Yamaha TRX850 Enthusiasts Forum

“ a small service project”
Six years later…

Tarwetijger wrote:“ a small service project”
Six years later…

Nice to see trx jedi still here, Tarwe .
Just use my topic, probably no need for a new rebuild thread.
But for myself, these 6 years were constant rebuild of different issues, like carb, fuel and water pump, rear wheel and swingarm, getting luggage panniers, replacement to oem blinkers, new driven sprockets and chain, camchain, valves service, rear brake light switch, crashbars and central stand.

rednikmarto wrote:

Tarwetijger wrote:“ a small service project”
Six years later…

Nice to see trx jedi still here, Tarwe .
Just use my topic, probably no need for a new rebuild thread.
But for myself, these 6 years were constant rebuild of different issues, like carb, fuel and water pump, rear wheel and swingarm, getting luggage panniers, replacement to oem blinkers, new driven sprockets and chain, camchain, valves service, rear brake light switch, crashbars and central stand.

Good, so by now you have a brandnew bike!
It's an interesting read too, so no harm is done.

Did you replace the generator, since the layer was crumbling?

The bike is in the state as shown on photos, in disassemlbed state.
Don't have a decision for the stator that makes particles.
Still have not ordered new connecting rods, piston wrist pins and etc, next month earlier date.
The 'key' at (new std size) piston rings into the honed bores is somewhere between 0.40mm (feeler pass) and 0.45 (feeler does not pass), and bores are scratch not free.

Currently i will wait if some of way more experienced guys (than me) here wants to advice me about proper tightening of connecting rod bolts.

Tried to measure what's the state of plain bearings.
At cyl.2 two unsuccessful attempts, as twice the conrod rotated and measurement is not trusted. Just couldn't hold the conrod properly.
Tightening i used was in small steps until reach of 30Nm (to both bolts) then in a single move up to 48Nm.







At cyl.1 everything went correctly at once. Somehow the conrod got fixed as the supporting shaft backed to the vice.
Measurement should be wrong (? or not) again, the clearances are almost the same as on a factory new (TRX/TDM) engine (0.025mm-0.038mm).









Checked earlier the oil pump that lubricates the engine (pump2) with feeler gauge, its in the good range.

Then what could be the reason for the connecting rods and wrist pins being damaged ?

It came time for this story to be completed..

Lets continue from the point we previous interrupted. The crankshaft is clamped in the vice.


Wash the brown sludge:




Little painting attempt:


The new connecting rod for piston in cylinder 1:

All journal bearings and connecting rod bearings are new.
All gaskets also new.



I had to realize (for the cost of 90USD) that the used cylinder block i purchased will not help, it also had wear.

Worn in (+) as my original cylinder block.
I saw no other decision, but go for 858,8cm3, oversize 1 (+0,5mm) over normal, new pistons and rings.




At the photo below, a stamped "50" on the top of the piston is seen. Not found at "normal" pistons, reserved for oversize pistons.

Same "50" at oversize rings. Normal rings do not have such digits there, only the markers for "top side" - T.

New parts have protective plating, dark gray. The old wrist pin is the shiny one.


The red is Loctite 518, anaerobic acrylic flange sealant (Cobba's invention in this engine). The factory sealant was gray silicone.



Had some little confusion until i coupled properly the crankshaft and the balance shafts.
The marker "arrow" points to "left" side of the woodruff key slot. Its Haynes manual that helped, thanks to a friend who knew this fact.





had to support the balance shafts with some carton pieces to stand still as i am coupling them to the crankshaft:






Did assembled pistons and cylinder block to conrods by the easiest way for myself. With pistons preliminary inserted.





Video from "almost" first start of the rebuilt engine:
https://rednikmarto.info/tdm850service/2022/after_first_start.mp4


In the night of 15 Oct to 16 Oct did short but intensive run-in.

Did also the first oil change at about 20 miles.
This is with the new oil:


Thanks to TRX forum members for sharing knowledge!
Thanks to the local professional workshops for the head service and cylinder block machining.

Happy End of the story.
Sold to an ex-colleague, who recently become a motorcyclist.

I'm very happy to see that you finished this and got a good result.
Well done.

As it should be, i am obliged to transfer the "Thank You" to more material aspect and helpful matter back to the forum.
I sent small donation to the forum email address.

I’m wondering how you got the brown sludge off. I never made an attempt to remove it.
There’s a bottle on the picture it just says “cleaner”. Can you tell what kind of stuff this cleaner is made off?

Hi Tarwe,

It is water solution of surface active agents for industrial cleaning / de-greasing.
Harmless for paint and non-corrosive. Translated by Google: It is an aqueous solution of surfactants (non-ionic surfactants) and additives with cleaning and degreasing properties.
The only information about it is here and is in Bulgarian language: https://shop.lackprom.com/klinar-pochis ... -1234.html.
Kept the original pistons 3 days in this cleaner, just to be able to clean inside the ring's grooves. At the end, i left the old pistons with a spare cylinder block to the new owner.