Mystery oil burning on AT
 

Hi from cape town

Sorry it has been so long since i have written any thing but we have been very out of contact (playig wiht cheetahs and leopards --NO JOKE!!). Any way i have a mystery on my hands. I am burning oil at a alarming rate. (1300ml in 200k!!!!). I have ripped the engine out and the pistons and barrels are fine the oil rings are in spec, 1 of the 4 comression rings is out of spec. I am going to change them all anyway. I dont know about the valves yet (pulling them out as soon as i can make spring guide.).. there is no leaks from the engine or anywhere else that i can see. (pan is clean). Any hints or ideas... plus any one know how to get the engine in with out lossing a finger or two.. (it was a major pain to get out..).
cheers all Xander
pics soon i hope now that i am back in the 1st world.

This AT had similar symptoms: http://www.horizonsunlimited.com/hub...l-filter-49118

HTH
Chris

PS. I'm sure you've already posted this question on Honda Trail Bike Forums There might be more AT-technical expertise there. I never go there myself as they charge money to post.

Is the engine smoking?? possibly valve stem seals????

Any water in oil? How does the cyl. head look? Compression check out OK? (leak down test performed?)

As indicated, Black plugs would indicate oil burn on one or both cylinders. Rings can be hard to measure. I think it is SMART to replace them all. Don't use Diesel or synthetic oil after rebuild ... rings will never seat with Syn oil. Standard mineral oil for first 3500 miles, IMHO.

Bad valve stem seals would mean significant smoking on start up. You would have seen this early on.

Getting the engine back in is a bitch. No easy way. I've not pulled an AT motor but have done BMW, Triumph, Moto Guzzi, and Honda singles to name a few. Recently a DR650, which was easy!

I like to have plenty of spare hands to help, lots of wood blocs, wedges and cloths. Try to stabilize chassis (not easy) tape over frame rails to prevent scratching. Rig some kind of block and tackle from above to take the weight. Work slowly ... it's like a frickin' puzzle.

Just repeating what others have said really...

Oil can only go a few places..

You said there are no external leaks. I'm sure you would notice if you're losing that much externally.

1. Check the coolant for oil. Could be losing it into your cooling system through the head gasket. It's a lot to lose this way though. Your expansion tank would be full of milky coolant. Drop the coolant and check it anyway.

2. Valve stem seals. You sometimes only get smoke on start up if the offending valve/valves seat in an open position. Thats still a hell of a lot of oil to be losing through a valve seal though but not impossible.

3. Cylinder & rings . This type of leak grows gradually. Not over a litre in 200k overnight. Are you sure you wern't burning oil before ???

Did you measure the bore or the ring gap ? It should be measures at the top, middle and bottom of the stroke. maybe your bore has developed a taper.

4. Any oil in the airbox ?? Breather pipe ???

5. What mileage is the bike on ??

Your problems aren't the hardest to fix as long as you have the parts !! Where are you ???????????


I've had a few AT engines in and out. It's a right old pain. Drop it in from the left hand side. You need 2 people at least. Protect the frame with rags, rubber mat etc. I left the rear head off mine and the side cases.

Were you riding differently those 200k? Mine got through more oil in south Africa than anywhere else trying to keep out of the way of the high-speed pick-up trucks - was cruising everywhere at 80mph.

Sustained high engine speeds on a v-twin results in huge amount of air being pumped into and out of the breather (every time the crank rotates). Higher loa results in more blow-by too, so high speed riding is a double whammy. My conclusion was that the oil separator in the breather system wasn't up to the job and the oil was going that way. Certainly when I went back to a more erm... relaxed riding style, the oil consumption got back to normal - though in fairness it was never as high as yours.

This is a good point, I should have thought to mention it. Could be something as simple as a kinked crankcase breather hose or mis routed or blocked up somehow. Once you block the crankcase breather the motor will pump oil like a ditch pump. So check out your breather system and routing.

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