DT125R ARCHIVE

Calum122 · Guru

RE: Dt Engines

Calum122 · Guru

Like I said Bradders. For the price you're asking I'll take it. As soon as I get some money in. My only thought is, is i'll be looking to have the barrel resleeved and refurbished. At £200 a pop aint cheap for something that won't even fit. I quite fancy the Starter motor option, so don't want to downgraded to just kicker alone. Of course I've got both on mine.

Calum122 · Guru

But yeah. You could just use two base gaskets. That might be all you need.

Cameron · Guru

Calum122 wrote:
But yeah. You could just use two base gaskets. That might be all you need.

Only thing is could that could alter the port timing enough to make it run worse?

Calum122 · Guru

Fûck sake

this is what I mean. I'm not a mechanic. I don't know about these things.

eG x LoGiKzZ · Guru

adding more base gaskets will lower compression so will be down on power a little bit, not sure on port timing tho, only one definitive way to find out..

FunkeyMunkeyDavid · Guru

the 3bn stroke is 50.0mm 3mb is 50.7. the 00.7 will give bonkers compression (short crank life with ultra thin high compression base gaskets and a highly skimmed head though biggrin ) doubling up on base gaskets will raise the ports higher (good thing) moves the power lower down the rev range too. happy days i reckon

Calum122 · Guru

So what are we saying?

Is it possible. Or is it just a case of having a go.

DT-R_bradders · Guru

I think with the cc thing tho the heads alone could change that as there less material in the combustion area on the 3mb upping the comp slightly ill check the 2 barrels tonite n see if there are different heights

Cameron · Guru

The head doesn't have anything to do with the displacement though lol ;)

Another weird thing I noticed is as well as my bottom end saying 3bn, it has 2rh written on the conrod which are the one's with a shorter stroke. Wondering if mine's even got the right cylinder fitted lol.

eG x LoGiKzZ · Guru

im sure NORFE is right, if the 3mb has less material on it so more space, that gives a bigger gap meaning more CC, piston at BDC then measure the stroke and bore then work out how much space the cylinder head gives then you can work out the CC

think im getting confused with compression ratios! nevermind haha

-- Edited by eG x LoGiKzZ on Thursday 25th of October 2012 09:26:26 PM

Calum122 · Guru

I thought we are saying the 3bn is the shorter stroke.

Calum122 · Guru

DT-R_bradders wrote:
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
Right so help me here.

You're going to be running the 3BN bottom end with the 3BN Barrel and the 3MB head.

Surely that would be the exactly same setup as me?

Am I missing something here?

I'm guessing I'll have to take the barrel off and check the conrod since the engine stamp isn't helping here?

Calum122 · Guru

Obviously I haven't bought the cylinder yet.

NORFE · DTR Trusted Engine Builder

i read some where about the different strokes not sure which is wich

the head has a big part in cc's with shape/size of the chamber

id of thought the 3bn would have a longer stroke coz the head has the dishd ring in it if it was same stroke it would be more ccs than the 3mb as the mb head is just normal if u get me

Cameron · Guru

NORFE wrote:
i read some where about the different strokes not sure which is wich
the head has a big part in cc's with shape/size of the chamber
id of thought the 3bn would have a longer stroke coz the head has the dishd ring in it if it was same stroke it would be more ccs than the 3mb as the mb head is just normal if u get me

I'm pretty sure the head has nothing to do with cc's though? It's just the amount of space displaced by the piston...

What I can't understand is why do all the newer dt's still say 3bn even if they come standard with 3mb cylinders? And 3bn engines (older one's) definitely have a shorter stroke because of the bigger bore smile

Calum122 · Guru

So what. The bottom end on my bike won't support the 3BN cylinder

NORFE · DTR Trusted Engine Builder

bigger the combustion chamber the more ccs your gonna have obviously

some have big dome heads on engines some flat heads some wierd shapes all to do with cc's/ comp ratios

ccs are measured from the top of the piston to the cylinder head, bigger the space more cc's ur gonna have, but 2much room and the compression drops so bigger bore needed. it all has to be in fine tune to be right really fookin complicated

thats why tuners blue print engines before they tune them

to get the engine to its original ideal state of tune then they will dyno it and take it from there

DT-R_bradders · Guru

cc is measured by, bore x stroke, the gap left at the top when the piston is at tdc has nowt to do with the cc size, i jus realised wat i said earlyer was wrong wen i said bout the head making a different cc, all ur gain from the 3mb head over the 3bn is more effiecient fuel air mix burn and more compression,

Nathlaad · DTR Legend

I'll CC you in a minute Bradderz then i'll bore out you're holes

DT-R_bradders · Guru

nath ur tiny boring bar wouldnt touch the sides m8 lol
n wat u mean urll cc me...co.ck clout me? lol

Nathlaad · DTR Legend

hahahahahahaha

Calum122 · Guru

Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre (TDC) to bottom dead centre (BDC). It is commonly specified in cubic centimeters (cc), litres (l), or (mainly in North America) cubic inches (CID). Engine displacement does not include the total volume of the combustion chamber.

NORFE · DTR Trusted Engine Builder

yeaH I WAS BEEN A SPAZ I WAS thinking 1 thing and typing another i got it in my head we were working chamber size out...ha jet jag heads still up me arse lol

confuse

FunkeyMunkeyDavid · Guru

this is making my brain hurt lol and i'm wondering if the difference is purely in piston height/bore? i've ran loads of combo's of heads and barrels (3bn/3mb/4fu) while trying to find the best one. like i say,only grief i had was with 3bn skimmed barrel/3mb skimmed head/ultra thin base gasket. bike went like fook till it locked,felt like it siezed. was a hydraulic lock type of thing? it freed off when i rocked it but big end bearing was shagged beyond belief on strip down,rollers turned sideways confuse

DT-R_bradders · Guru

riiiigght then went and checked out the 4 barrels i got n found this, the 3MB y-1 and y-2 are the same height as the 3BN y-1 (dont have a 3BN y-2 if there is one?)

but.....iv got a 3MB y-2 with the letter A stamped upside on the front skirt which is signifantly shorter than all the others inc 3MB and 3BN???? WTF is that all about...pics

THE DIFFERENCE IN HEIGHT...

PICS WITH THE CODES ON THEM

AND THE RANDOM "A" ON THE 3MB Y-2

so cal looks like ur gonna av to take ur barrel off n check if its got the "A" stamp. if u havnt got the stamp then i reckon urll av no probs running the 3BN barrel

Calum122 · Guru

My barrel is the 3MB Y-1

Well done bradders.

Well done.

Calum122 · Guru

That is really...weird. Just strange to see so many different combinations.

DT-R_bradders · Guru

i know wats the point could of saved yamaha time and money by making one badass combo n keeping it the same throughout the dt range on all years...

wheres nev when u need him hes the engine code breaker lol

Calum122 · Guru

Where is he?