honda mb5 tuning help?

hey guys any help tuning a 82' mb5 to get all the strength the little motor has? im trying to keep the bike stock so no major stuff like a new motor or anything, just simple things.

Re: honda mb5 tuning help?

Pipe, Boyesen reeds, Mikuni VM20 carb with 20mm intake. Go to (or other places) to get your stuff.

Re: honda mb5 tuning help?

The air filter + air filter hose are really restrictive, so swap those out for a high flow foam filter. Get a good pipe (, the Proma GP they have is a nice pipe. Don't bother for the Homoet Racing or Homoet Special Racing as those are both high rev 70cc pipes, not worth the money unless you get a 70cc kit with it.

This should be getting you high in the 40's, low 50's maybe.

You might want to swap out the carb for a bigger one, say 18mm or 20mm. I am personally very fond of how the KeiHin 18mm performs on a stock MB5, tho the original KeiHin 18mm carbs are a bit pricey.

If you want you can also get a 50cc high compression head. Won't give you much top speed but it will help the acceleration.

That's all the stuff you can easily change. Don't forget to change your jetting accordingly.

Personally I would get a 70cc kit. You won't know what hit ya :P has a cheap one for 50 euro's. That a nice kit for the money, but I'd put in 30 bucks more for the Eurokit.

And if you ever want to go crazy fast, get the Polini 70cc kit with the Homoet Special Racing and a 24mm flatslide carb. That shit's just nuts :P

Re: honda mb5 tuning help?

It all depends on wich version you have.

The bikes in the states were derestricted and should do 50 as is. There isnt really a whole lot you can do to the derestricted U.S. version without buying a kit.

The restricted version can be ported and the reed stops modified There are a few of these restricted bikes around and it is tough to tell them apart.

My first MB5 was slow. It would top out at about 34mph. It was a canadian bike so I am guessing canada got the European restricted bike and some made it across the border.

In comparison my new one tops out around 53 with the stock gearing.

You can try upgearing with a bigger front sproket but it slows the top speed of the bike. But does make it accelerate better. Kind of the opposite of what you would expect... It seems to have the effect of making first gear accelerate longer and fith ends up more of an overdrive on a stock bike.

Re: honda mb5 tuning help?

Стев Браун /

Roald's right about the Homoet...

I'm running one on my otherwise stock MB5. The bike does top out at 58 or 59ish, but I've suffered some significant loss of low end.

I had a Polini on my last MB. I'd like to grab another, but at 325, they're a major purchase.

Re: honda mb5 tuning help?

high 40s' low 50's? i can pull 60 stock.

Re: honda mb5 tuning help?

yeah with mine all i did is add honda oil and replacep the old airfilter i=with a foam pad a my last run was 60 mph its the us version.

Re: honda mb5 tuning help?

yeah the low end is really slow put the little bikes can go. i got my bike last year pretty nice for 40 bucks

Re: honda mb5 tuning help?


I wasn't aware that there were unrestricted versions of the MB5 sold. The European MB5 engines are very restricted. It has a cylinder with small ports, low compression ratio, small carb, restricted air hose, restricted air filter, restricted exhaust and sometimes even a restricted ignition.

So hence my advice to make it faster by replacing all that.

You can still make it faster by replacing all that, but you won't gain a lot of speed if you keep it 50cc.

Re: honda mb5 tuning help?

ahh i think its enough speed i might do a little tinkering with it

Re: honda mb5 tuning help?

It's not for everyone, but I really liked switching to a 15 tooth sprocket up front with everything else stock. I did gain a few on the top end (55), and the low-end drivability was very improved.

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