DT125R ARCHIVE

couldn't you make your 125 Powervalve like your 170 by dremeling it?

So the piston is damn hard or next to impossible to fit inside the barrel with that extra ring underneath the bottom ring. Do i need it ? The ring clearance is fine without it !

I just read in the manual that it is 0,3-0,45 ? This seems like a small tolerance, And then my new rings suddenly isnt perfect anymore. The 0,4mm plate went trough nicely. But the 0,5 was too big. This means the ring is somewhere between 0,4 and 0,5. Its proboably just fine then. Im not gonna be using it for more than a week or two anyways, Since this is just a backup option while im waiting for the new powervalve for the 170cc.

Th third ring is an expander ring and should be put under th bottom ring,it is so gasses can get behind th ring and press it out towards th bore for better sealing ,it's supposed to be in there

I just finished my top end rebuild i compleatly forgot about the 3rd ring until i came up to my bedroom and see it sitting on my speaker its staying out now i can't be bothered to rip it apart again.

NorDt wrote:

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hahaha gooner, did you meassure the clearance on the rings before you put them in ?

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Yeah it was all good now has new rebore,, new mitake piston kit, new small end bearing , and the 3Bn head on it i have just to run it in gently for the next 500 miles
though it needed it though the piston i took out had done 14000 miles.

NorDt wrote:

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Okey. Well i just got back inside after being in the garage for some time, I cant get that damn piston into the barrel.

I already put the piston onto the crank. Wich was pretty damn stupid cause now i remember maybe its easier to put the piston half way into the barrel before putting it onto the crank..

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I had the same trouble i tried putting the piston in the cylinder but i could not hold the cylinder and line up the small end bearing hole and put the wrist pin in at the same time. I managed to do the normal way of fitting the piston then sliding the cylinder over the piston/rings it took a few attempts but i got there in the end.

Ok, so finally got this together, And daaaaamn !, That barrel is definetly not slower than the 170cc. ,
Did some porting on the exhaust. not much, And didnt do any meassuring xD. Im not shure if i dear say it, But it just might be faster than the 170cc, atleast up to like 75 mph. Thats in 5th gear, But then when i shift it into 6th, It kinda slows down a bit. think its because the major kick comes just a bit later in 6th.

So maybe the 170cc is a bit faster after 75 mph. But this is definetly not slow. I was expecting this barrel to be boring really now that ive driven so long with the 170cc. But damn this surprised me. The sound is just awesome !!,

All of this might be the placebo effect xD It sounds wild because its noisier, And it feels wilder because theres no low rpm power.. Idk, Like i said, It might be faster than the 170cc untill you get to 75 mph.

Yeah im talking about the 125 barrel, I ported it some and did the powervalve thing you see on the pictures on top.

Combined with a 34mm carb and powerfiltre.

Yeah im really happy about it, Cant wait to try out some wheelies with it, Its proboably alot worse to wheelie than the 170cc because it barely pulls from the bottom..

Well, I left it out and the bike is running nicely. Might be doing a YouTube vid today showing off some acceleration. And I might attempt some wheelies. Don't know how that's gonna work though xD

NORFE wrote:

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Harry wrote:

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The ring is to use with worn barrels, with a fresh rebore you should only use the two standard ones

Not sure if you should use it as well, just helps keep compression

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 if an expander ring is supplyed with the kit its to be used !!

not just for worn barrels

its to help ring seal most road going 2 strokes have them in well most iv had have

there is also 2 different shaped rings cross section the rings have to be installed correctly to achive oem compression ratings

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 Just repeating to me what the two stroke builders told me mate, they even supplied it to me and told me not to use it if it's a fresh re bore haha

NorDt wrote:

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I think harry is right,even on my worn barrel and piston I left the expander ring out and its still a rocket xD

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I run my piston in for around 100 miles and have been riding it properly today & it feels like a different bike its so much stronger on acceleration i have only taken it up to 60mph so far i do not feel comfortable keeping it pinned down my local bypass just yet i cannot ride it at the moment though as it failed its m.o.t this afternoon because of the front tyre.

every year you have to get it m.o.t in uk