Yamaha TRX850 Enthusiasts Forum

What do you get when you add: second hand bike - no history - cheap price to the vision of a track day bike Noise in the bottom end? Can't be that bad

Cam runner picked up on inlet near side to the point where we couldn't get the bucket out without grinding the journal away



Head had these strange clear (no carbon) marks on it (stretched conrod - I don't think so )

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Strangely the corresponding piston had corresponding marks



Black conrod in grey engine - not looking good

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and finally the problem - bigend bearing failure



Point to note: we checked (cut it in two and layed it out flat) the filter for "bits" prior to stripdown and all was clear - no bearing pieces - where we did find all the bearing parts was in the well at the bottom of the dry sump 8 eyes can vouch for this - the filtering system did not pick it up the contamination. Complete strip down now required to clean all the crap out of the oiling system.



Bottom line Scott's looking for a crank and rods if anyone can help out

Obviously the engine's been run out of oil and ran the bigend. I can't believe it was still running

Thanks Scott, Kev and Ridgie for assistance in the dismantle (and Kev's new TRX engine frame )
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What do you think Scott and Kev are thinking here:?:

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Thats very Ugly guys

Looks just like the engine that was in my rex when I bought it off ebay, I dare say thats gunna cost a few bob to fix up, I was quoted around $1400 for a rebuild from local bike shop.
Good luck with it

Cheers mick

Glen1TRX wrote:What do you get when you add: second hand bike - no history - cheap price to the vision of a track day bike Noise in the bottom end? Can't be that bad

Bummer!!! Mind, being cheap it's probably less painfull than the same thing happening to a $7k bike (Trying to look at the positives here!)

Glen1TRX wrote:Black conrod in grey engine - not looking good

How the f*knuckle does that happen? Is it a heat related thing?

Glen1TRX wrote:Bottom line Scott's looking for a crank and rods if anyone can help out

The Import bike joint - http://www.importmc.com.au/CMS/index.htm had 2 TRX's for wrecking when I was there picking up pegs last week.

Glen1TRX wrote:Obviously the engine's been run out of oil and ran the bigend. I can't believe it was still running

Could an oil pump failure have caused this? Or just poor maintance from the previous owner?

Glen1TRX wrote:What do you think Scott and Kev are thinking here:?:

"Beer will fix this!"

Good luck with it guy's, and let me know if you need an extra set of hands?

Oil pump failure would cause this, yes, but it's simply been run low on oil. I have 3 motors like this...well they were.......one is completely rebuilt, another nearly finished and the third went in the skip cos I couldn't get hold of a crank for it.

To say the filtering system didn't pick up the debris is not true. If you look at the lubrication diagrams you'll see that the filter is on the discharge of the pump, so if there was debris in the filter it would have passed through the pump already. What has happened is that the mesh strainer has stopped the debris going through the scavanging pump, and it's dropped into the pan as intended. It didn't go anywhere or cause any more damage, just lay in the oil pan. Have you looked in the mesh strainer? All of mine had heaps of shrapnel in there but it can shake loose when you're rolling the lump over to get the pan off.

If you look carefully around the cap on the blackened rod you'll see a multitude of colours where it's overheated.

How bad is the crank? If the timing gear is intact then it's probably salvageable. One of mine was, 2 were not.

Is that head serviceable? I have one in similar condition...probably will get to look at it in the next couple of weeks.

youngy wrote: To say the filtering system didn't pick up the debris is not true. If you look at the lubrication diagrams you'll see that the filter is on the discharge of the pump, so if there was debris in the filter it would have passed through the pump already. What has happened is that the mesh strainer has stopped the debris going through the scavanging pump, and it's dropped into the pan as intended. It didn't go anywhere or cause any more damage, just lay in the oil pan. Have you looked in the mesh strainer? All of mine had heaps of shrapnel in there but it can shake loose when you're rolling the lump over to get the pan off.

Youngy, wise words - you've obviously had more experience than us in these matters. Both stainers had very little debris in them hence the concern it had gone through the entire oiling system - it was all in the "depression" of the dry sump resivour. I'm guessing whoever blew her up went looking for the noise and may have changed the oil and filter anyway. We haven't checked the oil pumps as yet but we will get to it. Rod's obviously knackered and the crank may clean up at .010 / .020 under if we can get bearings. Won't know until we get it to a shop and have it measured correctly. All the other bits look recoverable.

youngy wrote:
How bad is the crank? If the timing gear is intact then it's probably salvageable. One of mine was, 2 were not.

Youngy - what happens to the timing gears? We did notice some FOD to the nylon oil pump gears but nothing too serious

Looks pretty nasty, but best of luck with the rebuild, hope it doesn't get too exxy. Good to see you have some help - look forward to seeing it up and running and on the track!

that clear stuff is glass.

Or commonly known as "melted silicon". Tiny bits of sand heated up, melted, turns to a resin like substance, and is hard as hell to remove.. Its probably what caused your bearing failure in the first place.. Contamination of the oil system, which was never put together properly in the first place.

Least you have it sorted and know what to do.

Can you please take a few nice clear pics of the TRX engine stand ? I wanna see how you made yours.

Looks like you have a bit of work ahead of you.. Oh, while your at it, clean out your ports. Just hand smooth them with a bit of emery tape to get the casting lumps off. Dont go nuts on it and wear it all away, but smoothing it out in a "in and out" motion, rather than "round and round, side to side", you can pick up a touch of CFM ive noticed (via flow bench).

GL and post pics on the rebuild please.

Quan-Time wrote: Oh, while your at it, clean out your ports. Just hand smooth them with a bit of emery tape to get the casting lumps off. Dont go nuts on it and wear it all away, but smoothing it out in a "in and out" motion, rather than "round and round, side to side", you can pick up a touch of CFM ive noticed (via flow bench).

Cleaning the head up was on my list of things to do. Do you have any pics of before and after QT to use as a guide or is it just a case of cleaning off the casting marks in the direction of flow and then polishing. (I love my Dremel)
Any other tips for headwork would be appreciated guys.
Next time we drag it out we'll take some pics of the engine stand.

Glen1TRX wrote: Youngy - what happens to the timing gears? We did notice some FOD to the nylon oil pump gears but nothing too serious

Glen have a look at the timing chain gear on the crank. Nothing else matters. That gear is soft, and takes the brunt of any partial siezure of the motor.

You are looking for any missing teeth.

That gear is machined into the billet of the crank, not shrunk on like all the other gears on there, and to replace it, although possible, is not commercially viable.

The guys on the French TRX forum were collecting busted cranks to have these gears replaced, but even in a large batch it was still too expensive to warrant the work.

Of all the TRX/TDM cranks I've seen with my own eyes, the big end pins have been reclaimable. I'd be surprised if you end up with an undersize, as the bearing is so soft it just tends to cover the pin. Stick it in a lathe on the slowest speed possible and wrap some emery round it to clean off all the high spots, then use a fine wet and dry to polish it. If the pin has a scratch in it, it won't matter unless you've lost mega amounts of bearing surface. What you don't want is high spots.

inept wrote:
Good luck with it guy's, and let me know if you need an extra set of hands?

Allways welcome inept - pm me your mobile and we'll put you on the hit list. Glen

Glen have a look at the timing chain gear on the crank. Nothing else matters. That gear is soft, and takes the brunt of any partial siezure of the motor.

Will check this weekend and report back with pictures