ss valves bigger?

[burty]

Wasn't it originally a 650?

I think one major limiting factor is the size of the exhaust ports.

[youngy]

What was the 650 motor used in?

[burty]

Dunno. I'm sure I read that somewhere, but it may be the case that the writer was confusing the Tenere (660cc single) with the Super Tenere (750 twin).

[slow codger]

Was originally the XTZ 750, before being bored out etc for the TDM. I know that Stefan Peterhansels XTZ was an 850, but not sure in what guise (TDM or forerunner of TRX), but it was a tricked up motor.

Dave E

[Banger]

how far is safe to rev it to as mine now pulls 9000 rpm without any show of reduction in power

Well, 9500 is the limiter so rev on!! ....or do the CDI mod and get 10k....

Mine is a u.k 97 model has mine got a 9500rpm rev limiter

[cobbadiggabuddyblooo]

yes 9500 is std inbuilt limiter on the trx.. unless you have disconnected the TPS(throttle position sensor..acts like an auto advance) and modified where the TPS loom plugs into the ignitor unit under the seat . This modification set the it unit to constant full advance and rev limiter to 10,000rpm with gains of 1 to 2 h/p.

[Banger]

yes 9500 is std inbuilt limiter on the trx.. unless you have disconnected the TPS(throttle position sensor..acts like an auto advance) and modified where the TPS loom plugs into the ignitor unit under the seat . This modification set the it unit to constant full advance and rev limiter to 10,000rpm with gains of 1 to 2 h/p.

Good to know Cheers Cobba

[cobbadiggabuddyblooo]

Thanks to all those who taught me all about these great motorcycles on this site to start .. I'm just passing on what they have taught me...

[sanddune51]

I have been eagerly catching up with all the great posts and topics here as a new member . I for one appreciate the more technical aspects...thanks to all those who are happy to share the hard earned knowledge they have acquired .

I really have tried to research the information I am now requesting but have come up short. I apologize in advance if this information has already been posted .

I would like to know what the standard valve head diameters are for the various 5-valve Yamaha engines including TRX and TDM (850 & 900)

I have previously found very useful performance gains from very careful cylinder head porting and now wish to try to the same trick with my TRX. I would really appreciate any data that you guys can provide. I really need to gather together all the relevant information before I begin so I can plan a methodical scheme of work. In summary I plan to port the head and only fit bigger inlet or exhaust valves if I consider it absolutely neccessary.Hopefully Yamaha have got it spot again and will have designed the head with 23mm inlet valves and 30mm exhaust valves.(bigger I can live with,smaller I can't)

I am also planning to fabricate a new stainless (304 grade) exhaust system with larger than standard header pipes. If all goes to plan the TRX will donate it's standard headers to my little SZR 660 which appears to be exhaust limited...... so all in all plenty to be getting on with

Thanks in advance,Mark.

[Mincehead]

Ahaaaa a fellow SZR660 lover.
I`ve also got an SZR660 engined bike,the MuZ Skorpion.Cleverly designed (Seymor powell/Dave Pearce of Tigcraft) little beast with an amazing ability to outhandle pretty much anything else I`ve ever ridden but still with plenty of scope for improvement by engine mods etc.The motors can go out to 720cc without stroking the crank,760cc with I believe
Talk to Straightline Racing:

http://www.straightlineracing.co.uk/index.html

Those guys know the SZR/XTZ660 motors inside out and may well be able to help in your ideas about valves for the TRX/TDM motors.

[Quan-Time]

@sanddune51
"special" porting technique ? PLEASE tell me you have a flow bench !. and by "special" do you mean "motomans" 65% rule ? heh.. its a concept, its by no means perfect tho.. Think of it as a "starting point".

The main reason a TRX doesnt rev all the way out is due to excess weight. You have a HUGE crank, its like 3x the weight of a R1 or a ducati, 5v not 4v, so more spring weight and valv weight, and cos its a parallel, you have a huge counter balance shaft(s). All this added up really saps out power, or the ability to produce it "easy". With that said, it helps produce more torque from the old inertia rule "a body in motion wants to stay in motion"..

If you used Ti valves, with 4.5mm stems, Ti retainer caps, new springs to accommodate them, hollowed out cams, revised port work on exhaust, its possible to make the TRX rev much like a modern sports bike. Where it can rev quite freely. BUT you will sacrifice other characteristics.

The main benefit of stainless over stock ones is price and having them cut to your own shape. (you can find SS ones CHEAPER than stock yammy ones if you look around). Some of the car guys have "sodium impregnated" valves. they are noticing more power up top over stainless. This is on RB26 turbo motors. Its actually recommended to stick with the stock sodium ones as they are fine. And pushing 800hp from 2.6litre, thats a fair bit of mumbo.

Its also note worthy that the carbs are the biggest restriction on the engine, followed closely by the exhaust. If you want to start increasing valve diameters, id STRONGLY suggest going bigger than 41mm carbs, else your not making a huge "bang per buck" investment.

Summary: ride a TRX stock, its got plenty of power, and soon as you start doing one thing, its a HUGE chain effect and your wallet empties before you know it.. Im a living example of that.

[Mincehead]

A company like this one found during a very quick search,custom stainless steel valves for just about anything,this one in South Africa but there are companies in the UK that can do the same:

http://www.sportflo.co.za/Custom%20Stre ... alves.html

http://www.sportflo.co.za/valves_specs.html

[sanddune51]

Mince,
I thought there may be one or two others here harbouring a soft spot for the SZR or MZ Skorpion Sport. I loved the concept when they first appeared around '95 or '96 but they were hideously expensive at arouund £5300 .
They are a little left field and have a small but dedicated following.Much like the TRX in many respects.
They respond very well to tuning . The same basic engine is fitted to the Raptor quad (complete with reverse gear!). In the States there are dozens and dozens of companies offering more tuning parts and options than you can shake a stick at.
My newly purchased SZR requires me to sort out a few little niggles before becoming a pleasant ride, broken and sticking twistgrip,badly worn and appallingly sloppy gear linkage and a high speed carb glitch which is knocking 30mph off the top speed.Will start rectifying those next week.

Qaun,
Thanks for the reply. Don't have time to reply right now , but will get back to you after work this evening.

Mark.

[sanddune51]

Quan,

Thanks again for your reply.

"special porting technique" absolutely not! I would run a mile from that sort of bullsh*t.

What I said was "useful performance gains from very careful cylinder head porting" and thats exactly what I meant. Experience gained by porting cylinder heads has shown me conclusively that very respectable gains in performance can be achieved in the home workshop.

I only take my bikes to a bike shop for their mandatory road worthyness check (MOT)

I would rather carry out my own modifications and upgrades. Far more satisfaction is to be had doing this work myself than giving "snake oil salesmen" good money for who knows what.

I dont want to completely change the character of my TRX or try to alter it out of all recognition to the bike I love.What I would like to do is to "plump up" the torque curve using incremental modifications carried out by me alone.I don't want to raise the engine speed of maximum torque by more than a few hundred R.P.M. I don't want to turn turn it into an unreliable "roadracer wannabe" and never want to rev it "all the way out"

As for having a flow bench,thats a very heavy investment in time and or money and in my opinion totally unneccessary. There are plenty of publications and papers by eminent engineers who have spent cumulatively thousands of hours testing cylinder modifications on a flow bench.These Engineers/Journalists are happy to publish their work for the amateur reader to benefit from their experiences . Two of my favourites are Graham A. Bell and David Vizard.Some of their books have been thumbed by me so often over the last 25 years that they are now falling apart .

I have never heard of "Motoman" but will certainly check out his views as I can never have enough knowledge. Tell me where his work can be found.

I am in total agreement with your summary.Any sort of tuning will always leave you looking for the next weakest link in the chain. It is all so easy to become an expensive obsession which leads nowhere.

Back to my original post..... I now have the information I was looking for:

TRX std INLET VALVE DIAMETER - 26mm

TRX std EXHAUST VALVE DIAMETER - 28mm.

Mark.

[Quan-Time]

AH... the old steve visard,, i know him well (not personally) !.

As for a flow bench, im still a STRONG believer in them. Help to "confirm" how much things are changing. Im a bit scared of people who go in start grinding WITHOUT confirming any numbers or proof on a setup (flowbench or dyno). Yes its possible, No its not a good idea.

Modifying your own bike ? man after my own heart !!

http://www.mototuneusa.com/think_fast.htm - webpage is HUGELY messy,
www.speedtalk.com - i have most of the audio books on that site.. Mainly the "engine tech" ones and none of the sponsorship / chassis setup stuff. Interesting ideas on how the "pros" go about it.

Wouldnt mind contacting you off list and bouncing ideas off each other if your open to the idea.