake system. I am pretty sure that I can use the coaster brake chain on the big drive wheel of the mountain bike to stop and start it.

There isn't a lot of pedaling with this setup.

[deacon]

If your motor comes with the short throttle cable connected save it. You can marry it to your on bike control cable and if you front mount the engine you probably won't need an additional spring. If you rear mount it you will need a spring to pull length of cable from the front controls. Once you have them pulled back the carb spring can do the rest so still use the cable on the engines carb if you have it

[deacon]

I found out something interesting today when working on my chainsaw bike. A turkey baster works great to fill those weed eater tanks that aren't quite level.

Well I know it's not much of a tip but it's the best I could do on short notice.

[Ranger]

Is there any solution to fixing the primer bulb? Both of my engines have broken ones. At the moment they are just plugged up but I would like to fix them. I may just breakdown and buy 2.

[deacon]

Thats what I had to do but be careful the ryobi bulb comes in two sizes now. You probably have the larger one. I bought a smaller one thinking it was the right one. I'm not sure how you can tell them apart when you order on line. If you have a supplier in your town pull it off and take it with you.

I did try to use a generic but it was a waste of my time. I once used and ear syringe to pressurize the tank. It worked on an old lawn mower but I don't think it would on a weed whacker.

[deacon]

Something I learned yesterday when the engine flew apart is that the cast aluminum case of a weekwacker can't be abused too much. Okay so that was then this is now. The cast alum case of a weedwhacker can be twisted not just broken so be careful how you mount it.

[Radmanfly]

Hi D,
I recently built two weedwacker bikes. I mounted one engine to a flat piece of 1/8" steel using the four holes around the crank. Had to do some pretty accurate hole drilling and a lot of filing to get it to fit tightly but being mounted tightly to the plastic keeps the vibration from cracking the cast aluminum and the plastic will give before the casting does. This mount plate has a hole in it under the engine used to pivot it for belt slack when I need to clutch. Also a spring to hold the belt tight.

Check out my pics.

The belt drives a pulley welded to the free end of a 10 speed bike hub and the other end ratchets for a freewheel. When engine is running and clutch is out, it drives a bigger gear on the left side of the rear wheel. This gives me the ability to pedal with engine off and clutch out. No belt friction as the 10 speed hub ratchets freely, just the chain goes around but hardly any friction there. A free wheeling gear on the rear wheel would have been better but I didn't know about them until after I built this. I also used turnbuckles to refine the chain tension to eliminate a tensioner there. So far I have logged over 200 trouble free miles and I estimate the top speed on a flat at about 34 or 35 mph. Can't wait to get a speedometer on it to see, but it goes way faster than I can pedal even downhill.

Hope this is helpful, Scott

[gadgetman80]

Hmm.....

Now where did I put that weedwhacker last time I used it?

come to think of it, I have 3 or 4 of those old homelites sitting in the shed. Might have to dig 'em out.