DT125R ARCHIVE

stillbroke · Guru

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

GADGET · Guru

Is the skirt smashed every time ???

AndyYam · Guru

You should be lifting up the skirt before you start smashing!

GADGET · Guru

He likes it messy tho

stillbroke · Guru

GADGET wrote:
Is the skirt smashed every time ???

no never its getting stupid now im seriously thinking of getting one of those pulse adrenalines as its more reliable than the dt !

GADGET · Guru

Ok fella what is wrong with it when u take it apart

stillbroke · Guru

il get some pictures up looking up the exhaust port its lost both rings again and the piston has turned to a white colour

Reef · Guru

Turning white would that not suggest it had been running lean

GADGET · Guru

+1 on the white ,Have u checked your seals ??? They will give telltale signs if they r fooked ,where have u been having the top rebored etc as it looks real tight on the piston

but gotta be carb/ oil/air to eat top ends like that

or it's been bored too tight Each time or you havnt run it in properly and heat seized it ....ok number 1: what size are ur carb jets ??? 2:oil pump setting picture 3: what size piston etc ( if realy big then it's hittin the valve) pics pics pics and we'll get this sorted

stillbroke · Guru

i have no idea on jet size ,i have got the top off completely now the piston has an almost identiacl piece of damage the same as the other one and i have both pistons so will take pics ,i will get the pump pic today sumtym i really need to get to the bottom of this this time as you can imagine it is coting to much time and money ! the plug was white as well nd the bike did overhheat when it broke down .i waited an hpur for it to cool then it went another 17 miles got tit home then the next day after the 17th kick it went i got 3 very long miles away from home and it went again and that was it .the bike never idles properly and will always cut out despite air filter and iridium plug .she is drinking 2 stroke normally. i did really push the dt b4 it went this time i had it off the clocks whichh i didnt think was possible .
thanks ppl

GADGET · Guru

No probs man il check back later

NORFE · DTR Trusted Engine Builder

there needs to be 1 mm minimum clearance from the pv to the rings

put the piston in the bore level with the pv and put half the valve in at a time and look from either side to see if the rings are clearing the pv drum smile

if not

grind

stillbroke · Guru

pics of oil pump and piston

GADGET · Guru

this is trhe shizz, 1242023?AWSAccessKeyId=1XXJBWHKN0QBQS6TGPG2&Expires=1358380800&Signature=1%2Fa6BUo9koYiTDhBghVVmJd7mh8%3D that "zero" should be inline with the line on the nipple

AndyYam · Guru

Jesus, take your photos in focus please! lol. Yeah does look like your oil pump settings are out. You're running with way too little oil and its just grinding the metal, getting way too hot and the piston is expanding and thats probably causing the rings to hit the piston.

Take your oil lines off and clean them through, re fit and set the pump correctly following the haynes manuals guide.

re bore the barrel and get a new piston kit. Put it all back together with plenty of 2 stroke on the rings, bore, little end bearing ( use a new one of these as well) and piston during assembly.

When you first start it, leave the oil pump cover off and once the engine is running, use your hand to turn the oil pump round to on to help bleed the system.

stillbroke · Guru

can someone put a pic up a correctly set 1

AndyYam · Guru

Follow the Haynes manual, it has photos and is your best bet.

stillbroke · Guru

GADGET wrote:
this is trhe shizz, that "zero" should be inline with the line on the nipple

what nipple and what line m8

Reef · Guru

There's a little notch on that nipple (see the black cable in the picture, then that little brass thing, then after that a silver circular thing, that's the nipple) ideally the 0 should sit just back off the notch, hold on ill find my thread

Reef · Guru

http://dt125r.activeboard.com/t51050540/carb-problem-bigger-problems-helppp/?page=3&sort=oldestFirst

There look at that, go through the next few pages and you should get it

stillbroke · Guru

cheers m8 i dont understand what they mean in the haynes manual

NORFE · DTR Trusted Engine Builder

all the damage is directly in line with the exhaust port, thats deffianate contact damage from hitting the valve, 1st place an engine wears due to lack of oil is the intake side of the piston

stillbroke · Guru

thanks norfe but my pv is flush with the port and i have a 0.50 overbore so it shouldnt be hitting it ?

stillbroke · Guru

definetely not hitting pv but it seems as if ringa RE HITTING EXHAUST PORT

NORFE · DTR Trusted Engine Builder

stillbroke wrote:
thanks norfe but my pv is flush with the port and i have a 0.50 overbore so it shouldnt be hitting it ?

if the exhaust valve is flush with th port then theres no clearence for the piston & rings then if its .50 over size then theres deffo not enough clearance it will be the rings catching on it as the engine warms up and expandt things get tighter

pv drum in red

where the yellow is on the picture u need at (least 1 mm) clearance and the top of the exhaust port needs to have a decent chamfer on it to guide the rings back in the grooves when its on the up stroke

if you have over bored the cylinder and not modded the pv drum and got a decent chamfer on the top edge of the port it will just contact and destroy its self as it shows in your pictures of the pistons

stillbroke · Guru

it is definetely catching i did this last night with the piston and it is hitting the red area that youve put on the image whats the plan norfe?

Calum122 · Guru

Simply poor design on yamaha part NORFE. there isn't much clearence for the valve as it is. I don't feel comfortable riding around knowing that the rings are so close to the valve. On the Aprilia rs125 the RAVE system makes much more sense. Just have a blade that is cut into the exhaust port controlled by a solenoid. Much better design and easier to keep clean and maintain.

-- Edited by Calum122 on Tuesday 15th of January 2013 08:26:32 PM As for the wear I'm sure by peggin the port open you put note strain on the bottom end. Since it doesn't have the torques to pull it through the revs as it would if the valve was working. You know it's bad for the engine when you pull the throttle back when you're not in the engines power range.

-- Edited by Calum122 on Tuesday 15th of January 2013 08:29:28 PM

NORFE · DTR Trusted Engine Builder

U NEED TO GRIND THE POWER VALVE TO GIVE ADIQUATE CLEARANCE MATE, LOOK IN 1 OF MY OLD POSTS "Modding pv after reboreing" all on there nate all u need to no smile

stillbroke · Guru

ive been testing it again but its not hitting powervalve the pv is pegged wide open it seems to be hitting the top of the exhaust port not the p.v ?

NORFE · DTR Trusted Engine Builder

with the port been so big it needs a good chamfer on the edge 1mm at 45 degres itats how i always do them any way did u see if the port edges were chamfered who did the rebore last??