DT125R ARCHIVE

FunkeyMunkeyDavid · Guru

RE: crankcase tuning...

mr karnage · Guru

**** that, its massive lol

FunkeyMunkeyDavid · Guru

lol yeah its not what i expected biggrin works well for the cutting discs though,better hold for straight lines confuse

the only way is YAMAHA DTR · Guru

FunkeyMunkeyDavid · Guru

where did you find that pic? lol so those ports are straight where mine go off at an angle.... saw the powervalve pic,will be altering mine to suit... biggrin

the only way is YAMAHA DTR · Guru

dunno lol

GADGET · Guru

Any chance you could cut down the shaft of the burr bit to make the whole thing smaller ?

eG x LoGiKzZ · Guru

did you ever finish this? try starting it?

Calum122 · Guru

I havent read this thread, but you're not trying to dremel out you boost ports are you? Surely that isn't going to work. That's a highly specialist job.

FunkeyMunkeyDavid · Guru

eG x LoGiKzZ wrote:
did you ever finish this? try starting it?

not got round to building this lump up yet had a sick dog....

£400 worth of sick,which has eaten a lot of my bike budget ashamed and yeah calum,its done.... biggrin got the measurements off a portugeuse site. plenty of people have done it... if it'll run or not is a different matter biggrin i'm gonna make a vid of its 1st start up though,should be a laugh

eG x LoGiKzZ · Guru

ahh hope the dog is getting better! interested to see the first start up of this, be good to see if it does work if theres anymore performance gains

FunkeyMunkeyDavid · Guru

got a mate who's an engineer,he keeps laughing at my tuning confuse but he didnt see a reason why it wont work. i'm not expecting miracles,just a bit more more midrange to topend oomph. the woofs better but the lump couldnt have been worse. its a ticking timebomb,but the vet bought her a bit of time....she's killed a rabbit,eat through 2 fences and 1 of my rigger boots in the last week,think she's fine biggrin

the only way is YAMAHA DTR · Guru

all the porting, but you need to change your reed block, carb, manifold, airbox to get more flow in to the cases

FunkeyMunkeyDavid · Guru

yeah its a non stop ball ache of upgrading bits.... i'll worry about the rest after it runs without eating itself biggrin

FunkeyMunkeyDavid · Guru

funny you should mention it,i've been sizeing it up this week for rebuilding... i've yet to order the seals/gaskets for it. need it to go in this

cough**yz frame**cough

cant wait to run the lump and find out it dont work lol

Calum122 · Guru

Probably ragged or using the 3BN head. The head is restricted. The best combo (apparently) is 3BN cylinder + 3MB head.

-- Edited by Calum122 on Sunday 3rd of February 2013 10:31:05 PM

FunkeyMunkeyDavid · Guru

not yet lol i've been a bit thrown by the 3bn barrel thing confuse gonna start a 3mb cylinder from scratch bleh cant risk destroying a rebuilt crank....

NORFE · DTR Trusted Engine Builder

bit thrown by wat??

Calum122 · Guru

Yeah, NORFE what do you reckon.

The 3BN barrel has a very slightly bigger bore. Therefore it has slightly smaller stroke. I think that's right. Will it make a difference? Will you have to compensate the stroke?

FunkeyMunkeyDavid · Guru

there a different bore and stroke,slightly. the porting is different too.

looked at an early dt with a 3bn barrel recently and it was gutless and not very revvy if that makes sense? confuse

NORFE · DTR Trusted Engine Builder

no difference what so ever bang it 2gether, i had both barrels on mine noticed no difference both ran sweet

un les ur looking for differences only way ull see it is on a dyno, alot of small mods people do us common folk wont even notice, its all the placebo effect u put a new exhaust on and coz it sounds different u think its 20 mph faster wen really its no different

only way you will ever notice and different is visually on a graph off a dyno evern then it will be minute, just think about race teams they spend 100.000's of pounds just for extra 10-20 bhp, to gain any noticable difference in any 2 stroke tuning u need to go the whole hog, exhaust,porting,timing,carburation even then it may only be a slight raise in bhp, good tuning takes serious money, while porting is good for smoothing out the power it womt make to much difference without other mods smile

NORFE · DTR Trusted Engine Builder

FunkeyMunkeyDavid wrote:
not yet lol i've been a bit thrown by the 3bn barrel thing gonna start a 3mb cylinder from scratch cant risk destroying a rebuilt crank....

the only way possible to destroy a crank is, air leak,lack of oil, no air filter, as long as its in a sealed engine with addiquate lube it will run till it wers and exeedes the wear limit so dont worry smile

NORFE · DTR Trusted Engine Builder

Calum122 wrote:
Probably ragged or using the 3BN head. The head is restricted. The best combo (apparently) is 3BN cylinder + 3MB head.

-- Edited by Calum122 on Sunday 3rd of February 2013 10:31:05 PM
yeah thats what i was running due to reading stuff online

FunkeyMunkeyDavid · Guru

happy days lol its back on then biggrin

NORFE · DTR Trusted Engine Builder

crack on biggrin

Calum122 · Guru

So NORFE, you never did anything about the shorter crank on the 3BN cylinder then? You interchanged the cylinders without changing the position of the con rod on the crank?

NORFE · DTR Trusted Engine Builder

nope no crank mods as thats not a garage job, thats a specialised bit of work

all i did was use a paper thin base gasket on the barrel to drop the barrel to compensate

Calum122 · Guru

So I am going to a longer barrel to a shorter barrel. So I'll just want to use a bigger bottom gasket then.

eG x LoGiKzZ · Guru

got 3 base gaskets on mine atm as 2mm oversize piston was tapping the head, works like a good'un now lol

NORFE · DTR Trusted Engine Builder

yeah its a good quick mod gasket thickness wen u buy a cr 125 top end kit u get 3 base gaskest to choose from, and same in the factory spares kit

mostly swap them for different fuel depending on what octane rating is your running