DT125R ARCHIVE

gasto · DTR Respected Member

Maximum bore

DT-R_bradders · Guru

i think 2mm is the maximum over size u can go m8y not 100% tho

the piston in my original barrel from my bike wen i brought it was 1.75 OS so i think it had one more rebore left in it especially as the liner was starting to get a bit thin compared to the other spare barrels i have

NathanDavies · Guru

2.5mm im 99%, anyone?

bkray · DTR Senior Member

Sorry, gotta go with Bradder's on this one. was sure you could only go 2mm os.

ToySoldier · DTR Legend

just found out mine has had a +1 so i looking into it and the biggest piston i found was a +2 the ones i found was +0.25 +0.50 +0.75 +1 +1.5 +2 there the ones i found

NathanDavies · Guru

Sure people on here in the past have been on there 5th .5mm overbore, and one person went over that and there powervalve smashed the piston iirc.

Dickhead · Nonce

i sold a dt with a 59mm piston im sure lol also wossner make up to a 61mm piston i think for the dt

NathanDavies · Guru

Yeah noticed that with wossner, robin what you think of those wossner pistons, found one for £77 from TNT racing, im pretty much stuck on getting one now, you know if they're any good?

fuggie · DTR Respected Member

59mm is pretty much the limit using a powervalve as the amount you need to grind off the valve bobbin to clear the piston leaves hardly any metal left for the powervalve centre locating pins to go into, without a powervalve on a standard barrel you can resleeve and go very big bore, the wossner pistons look pretty good, i'm pretty sure the piston with the athena kit is wossner unbranded for the kit.

tripr · Guru

iv got a 59mm m8 in one off mine an a standard in the other sure iv seen +2.40 floating around on ebay though

NEV · Guru

This will give you an idea on the sizes you can go oversize,

I went for the 4mm O/S

stillbroke · Guru

ive just had a 2.5

fused420 · DTR Senior Member

2.5

Sam M · DTR Respected Member

Hello there. Been thinking about getting a wossner 61mm piston to get the bike up to 148cc maybe do abit of porting to it aswell. Did you notice an increase in torque with the 60mm piston NEV? (by the way love the tzr hybrid build thread going well :)) The 60mm piston would make her 144cc i believe, im after abit more midrange you see as iv got a pinned valve and shes abit lacking untill it gets on the pipe.

NEV · Guru

If you are ok with pinning the powervalve full time, then yes go for the 61mm piston, but remember you also need to reline the barrel, as there wont be enough meat left on a conventional barrel liner.
As for torque aye deffo feels very torquey

Sam M · DTR Respected Member

Exellentay :) Yea il be running a pinned powervalve all the time, dammit was hoping to get away with it not being relined :( oh well that will add abit of cost. Where did you get your barrel relined and bored out? PJME? and how much did it cost you if you dont mind me asking. Ta Sam

NEV · Guru

I had mine done by a local Newton Abbot bloke I always use called Brian Loram, who sent it off to an engineering firm he uses, as he hasn't got a press, he did all the stage 3 porting on it though, to just have the barrel relined and bored out cost £150.

NEV · Guru

Oh and you also have to have the cylinder head machined out, so as to take the oversized piston, that was in with the £150 overall cost, plus the head gasket needs reaming out too.

-- Edited by NEV on Wednesday 29th of January 2014 12:25:50 PM

Sam M · DTR Respected Member

well im thinking about machining the head and gasket myself at work but id need to send the bore away for relining ect. £150 eh thats not too bad you sure theres no way you could get away with using the standard liner? havent got a bore to hand yet (its in the post) would it deffinately be too thin or did you get yours relined for peace of mind? how much does he charge for porting then? id only be after the stage 1 want to do it myself really but probly better giving it to a professional if im spending £150 on a rebore

NEV · Guru

Nah you deffo need a bigger O/D on the liner to bore it out to that size, you'll see what I mean when you have your original barrel to hand.

Sam M · DTR Respected Member

Okie dokie cheers for the help NEV