Dr. Frakenstrom's next patient

[patracy]

I picked up two 1982 Honda MB5's. (it's a full size 50cc street bike) I've torn it apart right now and have a top end coming to rebuild the engine. (along with several other parts) I've entered into the true grits 50cc fun run. It'd be great to have some ADV'ers watch me on the 29th of Oct.

Got it stripped down and started to clean the 25 years of grit and grime off the one with less rust.


Pulled the top end apart on that engine and found this...




Cross threaded spark plug as well..


Atleast the other engine is in much better shape. (I probably could have had it running without a rebuild, but then again, it's possibly using 25 year old parts)

Check out that fat rear tire!


Got a carb torn down and in the vat right now. Been cleaning up all the other parts as well.

I think I'll put the other one together as well. But it won't stay 50cc. Just need to find a CR125 or something...

[GB]

Yikes! You've got your work cut out for ya!

[patracy]

Originally Posted by Gadget Boy

Yikes! You've got your work cut out for ya!

Huh?

I stripped the complete bike down to what you see in about 2hrs. Washed up most of the parts as well. Heck I've even got the engines out of both bikes and the top end apart. Once all my parts get in. I can have one running in about 4hrs I'd say.

Something to do with the fact the engine is held in place by three bolts I guess.

[GB]

Be sure to post pics when the tranformation is complete!!

[KTMRyder]

I saw a kid riding one of those the other day on the highway no less!
kid was tucked in and that little motor was screaming, looked like he was doing 50 or better.

[rich_mc]

See you at the Grits....

I'll be there on a Honda Ruckus.... I've got a buddy with an MB5 and another buddy with a Yamaha RX50L who'll be there with me. Be sure to say hey....

[familyman]

Very very cool. Take lots of pictures as it goes back together. I'm a huge fan of very small displacement bikes, the smaller the better so these must be great! Take lots of pics at true grits as well. Damn it's all so cool.

[Motomech]

Originally Posted by patracy

I picked up two 1982 Honda MB5's. (it's a full size 50cc street bike) I've torn it apart right now and have a top end coming to rebuild the engine. (along with several other parts) I've entered into the true grits 50cc fun run. It'd be great to have some ADV'ers watch me on the 29th of Oct.

Got it stripped down and started to clean the 25 years of grit and grime off the one with less rust.


Pulled the top end apart on that engine and found this...




Cross threaded spark plug as well..


Atleast the other engine is in much better shape. (I probably could have had it running without a rebuild, but then again, it's possibly using 25 year old parts)

Check out that fat rear tire!


Got a carb torn down and in the vat right now. Been cleaning up all the other parts as well.

I think I'll put the other one together as well. But it won't stay 50cc. Just need to find a CR125 or something...

Meat Ball 50's, I know them well.
You deffinatey don't want to try and put a 125 MX motor in it(won't fit anyhow), or even a 80 MX'er. You would lose the lights and with the Flexy Flyer frame you would end up with death on wheels.
A more satisfying approch would be:
Over bore with a KX60 piston, this would bring it out to 62cc.
From an air-cooled CR80, you can use:
The close-ratio 6-speed tranny, bolts right in.
The reed block ASM with boot. You have to clearence the cyl., but it will fit. Use Boysen's, of course. You could try the CR round-slide carb, but it's really too big, A 24m/m flatslide is better. A Mikuni is easier to tune, but a Keihen makes more power.
The CR internal rotor ign. bolts on as well, but you would lose the lighting coil.
The cyl. would need porting, of course and the combustion chamber should be re-shaped using the 1/3 rd. squish band technique and reduce volume at the same time.
A pipe is probably the most difficult thing. I hand built mine, but was never totaly happy with it. An option might be to use a custom pipe made for the Honda NS50. There is a guy in S. Calif. that hydro-forms them. You could contact Calamri racing for more info.
This is the basic formula I used to build my first 50cc mini racer to play around on tracks we made in Az. I think this would have been about 1990. When I got serious and started racing in S. Calif, I had to start over with a different model. The poor frame(for racing), heavy wheels and lack of suitable 18" racing tires were the main issues.
I ended up using these exact eng. mod.s with a liquid-cooled Honda NS50 to create a world beater. That motor made 15 h.p. @ 15,000 r.p.m. and was, for many years the fastest racing 50 in the States.

[Photog]

Woohoo! I had one in college. Used to ride it from Fayetteville to Raleigh on Hwy 401 and around the Spring Lake area.

Loved that thing.

[KTMRyder]

I actually passed my motorcycle test on one, a local kid loaned it to me.
my 500 Interceptor was bit too big for weaving around the tight cone course they had.