TRX 900 D= 92mm 11,5:1

[phuk72]

I don't want to piss on anyone's chips but after market rods are a complete waste of money.

Rod failure (even on heavily tuned TRXs) is virtually unheard of - in fact I am only aware of one letting go (and that was mine and in part due to other factors).

OK, they may be a few grams lighter but the cost is bonkers IMHO

[Killerwhale]

I don't want to piss on anyone's chips but after market rods are a complete waste of money.

Rod failure (even on heavily tuned TRXs) is virtually unheard of - in fact I am only aware of one letting go (and that was mine and in part due to other factors).

OK, they may be a few grams lighter but the cost is bonkers IMHO

IIRC there where issues with some TDM overbore pistons wich was fixed with carillo´s...pistonslap me thinks. Maybe they´ve experienced the same "remedy"....don´t know though!

[MGScandalo]

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!

Hi,
it is a tdm 900 block. You can use the TRX rods. The pistons are much better than the original TDM900 piston!
The TDM 900 has a compression: 10,4:1 ! My piston : 11,5:1.

I have two sets, now! One is sold for a german TRX900. The other one stands in the ebayyyyyyyyyyy.
Sorry for my bad english!

@Killer:
Gehirmschmalz = google translater= brainpower
You need Gehirnschmalz to create a 92mm piston with compression 11,5:1

Regards
MGScandalo

[NWS870R]

Those are Coerce rearsets - hardly a moto twins project?

My 870 motor has a comp ratio of 12.5:1 with skimmed head - maybe i have Gehirmschmalz?

[devlin]

Is this a pissing match? Where's the line?

Guy's there are more than one way to skin this cat. Personally I'd stick with stock and go for a rotrex supercharger. What ever gives you wood.

[misterdimwiddy]

Those are Coerce rearsets - hardly a moto twins project?

My 870 motor has a comp ratio of 12.5:1 with skimmed head - maybe i have Gehirmschmalz?

Morning NWS870R

My name's Phil and I am a new forum user currently trawling through the huge amount of useful info available.

Your msg caught my attention because I am struggling to find a definitive comment on the maximum recommended compression ratio to use with the TRX. I have seen figures in excess of 12 or 13:1 but feel this may be asking for trouble.........

I have owned my P reg TRX for 5 years and now use it as a (surprisingly capable) track day only bike which I am rebuilding this winter with JE 878 pistons. As I rebuild the motor I will be measuring the squish clearance and then skimming either the head or the barrels to optimise the squish to 1.0mm (Richard at TTS recommended this as a minimum value) and raise the ratio. At the same time I will use a burette to confirm the actual ratio using the JE kit.

I want to up the ratio to get as much benefit from the piston kit (and because my brother is giving me a hard time round Brands Indy on his naked Z1000) and had 11.5:1 in mind as a safe limit and then saw your comment that you use 12.5:1. Was this achieved by skimming the head alone; it appears to me that you can only remove a small amount of material before contacting the centre inlet valve seats. Any problems with detonation/reliability?

Maybe I should just track my VTR SP! but I'm too scared of trashing it and love the forgiving nature of the TRX.

I almost turned round and went home arriving at Snetterton 300 when I was the only bloke who rode to the circuit. Felt like a full race meet with vans, tyre warmers, the finest machinery everywhere and I saw myself being blitzed by the lot of em. Reality was however quite different and I can't tell you how much fun there is to be had taking 100yds out of a bunch of R6's/750k5's on the brakes down the back straight or passing an RSV4 around the outside of Corams. Love it and recommend it to all TRX owners.

Definitely need a bit more grunt though; hence the winter mods. Probably end up with all the usual stuff such as FCR's, TPS mod, big headers etc but at the end of the day, looking forward to 2012 track days and annoying the lads on their trick modern machinery.

Any help with compression ratio limts/mods would be appreciated.

[Mincehead]

The Over OV-15A TDM based racer was running 12.8:1 Arias pistons, albeit on race fuel I guess:

http://www.motorcycle.com/manufacturer/ ... 16115.html

You are aware that you can machine the bottom of the block as well as the head to achieve the desired compression ration / squish band?

[BigAl-TC]

Reading Mr Widdy's post , it would appear he does realise he can machine the block as well .

[Stankflapper]

Reading Mr Widdy's post , it would appear he does realise he can machine the block as well .

Machining cylinder heads and blocks to try and achieve 12.5-1 will still have piston to valve interference, in my opinion you would need to buy high comp pistons, to avoid all the associated problems with cam timing , valve contact when you machine that much material off components.

[NWS870R]

Different base gasket thicknesses anyone

Mines done 14K miles on oversize Yam pistons at 12.5-1 comp with no problems at all - if i'm honest i wouldn't use aftermarket pistons but that's just my opinion not 'bible' or owt!

[Stankflapper]

I am a little confused here as the standard TRX runs 10.5:1 comp and I agree that over size pistons will lift the comp slightly, however lifing the comp ratio 2 points is a verrrrrrrrrrrrrrry big ask without the use of a big bore kit and high comp pistons.

If I am wrong please correct me

[Mincehead]

I believe NWS870 had his head skimmed / machined. He modified the TRX motor too!