DT125R ARCHIVE

stillbroke · Guru

RE: could my powervalve being flush with the exhaust port be causing so many rebuilds ?

Calum122 · Guru

Personally I wouldn't mod the PV since that is irreversible. Personally I would have that barrel resleeved it isnt going to be cheap but it's better in the long run.

stillbroke · Guru

how much for a re sleeve? ,and i dont really care about the valve its more hassle than its worth ive taken the servo off and pegged it shut

eG x LoGiKzZ · Guru

i paid £130 posted for a resleeve and new piston from PJME

Calum122 · Guru

That's besides the point. The bike WILL run better with the vale working. Why would you purposlly restrict the bike lmao. Not only that you'll cause more bottom end strain without the valve causing
Premature wear to the engine ultimately costing you more money.

But what do I care it's not my bike or money...

NORFE · DTR Trusted Engine Builder

Calum122 wrote:
Personally I wouldn't mod the PV since that is irreversible. Personally I would have that barrel resleeved it isnt going to be cheap but it's better in the long run.

ha ha whats this fettish of urs cal with re-sleeving or replating lol

the manufacture offers a decent selection of os pistons and a thick std liner on most 2 smokers for the reason that it is a general routine maintenance to rebore and go over size on cylinders

a 1.5mm bore oversize runs just as good as a std bore if run proply and looked after

the engine will run better if the valve is working, with the valve pegged open or shut it wont wear any different if the engine is warmed up proply than it does with the valve working

all 2 stroke ports need a good chamfer on them to stop any ring snag no matter if its a 20 cc hedge trimmer or a cr 500

NORFE · DTR Trusted Engine Builder

stillbroke wrote:
how much for a re sleeve? ,and i dont really care about the valve its more hassle than its worth ive taken the servo off and pegged it shut

more hassle than its worth, its there for a reason to do a job its simple 2 stroke mechanics

if u r gunna pin it shut u deffinatly need to make sure its clearing the bore or ull wreck things even more mate

if you read a manual on an engine it describes how each function works, it tells you the pv runs in close proximaty to the piston, so simple thinking would tell u "oh iv had a bigger bore put in the cylinder so that would mean the pv will need attention, am sure it says some where in the manual about after boring sort of check list, may be wrong, simple common sense would tell u the answer tho lol

stillbroke · Guru

by the way did mean ive pegged it open not shut hahahahah

Calum122 · Guru

Yeah gathered that. Pegging it shut just gives you bottom end. Bike will rev to about 6k and won't go anywhere.

stillbroke · Guru

what would be the benefit of getting it operational again?

NORFE · DTR Trusted Engine Builder

it would be how it shud be the pv is there to give a good range of power by optimating the opening of the exhaust port to match rpm range...

do some research have a good read and u will understand it better

http://www.youtube.com/watch?v=GD8QnsY925Y

stillbroke · Guru

everytime ive tried to set it up though ive fainled :( i dont get why 1 goes to 2 and 2 goes to 1 it means twisting the cables which makes no sense at all

stillbroke · Guru

this was interesting
http://www.dansmc.com/powervalve.htm

stillbroke · Guru

dug my servo out and will be looking at getting this oprational again,however im still not seeing the benefits of doing it as it seems most people are pegging theres open to so there has to be a reason for having it pegged open? otherwise no one would do it and i have found the original reason it didnt f ****ing work it was because my haynes manual says to cross the wires but this is shutting the the valve not opening it lol!

stillbroke · Guru

now i am confused should my cables be crossed or not

eG x LoGiKzZ · Guru

they shouldnt be crossed as far as im aware, i thought them being crossed was another restriction on some bikes

Calum122 · Guru

Wtf mate. It's very simple. Even full blown mxers have PV.

Trust me it gives power to the bottom end. A very easy way to see what the difference is is to close the valve and ride the bike. You'll notice you get lots of bottom end torque but wont rev very high. Opening it gives the reverse effect. Having an operating PV gives both the benefits without the draw backs.

stillbroke · Guru

all i know is my bikes alot faster with it open which is mind boggling

Calum122 · Guru

That's because you obviously haven't set it up properly. Hardly mind boggling.

It's so easy to check. It should be slightly open at low rpm. Then at high rpm it should be open fully which is what you have pinned at the moment. So If after 8k the PV is fully open how can it be slower than at 8k with it pinned open. It's one and the same thing no?

The way to set it up correctly is to take off the PV cover. There's a prong sticking out of the end of the valve. This should line up with zero parralax to the little hole in the cylinder. That's how you know it's set up correctly.

scrimsmustang · DTR Mechanic

The cables should not be crossed over. Its easy to set it up I will try to explain in an easy way.

Take the cover off the pulley wheel housing so you can see the wheel moving when u turn the ignition on without the engine running.

On the pulley wheel in-between the cables is a notched piece, when u turn the ignition on and the powervalve goes through its cycle the notch should line up with the hole behind it when it finishes the cycle. If it doesn't loosen the lock nut on the right hand cable and turn it anti clockwise till the pulley wheel comes to rest in line with the hole when you turn the ignition on again. Both cables should have a slight bit of slack in them when its all set up as-well.

Also the end of the powervalve were the pulley wheel bolts to it has a dot stamped on it, this dot should be at the top.

stillbroke · Guru

cheers scrim ,its being bored to 2mm now so i may just leave it open

MDK · DTR Legend

no expert but it they are reboring they are taking away any chamfer that was there or reducing it so it would need chamfering again

stillbroke · Guru

yea thats right mdk so will be doing it again which is so much fun

dread123 · Moderator

Depends on what they bore the sleeve with I believe? Different hones etc

MDK · DTR Legend

common sense says that if you rebore anything that has a hole with a chamfer round the edge that you are going to take away from the chamfer and it will need redoing regardless of how or what you use .