250-500cc Main bearing failure

My WR360 got noisy in the motor, so I opened it up to check on things.
(go to the end for the Q&A if you dont want the whole sad story.)
It wasn't clutch rattle or piston slap but something deeper.
First I checked the ignition flywheel with the Steahly FWW, OK. No noticeable play in the main bearing.
Opened up the clutch side and there was some movement in clutch basket assembly but no worse than normal. all the bearings, clutch plates and parts were OK.
Off with the head and find some marks in the cylinder and on the piston.
I have been running some left over fuel mix with R30 castor from my vmx bike along with the usual TTS fuel mix so had more carbon deposits than usual and blamed loose carbon for the marks.
Take off the barrel for a better look and to check out the bottom end. 187hrs since last rebuild.
crank turned over OK with an oil pool in the bottom of the cases and no noticeable movement in the mains, rod had some sideways wiggle but no up/down. No sign of metal particles from flaking rod bearing surfaces like the last time it failed.
So with nothing obviously wrong I cleaned up the barrel and put a new piston in it and gave it a test start. Sounded better so thought maybe it did just need a new piston and went for a proper ride. I was expecting to get a least another 100hrs out of the crank.
About and hour into the ride I was just starting to get it going nicely when I take a tumble in a rooty piece of track. Handle bar in the ribs again too so I was slow in getting the bike up.
Go to start it and it wont kick over. WTF.
Maybe it wasnt my lack of riding talent why i tumbled.
I let it cool down then put it in gear and by rocking it back and forwards get it to free up.
I am out the back of the riding park by myself so have to start it and ride back in the shortest possible way. It ran, but now it was really noisy. No doubt I would find the cause this time.

So I pull it all apart again and find my new piston marked with some scores and the barrel similar.
This time things are gritty inside and it turns over with a rough sound with odd clicks, so the crank needs to come out to see whats happened.
Separating the cases shows the ignition side main bearing cage has been broken apart.
Presumably this occurred when a ball has jammed breaking the bearing cage and locking up the motor. Lack of lube can only be the primary cause?
The bearing seemed fairly dry even though the cases still had oil in the bottom that wetted the crank wheel OD. The piston and barrel was wet when removed, so there seems to be oil everywhere except in the main bearing. FYI using TTS @ 40:1

Q= Has anyone else noticed dry main bearings when doing a rebuild?
On the ignition side I would guess the main seal could be sucking air in so not seeing the fuel mix but I hadnt noticed lean running and if anything I had been leaning off the air screw with our hot summer weather. The clutch side main bearing could also have been wetter and has no excuse like the ignition side.
Q= I am thinking about trying to add an oil catch groove to the transfer port hole to improve the mains lubrication. Has anyone seen or done this?
Im looking to improve the life of the 360 and save me some time and money.
Thanks for reading if you got this far.
Mike

Just check those oil holes for the mains are clear.
That sucks about new piston being scored hopfully it will go again as they aint cheap.

Not had dry mains am afraid but i check mine by wiggling the flywheel up and down that normally is the second sign to the sound of rumbling when motors running.
P.s. The original skf bearings were a fenolic resin cage but im running the metal caged explorers at the moment, rumour has it skf do uprated explorers x2's... I seem to remember trying to find some.

[Q= Has anyone else noticed dry main bearings when doing a rebuild?[/I]
On the ignition side I would guess the main seal could be sucking air in so not seeing the fuel mix but I hadnt noticed lean running and if anything I had been leaning off the air screw with our hot summer weather. The clutch side main bearing could also have been wetter and has no excuse like the ignition side.]
Never on a bike (have on a car) and it looks more like a blocked gallery. If the ignition seal was leaking you would have known as the bike would erratically idle/off mixture and the only two definite ways that l know is to sprinkle talc in the ignition and see if it sucks it in and of course a leak down test...the clutch side, you would have burned through your tranny oil if that seal was leaking and possibly sucked the crankcase dry but l've never witness it this.
IMO, maybe you lucked out and the bearing just shit itself through age or crap quality or bad seals...?
Q= I am thinking about trying to add an oil catch groove to the transfer port hole to improve the mains lubrication. Has anyone seen or done this?
Im looking to improve the life of the 360 and save me some time and money.
Like Juicy, l've never encountered big end lube issues on any of my 2T's and 187hrs, is that the entire motor or just the top end? Do you know when the bottom end was done?

187 hours would be a pretty short life for a bottom end, especially a 360..and very odd the bearing was dry.

Well I got the main bearing off the shaft and can now read the name and see that it was an SKF Explorer.
The oil gallery is open and the main seal not pressed in past casing surface so there is no obvious fault.
Looks like this one is down to shit happens and get on with it.
Going to get a new rod kit fitted to the crank next week then reassemble with new mains and seals and see how we go.
The cylinder got checked and they gave it a diamond hone saying its still within spec so good to go once i get all my new parts together and fitted.
So spend the money and fix it, cause its no good if I cant ride it.

Mike

On ya Mike!!!
At least you caught it early, rather than 6th gear WFO

What was the other bearing like and make?

I got most of the parts together including the NZ$860 rod kit but was having to wait to get the rod fitted and still not happy with finding no reason for the failure.
As the crank was not that bad and the barrel is half worn I figured i would roll the dice and put it back together with new mains and clean up and re-use the 1 hour old piston to run it and see what happens before I do the full rebuild with all the expensive new parts. So i have been putting it back together over easter and got to test run it today.
Started 3 kick with plenty of smoke from the assembly oil and was sounding good while warming it up. Did a loop of the back yard and then it died like it had fouled plug. started again and died again. Changed the plug and it runs for a bit and dies again. so I check fuel tank breather is not blocked, drain the carb by removing the main jet plug to flush out any possible moisture or crap.
Still doing the same thing, so check the plug for spark and check the rotor is still in position. while turning it over checking the spark I noticed that some white smoke/vapour was coming from the exhaust. OK, Coolant water in the engine seems likely now. check the radiator and yes its down and some fine bubbles on top.
I can only guess the head O ring has not seated properly. so pull the head off to check. the O ring etc looks fine.
Being a 360 the head has had a decomp fitted that looks similar to those special cast versions but this one does not weld to the inside of the combustion chamber just the outside.
Undoing the decomp mounting insert shows an extended nose that butts up against a spot face on the water side of comb chamber with an O ring to seal the face.
this O ring was in pieces and i think as the bike warms up the ali head expands and opens the gap between the insert which the O ring would normally seal so allowing water in.
This could explain a lot of my problems. the water ingress getting worse with time and quietly killing the bearings.
I had found earlier that the radiator cap rubber seal had started to fail and I was having to top up but thought that at 12 years old its just rubber getting old and replaced it.
I have now replaced the decomp O ring and will test run again tomorrow to see if I really have found the problem.
Anyway when it comes apart next i will get the head decomp fitting redone so it has an ali bar welded both sides and the decomp valve only seeing the gas side.

Mike

I welded mine both sides no issues with waterlosses, good effort on keeping a methodical head on and approaching it logically.

Most if not all my mates would of been kicking it down an stomping of cursing under their breath like childeren.

I was cursing at having to pull it apart again but at least I found something.
I started it up today and it ran, but only until it got hot again. water level stayed steady.
I didnt change plugs or anything this time but walked away to cool off myself and the bike.
It Started back up from cold and died once hot again.
Now i think it has to be the stator or coil thats failing so they are next to get replaced.
With the motor running quieter now the clutch rattle is sounding bad so will have to look at changing the basket cushions and fitting a FBF basket.
Hopefully then I will get to ride it again and not have to worry about whats next.

Mike

I managed to get a complete stator rotor set for a WR250 from Poland via Ebay.
there was just 1 number the last digit that was different to my original, an 8 instead of a 9 and the timing mark on the stator was further around.
I marked the 360 position on it and bolted it in. It was giving spark so looking good.
I got to test start it today and it ran for more than five minutes even after it got hot and felt fine response wise around the back yard.
Now if the clutch rubbers come in next week I should be all good to go again.

Awesome hate not having a bike up n running.

curious on the 250 ignition, which years was it for and please report back on how it works performance wise
my trust of my existing ignition is not solid if you know what I mean