Yamaha TRX850 Enthusiasts Forum

Hello,
New TRX owner here with what I suspected was emulsion tube problems. Bike is popping on tickover and over run, low speed part-throttle riding results in the bike lurching as if over then under fueling in quick succession. It just won't hold a constant speed.

After hunting on here though I don't have any problems starting the bike either hot or cold, she revs ok and pulls to the redline ok so not too sure now.

The bike has 15.5k miles but had been stood before I got her. Drained the fuel tank and float bowls, put in fresh fuel and carb cleaner, replaced the plugs (NGK) and fitted a K&N and also replaced what I thought was causing the problem with a new coil on the left hand cylinder.

Should I do a TPS check first then strip the carbs anyway?

Thanks
BBB

Check the TPS for sure but I`ll bet good money on it NEEDING a carb strip,fuel/float level check/adjust and possibly emulsion tubes and needles.
Fuel additives nowadays lead to `varnishes` building up in carbs if stood for any length of time,tis a common problem.

^^^^^^^^^^^^^^^^^as above,, tubes and needles plus set float hight to 11mm show us a picture of your trx

Right carb strip and rebuild it is then. Where is the best place for emulsion tubes and needles?
NRP in Manc do the emulsion tubes cheaply enough, had a look at Kedo and their Anti-Ruckel-Kit.

Have read that (on an XT600) the kedo kit can cause the bike to run lean, any known issues on the TRX or should I just get the needles and tubes as I want to run noisy cans at some point.

i used factory pro tubes and new yamaha needles

Factory Pro are marketed by Straightline Racing:

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

But you could always try these boys too:

http://www.nrp-carbs.com/

I`ve heard they`re really good price wise.The Factory Pro emulsion tubes are nickel plated(although I`ve just looked at the Straightline Racing image of them and they appear to be plain brass) nickel plated brass will definately wear much more slowly than the stock brass tubes but they are FORTY`ish quid!

Done the TPS check, was reading 8k, now set to just over 4k couldn't get it bang on 4k. Still flicks between 1 and 4 though if you just touch the sensor

£80 for two tubes plus whatever Yamaha needles cost seems a bit steep. Anybody had experience of the NRP tubes?

Did you note the cost of the Factory Pro needles in titanium?
80 frigging quid!!!!!!
The NRP tubes will likely be copies of Yamaha originals,likely in plain brass so you pay your money you make your choice.
Plain brass will wear faster than the nickel plated chaps.

BBB wrote:Done the TPS check, was reading 8k, now set to just over 4k couldn't get it bang on 4k. Still flicks between 1 and 4 though if you just touch the sensor

£80 for two tubes plus whatever Yamaha needles cost seems a bit steep. Anybody had experience of the NRP tubes?

My stock Mikuni (that's what the Yamaha dealer will sell you) tubes lasted 20,000+ miles before dying. Unless you want to go with the German solution, I would suggest you save your money and buy plain brass. Spend the money on all the o-rings and seals you'll need.

Straightline are about 25 miles from me, got stuff off them when I had the Suzook streetfighter, very helpful, and if they didnt have something they would order it straight away for you.

Dave E

think I will go down the cheap route with NRP tubes and play it by ear on the needles.

am I going to need new float bowl etc gaskets or are they re-useable?

Cheers
bbb

It all depends on how soft the material is,or if it seems compressed beyond a point whereby you can reuse it.The `thumbnail` trick needs to be employed.
If they seem soft,likely you`ll get away with it,but remember it`s going to be you who has to have the bu**ers off again if the carb/float bowl gaskets don`t hold back fuel.
Likewise with the O rings,even the tiny little ferker on the slow running mixture screw and the one under the black plastic carb top.
There`s also a black formed viton gasket under the main jet/emulsion tube holder(alloy)inside the carb,if you suspect they have hardened beyond use or there`s signs of them breaking up etc,it`ll save you a hell of a lot of headaches if you just bite the bullet and get the gaskets/O rings in case you NEED to use them.
Another tip,make sure you check the clip in choke needle assemblies,they are black plastic/nylon and the ends(points)tend to wear and undercut after the vibrations get to them over time.
And if I was stripping the carbs I would do it on some kitchen towel(tissue)the bleached white tissue paper will show ANY contamination/rust/paint flecks/crud, clearly as the petrol evaporates leaving the rest behind.
Remember,ONE CARB AT A TIME,mixing parts from two carbs is not good practice and often accelerates wear and causes more running problems.
I also replace ALL phillips headed screws with stainless cap screws wherever possible but I`m just a perfectionist and cannot abide seeing corrosion on fasteners and cannot abide struggling to undo stuff with chewed heads even more!

I paid 40 notes for the plated, factory pro tubes via straightline which is the exact same price as Yamaha ones. Didn't realise you could pay 80 quid for a titanium pair ! Not that I would have.

No the 80 quid is JUST the needles I believe!
Although I`ve not spoken to Straightline to confirm that,just saw it on their web site.(in the link I posted a couple of posts back).

Called NRP today and ordered a pair of emulsion tubes and a pair on needles. £14 for the emulsion tubes and £12 for the needles (genuine Mikuni).

Not ordered the gaskets yet but may play that by ear when I open the carbs up. Will give them a good clean out and check float height (15mm?).

Anything to be wary of?

Should have ordered the gaskets in advcance