Yamaha TRX850 Enthusiasts Forum

At the moment, I've got some FCR41's with foam pod filters and a full exhaust system on a totally standard motor, which equals 90 ponies at the rear wheel.

I'm happy with my handling and braking (ohlins springs, hagon shock, bluespots, 180 rear tyre) so now I want to spend a few more quid on the motor, so whats the best next step?

Not after spending mega-money on overboring/fancy pistons/rods/cams etc, so I presume I should be looking at a clean up or gass flow of the head and inlet/outlet ports?

Suggestions please.

Cheers,

Dave.

trixynut wrote:At the moment, I've got some FCR41's with foam pod filters and a full exhaust system on a totally standard motor, which equals 90 ponies at the rear wheel.

I'm happy with my handling and braking (ohlins springs, hagon shock, bluespots, 180 rear tyre) so now I want to spend a few more quid on the motor, so whats the best next step?

Not after spending mega-money on overboring/fancy pistons/rods/cams etc, so I presume I should be looking at a clean up or gass flow of the head and inlet/outlet ports?

Suggestions please.

Cheers,

Dave.

Have a look at the pics of HansJ´s head, copy that and i´m not surprised if you get close to 100 ponies....at least with a hotter cam (but you didn´t wan´t that.... )

turbo

turbo

..isn't that a fish?

keep 'em coming...

well ok, if it were me I'd look at big bore next. depends on your budget though. what other options are there? head work, cams, lightened and balanced crank and rods.

cams are the cheapest option but maybe not much use on their own.

to my mind the big bore is the simplest, and least risk of the tuner getting it wrong.

of course, super light weight wheels might make you quicker in the real world.

youngy wrote:turbo

There are one TRX soon finished in Sweden, will be very interesting!
....and if done yourself i´ve heard of around 700€ all in for a IL4!
Talk about bang/buck!

I think that when Simon Hargreaves built a modded TRX for PB magazine, it had flow work done and didn't get a huge amount of extra power - but that's just from memory. It was sort of like their ZXR400 'special' where they spent the Olympic budget on it and got 5 bhp.

Weight reduction would of course help the power to weight ratio and the handling at once. Homemade lightweight tank perhaps? Lighter wheels would probably be a very good idea, as I'm sure those things are made of rocks. Makes a lot of difference in getting the power down over the sort of twisty roads TRXs are good on. If I compare the adhesion of my (proflex/maxton rebuilt) suspension with the standard stuff on my Duke II, the Duke slaughters it. I suspect a lot of that is actually unsprung weight.

Remove a decent bit of sprung and unsprung weight and your power-to-weight ratio might well increase as much as it would with head work alone while making the bike handle even better.

Dave

don't bother unless you are going to do it all. IMHO gas flowing and cams are a waste of time in isolation. Big bore is good for extra torque / mid range but if you are going to do that you might as well do the rest while you are at it. All three will get you about 10bhp.

You've done everything you can in terms of easy power and I'd be happy with what you've got

But if you are going to do anything to the engine, I'd suggest head off, quick skim and gas flow, new rings and new cam chain. But you are still looking at £200 for the flowing and £50 each for rings and chain plus labout if you can't do it yourself. And new gaskets, oil etc.

Or you could do soemthig different? Get the crank knife edged, balanced and polished.

Or, as has been said, spend some money on wheels.

or spend it on beer and trackdays

Or buy a shitter and do it up

quote ...£200 for the flowing and £50 each for rings and chain plus labout ,

labout ?????
or you could just go and buy a R1 with 50bhp more ,,, chasing 10 or even 20 bhp on a trx is not for me ,,but do what you do and good luck

idl1975 wrote:I think that when Simon Hargreaves built a modded TRX for PB magazine, it had flow work done and didn't get a huge amount of extra power - but that's just from memory. It was sort of like their ZXR400 'special' where they spent the Olympic budget on it and got 5 bhp.

Weight reduction would of course help the power to weight ratio and the handling at once. Homemade lightweight tank perhaps? Lighter wheels would probably be a very good idea, as I'm sure those things are made of rocks. Makes a lot of difference in getting the power down over the sort of twisty roads TRXs are good on. If I compare the adhesion of my (proflex/maxton rebuilt) suspension with the standard stuff on my Duke II, the Duke slaughters it. I suspect a lot of that is actually unsprung weight.

Remove a decent bit of sprung and unsprung weight and your power-to-weight ratio might well increase as much as it would with head work alone while making the bike handle even better.

That was Mark Forsyth built that bike. Last time I spoke to him he still had it.

steve speed wrote:quote ...£200 for the flowing and £50 each for rings and chain plus labout ,

labout ?????
or you could just go and buy a R1 with 50bhp more ,,, chasing 10 or even 20 bhp on a trx is not for me ,,but do what you do and good luck

Labour! Or in my case maybe I meant layabout!

I think you're missing the point with the R1 comment - it is (for the sake of stating the bloody obvious) a completely different machine.

I see any changes made to the TRX as evolution and updating of a classic design. Better handling, more power, some bling - who cares. Making it that little bit better is what it's all about. Oh, and having something different.

You may not see the point of chasing extra bhp but as someone who has extensivley modified their bike I am somewhat surprised by your "do what you do comment". I don't see the point of putting flat bars on a TRX or painting the cam cover - but nobody has told you to go and buy a bandit and a paint by numbers kit.

the term do what you do means just that ,,if spending a £1000 on your engine is what you fancy doing then fine (do what you do )if making your trx into and looking like something that you like thats fine also ,,but perhaps what i should have said is that as a road bike you will get more out of suspension mods for your £1000 than 10bhp from your engine ,i am sorry if i upset you phuk it was not ment to

youngy wrote:

idl1975 wrote:I think that when Simon Hargreaves built a modded TRX for PB magazine, it had flow work done and didn't get a huge amount of extra power - but that's just from memory. It was sort of like their ZXR400 'special' where they spent the Olympic budget on it and got 5 bhp.

Remove a decent bit of sprung and unsprung weight and your power-to-weight ratio might well increase as much as it would with head work alone while making the bike handle even better.

That was Mark Forsyth built that bike. Last time I spoke to him he still had it.

Ah, apologies! So it was the other half of that well known journalistic tag team...

Indeed so. Cumbrian Monkey!

I have to admit that I would look towards a larger bore, but again If I was after more ponies for the track, either buy another bike and set it up specifically for track use and keep the one you have for road work, or get a different bike for the track. Over only got so much out of theres, and it would still have been trounced by an R1 or gixxer thou. Horses for courses.

Dave E