Specialized DIY Shifter/Scooterguy

Albula vulpes · Feb 10, 2014

Well here goes the start of it. Got a bike and just ordered the engine.(Honda GX35) Already had the 5:1 pocket bike tranny and freewheel cranks. Already see obstacles but it should be an interesting challenge.

Albula vulpes · Feb 11, 2014

Jump stop? Does anyone have this problem with the Shifter setups? I've got the 5:1 pocket bike tranny which I was going to go with the 12T 410 BMX chain sprocket on it. From there it was going go to SBP 44 tooth Freewheel crank sprocket. On the backside is where I'm contemplating what I should put on. I've heard that many have had problems with the chain jumping off on a small sprocket. I've got a SBP 24 tooth and a SBP 30 tooth. Would probably get better drive ratio reduction if I went with the 24 tooth, but wondering if I would experience chain jump? So I'm considering putting on a 30 tooth instead. What would you put on the 24tooth or the 30tooth and why? Thanks

lowracer · Feb 11, 2014

I have a similar setup on 'The Beast'. I am going from 10T pocketbike tranny to 44T large ring to 24T to 11-34T cassette. The 24T works out better for me. See how I added another chainring to protect against chain drop in post #66. http://motorbicycling.com/showthread.php?t=50454&page=7
-Low-

Albula vulpes · Feb 19, 2014

Thanks, I've only got the 44/24T combo now on the freewheel cranks because my bolts are only long enough to hold 2 chain rings. If I experience chain suck, I've got a 30T I can add on to the outside to try to prevent it, just have to buy longer bolts.

Went to Home Depot/Lowes today and the thickest sheet metal I could find was 16 Guage. Does anyone know if this, and only this will be strong enough to support a Honda GX35 w/Pocket bike tranny using the 5 bolts? Sheet metal would be held to the bike frame with Mc Master Carr Pipe/Tube Mount/Clamps. Thanks

curtisfox · Feb 19, 2014

You don't have a steel supply place there? can get just about any thickness there and a lot cheeper.............Curt

lowracer · Feb 20, 2014

AV,
I only use the 4 bolt holes on the tranny that also go thru into the engine for mounting. The other tranny bolts are for keeping the case together and the case is easily stripped. I use angle aluminum or angle steel to mount.
-low-

Albula vulpes · Feb 21, 2014

Made some progress today on the motorized bicycle. Shaved down the Mc Master Carr pipe clamps so they would fit. Mounted the engine to the 16 Guage sheet metal using the 5 bolts on the pocket bike tranny. Right now I'm waiting on a crank puller from amazon to pull the cranks and put on the SBP freewheel cranks. After that I'm going to have to cut the 16 Guage sheet metal to make it astecicaly pleasing using straight lines only. Does anyone have any idea what a good tool would be to use to cut 16 Guage sheet metal? Would straight tin snips work or should I try a hack saw instead or any other ideas are welcome? Thanks

GearNut · Feb 21, 2014

Tin snips will tend to slightly roll the edge on one side of the cut and also leave a serrated edge. The snip's jaws are serrated and leave the imprint of said serrations.
A hack saw will work, but your arm will pay for it. That's alot of sawing. Use the finest tooth blades you can get if you choose to go this rout.

If you have access to a sabre saw and a large pack of very fine tooth blades it would be your best bet. Use eye and ear protection!

Theon · Feb 21, 2014

1mm cutting disc on the angle grinder?

Albula vulpes · Feb 24, 2014

Got the crank puller in today and pulled the cranks and put on the SBP cranks. It is starting to turn into a motorized bicycle. Here are some pics of where I left it for tonight to ponder the next obstacles I've got to overcome. Thanks for your help.

maniac57 · Feb 24, 2014

You should double or even triple up that sheet metal. 16g is too light in my opinion. It will move under load and make getting a reliable chain difficult.
Maybe a sandwich of stout plywood and sheet metal?
Tin snips will work fine for cutting 16g. There are three color handles, green, yellow, and red. One cuts left, one right, and one straight. Using the correct snip allows straight, perfect edges on your cuts with no further attention, except the straight cut. It usually leaves a slight burr. Use the set that allows you to have all the metal distortion from the snip jaws outside your cut line.

Wickedest1 · Feb 25, 2014

I agree...that metal isnt that thick...some sort of doubled metal samich might work....

Or just go thicker.

Nice progress tho...

Albula vulpes · Feb 28, 2014

You might be right about the 16 Guage metal. I did though decide to use it and used a hacksaw and a bench grinder and got it looking better, after I sanded off the rust with 220 grit sandpaper and gave it a clearcoat of spraypaint. (see picts.)

Where I'm stuck at now is the bottom bracket. It is too short on the drive side of the bike. The first shifter build I did, I created an extension made from a grinded down nut and put on and it gave me the spacing needed. Do you think I should try again or just go to a bike shop and get a longer bottom bracket. What size should I get? Thanks for the help.

Also is my engine missing a part? Is it missing the part that the throttle cable hooks into? Where can I get if you know? Thanks

GearNut · Mar 1, 2014

SBP sells the longer bottom brackets.
Looking at the photo of the carb, besides not seeing a cable attachment I also do not see an idle speed screw.
I do see a U shaped plastic boss that could be used to hold a home made cable housing stop/ adjuster.

lowracer · Mar 1, 2014

AV,
I bought the SBP 153mm Bottom Bracket for my DIY shifter bike. It works great without needing bototm bracket spacers and allows pedaling room on the left side to clear the engine bump. Your engine is definitely missing the throttle pieces. Like GearNut said, you could jury rig it using bicycle shifter/brake cable hardware. You could also make a cable stop further away from the engine and run a longe piece of exposed cable into the throttle assembly. I'd even add a return spring for better throttle response.
-Low-

Albula vulpes · Mar 1, 2014

Thanks guys, I ended up going to the local bike shop and got the longest bottom bracket they had (127mm) It seems like it works fine and I don't have too much shimming to do to line up the sprockets.

Went to a mower shop and ace hardware(where I did find the snap rings, thanks lowracer) but couldn't find a carbuerator cable throttle adjuster. Looks like I'm going to have to go online unless you can look at the picts I took and see if a cable will fit in that hole and then I just run the cable around and put in the socket? Thanks

maniac57 · Mar 2, 2014

The silver thingy with the slot in it is meant to hold the molded throttle cable end. You can simply hook it up with a clamp like the clutch cable on a chinagirl as long as there is room for the clamp.

Intrepid Wheelwoman · Mar 2, 2014

That's a nice and tidy way to mount an engine. Do your knees clear the engine Ok while you're pedaling?

lowracer · Mar 4, 2014

IWW,
On 'The Shifty Beast' my Tanaka 47r powered bike, pedaling isn't necessary. Just gotta remember to downshift into 1st or 2nd before coming to a stop, then the engine can always be in its sweetspot. The pedals are there mostly for show or in case of emergency. Pedaling also turns the chain that is connected to the transmission creating some drag resistance.
-Low-

Albula vulpes · Mar 7, 2014

This thing is awesome. I love riding it with the 34T cassette gear. That gives me a gear ratio of 25.97:1 with a speed of 21mph. It has nice torque in that range. Lowracer where did you get your 10T drive gear at? Is it any good/Does it last as long/well as the fancyscooter 12T #410 sprocket? Thanks

Specialized DIY Shifter/Scooterguy

Member

Attachments

Member

New Member

Member

Well-Known Member

New Member

Member

Active Member

New Member

Member

Attachments

Old, Fat, and still faster than you

Member

Member

Attachments

Active Member

New Member

Member

Attachments

Old, Fat, and still faster than you

New Member

New Member

Member