Hi guys,

Bike was running odd and felt a little hot and also the clutch felt jumpy. Started an investigation and found that there seemed to be coolant in the gear oil

Then checked the coolant and only got 500mm roughly out of it

So decided to pull the top end and found this on everything below the piston rings

Does anyone have an idea as to where to start looking for the leak??

Cheers

Andy

Edited March 12, 201511 yr by andilicious

could be a head gasket problem and seal gone on the water pump leaking into the gear box

think id fully strip and replace all seals and gaskets , and check all bearings

Total strip and everything fully cleaned and rinsed with 2t fuel / oil mix until no more dirt comes out.

What coolant have you been using? and how old is it?

Iv had the bike since November but only rode it 8 times maybe. No idea how long the coolant has been in but it was surprisingly clean when it came out. The jug in the picture makes it look cloudy but it was fine really.

It doesn't run too bad so it must only be a slight weep somewhere. It's ran perfect for 3 trials, 3 playdays and 2 long evening rides. Guess it only just started overheating when it got down to this level of coolant.

I'll give it a proper clean tomorrow night and see if I can spot anything obvious before I tear into it!!

Top end orings looked fine too. Base gasket tore as I lifted it so can't comment on that. May just be that that's gone?

Andy

To get into both crank & gearbox I'd say the centre gasket must be the problem, possibly there are a couple of the case screws not fully tightened. Fill the crankcase with fuel & see if any escapes into the gearbox, at the least it should it should help remove the coolant from the big end etc

Safest thing to do will be full strip & clean, replace the main bearings with the newer sealed type & fit Viton crankseals. check that the tapped holes in the cases are clean to full depth

Since you've taken the head off the barrel you'll also need to replace the o-rings

Chances are you may not find the obvious cause while rebuilding the motor but will fix it in doing so

Jesus man, that don't look like coolant entry to me.

Cannot tellall from the pics. but gear oil is normally metalized if it has not been changed,

Coolant quantiy, well you had over 300ml, cannot recall how much they hold but not a lot more than that.

The black in the motor is like grinding paste, which suggests you may have been hosing the bike without blocking the airbox, which will wash all sorts of muck throuth the filter and into the box which sloshes its way into the motor and grinds it to bits! Also leaving a flat finish on the piston fron the abrasion.

What is in the bottom of your airbox?

Have you checked or changed any of thi fluids since you have had it or did you just ride it till it quit?

I changed the gear oil about 4 hours use ago, it loo perfectly normal at that time.

I always have a bung in exhaust and put a rubber glove over the filter and I always run it up after cleaning too.

Airbox is clear inside too!

I'm at a bit of a loss as to what's happened as I do take care of my bikes!!! It was running fine for an hour last night and then just started to run a bit hot. I just thought for the sake of 10 bolts I'd pull the cylinder and have a look for some obvious and found this!

Fine grey sludge like in your photo can be formed by old coolant dissolving the aluminium casings. I have seen this in coolant systems but not dispersed over the piston like in your photo.

Coolant should be cloudy not clear, colour dependant on type. If it was clear someone has maybe put just water in.

Water pump seal is a possibility, the bottom cylinder gasket looks fine around the coolant port.

Have you been riding through water at all? if so check were your gearbox breather pipe runs, if it's pointing down there's a chance you've sucked up water in to the crankcase, if it's pointing up there also a chance you've jet washed water into in.

But if the water is in both the gearbox and crankcase there must be a seal gone between the two.

Play it safe and strip, clean, replace all seals, crank bearings and gaskets

Just a wild guess,

Water pump seal gone. Bike eventually overheats, pressure in cooling system pressurizes gearbox and pushes coolant that's leaked in box through right side crank seal?

Also I have seen same symptoms in a Gas Gas, In this case the barrel was cracked causing overheating and excess pressure that failed the waterpump seal and when engine was stopped water pressured direct into cylinder through crack.