Oil leaking onto exuast from ....... why?

[epod]

G'day all, I recently did a port job on my yx klx style head on pitsterx4 160. First thoughts after first ride were unreal its flying pulling harder all through the rev range. I only got about half hours riding at home before packing up the bike to drive to lake's for the race last weekend. Entered in vets but managed to get 3 practice sessions in with vets china's and pro's. At the end of 6 laps the bike is still flying but oil is leaking onto the exuast and burning off. It seems to be leaking out the exuast port flange somehow and not going into the exuast just leaking down the outside of the exaust header only. I was only losing about ten mills of oil during a 5 lap race but it smoked alot as the oil burned on the pipe. I ran it all day like this and won the vets.
I have since taken the head off and cannot work out how it could be leaking at this point justoutside the exuast port on the outer edge of the flange as the does not seem to be any gap. Put it back together same problem.
I have noticed the casting on this head is very poor quality compard to the crf dirtmax head on my yx 150cc. Has this happed to anybody else out there.
Note most of the port work was to the inlet port just straitening the flow to the valve. as for the exuast I just cleaned it up a little. There is no oil leakage inside the ports at all and the motor is running clean and very fast. I still can't believe it. I have never seen a motor smoke so much from, oil leak and run for more than five miniutes. The head gasket is not blown.
Any ideas? Any body want to donate another head?
Peace ride on. DD

 

[tez350]

my bottom valve cover randomly started leaking on my yx150 onto my exhaust and smoked a fair bit too.. even tho i hadnt touched the valve cover. so bit of gasket cement and she hasnt leaked since..??

 

[epod]

Cheers mate but is definatley not leaking from the valve cover i sealed it good during rebuild. Thanks anyway.

 

[sean01]

hey mate... any chance of getting some pics up

 

[Dreadful]

yeah well I dunno man you're my mechanic but someone will have an idea ... congrats again mate.

 

[pbk]

oh i remember your bike mate smoke was poring everywhere when you came out

by the way i was one of the guys in the first blue tent just when you come off the track and into the pits

my input is that maybe the o ring seal thats in the head gasket has worn and is leaking there or maybe a o ring gasket has worn out on your valve cover, but you would think you would loose power from one of those happening

 

[epod]

Cheers for you input but I have eliminated both of those scenarios.
I think maybe the head is cracked somewhere where oil can get to the exuast port flang. It is the first one I have seen do this, just bad luck i guess. Ran it for an hours riding today still flys, took the pipe off after and oil is leaking from outer edge of the exuast port but only when the motor is reving stops leaking soon as engine is off.
Ride on DD

 

[sean01]

is it anywhere near the exhaust valve spring seat.. maybe cracked thru there from the springs coil binding or fretting. iv noticed on some heads they dont have spring seat washers fitted and as the spring rotates they eat the head away a bit..
but could be a casting issue too..

but without pics its hard to tell

 

[Peter1230]

yeh i remember that bike.. thought it was on fire hahaha..

that sucks but ay.
so u were in 3 classes!?

 

[epod]

Cheers Bro's I think sean01 may be onto something. I think I will have another look at it stripped down with the cam and valves out. It must be cracked somwhere.
Ride on DD

 

[epod]

Hope i have fixed it.

Hi all, I hope I have fixed this problem with JB weld. The oil leaked from two places.
1) The inside of the exuast port flange where the header pipe seats. It must be leaking through the inlet valve oil gallery. I filled the inner edge with JB weld.
2) The right head stud also had oil leaking through it. I reinstalled the stud coated in JB weld. One of our american friends says he has seen this leak before and has fixed with plumbing tape on the stud. lol
I also sealed the exuast header with mani seal.
I have to wait tilll tomorrow to start the bike. Lets hope it works as I don't want to buy a new head right now.
My only dissapointment is how cheap and nasty the cast of this YX KLX head is compared to my dirtmax YX CRF 150cc head. The small amount of dremel work I did when porting should not have caused cracking in the cast.
Get it together China, you know how to make quality now so stop producing lots of second rate crap as well.
Can anyone get YX KLX head blanks (no cam or valves) from Tiwan for under $125
Dirtmax have a blank for $125 but it is CRF and I will have to change my pipe to fit.
Ride on DD

 

[wogtaz ryder]

i got a Z155 head with a few hours on it .

with covers/cam etc for cheaper if ya really need one.

Im sure you would find alot of people with spare yx heads laying around.

 

[sean01]

wat do you mean by YX CRF 150cc head... you talking about the yx daytona head?

 

[epod]

Thanks for the offer I will see how it goes with the repairs. If it fails I get back to you mate.
There are to different YX heads out there. The YX heads with dirtmax printed on them are crf style (the manifold port and exuast flange are on a differtent angle to KLX style YX heads which do not have dirtmax printed on them.)
Ride on.

 

[epod]

It is not cracked anywhere I think now it is just a badly sealing head gasket. Anyway I am putting a new gasket and some sealant on when it is built into a 191cc soon.
Just gotta get a decomp kit as well for safe starting. Before that I will just clucth start it. I hope I can still get the power down.lol
Ride on DD