Big End Failure

Tigcraft TRX · Post by **Tigcraft TRX** » Wed Aug 06, 2008 6:14 pm

Just as I was about to turn from Tigcraft TDM into Tigcraft TRX, something disastrous has happened!! Ran the TRX engine up for 1st time (ebay engine

) and noticed that it seemed tight. Then spotted 1mm grey sludge in oil tank. Stripped motor to find no 2 rod very stiff, but no play in it. Rest of engine looks ok.
Any of yo good ol' boys know of why this happened?? Engine from 7000 mile (supposedly) TRX from breaker's. Is the greyish looking sludge a red herring? Or do big end bearings have a habit of mounting each other?! Want to do a good re-build, and not arrive with same problem again.

Cheers Guys, Nick.

brockzila · Post by **brockzila** » Wed Aug 06, 2008 8:01 pm

are you sure the sludge is not oil in the water causing over heating and the bearings to go after the oil shat its self??????????????

Tigcraft TRX · Post by **Tigcraft TRX** » Thu Aug 07, 2008 5:35 pm

Not sure, the sludge had that pungent soft metal smell?! about it, Has anyone looked in their oil tanks and seen what's in the bottom??
A guy I met recently reckoned his big end shells had moved, and wrecked his crank pin.

steve speed · Post by **steve speed** » Thu Aug 07, 2008 5:54 pm

from memory i think its oil starvation which then makes the shells spin in the con rod so this will probably wreck the rod and the crank pin,,,don't sound to good whatever it is and will have to come to bits ,, evilbay strikes again

good luck with it and keep us posted

Tigcraft TRX · Post by **Tigcraft TRX** » Thu Aug 07, 2008 7:42 pm

Reckon you've hit nail on the head there steve, need to get motivation now 4 re-build. Check out piccy of magical con rod that stays in any position you'd wish to leave it. Sigh.

Killerwhale · Post by **Killerwhale** » Thu Aug 07, 2008 8:40 pm

Tigcraft Tdm wrote:Not sure, the sludge had that pungent soft metal smell?! about it, Has anyone looked in their oil tanks and seen what's in the bottom??
A guy I met recently reckoned his big end shells had moved, and wrecked his crank pin.

I know HansJ found quite a lot of metal shavings and assorted stuff in the oiltank...

Did i understand it correct that you started the engine without changing fluids??

Tigcraft TRX · Post by **Tigcraft TRX** » Fri Aug 08, 2008 8:55 am

Nah used recent race oil in frame (oil tank), and some finest UK tap water. Was knackered before I started it up judging by oil tank residue - been there for ages. Joey Dunlop finished a race once by using fork oil from his fork leg in his rs250 once!!

youngy · Post by **youngy** » Sun Aug 10, 2008 3:03 pm

what colour are the rods at the big ends? they will blacken and get burnt with oil starvation alot of the time. They then go out of round but can be "straightened".

the grey sludge is probably melted bearing material. I had a motor where the bearings had melted and run out of the rod ends down the sides of the rods.

as Steve said - oil starvation is the likely culprit.

sherlock · Post by **sherlock** » Mon Aug 11, 2008 11:05 am

Youngy, you mean like this

? http://trx850.motomaniac.net/forum/viewtopic.php?t=2498

youngy · Post by **youngy** » Mon Aug 11, 2008 12:29 pm

indeed so

Tigcraft TRX · Post by **Tigcraft TRX** » Mon Aug 18, 2008 5:36 pm

Pulled rod out, both Crankshaft pins looked scarred, and the problem rod has turned blue. The engine came from a crashed TRX, and I reckon it went on full throttle still on it's side. Gonna have to send crank away for Chris applebee rebuild, and get it balanced, shot peened for race use me thinks.

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