Yamaha TRX850 Enthusiasts Forum

Engine oil stinks of fuel so took the carbs off this morning to check for a worn or blocked float needle. I can see fuel sat on top the valves of the left hand cylinder but the right looks ok.

1. Should i just check / replace the left carb float needle or do both? bit reluctant to mess about if its fine.

2. Whilst the carbs are off is it worth fitting a dynajet kit (or similar)?

thanks
bbb

float bowl is spotless inside no sign of dirt blocking anything and no obvious wear on the needle will order a replacement any way.

I would STRONGLY suggest having a damn good look at the vacuum fuel pump too. When the diaphragm is failing or a similar one in the fuel tap (check that too), fuel can make it`s way down the left inlet stub through the vacuum hose.
Wemoto do a fuel tap repair kit and for the vacuum fuel pump diaphragm try Yamaha and if the price is silly just replace the fuel pump. Ebay UK normally has at least one on there. Alternatively get new from either of the folk in the second and third links.

http://www.wemoto.com/bikes/Yamaha/TRX_ ... epair_Kit/

http://www.cyclewareables.com/pages/fue ... _pumps.htm

http://compare.ebay.com/like/1206920196 ... s&var=sbar

See this thread:

http://trx850.motomaniac.net/forum/view ... +fuel+pump

fuel tap looks ok, have had it apart before, no leakage when i had the tank off last saturday. not checked the pump but will do next.
have used wemoto stuff in the past on my old gpz and was less than impressed, float needles wouldn't seal and the float bowl gaskets expanded and deformed as soon as they came into contact with petrol. Yamaha wanted £65 inc vat for the float needles

if i take the hoses off the inlet stubs and let them hang down should i see fuel dripping out? depending on which vacum hose is dripping points to either a fuel tap or a fuel pump (or both) failure?

thanks
bbb

got a mity-vac vacum pump. if i attach it the the vacum connections on the fuel tap and fuel pump if there are tears in either of the diaphragms should i see fuel running into the vacum pump?

Could i potentially damage a good diaphrapgm with the vac pump?

thanks
bbb

edit: both the fuel tap and fuel pump are holding the vacum admirably - both lines were dry inside, never had the pump line off before and there was a lot of white powder (al oxide??) so doesn't look as if the vacum lines are the culprit.

Strong petrol smell when i took the cover off bit oil smelt fine and looks thick / sticky film on site-glass.

have ordered the parts for the fuel tap from yamaha - very slight drip from the tap.
the bike isn't idling too smoothly so guessing the emulsion tubes are worn again, replaced them 10k miles ago so probably about due a replacement.
got my aux fuel tank so going to check fuel height today as well.

could worn emulsion tubes on their own be responsible?
cheers

hi bbb
i just sorted a similar issue with my xv250.
there was a strong smell of fuel wafting up from the garage, so i went to investigate.
under the bike was a pool of fuel !
i stood it up and fuel poured out of the exhaust drain hole. i mean Poured out !!
everything full of fuel..ar filter..air box..exhaust..bloody oil like consomme' !
i took both the fuel tap and pump apart.looked good.
drained everything..cleaned up everything..put it back together..ran for two minutes like a dog..stood it up and fuel poured out of the air box overflow !!
same deal..oil stuffed..frame full..air filter full etc etc.
so i got a new tap..installed an inline filter(just in case something gets through to jam the needle and seat open), new oil, cleaned everything again and now no problems.woo hoo !!
P.S. to check the fuel tap, you can use a piece of fishtank air line and a 6cc vet syringe to give negative pressure. with the outlet disconnected, it should flow with vacuum and stop almost straight away without.
cheers
fung

is it simply the weight and height of fuel in the tank that can push it past the pump with the engine off and a leaky tap?

sometimes get a strong whiff of fuel when riding as well usually when slowing for a junction, tap passing too much fuel?

will check fuel height asap, if that is within tolerance (15mm - 16mm off the top of my head) can i assume the float needles and float heights are fine?

thanks
bbb

the leaky tap may be flooding the bike if your needle and seat are not closing fully or the carb has ingested some tank bottom dirt (fine black grit) and it is in the seat/needle not letting it close.
a small inline filter will help.

worn tubes will make it rich on the overrun.

what tubes did you put in last time?

The FactoryPro kit seems to work well in my scoot (there is a thread somewhere on 2-1 pipes and filters).
check their website fornice video and some specs.

cheers
fung

So am I right assuming that the fuel entering the engine oil occurs only when the bike is not running?

I would say yes, otherwise it would be spat out the exhaust still burning.

Finally an update and it has been epic and V.V.V. expensive.
Sorted

but...
Ordered new emulsion tubes as they had been in for 10k miles and the idle was fluctuacting a touch and the bike didn't need any choke to start. Ordered the fuel tap parts as well alongside an aux fuel tank as well.

Checked fuel height - within tolerance
Stripped carbs, clean as awhistle, replaced the emulsion tubes -
Carbs back on fuel tank off to replace fuel tap seals -
Tank upside down on a box on the grass sitting on a blanket bit of Plus-Gas on the screws and letting it soak -
Mrs carries washing past it, catches the fuel tap with a blanket lifts it off the box, clears the grass and lands it half on the the edging stones and half on a concrete slab -
I go for a long walk.
Tank is dented and scratched, big dent in the top edge where the knee cut-outs are. Mrs finds these people on the internet http://www.cordwellsmotorcycles.co.uk/
they turn it around in less than a week, the repro script on the tank is much better than the original Yamaha sticker, individual letters under the laquer as opposed to a cheap sticker on top. Paint colour match is spot-on, awkward metallic blue, two coats of laquer £170 inc vat. If i was/am keeping the bike would look at getting the rest painted.

Carbs back on, gravity fed aux fuel tank set-up, get the carbs balanced, they were way out and know the engine sounds much better. Disconnect the balancer and the engine runs like crap, won't rev, pops and bangs and only runs on choke feels like a blocked jet. No fuel in no.2 float bowl either, really can't face removing the carbs so jack it in for the night.

Set the fuel tank up again the next day, this time a bit higher up, start her up still runs like crap, won't rev or tick-over, feels realy lean. Carbs off and set the idle mix screw, still runs bad and can hear a spitting / hissing sound near the seat. Aux fuel tank doesn't have a vacum operated tap or fuel pump. I had left the vacum lines open , thumb over the end and she runs super fine . Stand up in excitement knocking the aux fuel tank off it's stand all over the exhaust and floor, thankfully no one goes up in flames .

Tank back on and oil / filter changed, used it for work today, no fuel smells any where and the engine is really crisp and responsive.

Good job mate.
Persistence often bears nice fruit eh, although throughout the process you can sometimes feel both stewed and dried out at the same time.
I chased a misfire for 5 months with my 1969]Mazda R100 some years back.
I replaced the fuel system(lines,pump,carburetter), replaced the ignition system(coils, distributer), added earth straps, skinned many knuckles, swore, used up favours left, right and centre.
I finally found the culprit to be a baffle in the last muffler (it has a primary and a secondary).
The top tack weld had broken, and on right hand corners, ONLY right hand corners, it would swivel down and block the exhaust outlet enough to cause a misfire !!
I was straight down to my local exhaust shop with dollars in hand and what a relief !!
cheers
fung

That was Mazda`s first rotary was it not? how reliable is she, I heard they were buggers for crank seals or was it rotor tips, maybe both?

The 1967 cosmo 110s was their first production model. it looked like an alfa spyder.
My one is a series 1 R100 1969, but the car has seen a few incarnations.
Appendix G rally car, but now tarmac rally/flat gravel sprint.
Today it runs a series 2 RX2 twin dizzy motor(RX7 rotors and counter weights), extend port primaries and bridgeport secondaries, 4 barrel nikki with milled venturis, 5 spd, billet flywheel, 8 point cage, RX3 diff, 4 wheel disc brakes(commodore fronts..skyline rears), etc,etc..
Around 200 horses at the flywheel and 850 kilos with fuel,oil,water.
Think motorcycle with 4 wheels.
I've owned it since 1992.
cheers
fung

Nice Fung and it`s nice that you know her so well too, obviously a passionate owner?
I guess the later motor is for reliability with the bonus of more power too, nice compact motors those rotaries. I was speaking to an old fella with a Norton rotary (interpol) while at St Mary`s Loch cafe one day, lovely fella who like you knew her little `ways` like the back of his hand.