Yamaha TRX850 Enthusiasts Forum

Hello

New to the forum.

Bought my first TRX a few weeks ago. Have so far changed the fork oil, engine oil and rebuilt the brakes ( blue spots up front with braided lines).

Finding it a brilliant bike, but it seems to be lacking top end ( compared to other people i ask who have owned them). The max i can get from it is 110. The gearing is all standard.

Its running a set of ART cans and there is no popping or burbling on the overrun. There doesnt appear to be much in the way of engine braking either! ( about the same as my track zx6r).

My next port of call is the airfilter and carbs, but just wanted to ask on here if theres anything else i can take a look over while the bike is apart?

Thanks muchly.

I would say it needs fuel circuit checked.

Air filter is the first thing to check.

Starting from the fuel tap (rubish inside the tank) , checking for cracks in vacuum rubber hoses from the intakes to the fuel pump and petrol tap. If you cant find anything wrong here and assuming the bike starts ok (good cylinder compression) move on to cleaning carbs and jets and checking diaphragms for holes.

That's my 2p

110!!!! Ferk, mine can pull that in third on stock gearing. As Hugo says, very likely carburation. The TRX carbs always seem a tad `fat`, (rich) on standard settings.
Get the airbox off, carbs off, good clean and check over, especially the emulsion tubes and float heights.

Cheers for the replies.

It seems to pull and ride fine ( bar being a bit juddery around 2-2.5krpm's).

After looking the oil that came out of the motor, im hoping to find a blocked airfilter!

What should the float heights be set to out of curiosity? Also the slow running/pilot screw standard setting?

110mph equates to 180kph or so ..I'm betting its that limiter problem in the speedo..

cobbadiggabuddyblooo wrote:110mph equates to 180kph or so ..I'm betting its that limiter problem in the speedo..

It has MPH clocks on it? Unsure if its an import or not, im in the UK.

It doesnt need the choke to start from cold either...

Those float heights, from memory, should be 14 mm. SEARCH facility, top right is your friend. There`s loads of stuff to read through here, kind of like a Mills and Boon without the mushy shite.

Replaced the airfilter today. Not much difference.

Reset the pilot screws as they were both out, better low down (less juddering).

The absolute max it will do is 120mph at 8krpm. But running through the gears it will rev well into the red. (didnt take it anymore as i was afraid to blow the thing up!)

Mate........ as cobba said, it sounds like it is an import,
Imports ( in Aussie) usually have black motors, black speedo and white faced rev counter, brembo calipers on front,
they are restricted to 180 kph, through a tab in the speedo, there are plenty of threads about this tab, search.
If your bike does not have these features they could have been changed at some time in its life,

Just did all the work for you
http://www.trx850.motomaniac.net/forum/ ... ors#p12922

As much as the Search function should be my friend, it isnt, as i cant find much in the way of useful info, just the same posts over and over. ( Probably doesnt help as i dont really know what im looking for in the way of problems, just guessing/going through what i know).

The bike has 4UN on the frame and CDi.

Heres a pic, it might help tell if its an import or not?

You've answered the biggest question - if your bike was an import (regardless of colour ) your CDI wouldn't have a 4UN marking so ignore any suggestion that it might be because this is where the top speed restrictor comes from (the CDI)

Try sitting at around 100mph on an open motorway in top gear then snap the throttle open to full opening, if the engine dips power or bogs down noticeably you have a fueling issue which could be as simple as a badly attempted re-jet. TRX's are a bugger if not carb'd correctly so worth looking at properly.

i had the factorypro TI needles, new emulsion tubes and jets installed along with a K&N filter; took it to a good mech, who set it all up.
Happy i am..
P.S. also check for airbox mods as the std carbs like still air to work with; and check the two little breather filters (strainers really) under the back of the tank.
they can be disassembled and cleaned. these two give the cv carbs the atmospheric pressure they need to work with.
Cheers
fung.

Another thought......

I had a Triumph 900 which had a top speed/accelleration issue.

Came down to a blocked vent hose/breather into the tank.

Would let enough air in when it was sipping fuel, but not enough when it needed to gulp it down.

Easy enough to check the breather pipe, or take it for a spin, high speed, until it does the problem, them pull over quick and listen for a sucking-air sound from around the filler cap, or open it and see if it draws in a big slug of air.

On the restrictor thing, yep its a uk bike, but isnt there also a restrictor in the back of the speedo? (a small metal tab that can be bent out the way?) but would only apply on your bike if the clocks had been changed?

Evoboy, I take it the chain is not too tight, or you have a brake binding issue?
Could be clutch slip too, try this:

Accelerate hard when in top, pull the clutch lever in quickly (usually termed `dipping`) then as you let it out crack the throttle open. If the motors revs sail into the redline but the bike doesn`t accelerate it`s cluch slip.

I still reckon it`s very likely fuelling though, check your mirrors or glance behind you at the exhausts while giving it the beans (through the gears), if you see black smoke it`s as rich as a Russian oligarch!