878 kit

[steve speed]

went for a thrash today and i think its getting a bit worse ,,there is noticeable blue smoke now on the overrun which i think points to stem seals anyway i will be extracting the lump soon

[Tigcraft TRX]

Don't mean to stir the pot but in the interests of engine development.... The 878 pistons are a lot heavier then std TRX ones - go compare on a set of digi scales. If you're gonna use 'em and want to do the job right you need to balance crank AND balance shafts. I had quite a bit of weight whipped off my crank. But I also know that a few of you lads have had no issues with not doing the above. I've had long conversations about this with TTS, Chris Applebee, Nial Ball, and Dave @ Tigcraft when comparing mine to the Over racing + the holy grail of TDM/TRX engines - Alan Cathcart's one which he wanted stupid money for..

[steve speed]

thanks for the heads up nick,, any info is good

[Quan-Time]

JE do pistons for whatever you want.
the 878cc kit is locked to a supplier in Euro somewhere.

Its basically like this. Someone went out and got a set of +1.5mm (878cc) pistons "designed" by sending them a sample to copy. The place they used (JE no longer deals with customers directly) payed for them to be ONLY distributed via them.

Ive spent some time developing some +2.5mm (907cc) TRX pistons. Also up'd compression a bit. TDM900 is +2mm (900cc).
Ive made a head impression and measured deck height, gasket thickness, etc.. everything was calculated. So if someone wanted a +1mm kit at 11:1 comp, or some other weird number, it could be done very easy. Saying all this, the supplier i used (Albion Cycles, in Qld) is going to lock them to him. At his expense.
For the record, JE only do a min order of 4. Yes, that means i have a spare set of 907cc 12.5:1, race prep (max weight removal) on its way over. they were ment to be here today, but yer.. such is life.

To fit 907cc, you need to punch out your old sleeves, machine your block, make new sleeves to push in. Fair bit of work compared to a 878cc, which is just a bore of the existing sleeves.

As for power benefits ? wait and see. Gotta send the crank off for balancing when they arrive with the new conrods (carrillo).

[steve speed]

Don't mean to stir the pot but in the interests of engine development.... The 878 pistons are a lot heavier then std TRX ones - go compare on a set of digi scales. If you're gonna use 'em and want to do the job right you need to balance crank AND balance shafts. I had quite a bit of weight whipped off my crank. But I also know that a few of you lads have had no issues with not doing the above. I've had long conversations about this with TTS, Chris Applebee, Nial Ball, and Dave @ Tigcraft when comparing mine to the Over racing + the holy grail of TDM/TRX engines - Alan Cathcart one which he wanted stupid money for..

if the 878 pistons are heavier is there no way they can be matched to the std ones ? or are we talking a lot of weight ??

[steve speed]

sent the barrels off to TTS today only problem is they have no pistons so its a three week wait until they come in from JE , started to check and measure valves today and they are well within spec so it looks like my engine has the later set ( the ones that don't stretch ) cam bearings are all ok as are the cams

[steve speed]

barrels and pistons back today and ive now had chance to weigh the bits
the std pistons ,(this is a bare piston)316.5 gram
std gudgeon pin 72.8 g

je piston 335.5g
gudgeon pin 84.4g
so that's a 30.6 gram difference per piston ,,it sounds a lot to me but what do i know !!!





now one more thing the manual says that the trx has 10.5 to 1 compression so what is it with je pistons ???

[Killerwhale]

barrels and pistons back today and ive now had chance to weigh the bits
the std pistons ,(this is a bare piston)316.5 gram
std gudgeon pin 72.8 g

je piston 335.5g
gudgeon pin 84.4g
so that's a 30.6 gram difference per piston ,,it sounds a lot to me but what do i know !!!
now one more thing the manual says that the trx has 10.5 to 1 compression so what is it with je pistons ???

11,5:1 i will probably skim the head to 12:1-ish for the next season...
Hope you told the one´s doing your barrels that the pistons are different size...i told those doing my barrels but they forgot and had to take up one of them again....could have gone bad!

[steve speed]

barrels were bored by TTS the firm that supplys the pistons in the uk , and they tell me they have done loads of them ,,,now can someone confirm the ring gap ? is it 0.30 to 0.40 top and second ring and .020 to .070 oil ring ??

[honkdawillydahonk]

barrels were bored by TTS the firm that supplys the pistons in the uk , and they tell me they have done loads of them ,,,now can someone confirm the ring gap ? is it 0.30 to 0.40 top and second ring and .020 to .070 oil ring ??

Didn't TTS gap them and send them labelled up for each cylinder?

[phuk72]

wot he said ^^^^ - they wrote mine on the box (do a search, I have posted them before)

[steve speed]

no they didn't only one piston had been unwrapped,, rings were still sealed in boxes ,,second ring was bang on gap .30 but top one i had to do it was .15 ,,oil ring is also ok at .20

[HansJ]

Real men don't need help with the gap...

[steve speed]

Real men don't need help with the gap...

you need help

[Tigcraft TRX]

Richard Albans (TTS) stated that the 878 pistons are 10.5-1 because the valve pockets are slightly deeper, but squish is improved through piston design. I told you that JE pistons were loads heavier Steve!! (joke)
I had to file a couple of the rings from my TTS kit slightly wider. TTS also don't bore the barrel as far as JE recommend, as JE produce predominantly car pistons, with clearances on the fitting instructions for V8's instead for bikes..
Make sure your gasket's bored as well.. The race is on for 878 rebuild - should get my engine back built mid next week. Tigcraft TRX is here!!!!!!!!!!!! (>100hp I hope)