DT125R ARCHIVE

SkinBobUk · DTR Respected Member

Dead piston.....

NORFE · DTR Trusted Engine Builder

where did u measure the barrell, to get an accurate sizing u really need a bore guage, as the bore wears in different plces is there a lip about 10 8 mm down were the rings stop when the pistons at the top lik this old barrell as if u measure the barrel at the top across it will be smaller than 10-20 mm down the bore, but like i tel every one building an engine if uv got it apart and can afford it, may aswell do the lot once proply than it breaking down and chukkin money at it every cupla months

if ur stripping it id do big end, mains small end, rebore/new piston

you could put a new piston in the bore to see how much play there is and chek it to manual; specs if its within tolerance

but put the piston in the bore then put the piston and barrel in the oven let them get nice and warm together to expand to running temp and see what the tolerances are like then, as putting a new piston in an engine measurements when cold are totally different when its warmed up and expanded if theres to much clearance it will slap its tits of and in the end it just breaks the skirts off the pistons and destroys the engine

but if its bored to that size id be scrounging round for a used barrel with a neara std bore as if u re use urs and it goes pop ur gunna have to have it re sleved 200 quid, were as u may aswell pic a barrel up off some one on here for 25-30 quid and have it rebored, then once engine back togetherit will be like new and good for a 15-2000 miles trouble free cruising if run right

all up to you tho mukka

bobc · DTR Respected Member

Norfe,

using the hot oven method, do you go for the same piston - bore clearance as reccomended in the manual ?

Bob

SkinBobUk · DTR Respected Member

Thanks again norfe. I didnt realise i had this much to learn. Thanks for taking the time to explain it all. Ill get looking for another barrel. Looks like i bought a bit of a nail lol.

NORFE · DTR Trusted Engine Builder

best thing to do buy a nail and rebuild it

then u no its gonna be good to u

http://www.ebay.co.uk/itm/Yamaha-dtr125-dt125r-barrel-head-/271102009664?pt=UK_Motorcycle_Parts&hash=item3f1ef06140

http://www.ebay.co.uk/itm/yamaha-dt125-r-cylinder-barrel-and-head-comp-dt125r-Dtr-/121018828880?pt=UK_Motorcycle_Parts&hash=item1c2d48c850

http://www.ebay.co.uk/itm/YAMAHA-DT125r-DT125-r-DT-125-r-barrel-bore-cylinder-/221148840102?pt=UK_Motorcycle_Parts&hash=item337d7f80a6

email em and see what bore there running biggrin

SkinBobUk · DTR Respected Member

Norfe your far too kind, thankyou.
Ill jump on the pc and get emailing shortly.

NORFE · DTR Trusted Engine Builder

no...r u ok doin your own engine rebuild?

where do u live im verry cheap and got itchy fingers ha biggrin

NORFE · DTR Trusted Engine Builder

they do run bores up to that big mate its the last size they do

shud be ok the new 1 then get it bored to the next size up and start from a fresh bore biggrin

make sure u use a genuine head gasket or athena

and re torque after running it

SkinBobUk · DTR Respected Member

Well i looked into the electrics today and the thing is a mess. Wires spliced in all over, relays with pins snapped off, you name it and its ****ed. Time to start saving for a new bike.

FunkeyMunkeyDavid · Guru

its easy to get disheartened lol build your bike back up and it'll see you right biggrin plus you'll be proud of what you've achieved. the 4dl loom is similar to yours and a lot easier to find (probably why yours is botched/not right)

SkinBobUk · DTR Respected Member

Your right. I was on a bit of a strop earlier, all that cash and i only made it twenty mins down the road, and now I gotta spend even more cash lol.

FunkeyMunkeyDavid · Guru

lol thats the way it goes sometimes. the dt looms cant be that different to yours either bud? got a 4dl loom on my dt cos it was cheaper... nevs done an awesome colour chart for looms if you fancy having a go at yours? cant get any worse can it? biggrin

SkinBobUk · DTR Respected Member

Well you would think not, but im starting to make some sense of it.

And today i think i've found one of the main culprits. For some strange reason one of the ignition wires was not connected, and the starter relay had a wire completely missing too. I connected them back up and the relay itself is faulty. Why someone thought it easier to chop wires off than spend £10 on a relay i'll never know. But im starting to get somewhere.