Yamaha TRX850 Enthusiasts Forum

In my 18 months of TRX ownership, I have made a number of "sensible" bolt-on mods: front mudguard extension, hugger, cockpit clock, rear grab-rail/rack, swing-arm bobbins, iridium spark plugs, blue spots, braided brake-lines, gold Art cans, heated grips, battery connector (for a solar-panel trickle-charger), & a chain-oiler. I have also removed the pointless lock holder in the underseat cubby, and I replaced the original kph clocks with mph ones.

The chain-oiler has been amazing; not only has the chain stayed in perfect condition with virtually zero stretch over 10,000 miles, but the free-running chain has let me regularly get 55 mpg.

My next project is to get a bit more poke out of the engine, and the question now is: what is the easiest and most cost-effective way of increasing the output of a standard TRX? I certainly don't want to mess with the crankshaft, and before I even consider changing cams or polishing the inlet tracts, I'd rather do easier "bolt-on" mods, which I presume might include new air-filters and carbs.

My TRX will be yielding perhaps 75bhp, with standard torque. I'd like to have up to 90 bhp, but my higher priority is to have even more torque. So what's are the best options for a quick and easy upgrade?

Bolt on power:

Keihin FCR41mm flatslide carbs
Foam pod filters
Bigger header pipes (Acra or similar)
End can or cans


Instant 90bhp on a standard engine

Search is your friend...

trixynut wrote:Keihin FCR41mm flatslide carbs
Foam pod filters
Bigger header pipes (Acra or similar)
End can or cans

Worth it just for the extra intake churtle and grumbling exhaust!

trixynut wrote:Bolt on power:

Keihin FCR41mm flatslide carbs
Foam pod filters
Bigger header pipes (Acra or similar)
End can or cans


Instant 90bhp on a standard engine

Search is your friend...

Yes but this ain't sheap. Me like flatslides

Get an Aprilia RSV Mille Factory, a Suzuki TLS, a Honda SP-2, a Buell, KTM, or a Ducati. or for just general lottery winners a Vincent Black Shadow, or even a Brough Superior SS100. There are others, as I'm sure you know.

Dave E

Rotrex bolt on super charger.

http://www.rotrex.com/Home/Technology/P ... _Data.aspx

If you want 90bhp from a TRX engine (from bolt ons), then Trixynut has given you the right answer - Flatslide carbs and a full aftermarket exhaust.

But, this will cost you around £1000 by the time you factor in dyno time.

As has been said, search around the site. Plenty (including me) have done a fair bit of engine tuning

trixynut wrote:Search is your friend...

Thanks chaps! ..... In fact, I did plenty of searching beforehand; but what I was hoping for was a clearer indication of the effectiveness (and cost-effectiveness) of each mod. There's lots of tuning information and knowledge on this site; and it is better to learn from others, rather than try to reinvent the wheel and make expensive mistakes along the way. Ideally, it would be nice to be able to generate a table such as this (figures are random):

Keihin FCR41mm flatslide carbs: (say) extra 3 bhp
Foam pod filters: + 2
Keihin FCR41mm flatslide carbs AND Foam pod filters: +6
Bigger header pipes : +2
End can or cans: +2
Bigger header pipes AND End can or cans: +5

I have already fitted some nice Art cans that yield a nice rumble, but whether the performance is better, I can't say. Regarding the Akra header pipes - do they have a substantially larger bore than standard? And if one fits new foam filters alone without new carbs, would that give a noticeable difference?

Broadly speaking, you will get the following over stock:

End cans - 4 or 5 bhp
Free flowing filter and air box mods - 2 bhp

Neither of the above should require any rejeting. Anything beyond this requires proper jetting and dyno time

Gas flowing, cams, big bore kit - 10bhp (and lots more torque)

Free flowing exhaust (e.g. Akrapovic) plus end cans - 7 or 8bhp

FCR41 flatslide carbs - 8 ish bhp with airbox, 10 with pod filters

You can further if you want but then you are getting into big money for comparitavely small gains.

Mine has all of the above and I have dyno charts taking it from low 70s as standard to over 102 bhp

phuk72 wrote:Broadly speaking, you will get the following over stock:

FCR41 flatslide carbs - 8 ish bhp with airbox

Yep. Mine has the TPS mod and will happily pull well past 140mph on standard gearing and is faster than my bf's Buell XB12R.

phuk,
you reference "Free flowing exhaust (e.g. Akrapovic) plus end cans - 7 or 8bhp", I have a full OVER stainless system, I noticed an improvement in Ponies to the rear wheel but would you think an Over exhaust would give a similar result to Akrapovic ?

Sniffing around the idea of FCR41s but I'm baulking at the Oz price.

Off to buy a lottery ticket.

Kais wrote:phuk,
you reference "Free flowing exhaust (e.g. Akrapovic) plus end cans - 7 or 8bhp", I have a full OVER stainless system, I noticed an improvement in Ponies to the rear wheel but would you think an Over exhaust would give a similar result to Akrapovic ?

It should do. I've not direct comparison to make as I've never owned Over pipes (but I have owned other Japanese market big bore headers) but the stock pipes really are restrictive and anything by a big name brand should give you a 10% power gain.

IIRC the best gains were to be had from either Akrapovic (at the top end) and Renegade (mid range)

I thought the OVER pipes are even bigger than the ones from Akrapovic?

Tarwetijger wrote:I thought the OVER pipes are even bigger than the ones from Akrapovic?

I have both Akra & MAB and the Akra is tiny at the head compared but taper up further down so bigger there...
MAB ends up in 2x55mm and the Akra 1x60mm (there are smaller bore Akra as well, 52 i think it is...)

MAB´s are a nice road setup as the power delivery is immidiate...
Akra kicks in quite a bit higher up in the rev range and are a complete dog with standard can, i´ve put a stubby arrow on mine and what a difference!

I had an Over system for a short while but they did not clear the YZF swinger, but when measured they where in between in bore size where MAB has the biggest. BUT bear in mind that you have the aftermarket Over in stainless and the "real" ones are titanium one´s (like the one´s Peder has on his) Rare item that is....

Tarwetijger wrote:I thought the OVER pipes are even bigger than the ones from Akrapovic?

Bigger isn't necessarily better though

I have already typed a reply but it seems to have disappeared and I CBA to type again but it is all to do with how the gases flow (ID and taper affect this)