Yamaha 426 milky oil - help
Posted July 21, 2014 - 02:25 AM
Just got the bike and having bad luck with it, supposedly had a weisco high comp piston fitted a few months ago.
Starts ok and rides fine, feels really fast and idles ok.
But the oil is fully milky coloured, drained it and refilled it and it happens again straight away. No leaking coolant or dripping anywhere though
So I reckon it must be head gasket?
Thanks for any more help
Posted July 21, 2014 - 02:29 AM
Yes, head gasket is a possible
So is a cracked head, or freeze (welch) plug (not sure if the WR has these)
Is your coolant level going down?
Another possible is short trips doesn't get the engine hot enough to get rid of the condensation that gets trapped in the engine
Posted July 21, 2014 - 03:05 AM
If it was cracked head wouldn't performance be affected?
Bin told condensation but it's warm weather here and new oil goes fully milky within minutes of it running so kinda guessed it wasn't that
A lot of coolant must be getting through
And coolant doesn't appear to go down but iv not ridden it for more that few minutes
Posted July 21, 2014 - 05:40 AM
My WR suffered from milky residue in the breather pipe from the starter clutch housing, when I first had it, coz I was riding it on the road
They have no thermostats so it was over cooling
If yours is going milky within minutes, then its something more serious
There could be a crack from the water jacket to the where the cams are, and hence it would run OK but loose lots of coolant
If the coolant has frozen at anypoint in it like then it may have cracked the head/cylinder somewhere.
It's got to be coming from somewhere, so if you have a crack then you will loose coolant fast
As its recently had the head off, then head gasket is first place to check
Usually leaking head gaskets result in gas being forced into the coolant (under the force of the burning petrol) resulting in it blowing coolant into the overflow bottle, coz if its leaking enough to allow coolant into the engine, then the pressure of combustion will blow gas into it much faster
Yes I know its been warm here in the UK recently!
Posted July 21, 2014 - 11:00 AM
Just bin for a ride on it, no coolants gone down in the rad?! But the oils gone milky again. Rides fine and bloody fast
What the hell
Posted July 22, 2014 - 12:00 PM
The step belongs there, but the grroove where the coolant seal runs is a wee bit deep looking. (see attached pic) Replace the shaft, both seals, and the bearing.
Pay attention to the seal orientation; it looks backward to most people. Read: http://www.thumperta...0-coolant-leak/
BUT.... No, that will not turn your oil milky unless someone or something has plugged off the weep hole under the pump. The space between the seals is vented down and out into the atmosphere specifically so that that won't happen. Possible points of coolant entering oil are, head gasket, base gasket/O-ring, the O-ring at the right crankcase cover/crankcase joint behind the water pump, or a crack or hole in any of the water carrying sections of the RH cover, cylinder, or head. There's a hex head plug in the cam box area of the head that can also leak, but it won't unless someone has disturbed it.
Posted July 22, 2014 - 12:36 PM
So there's another seal on the crankcase iv already taken off then that I should check?
It's apparently had a high comp piston fitted recently so it could be anything once I get the head off
Posted July 22, 2014 - 12:38 PM
Posted July 23, 2014 - 01:40 AM
And to turn the oil milky within minutes I guess must mean it's a big leak somewhere
Yes, a big leak which should also be confirmed with the coolant level dropping in the Radiator - do not judge it by the level in the overflow bottle under the rear mudguard if you have some coolant in this. You must check the coolant level by removing the rad cap
As grayracer says, if the water pump seal leaks, you get a dribble out of the vent hole which drops onto the ground, under the engine on the right hand side
There normally start leaking when the engine is first started and then stop as the engine gets warm - a kind of early warning system to let you know the seal needs replacing
Check that the hole is still present, and the PO hasn't blocked it up - its not unheard of for people to think this drain hole is the problem and block it instead of the seal
picture here http://www.thumperta.../#entry10808681
Edited by GuyGraham, July 23, 2014 - 01:48 AM.
Posted July 23, 2014 - 08:41 AM
Guessing a valve has snapped and caused damage round where the bucket sits? Would this be leaking water ?
Piston and cylinder look ok so I'm guessing a reconditioned head is the way to go?
Posted July 23, 2014 - 02:57 PM
The tip of the center intake stem does look so happy, either. I'd say your guess was correct.
As to the water seal on the crankcase cover, it's an O-ring, about 16-18mm in diameter, directly behind (Looking from the right toward the cylinder) the water pump. #13 in the image below:
Posted July 24, 2014 - 09:09 AM
Is it a crack or a score in the plating
If its a crack through to the water jacket then yes its enough to leak water a good rate
Posted July 24, 2014 - 09:47 AM
What would of caused that? Over heating ?
Posted July 24, 2014 - 10:35 AM
Hard to say with any certainity
Yes overheating, previous blown up, metal fatigue or the water froze due to lack of anti freeze (most likely). At least you found your problem
Don't despair - Langcourt can repair it http://www.langcourt.com/page16.html
There are only two places in the UK who actually do cylinder replating. Langcourt is one, and Aptec is the other
Everybody else sends it to one of these two places
Had my WR cylinder done by Langcourt over the last winter - top job
Edited by GuyGraham, July 24, 2014 - 10:39 AM.
Posted July 24, 2014 - 10:57 AM
Iv ordered a cheap second had cylinder from a breakers which is apparently in good condition, just to get it running and make sure everything is ok