Hi,

I have a problem with my ΧΤ600E. The engine has very low miles(racing engine), recently rebuilt, 12.4:1 compression, forged piston, webcams 282o cam, ti retainers, uprated valve springs, new cam sprocket-chain.

Recently, it started making a ticking noise from the head, mainly in idle (1600-1800rpm). In higher revs, the noise from the exhaust doesn't allow me to hear for the ticking. It sound a bit louder than incorrectly setup valve clearances, but i checked and adjusted them, with no change.

The engines runs fine, idles very good(for this cam), no-oil burning and generally nothing strange than the ticking noise.
Inside the valve cover (seeing from the port for the adjusters), everything seems fine and neat.

I read about cam chain, but as i have changed it recently, together with the sprocket, i don't think it's the problem.

What else it could be?

Recently we had some time to work on this engine...

It has done some tough races during the season and in one of them an oil line leaked and it lost most of its oil, but it was rapidly stopped so no more harm has been done.

After the season, with no rebuilt, we had some testing and the problem that i describe above has started. (the rattling)

So today we removed the engine and disassembled it.

That's what the piston looked like...




It's only this side, at the opposite face there is some scars, but not serious. The barrel has some scratches but not as bad as the piston.

I have suspected the oil-pump, but i checked as the manual say, by removing the bolt at the oil filter housing, and oil come out right away, but not with much pressure. Also in the engine, if i open the drain plug some oil comes out, but as much as ~250ml.
Finally, as i found out today, on the head, under the camshaft, the gallery there had a lot of oil and the cam is in very good condition.
So i think that the pump is ok.

I also found some damage to the piston pin, at the point that is in the rod, and the piston has also some damage at the points where the pin is.

Why did this happen? How should i eliminate it?
I will probably go for an over-sized piston and barrel machining, but i would like to take an opinion on what's the problem.

I've got a piston/barrel like that!!! (see my thread in the archives).

It was a simple case of lack of oil.

Have you got the full spec of the engine?

I'm holding onto a XT600 hybrid lump that I'm going to graft into a fizzy or something stupid.

__________________
Tom
I'm a country member...

What you mean the full spec, it's as i have written in the first post.

I thought about the oil, but the facts i have written in the second post, i think that exclude the lack of oil.

Theres an internal net-oilfilter, you might wanna check that.

Take of the engineguard, and the plate arund the front of the frame, where you drain the oil from the chassis (in lack of better word)

Take of the oil line, and use a size 27 key (thats what it is here in Denmark europe, dont know your're messures) and screw out the filter. It's screwed in there real tight, something like above 100nm. Rock it, and put all ya' weight in it, and it will come of.


The filter shouldn't be clogged, mine has done 70k km and i dont think it has ever been cleaned, and there was next to nothing in it.

But its worth trying.

Sorry, i forgot to mention it...

The engine is not on a bike, it's on a small single seater car.
i use a custom oil tank (~3.5L capacity) with hi-pressure oil-lines and in-line oil cooler. So no in line oil filter.

Is the oil tank above the engine like it would be on a bike?
That could be the problem - there is deffo a lack of oil somewhere!!!

__________________
Tom
I'm a country member...

I've seen pistons looking similar to that caused by overheating, so may not have sufficient air flow?
Bob

__________________
Remember that Assumption is the mother of all f**k-ups.

Wow... That's some nice work ya got there :\

It does look like you got some overheating due to not enought oil flow or not cool enough.

Bobmech mentions a good point...how about improving the airflow?
some fiberglass work isn't that hard and would probably help to cool down your engine...

Also, if you could fit a oil radiator on the front of that car with fiberglass "wind tunnel" would surely cool down that oil

There are some older XT's that have some small oil radiators...good starting point?


Vando

Yes, it's over the engine. The bottom of the tank is at the level of the head. But i don't think that it would be a problem, if it was sitting lower.
The oil will flow to the engine.

I must say again, that the engine is in very good condition except piston-barrel.

The cam, rockers, gearbox, crank are in excellent condition.

The airflow is a possibility, but judging from the oil-temp readings, i thought it's ok.

I have oil temp sensor and it reads about 90-93oC when idling for some time and the highest i have seen is 103oC. I don't think that it's that bad.

And yes, i have oil-cooler, in line with the tank. The only thing i would think about the oil-cooler is to be in the wrong place. It's between the oil-tank and the engine, so to have the coolest possible oil entering the engine. I was thinking that i had problem with the oil pressure, but as i wrote before, oil comes out when removing the bolt from the oil-filter housing, and there was a lot of oil under the cam when i opened the engine.

Where does the "standard" oil coolers connect to the engine?

On my srx, xt engine based, the oil cooler is in line with the return oil feed and i believe that to be the standard yamaha system. Iv certainly read NOT to put one inline with the oil supply feed.

Wot size are the cooler lines..... if too big/small this can effect the flow/pressure.

As its hi-comp.... heat will be a big issue.... even with the temp readings....

Ideally you want oil to be at 85-90 degs. Once it boils it degrades fast.

Sure its not running rich at full throttle... as in "wash out" of the bores?

Running a race engine, I'd have thought an upgraded pump would be wise.

The oil-lines are ~10mm internal diameter. The stock barbs I've got it's 9.5 internal.

I use fuel-injection and a wideband O2 sensor, it's tunned very well.

Also some extra photos

The front face of the piston...There's damage, but not as the back.


The pin...also some damage to the rod small-end.



The pin pockets on the piston. There are those deformations that i don't know why occurred...the pin-piston tolerance seems ok (i will check it), no movement.

100 degrees aint bad for a big aircooled single.
How about to much throttle when the oil isn't up in temperature?

I need to hold it at about 3000-3500 until it gets to 40oC oil-temp (then it idles nicely at 1800-2000) and usually the temp is 80+ when driving on high load.

As i told, the temp is between 85-95oC. I rarely see over 100 and this is due to very hot weather and car stopping and waiting after hard run (driver change, incident on the track, etc).