50cc motorcycle questions



Hey Guys, this is somewhat relavent to you guys and I have not found many other people to ask...

I was at one point looking into a motorized bicycle but ended up deciding to get a 50cc motorcycle... Which Ill be picking up in a week or two...

Its a honda MB5, 49cc, two stroke, believe its air cooled, 5 gear etc...

Anyways, ill keep it stock to start but am looking to do some performance mods....

I am looking at increased intake flow, some carb adjustments, a 70cc "big bore" kit and a racing exhaust....


I could possibly do the exhaust without the 70cc kit (although they are designed for the increased displacement) but will the 20cc's make a difference in power?

Ill likely leave it with the increased torque to start but would eventually gear it a bit so it has torque like the stock engine but can get an extra 5 or 10mph out of it...


Also going to put clip ons, a new seat, engine spoiler etc... Ill post a picture later of what I hope to have...

Goes from older standard bike to a small sports bike :)





If I shouldnt have posted this here or on this forum at all let me know...

Its just that in the US 50cc's are a TINY market and you guys deal with them on all your vehicles...

And no, its a motorcycle... Foot peg's with brakes and shifter... No pedals...

Here is the stock bike

And with clip ons, after market exhaust and new seat, that Ill eventually be getting (as well as the big bore kit I am asking about)


So yeah, would I see a big difference from stock 50cc to 70cc big bore kit, intake and exhaust mods and some carb adjustments or would you guys recommend against the 70cc?

They have a $120 import 70cc kit, a $150 "brand name" and a $260 that is the "best" but I'd likely get the middle one...


Active Member
Dec 15, 2006
this thread is concerning a motorcycle so I moved it to the white zone

Large Filipino

Boost bottle.

Mmmm. I wonder if those wheels would fit my bike....maybe the engine and tranny on a rack mount....hand shift off the tranny get it long enough so you don't have to reach around..that whole front end looks like it may fit my frame....it has lights and turn signals...that would mean it has a small generator...
Yes. That bike has lots of cool parts.


New Member
Oct 24, 2008
What is object of your plan? To have a bigger motor displacement to yield more speed power?

Finding the correct parts will be a chore! Taking a Honda Z 50 and boring it to 70ccs is much easier as Honda made both models and parts not only will interchange but are readily available at you Honda dealer. Whereas the MB5 doesn't have a bigger brother to get motor parts from. If you intend to go 80ccs and use CR parts matching carb, piston pin height, and port arrangements will be factors. :sick:

Spending money will be the main thought of your project, whereas you could get a 70 or 80cc motorcycle first and fore go the work of boring and rebuilding. I would guess you have experience in such areas, if not this will be more work learning and making mistakes that cost you more money. :rolleyes:

I'm not being negative towards your goal and I respect anyone who thinks outside the box, and not that this can't be done but what is it worth to you and how much are you willing to spend?:eek:


Active Member
May 20, 2008
WOW - you really brought back some memories!
My first new vehicle was a Honda MB5 that I bought for $498. It was a poor selling model, and I got a 2 year old "leftover". My parents forbid me from having a motorcycle, so I told them it was a moped. (not too far fetched) With the MB5, everything was 50. It had a 50cc engine, would do about 50 tops, and it cost $50 a year to insure back then.

Personally, I'd sell it to a collector and put the money towards a Honda Twin of the same vintage. A 175-250cc Honda TwinStar or Rebel will easily outperform a modified MB5 and parts are a lot easier to get.