Motorizing Tandem

TheDeke · #1 09-18-2008, 03:38 PM

Fellow bikers,

I've got a steel tandem (translation: heavy) beach cruiser bike that I motorized with a .35 cc Sears weedeater engine w/centrifugal clutch mounted to the rear wheel via a spoke ring from Golden Eagle. The .35 cc is rather light but it still gets my wife and I up to 20 mph on the straight/level.

Trouble is, it pops spokes. I've gone to 16-gage spokes and the problem seems to have stopped but I'd like a beefier motor. I just received my "China Doll" engine kit from ThatsDax - good price/kit complete, etc. I downloaded installation instructions from their website.

Trouble is I donʼt have operating instructions for how to run the machine after I get it installed. I mean just simple things:

How do you start the engine? Itʼs got a manual clutch, right? So, do I have to keep it disengaged until I pedal up to a certain speed and then release the clutch to start the engine?

If I run out of gas and need to pedal it home, do I need to duct tape the clutch handle to keep the clutch disengaged?

Iʼm installing it on a tandem bike and might need a longer drive chain. It looks like motorcycle-sized chain. After I find out how much more drive chain I need, I probably would need to take it to a motorcycle shop for lengthening, right?

I use the tandem (minus bride) to commute to work (17 miles roundtrip) daily. (My satchet fits on the rear seat.) I'm selling my Jeep DJ-5L and making this bike my primary commute vehicle, so I'm serious about this engine setup.

Any advice about: 1) clutching and 2) drive chain? Thanx in advance.

deacon · #2 09-18-2008, 04:08 PM

The chain is a number 415 also a number 41 will work... you can buy it at a hardware store I'm told. I bought mine from a bike shop. You would need a chain breaker to cut it to size.

The clutch handle may have a lock on it. Some models they say work well, mine was trash and I put a brake handle on it. When I had to pedal it home a mile or so I just held it in. If the one with your kit is not suitable you can buy one with a push button lock that is supposed to be really good.

TheDeke · #3 09-18-2008, 05:01 PM

Thanx, Deacon!

Where could I get the clutch handle that has a push-button lock, any idea?

You say I could get the chain lengthened at a bicycle or motorcycle shop?

Where do you serve as a deacon, Deacon?

**Bikeguy Joe** · #4 09-18-2008, 08:22 PM

If you got your engine from thatsdax, it will more than likely have the locking lever with it.

You can buy a ten foot length of #41 chain at Tractor Supply Co. and also at Graingers, I think.

**Dan** · #5 09-18-2008, 08:34 PM

Deke, way cool! I have a tadem in the works and am making it a pick-up truck sort of deal. I was thunking put the motor at the rear station and get long control cables from Norman. That long a drive chain worries me although some folks have done great things with stretch bikes.

The only limits are imagination. Build a one of a kind!!!!

Great to meet ya and take/post lots of pics!

Saddletramp1200 · #6 09-18-2008, 08:45 PM

Hey Deke, Welcome to the forum! I just built a tandum and will be sending pics, as soon as I can. Those Dax motors are about the best as far as I can tell. I'm still learning tho, Been riding about 47 years, a lot more to learn. We have 2044 members at last I looked. I just shine in Pride with that. Were pretty good, at helping others, just post

TheDeke · #7 10-20-2008, 12:19 PM

I finally finished the install on the tandem. I'm still in the breakin phase but she works great! I have to hold the throttle checked just to keep it under 17 mph. I had to use two of the normal lengths of chain that come with the Dax kit. Also, I installed another chain roller on top to give the long chain some support to keep it from slapping itself. Tomorrow I should have pix to post.

**Dan** · #8 10-20-2008, 12:26 PM

Kewl!!! The Deke, just curious, you put the engine forward?

**Dave31** · #9 10-21-2008, 01:31 PM

Welcome to the forum

TheDeke · #10 10-21-2008, 06:07 PM

Dan,

Yes, the motor is forward, just like a single. Prior to the Dax China Doll, I had a 32 cc Sears weedeater engine mounted on the rear driving a Golden Eagle setup. That engine was just too weak to do much good without straining it. I put that setup on my wife's 24 in. bike. It's taking her a little time to get used to it. But it's a match made in heaven.

For my tandem, I had to buy another length of chain and a couple more chain guards from Dax. It's a lot more quiet than the Sears weedeater. During this breakin it looks like I'll get 150 mpg. But I pedal a lot, too. I put the engine on to make bike riding fun for me again. Albuquerque looks flat but it has serious grades. The valley floor at the Rio Grande is at about 4900 ft. elev. The valley rises to about 5800 ft. at the foot of the mountain range. (The Sandia Mountains which form the easter boundary of the city peak at over 10,000 ft. elev.). The 48.8 cc China Doll is exactly what the doctor ordered. It makes the hills and grades invisible to me.

I hope ThatsDax is reading this. Good product; good installation instructions; happy rider. The local bike shop guys have christened the bike "Frankenbike."

TheDeke