DT125R ARCHIVE

superted · DTR Respected Member

3MB00P

MDK · DTR Legend

question is what is your bike doing now with regards to speed and power ?

I think it all comes down to a combination of things to improve a bikes speed no point putting a good topend on if you have a restricted cdi or zaust .

superted · DTR Respected Member

iv put 3rm 20 cdi on me m8 said these barrels are ported better or sumet by Yamaha and cum of a tzr originally and with dep pipe on should be a good upgrade but I don't know if it be worth putting on so thought id ask

zander · DTR Senior Member

Isn't the 3mb00P the tuned/ported topends?? :O

zander · DTR Senior Member

check this out:
dt125r.activeboard.com/t54404549/4dl-tzr-engine-unmaintained/

the P stamped 3mb00 is a tuned/ported topend from Motori Minarelli in italy(..?) .

That should definitly give you alot more power if it's one of those topends
But bigger ports => you'll need a bigger carb, to get optimal gains

AndyYam · Guru

I'm selling a 32mm dellorto carb from a tzr125 4dl which is what these barrels came from. They were made for 125cc race series in italy to compete with the Cagiva Mito and Aprillia RS125.

P does indeed stand for ported. the head is also slightly different. If you're interested in the carb im after £90 delivered.

Calum122 · Guru

I've fitted the 3mbp on my standard dtr. I'm reverting back to the standard setup. Just doesn't run very well on the dtre.

dread123 · Moderator

in what way mate-explain for others please?

Calum122 · Guru

Well i was at a dinner table in a place with no signal.

When i get back i'll go into more detail. But bascially i've not benefitted from any of this porting. And i spoke to a specialist at Yamaha and he said the porting is identical bar the exhaust port being ever so slightly higher.

It's nothing special. It's the sp version that you really want.

Calum122 · Guru

Basically the higher exhaust port means more power in higher revs. But at a certain rpm my ignition is retarded and therefore it's actually worse off. Better with the lower port because the ignition benefits there.

zander · DTR Senior Member

So a CDI suited for those barrels would be needed then too to get any gains?

AndyYam · Guru

The P ported barrel isnt just exhaust port height. its the transfer ports as well im pretty sure. I've got one at home so ill have a good old look and try and measure some bits and get some photos up. It wont run better without a large carb. The 32mm dellorto is a much bigger carb than the standard 28mm carb that the 3mb standard barrel runs. If i were running p barrel it would have to be running a dellorto. I'd also have the head from the 3mb p too and yes a differnt CDI. probably a 4DL. The gearbox in the tzr was also a different set up.

Calum122 · Guru

Right. So my point still stands. A 3mbp on a dtr is crap. Unless you convert it to a tzr setup. Which i do have. I have tzr carb and cdi but haven't fitted it.

And Andy I argued that at Skellerns but the technician disagreed and said it was just the exhaust port that was raised.

AndyYam · Guru

Blimey. like i say id be very suprised. with the powervalve system, raising the port doesnt seem to be acheiving very much.

superted · DTR Respected Member

does anyone know the standard piston is on a 3mb00p as its off a tzr and some one say 56.40 but then they say its a dtr barrel which is 56mm ahhh it gets confussing all i want to do is a get the next o/s wosner piston kit for it

AndyYam · Guru

there are 2 different sizes. the 56.00 standard had a longer stroke. the 56.4 a shorted. if youre getting rebored then you'll get it bored to the piston. If not then measure the bore accuratly.

Calum122 · Guru

I just used a dtr piston mate.

superted · DTR Respected Member

so class it as a 56mm coz it standard and get a 56.50 for rebore

Calum122 · Guru

The 56.40 is for very old dt's. the 54.00 is for the current dt's and the 3mb's run those.

Calum122 · Guru

If! The barrel is on the original bore then yes. Otherwise no

AndyYam · Guru

Think some of the TZR's ran 56.4 too. never measured my 3mb p as I got a rebore.

Calum122 · Guru

Yeah old tzr's and dtr's but the 3mbp is 56.00 I have done the tzr myself.

Victor · Guru

Just get new sprocket's i'm running 13-57, top's out just over 60.

Lift's in third, pulls off in second nice

Could just as easy go up on gearing to achieve higher top speed i did 75mph(on the speedo on a flat surface) before on knobbly's with 16-57

So i bet with higher gearing and better tyre's i could get another 15mph