Yamaha TRX850 Enthusiasts Forum

After a great track day at Donnington this week, first time out in the fast group, I am thinking where can I get another 10+rwhp? No chassis/handling problems at all slowing me up, brakes are as good as they need to be but with a bit more go I would be there with the R6's I'm sure of it. They are not killing me totally down the straights (though the litre bikes obviously are) and I seemed to lose a few seconds a lap to a well ridden R6 even on a long sweeping circuit like Donny.

Have probably spent close to £1800 on parts and engine work (including full rebuild due to crank) to get from 70ish to 90hp but cannot see what else Over must have done to their BOTT racer to get beyond 100hp, never mind the claimed 115??

Other than running silly compression ratios, different cams, bigger valves, fancy ignition, Carillo rods to allow higher revs...........what more can you do and would these really combine to add the same power gain as my 878, FCR's and Akra?

Weight loss has to be one factor I suppose; 165kg's would help but I have probably junked 15+kg's already from stock (no road gear, 2 into 1). Losing lots more (new wheels, carbon stuff etc) is not financially viable.

Maybe I'm expecting too much from the 17yr old girl and I'd hate to see it go after the work I've done but I want more speed! I'm riding my nuts off and still going backwards.

TDM900 motor may have more potential power but have not seen claims of >100hp for these. Buying one and then tuning it will be a big pile more cash.

My dilemma goes on; I've got the most fun bike I have ever owned and yet I still want more! Human nature perhaps?

Chasing Silver on his virtually stock Rex round Bedford still puts a smile on my face; maybe I need to remember it's all about having fun and not being the fastest out there.

Seeing some more TRX's out on track would be good. How can I encourage the rest of you to abuse your pride and joy?

Back to work; I've got an exhaust bracket to make and a head to port/skim.

Overbored tdm900 barrels is the way to go...

MrD, You kind of answered it yourself with the smile. Got to remember mate, its a track day not a race. That's the difference I reckon. Whether you enjoy doing track days for the shear thrill of that,,,,or you want the race As for spending, every single lad I know who's had a go has never ever ever got enough speed. AND is always skint

As for seeing more Trx's on track

I have been looking at options myself like this , but I still have not seen any decent dyno charts or results from these. The dyno chart I saw of the 960 JE kit on the 900 motor was at peaking at 90hp at 7,000rpm and piston slap being an issue. They have tried to improve on this by tightening tollerences and TTS have a JE932 now but havent seen any results on these. Once bored you still have to coat them so an expensive ask plus 900 rods needed too.
So many ways to get that little more corner speed and braking. I've come to realise the R6 shock and yzf dogbones was costing me exactly that and causing the squatting issues trying to get that power down out of the corners. I'm keen to play with looking at modifying the swingarm mount to try a few different spacers to raise the pivot point and ride height adjustment on the shock would be a better option than playing with the rising rate ratios with yzf dogbones... Sprocket choice also has an influence here too.. who cares if that new bike goes past you on the straight when you just get it back under brakes and out of the corner just to piss him off again...

Taking the balance shafts out is what over did.I posted the article up here many moons ago. The engine spins up much faster, is considerably lighter but very lumpy under 3500 rpm. Cathcart kept it spinng and was very impressed with horsepower increases. May be the way to go for a dedicated track machine.
Food for thought anyway.

I don't think sinking more money into it is the way to go, with how much you can spend on bikes to get that little bit extra you could just buy another bike to go fast on and keep the trx.
But you will always want more, its human nature. Say you get it to 100bhp+, you will like it for a bit and then want more, you buy an r1 and you will enjoy it for a bit but then you will want your fun trx back.

Exactly so why waste the money on a R1 when underneath that other bloke on his Trx dives under you. The Trx is already open to post classic racing here 90 to 1995 and depends what you want from it . You want to go fast in a straight line or the twisty bits. We have a election happening here at present and its the same argument spend up and buy to keep in debt or tweak what you have to optimise performance for a little cheaper and not goin fast straight ahead or being held up in the corners by red tape and another R1 to pay off...they will both do the same lap times but it depends who is riding

Thanks to you all. I think you have collectively bought me back on track with the TRX (for now at least).

Lots of food for thought though I can't face splitting the cases again to remove the balance shafts!

Yoozy is quite right; it's not a race day and the fact that I am still doing laps in my head three days later tells me that it is not the TRX that is disappointing. I was as fast through Craner, the old hairpin and Scwantz as most and it's corner speed that gives me a rush. I was often able to make ground on the brakes and smiled when an RC8 ran on at the esses before the Melbourne loop trying to out brake me. Radial Brembo's say what?

Overall I think I've gone round my usual mental loop and will hang onto the Rex for a while longer. Developing my riding is the thing that has surprised me from doing track days. I have never been consistent or that smooth on the road but I now get real enjoyment working on riding technique and precision.

What did come out of Tuesday is the realisation that I can go a lot faster even on the 90hp bike I have. With new found confidence in the front (and seeing the huge corner entry speed of the faster boys) I was able in places to keep it one gear higher than usual entering a turn, get my braking done and turn in much much faster than I have been used to which then fires you out onto the next straight helping make up for being down on power. Up until now I have been a lot more 'really hard on the brakes, turn in and then hard on the power' instead of maintaining momentum.

Better get my head swapped to cure the puff of smoke on down changes, a light skim to get me more towards 12.5:1 and just enjoy what is a well sorted capable track bike.

Now, what about that Sigma slipper clutch....................that must help with rear wheel grip and entry stability/speed!!!

LOL; mods never end when you ride a TRX..........

Off to work now I suppose.

thats exactly why I bought a sigma slipper also to go in on this rebuild I'm doin at present..

I knew you had got one a while back and was hoping for lots of positive comment before I buy one myself!

Think I may take the plunge when I get my 3rd quarter bonus. Have been toying with the idea for a long time.

I am fish tailing going into slower turns and never get to see what the revs rise to on high speed down changes cos my eye's on the turn ahead but I reckon it gets very high.

I love the sound of the screaming 600's fitted with slippers as they go into the corners. Lots of used R6 Sigma slippers on Ebay in the uk but fitment is not compatible with the TRX I doubt although did you comment that Neil Spalding had suggested changing to R6 plates and using an extra plate on the TRX?

misterdimwiddy wrote:...need for speed...

Go racing

Yes Neil has been helpful on any info needed to get the most for what you want from it. One of the other lads here has already one set up so gained a few hints from him also, so I've got some heavier springs to add if needed. he's running 3 H/D and 3 std spaced alternately.

Kayla wrote:

misterdimwiddy wrote:...need for speed...

Go racing

I would if only I was 25yrs younger! Did some proddie racing when I was 20 (CB900F) but was very eratic and couldn't afford a Katana 1100 or a slabside GSXR750 which were creaming everything at that time.

50th b'day in 3 weeks and loving track riding more than ever but with one 5 and one 7 yr old daughter I cannot indulge in racing. The cost and time needed to do it properly would not fit with family life and so the closest I can get is track day riding.

In my next life perhaps I won't miss that boat...................

Decision made.

Ordering Sigma slipper clutch tonight!!

Got your bonus then