Opinions on Using Bike Motor?

[Arrowking]

Well I just saw a CL ad for a '80 CB750K motor(and bike if I want it). I want to put it on the frame below. Is there anything I need to know beforehand(a guide to hooking it up if there is one)? Any warnings?

I've contacted the guy and he says that he bought it as a parts bike(off the frame) and needs to get rid of the motor. He told me that there is water mixed in with the oil(guessing from the dipstick). He hasn't tried to start it. Price isn't set, he wants an offer. Any idea of the value of the motor?

 

[Doc Sprocket]

The first thing I'm going to tell you is that a 750 on that frame is a Darwin Award winner waiting to happen.

 

[minichopperfreak]

just see how long that waters been in there for

 

[Arrowking]

The first thing I'm going to tell you is that a 750 on that frame is a Darwin Award winner waiting to happen.

Figured as much. I've been doing a little bit of research and 77hp is a lot for a go kart. I'm guessing strengthening the frame involves a lot of welding?

 

[DS13]

Figured as much. I've been doing a little bit of research and 77hp is a lot for a go kart. I'm guessing strengthening the frame involves a lot of welding?

yes and tires that wont be melted off in first gear

 

[Doc Sprocket]

Strengthening the frame is only one aspect. Every single part must be up to the task- steering, brakes, bearings, wheels, tires- every single bolt, fastener, and bit of hardware must be up to snuff to avoid dying to death.

 

[Arrowking]

Well I dunno about this then. I don't wanna get in over my head with no way out. I think I could do it, but money is the thing holding me back. This teenager is broke.

Yeah, that picture is an old one when I first got started. Tires, kill switch, clutch, etc. have all been updated and added.

 

[exenos]

I agree, that engine would be better suited to a difference project. Mini buggy maybe?

 

[Arrowking]

What's a better bike motor for the frame then(something with a transmission)?

Oh and it has a roll cage now if that matters.

 

[KartFab]

(sorry if this doesn't answer your question, but I would do this instead)

It looks like that kart is set up for a centrifugal clutch. Just buy a 30 series torque converter/jack-shaft for $120 on ebay and save yourself a lot of headaches. The only headache you may get is trying to redo the motor mount so the jack-shaft sprocket will line up with your original sprocket.

Ideally you will probably want to gear the kart to top out at 28-36 mph with that engine.
We can help you out with gearing too! I just made an excel sheet with the formulas in it. It calculated the exact speed that my two go karts travel!

 

[OzFab]

What's a better bike motor for the frame then(something with a transmission)?

Oh and it has a roll cage now if that matters.

It won't matter what bike engine you use, you will need a jackshaft:

With an industrial engine (clone, B&S, Tecumseh, etc) you can run the chain down to the axle but, with a bike engine, the chain will only run straight back due to the casing design.

So, you'll need to run a chain from the engine sprocket backwards to the jackshaft then forward & down from the jackshaft to the axle sprocket

I just made an excel sheet with the formulas in it. It calculated the exact speed that my two go karts travel!

We have one of those here:

http://www.diygokarts.com/speed-calculator.html

 

[KartFab]

We have one of those here:

http://www.diygokarts.com/speed-calculator.html

Nice! I didnt even notice. The sheet I made incorporates torque converters. High end and low end ratios.

 

[desrtrat]

Sorry to go off topic, but what make is that kart? I have a frame exactly like that.

 

[Nodroz]

I have a 4stroke 150cc motorcycle engine with 5 gears and it goes like a blast! Pretty decent low end en the engine is more than powerful enough for me.

Check out my build with videos:
http://www.diygokarts.com/vb/showthread.php?t=18590&highlight=dirt+devil

 

[Arrowking]

The frame says Murray on it, but I'm not sure of the model number.

Nodroz, which engine did you use?

 

[OzFab]

Nice! I didnt even notice. The sheet I made incorporates torque converters. High end and low end ratios.

Sweet, even better

 

[Rustydog2010]

Well I just saw a CL ad for a '80 CB750K motor(and bike if I want it). I want to put it on the frame below. Is there anything I need to know beforehand(a guide to hooking it up if there is one)? Any warnings?

I've contacted the guy and he says that he bought it as a parts bike(off the frame) and needs to get rid of the motor. He told me that there is water mixed in with the oil(guessing from the dipstick). He hasn't tried to start it. Price isn't set, he wants an offer. Any idea of the value of the motor?

Water in the oil isn't a good start either, that could be a blown head gasket or a range of other problems.

As others have said that frame is not suited for something of that power.

 

[Swabbster]

If it runs at full power it will twist that cart into a pretzel!

 

[cumminsbayou4x4]

Those frames flex underneath you pretty bad when you run them off road, the most motor in that frame you could have is may be a 250. I took a chinese go karts swing are and cut some stuff off the back and welded the swing arm to the murray. I have pictures on here of it. I also welded the frame up so no flex.