DT125R ARCHIVE

Ur better off imo using ur bottom end with 3bn barrel and 3mb head, fresh rebore, wossner piston, head skim, new reeds, and full dep system if u wanna go a bit further, get a bigger carb, some modding will be required to fit the bigger carb, and u gan pretty much fit any engine as long as the drive chain is on the same side, depends on how confident and skilled u are at moddifing stuff m8.

Somone on here once fitted a gasgas 250 2t lump in a dtr ages ago but dont think hes on here anymore think it was robin?

i think but not 100% that the shape of the skirt/ports on the 3bn are less restricive, but the 3bn has a more restricted head, wer as the 3mb barrel has smaller ports cut outs on the skirt restricting flow, but has a much better head wer it has a smooth squish band guiding/forcing the fuel air mix into the center around the spark plug, the 3bn head has a wierd raised lip on the inside so its not guided into the center as much hard to explain much easier with pics lol think iv got some on PB ill upload..

3mb on the left, 3bn on the right but i modded the left one but u can see the gap size in the middle is is a huge difference that cut out is right in front of the carb/ backend of the barrels

 

best bit is that 3bn barrels go for cheap money on fleabay cos people think theyr'e naff  my 1st choice for my dremel attacked barrels for my dt

dave the barrel in the left pic i attacked, on the outer side of the rear skirt, sposed to be flat like the right one but i reshaped it to open it up a bit havnt run it tho still sittin in my garage with about 4 other barrels lol

aye cal thts wat im gonna run wen i come to do the engine on my build, the 3bm head in the pic is the one im gonna use, freshly shot blasted and polished ready for fitment ; )

lol if i had my own dyno.... or buld about 5 dt with all new engine parts n different mods....long

DT-R_bradders wrote:

---

aye cal thts wat im gonna run wen i come to do the engine on my build, the 3bm head in the pic is the one im gonna use, freshly shot blasted and polished ready for fitment ; )

---

 

 

I think me and you have the same agenda sometimes lol. I'll buy a 3BN barrel have it resleeved and fit it. Whilst the bottom end gets rebuild.

?

Yes bradders. Hold on to that mate. Spent my allotted DT funds this month. I've got some Yokes that I'm selling.

What price you looking for as well?

dunno m8 tenner plus postage? n yea will run fine on re altho u might need a pv from the 3bn as i think the shape is slighly different plus the end part wer the servo drives it is different, pv i dont have soz

Thts well interesting that the Bn barrel seems to give more performance but the mb head is better. So you have put the two together? I thought that the heads where interchangeable but the barrels couldn't be switched over as the mb engines have a slightly shorter crankshaft??
Makes sense that the barrels on the Bn have more power the power valve is so much bigger I couldn't believe it!

I wouldn't have thought their crankshafts would have been shorter. It's fairly generic the physical components of the DT.

I've got no real desire to mess about like that. I would mean spending a fortune on finding the right CDI wiring loom.

I was just interested. If the barrel off a 3BN fits on the bottom end from my 2005 RE

Hmm, the 3bn has a slightly bigger bore and shorter stroke so I'd of thought if you stuck a 3bn cylinder on a standard bottom end the piston would poke out the top of the cylinder slightly and hit the head? I thought about doing some stuff to my engine but having a look at what wr426's go for I think I'm gonna save up for one of them. You can throw so much money at these engines but in all fairness, it's probably not really worth it lol.

I doubt the stroke lenght is different between the 2 but if that is the case u could always double up the base gasket under the barrel, but theres only one way to find out cal if u get this barrel off me n try it jus see if the piston prokes out top,

Ill be running 3bn bottom end , barrel n 3mb head so it wont affect mine if this was true