Honda MT50

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13/09/2009 at 00:03

hi. here's the best one. i had an MT and my mate an MB. 23 years ago. we both had h100's put in( practically a straight swap except that you have to redrill the top bolt(there's only 3)through the head. engine numbers could be a factor if you want to keep as a 50. you can cut the numbers off both engines and swap and tidy, tedious but possible. my mate's did about 96 with an old type micron(welding needed) mine about high 80's until i blew doin a dt125. when i got my head rebored and changed back sprocket for the h100 one was mental. maybe low 90's but could lift off the throttle in 3rd. if anyone needs any help then get in touch.

20/10/2009 at 20:48
hi I have found a site that is from a mag from the time of the mb50. they have tryed t6 get 60mph out of it, I think they managed 55mph but thats still very fast for a 50cc bike. heres the site : 
18/11/2009 at 16:36

Hello ... I've just bought an MT50 and I suspect that the oil pump is not working.

Does anyone run their 'ped on premix ?

 And if so what ratio oil to petrol ?

 I have heard that a larger jet is required if running premix ..

 Any ideas which jet to use ?

Thanks in advance for any info ....

23/11/2009 at 16:27
there's no easy way to derestrict it fully,swivel usb
24/11/2009 at 10:12

We have been well and truly spammed

If the Earth is the size of a pea in Britain, then the Sun is a beachball 50m away, Pluto is 4km away, and the next nearest star is in Tokyo. Now shrink Pluto's orbit into a coffee cup, then our Milky Way Galaxy fills North America

24/11/2009 at 21:58

You CAN run many 2-strokes on pre-mix, but those designed to use oil injection generally last much longer with it,'cos it tends to be injected in via the places it needs it most.

By the time you've finished pratting about increasing jet sizes and changing plug grades to compensate, and possibly replacing the piston until you get it right, you'd be a lot better off just sorting out the oil pump in the first place.

What makes you think the oil pump's not working? If it's not using any oil could it just be blocked oil feed lines? Bad adjustment?

03/02/2010 at 13:02
Hi what would you say is the most easy and quick way to get an mt50 to do more than 35mph? replys would be much appreated thanks.
03/02/2010 at 14:27
My 1976 Suzuki AP50 would do 190mph. And I'll thump anyone who argues.
21/03/2010 at 11:29

I have a Honda mt50 1992 i put different sprockets on it, a carb off a 125, big one exhaust system and a big bore kit and it goes about 55mph

try all these haha

16/06/2010 at 20:37

hi there

i have a honda mtx 85, i not sure about it history but i was wondering if any of you know what fuel mix to rn it on, quik reply many thanks¬!

31/07/2010 at 18:01
Hi guys,

I am noe 34 but the Honda MT50 was my first ever bike, and I want to get one again to relive my youth Any advances on uprades since the last couple of posts on here? I can't wait to try all of the advice above and see how it changes the performance/speed of the thing! They are actually quite expensive to buy now you know!

I have read about a 'powerbox doppler' but have absolutely no idea whatsoever as to what they actually do, can anyone enlighten me?

Many thanks!
08/09/2010 at 20:54

hi all, i have recently bought a honda mt 50, i have put a 65cc bore kit on it new racing reeds. it starts 3rd kick when cold but when it warms up it doesn't kick start?   (have to bump start it) when accelerating it coughs about 3/4 throttle and when warmed up it doesn't idle very well. i have adjusted both the mixer screw and the idler screw so much. really starting anoy me now.  any help would be great. thanks

28/02/2011 at 21:14
right basically MT 50 first bike/ ped what ever, i am new to bikes, i cannot find out how do you change the oil input into the fuel? and i dont know about all you others but my MT 50 smokes like a bitch help would be appreciated
20/03/2011 at 11:53
Hi, i've just started restoring a 1980 MT50, i'm pretty sure it has a big bore kit fitted and is otherwise pretty much standard. any advice/tips on how to go about this or where to source parts etc greatly received.

Thanks in advance

22/03/2011 at 20:02

@studly many of the euro tuning sites carry parts for these. My fav is , has many parts too but shipping is a bitch from there. Ebay uk is great and as is ebay germany as they has the mt8 80cc over there.

@mt50boy  did you run in the new cylinderkit when you got it? did you rejet the carb to suit the new big bore kit, plug chopping etc? If not you need to google or search the forum for both these things Also when tuning the air screw you should be using very very small changes and then riding to feel the difference, it should be able to start at either end of the adjustment as long as the jetting is correct.

 @malakite i think the powerbox is a small chamber which you plumb into your inlet manifold after the carb to smooth out intake pulses, also called a boost bottle? If so then their effectiveness is dubious, i remember my rg250 and also my dt200r both had them from factory, so their could be something to it

07/06/2011 at 18:23

Hello, I've read most of the replies here, and agree that the Honda MT5 / MB5 is one of the hardest to destrict. The UK spec bike has a smaller carb than the US/EU model, which is the main restriction. (We hired an MT5 whilst on holiday in Corfu in 1989, and we got it to do 50 mph 2 up!) If you know a competant welder, the front pipe of the MT5 can be opened up, and the holes in the restriction cone inside can be made bigger. You need to leave the cone in as it provideds the back pressure. (You will need a competant MIG welder to do this mod), there after you need to change the tail pipe for Gianelli or something similar. I ran a Jamma on mine. Standard it did 33-35 mph. After these mods, we got it up to 45 mph. And technically it was still a 50cc. I didn't mess with the gearing; I was never 8 stone, and it only works if you're a really light jockey as the 50 cc motor does not produce enough poke to make changing the gearing worthwhile.  

My mate ran a MT5 with an italian big bore kit (can't remember the name, but I know it cost about £90 in 1984!). He managed to get it to do 55-60 mph, BUT it was shagged in 6 months. The bottom end was not/is not as robust as the Yam equivilents. (although I know someone who did the same with a Suzuki ER50, and had the same problem)

Good Luck !

14/07/2012 at 22:25

dont listen to all these muppets!!!!!!!!!! man has a honda mt5 1989 model fitted with a recondition honda h100 engine and a racing cdi unit, the thing does 75MPH!!!!!! it blows away any moped on the streets keeps up with all the 125's

By the way if you have a honda mt50 and are thinking off putting a honda h100 in it be aware that you need to take the stator plate of the 50 engine bolt it on to the 100 engine and also you need to drill a hole on the top mount of the frame where the engine bolts on any questions mail me

08/08/2012 at 22:04

If you want more power, but keep it all 'honda' and 50cc, get the barrell, head, piston, carb (16mm) from the USA spec MB5. You will also need the inlet manifold (h100 will do) and the airbox to carb and carb to airbox rubbers. Finally, fit a less restrictive exhaust. I used the Euro spec genuine honda pipe and can (marked 'ED'), although the cheap copy Laho front pipe will do the job. It will then nudge 50mph with 15 stone sat upon it!. I also got the USA spec stator, which will allow you to convert it to 12volts. You will then need to fit a full set of 12volt lamps and change the resistor (load shedding one under the headlight fairing) to one from a 12 volt bike such as the SH50 Express. The rectifier (just a diode) should also be changed to a more robust item, again the USA spec one will do the job. Finally a 12volt horn should be used. No need to change the CDI or coil, they will work just fine with 12 volts.

08/08/2012 at 23:22

Now there's a man that knows his Honda 50s!

10/08/2012 at 17:40

Cheers Tappy. Forgot to mention, you will also need a 12volt battery for the 12volt conversion.

If you are on a budget, then the cheepo ebay 60/65cc kits will do the job. You can (should) use a honda H100 carb, or a MBX/MTX80 one. They all line up with the airbox/carb rubbers just fine and work well with the same throttle cable/throttle tube as fitted to the MT. Jetting, start around 115 and go down from there. You will need a new front pipe, a cheepo Laho will work. If you want to retain the airbox, get the unresticted rubbers direct from honda, they are cheap and available. With these mods, you can easily go one tooth bigger on the front sprocket.

The ignition system does retard as opposed to advance the ignition, but for a basic tune dont worry about this. MBX80's etc also retard the ignition, and they go just as well despite this. The CDI's now have the same part number for both restricted and unresticted MT's.

Finally, if your feeling flush grab a van and go to switzerland where you can pick up mb50's which came with the six speed box as standard.


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