MB5 cylinder on RD50

Magnus Burkal /

Can anyone please measure the bolt pattern on the MB5 cylinders?

I would like to know if the MB5 cylinders fit the RD50M engines, or how much I need to alter the block.

I think it is a great alternative to the RD50 cylinders which is made from cast iron and have serious heat problems when running for longer periods.

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Re: MB5 cylinder on RD50

Dirty30 Dillon /

The MB5's have an asymmetrical stud pattern, and the stroke is significantly different.

Re: MB5 cylinder on RD50

Magnus Burkal /

thanks ;), I know, but I need someone to measure it for me. it is the closest looking cylinder I have seen to the RD50m + the power is better than the original 2.9hp cylinders. I am able to modify a lot of things here in my shop.. and I got all the time in the world because of this corona-quarantine :/

Re: MB5 cylinder on RD50

Blake Totally a real doctor /

What's wrong with the airsal, athena, polini, and malossi options already made for the rd50?

Re: MB5 cylinder on RD50

Why not use a DT80 Cylinder or DT100 ? For that matter Complete engine RS100, YZ100, DT100... or 125! ... So many simple probably near bolt in Yamaha options.

Re: MB5 cylinder on RD50

Magnus Burkal /

Well, mopeds in Europe is different than in the US, if you put on 75,80,115cc on the bike, it is no longer a moped, and you can get a big fine for riding an unregistered motorcycle on the bike path.

If you keep it 50cc it's still a moped.. then you only have to worry about the portable dynos that the police have.

And mopeds are by far the fastest way around Copenhagen :)

Basically I just need a cylinder that fits more or less, 50cc with the reed intake.

Re: MB5 cylinder on RD50

Pushrod Fifty /

Would a radial aftermarket head with more fin area do it for more cooling? Ive seen them on RDs. Also an extra .001 piston/cylinder clearance as long as it's within the spec limits?

Re: MB5 cylinder on RD50

> Magnus Burkal Wrote:

> -------------------------------------------------------

> Well, mopeds in Europe is different than in the US, if you put on

> 75,80,115cc on the bike, it is no longer a moped, and you can get a big

> fine for riding an unregistered motorcycle on the bike path.

>

> If you keep it 50cc it's still a moped.. then you only have to worry

> about the portable dynos that the police have.

>

> And mopeds are by far the fastest way around Copenhagen :)

>

> Basically I just need a cylinder that fits more or less, 50cc with the

> reed intake.

So you think all the kitted mopeds in the states are registered as motorcycles? The only way to tell if it's over 50cc is by measuring the bore. Not gonna happen (edited)

Re: MB5 cylinder on RD50

Magnus Burkal /

I didn't say that, it is just the law in Danmark ;) we do have some crazy laws when it comes to mopeds.

The police in Denmark are allowed to impound your bike if it is speeding. while the bike is tested they are allowed to check the bore and stroke.

that is the main reason for staying 50cc here.. I know the rules are different in states, so are they if I go to Sweden or Germany. but anyway, It has to be 50cc.

Re: MB5 cylinder on RD50

Magnus Burkal /

I have tried with extra clearance, but then there is the rattling from the cylinder.

I often wonder why someone would cast a cylinder of iron, and the cylinder head of aluminum.

The head does have some pretty long fins when compared to other 50cc.

Re: MB5 cylinder on RD50

I've never head of rd50/60 having heat problems even extensively ported or with aftermarket top ends and pipes. Are you taking head temperature measurements? What is your ignition timing set to? I would be inclined to check the timing timing and do a leak down test. (edited)

Re: MB5 cylinder on RD50

Magnus Burkal /

Timing 1,4 btdc.

No temp gauge,

The exhaust port is moved 3mm up,

Mikuni VM20 is fitted,

The exhaust was from a DT50,

sparkplug nice and brown,

but it starts seizing up if driven for more then two hours at 50 mph.

Cylinder clearnce is 0.04mm.

I just rebuild the whole engine but wanted to have a nice aluminum cylinder with better performance and better cooling :)

I think you are right about the possibility of an air leak somewhere. I will test it before running.

Re: MB5 cylinder on RD50

Beach Club Nick /

Buy a YSR50 cylinder, those should fit

Re: MB5 cylinder on RD50

What seat is that in the background?

Re: MB5 cylinder on RD50

Magnus Burkal /

Re: MB5 cylinder on RD50

Magnus Burkal /

Great idea, I will see if I can get a hold of one!

Re: MB5 cylinder on RD50

Re: MB5 cylinder on RD50

5131FB4D-A12E-4D1C-A6C9-9DF2EE895C2D.jpeg

We have next to no laws here in the USA … I have been here 37 for the UK ..

As long as the bikes got a moped plate they don’t care if it’s got peddles or not … what motors in it … how much power ,plus you don’t even have to buy any insurance on any motor cycle here in Florida …

I put a RD350 in a fizzy …. Lot of work would do 100mph in 4th and it was a six speed :)

It used 1 tank full to do 45 miles :)

I got stopped for speeding 79 in a 50 .. the cop said that’s not a moped ….. I said it was ,, I just swapped the motor … he cut me a brake and gave me a ticket for 58 in a 50 mph .. in the EU them socialist bastards would have took the bike and me to cop shop .. 10 tickets and a ban for a year or 2

It’s so commi over there ..

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