3bn Y-1.......3bn Y-3

[dt125Matt]

Does anyone know the differences between these 2 different heads? Please shed some light... been online looking for some time now and cant tell..

I can see the that one has "fins" o the bit below where it says y-1/3

See pictures below(if ii get this upload right!)

[Calum]

What is the difference from underneath, do they both have the restriction ring on the chamber?

The 3BN is inferior to the 3MB regardless, so I would be on the lookout for a 3MB head, or have that nasty combustion ring removed.

[dt125Matt]

Yeah i have been reading an older post of yours regards the combustion ring... i have these two, so which ever is superior will send for machining. Im going to have to look again because i cant remember who was recommended.

Once i take off the head that's currently on the motor i will update with internal information...
The other difference i can see is the banjo screw location on the thermostat housing.

[dt125Matt]

@calum 3bn 3mb.... is there a superior barrel ?

As under inspection of the pics i took today... and i have a 3bn head (x2) and a 3mb barrel!

[Calum]

I guess I'm more familiar with Y-3. At a guess, it's just an early head. Either way they're not the best heads,

Yeah the common barrels are 3MB. The older barrels 1988 I believe are 3BN barrels. Slightly shorter stroke, bigger bore, and the last heads were 3MB.

3MB Barrel with 3MB head would be a pretty sweet deal if you can get it.

[dt125Matt]

The y1 has had a slight rub with some wet dry multiple stages of grit mounted to a glass panel.

[Calum]

@dt125matt A favourite trick of mine lol.

But really that combustion ring needs milling out and the squish band altered to be any good. A competent porter will do it for £35 Sterlin. I had a 3MB head done for that much.

[dt125Matt]

Do you have any trusted porters ? Or machineists?
I like in harrow (london) or watford....

Im looking for sandblast/powder coaters
A rebore with new sleeve and forged piston
And porting/polishing

[Calum]

@dt125matt No, I mean I used Mick Abbey to get my cylinder done. Can't really comment on how it fairs to stock, since I did loads of mods and didn't really notice much...