Yamaha TRX850 Enthusiasts Forum

I think, each TRX should have 900cm3!
Best Regards
MGScandalo

now just market those at Aldi and we'll all be happy

Yumm! Where do I buy!?

would you really want to bore the liners out to 92mm?

Ask yourself why Over, JE etc didn't make them that big

I'd personally worry about the close distance between the bores - the same reason why i stuck with geniune Yamaha 868cc pistons rather than going another 10cc.

I WOULDN`T!
Yamaha only go to 90.5 mm (1mm oversize), the JE 878 cc kit goes a tad further (sorry can`t remember the exact size in mm `clearance` for the pistons), but as Phuk says if the aftermarket boys could have gone bigger they would!
The stock liners could of course be pressed out of the block. The block machined to take thicker liners, maybe even the crankcase mouths would need some machining too, then the 92mm would be achievable, but it`s all money and time for little extra gain and there could still be issues because of the proximity of the pistons to each other, obviously determined by the crank.
Boring liners beyond their permissable tolerances is a recipe for trouble, the liners cracking and / or distorting in use primarily.
A turbo on the stock motor would be the way to go if you really want to see big power gains (120 bhp plus on a moderate boost). You could utilise a small car turbo (used) and if you are handy with a TIG welder and stainless tube it could be done fairly cheaply in all honesty.
Even the stock Mikuni`s could be run pressurised with a plenum chamber taking up the airbox space.

Mincehead wrote:I WOULDN`T!
Yamaha only go to 90.5 mm (1mm oversize), the JE 878 cc kit goes a tad further (sorry can`t remember the exact size in mm `clearance` for the pistons), but as Phuk says if the aftermarket boys could have gone bigger they would!
The stock liners could of course be pressed out of the block. The block machined to take thicker liners, maybe even the crankcase mouths would need some machining too, then the 92mm would be achievable, but it`s all money and time for little extra gain and there could still be issues because of the proximity of the pistons to each other, obviously determined by the crank.
Boring liners beyond their permissable tolerances is a recipe for trouble, the liners cracking and / or distorting in use primarily.
A turbo on the stock motor would be the way to go if you really want to see big power gains (120 bhp plus on a moderate boost). You could utilise a small car turbo (used) and if you are handy with a TIG welder and stainless tube it could be done fairly cheaply in all honesty.
Even the stock Mikuni`s could be run pressurised with a plenum chamber taking up the airbox space.

JE are 2mm oversize and that is as far as I would want to go / have gone. It's not just the liners but the close proximity of the bores to each other and the water jacket. On talking to Paul at TTS (who were heavily involved in the development cycle for the pistons) he is absolutely convinced that this is as far as the liners can be safely bored. Any more would be a gamble.

The alternative is to drop TDM900 barells onto the TRX bottom end and then use TDM hi comp pistons. This isn't a straight forward swap but not massively complicated (I would probably have gone this route if hi comp TDM900 pistons were available at the time)

Would you need to use TDM 900 rods too, I seem to remember something about the gudgeon pin diameters being different?

Mincehead wrote:Would you need to use TDM 900 rods too, I seem to remember something about the gudgeon pin diameters being different?

Yes, by one stinkin mm!

...but cyl on pic is for sure a TDM900 one with that type of camchain tensioner!?
...also think i read on the german site he just mounted these to a TRX...and he also mounted a 900 clutch to a TRX engine (only gain was a 50% lesser pull to the lever)

sorry killer, you can use the TRX rods!!
Regards
MGScandalo

MGScandalo wrote:sorry killer, you can use the TRX rods!!
Regards
MGScandalo

Sorry, isn´t that o GOOD thing??

MGScandalo wrote:sorry killer, you can use the TRX rods!!
Regards
MGScandalo

Now I`m on Dawns laptop I can view your image from your original post.
So...................................
Is that a TRX or a TDM 900 block, I take it they are not stock pistons for the TDM 900 either looking at the piston crowns and valve cut outs?
And you CAN use TRX rods if you do the TDM block and pistons on the TRX motor conversion?
Where is the difference in the gudgeon pin diameter then, on the internal diameter / thickness of the wall of the gudgeon pin?

Questions, alll questions!

Mincehead wrote:

MGScandalo wrote:sorry killer, you can use the TRX rods!!
Regards
MGScandalo

Now I`m on Dawns laptop I can view your image from your original post.
So...................................
Is that a TRX or a TDM 900 block, I take it they are not stock pistons for the TDM 900 either looking at the piston crowns and valve cut outs?
And you CAN use TRX rods if you do the TDM block and pistons on the TRX motor conversion?
Where is the difference in the gudgeon pin diameter then, on the internal diameter / thickness of the wall of the gudgeon pin?

Questions, alll questions!

They are CP pistons, another German (the one who sold me my JE) is going for this spec:
R6- 6-Gang, Carrillos, CP-Kolben," Vee Two" Nocken und Hirnschmalz.
Don´t know what hirnschmalz is though....

It`s apparantly German for BRAIN POWER!
CP are Carillo, all the same company:

http://www.cp-carrillo.com/

Their pistons:

http://www.cp-carrillo.com/Tech/PistonT ... fault.aspx

Mincehead wrote:It`s apparantly German for BRAIN POWER!
CP are Carillo, all the same company:

http://www.cp-carrillo.com/

Their pistons:

http://www.cp-carrillo.com/Tech/PistonT ... fault.aspx

Hehe, i thought i remembered it from somewhere!
Yep, not to shabby engineers those Germans...love working with those siemens PLC´s
AFAIK he got a kit ready for sale on DE TRX forum...