HOLY SHIT! Glad I didn't push the button...

[R6_kid]

Recently I've been having a little bit of trouble with the TRX - on two previous occasions I've gone out to the garage to find that there is fuel leaking from the bottom of the exhaust headers where it joins from 2-1 :crazy: So as you would, I take out the plugs, turn the motor over and fuel splurts out of one of the cylinders... on one other occasion I couldn't see any fuel but it 'hydrolocked' and thankfully didn't fire - I've heard/seen that you can bend/snap rods/cranks/valves if it fires up and the other cylinder hyrdro-locks.

Well today it was a bit worse than that. I walked out to the bike to check if the problem had gone away after fitting an inline fuel filter. There was fuel in a puddle underneath the bike, and the engine was covered in fuel as well. I took the tank off and my stomach tied itself in a knot - the right hand cylinder has about 1L of fuel sitting in it, all the way up to the needle in the flat slide carbs... unfortunately my camera doesn't do justice to what I can see :sweatdrop

I'm about to rip the carbs off and check all the seals as well as cleaning out the float bowls.

So much for studying!!!

[White trash]

Fuck me! Petrol's expensive too. Fucken Yamama's........

[bungbung]

Clean out the float needle valve seat(s) and check the needle(s) itself for corrosion or unroundness.

[p.dath]

Sounds like a great anti-theft device. If someone took your bike you could locate them by the colour of their underwear. :)

[slofox]

Sounds like a great anti-theft device. If someone took your bike you could locate them by the colour of their underwear. :)

And the pile of smoking debris...

[t3mp0r4ry nzr]

yup check out your floats.
not sure if the starter motor would have had the juice to "compress" the fuel. probabley wouldnt have bent a rod, but wouldnt like to test this!

[kwaka_crasher]

Clean out the float needle valve seat(s) and check the needle(s) itself for corrosion or unroundness.

and sticking float pivots. Since you're there, check & reset the float heights as required.

[AllanB]

Has it a fuel tap?

Did you or some evil bastard set it to 'prime' and leave it there?

Prime setting is designed to flow fuel in to the carbs.

If it is left on this setting it will continue to flow fuel into the carbs and then through the intake valve (ones bound to be open a bit), into the cylinder, seeping past the rings into the sump, mixing with the oil. Apparently this stuffs the oil and can quickly cause bearing failure if used.

Apart from that I'd not be too worried ........:pinch:

[R6_kid]

It has a fuel pump (external from tank) AFTER the fuel tap (which is a vaccum tap) so it shouldn't be leaking THIS much fuel! Also it only ever seems to dump fuel into one cylinder, everytime I've taken the plugs out to pump out the gas the right cylinder is wet, but the left cylinder is not.

I've just bought a new oil filter and oil as it is HIGHLY likely that fuel has made it past the valve seals and/or rings and is diluting and breaking down the oil. I'm just using mineral oil this time through and will replace it in just under 600km (when it was supposed to be due) with the usual Motul 5100.

I took the carbs off and went down to Holeshot, the workshop manager said "go home and sort out the tap first, I don't want to charge you $90 for an hours labour and not fix the problem" then they came up with the idea of fitting an inline on/off fuel tap (the standard tap is on/prime/reserve) to see if it's just pressure from the tank that's pushing the fuel through, or if it is in fact the carb(s) that are leaking on their own.

Had to go down to Hauraki Mowers and Cycles to get the inline tap which will be showing up tomorrow.

You've gotta love problem solving by elimination!

Thanks for all the tips - no I don't leave it on PRIME, it's only ever on ON or RESERVE. Also the floats are not adjustable - the carbs are Keihin FCR's. The float bowls were clean as a whistle and the float valves are in good condition too.

I think I'll take the head off in the near future (after exams) and check that the valves are still seating properly and that the pistons are still making full-stroke. The bike runs fine otherwise, there are no extra vibrations or funny noises, and I haven't noticed any loss of power. From what I've read as long as it doesn't happen at speed (i.e through water induction), or if the other cylinder fires while the other cylinder is on the compression stroke it should be ok.

And to think the warranty only ran out 2 weeks ago :wacko:

[imdying]

Prime shouldn't actually matter, the needle and seat should be able to stem the flow adequately.

[R6_kid]

That was my thoughts...

Would a needle stuck open allow fuel to drain even if the floats are closed??

[quickbuck]

Also the floats are not adjustable - the carbs are Keihin FCR's.

Why not??????
You know you just bend the tab to get the correct height eh?

Also if you have been using Ethanol Blend fuel, check your Float Needle valve rubber... Conjure has it that this stuff drys out the rubber these are made from and shrinks it.... Causing the leak.

So, Fuel will not flow through the carb if the needle is open under normal circumstances.... as the float chamber will be full and the float needle will seal off the fuel

HOWEVER if the float needle is stuffed, then there will be fuel still flowing through.

Have a surf around This (http://www.motorcyclecarbs.com/Keihin_FCR_Downdraft_Exploded__W283C1611.cfm) Site....

[R6_kid]

Cheers, I don't think I've been anywhere near Gull with this bike, but can't be 100% sure...

The float needle valve rubber was fine, I'm pretty sure the whole float was plastic though - so no tab to bend. My old CB650 carbs were exactly the same.

[k14]

I'm just using mineral oil this time through and will replace it in just under 600km (when it was supposed to be due) with the usual Motul 5100.
Why would you do that?? Just dump out the old oil and put in some new motul. Not worth it for 600km :bash:

[R6_kid]

The oil that came out was a lot thinner than anything I've put in, I just want to make sure that any fuel that may be left circulating in the system isn't mixed with good oil. I'll keep an eye on the oil and may leave it in there if need be, it's Motul 3000 so not entirely 'bad'.

[george formby]

We have the same problem & more or less the same motor. After turning on the ignition my TDM has done the same thing, petrol coming out where the headers join the rest of the exhaust. I turned the fuel off, left it & had another crack at starting it. Off she went. I now keep the fuel turned off when I start it & have had no more problems. On the TDM forum, home of some real gurus, the concensus was a perforated diaphragm in the fuel pump. My problem only manifested with a full tank of juice. Their are photos of a stripped down pump on carpe-tdm.net, posted by a guy who had this problem.

[mud boy]

damnnnn!:rockon:

[SPman]

FCRs - same as the SP.........has someone been out in the garage playing "vroom vroom" at night and pumping the cylinders full of gas......

[The Pastor]

I had the same problem with my mc22, took the carbs apart - including the float valve, didnt see anything wrong, seals ok, carbs clean etc etc. Put it back together and it never happend again.

My guess was a tiny bit of dirt was on the float needle valve and i disloged it when i took them apart.

[R6_kid]

My problem only manifested with a full tank of juice. Their are photos of a stripped down pump on carpe-tdm.net, posted by a guy who had this problem.

Initially mine seemed to be the same - only after going from reserve to full after filling the tank. I might take a look at the carpe-tdm site, I'm on trx850.motomaniac.net which is the only TRX forum I can find that is in English (I don't speak French, German or Dutch, which seem to be where TRX's are most popular!)


FCRs - same as the SP.........has someone been out in the garage playing "vroom vroom" at night and pumping the cylinders full of gas......

A ghost maybe? No one goes in the garage except for me and my father - he knows he'd flood it if he "vroom vroomed" the throttle especially considering that it has dual throttle pumps!!!


I had the same problem with my mc22, took the carbs apart - including the float valve, didnt see anything wrong, seals ok, carbs clean etc etc. Put it back together and it never happend again.

My guess was a tiny bit of dirt was on the float needle valve and i disloged it when i took them apart.

Current setup has a fuel filter in the tank, and an in-line filter, both in good condition. I'm thinking it's got something to do with the either the tap/pump or the carbs (they are the only three things that could be wrong!). The carbs were clean when i opened them up, though one slide sits a fraction higher than the other.

[The Pastor]

Initially mine seemed to be the same - only after going from reserve to full after filling the tank. I might take a look at the carpe-tdm site, I'm on trx850.motomaniac.net which is the only TRX forum I can find that is in English (I don't speak French, German or Dutch, which seem to be where TRX's are most popular!)



A ghost maybe? No one goes in the garage except for me and my father - he knows he'd flood it if he "vroom vroomed" the throttle especially considering that it has dual throttle pumps!!!



Current setup has a fuel filter in the tank, and an in-line filter, both in good condition. I'm thinking it's got something to do with the either the tap/pump or the carbs (they are the only three things that could be wrong!). The carbs were clean when i opened them up, though one slide sits a fraction higher than the other.
did u spray some carb cleaner in there just to be sure?

[R6_kid]

Will be doing a full strip/clean/reassembly in the next couple of days - exams have to take priority for the mean time.

[kwaka_crasher]

Prime setting is designed to flow fuel in to the carbs

Unless faulty, the float valve prevents the fuel flowing up into the intake.


Would a needle stuck open allow fuel to drain even if the floats are closed??

The floats control the float needle valve. When it shuts, the level in the float bowl cannot rise and fill the engine.


We have the same problem & more or less the same motor. After turning on the ignition my TDM has done the same thing, petrol coming out where the headers join the rest of the exhaust. I turned the fuel off, left it & had another crack at starting it. Off she went. I now keep the fuel turned off when I start it & have had no more problems. On the TDM forum, home of some real gurus, the concensus was a perforated diaphragm in the fuel pump. My problem only manifested with a full tank of juice. Their are photos of a stripped down pump on carpe-tdm.net, posted by a guy who had this problem.

But again a float valve would have to be faulty. In this case some portion of the fuel in the tank would also have to be below the float level to cause the problem to not occur when low on fuel. This is highly likely, as if all the fuel in the tank was above the float bowl level, you wouldn't actually need a fuel pump - it could be completely gravity fed.

[Kwaka14]

That was my thoughts...

Would a needle stuck open allow fuel to drain even if the floats are closed??

Yes, the needle is the valve that the float "closes"..... if it's stuck, then its not closed.

[jonbuoy]

Yeah the on/off fuel tap should only be a backup the seat should be enough to stop the gravity fed fuel from getting past it - if not they are stuffed. Maybe a little leakage is acceptable. Could it be the float isn´t floating? If it has a hole in it it will have fuel inside and not float properly.

[R6_kid]

I wasn't meaning the float valve needle, I was meaning the Jet Needle.

[vifferman]

I wasn't meaning the float valve needle, I was meaning the Jet Needle.
That has no effect on fuel flow except when the engine's actually running.

Could it be the float isn´t floating? If it has a hole in it it will have fuel inside and not float properly.
Same thing will happen if the arm's bent or the pivot's sticking, or the needle valve seat is worn or grubby. Some models of bikes are also notorious for misbehaving when leaned over on the sidestand.

[R6_kid]

Same thing will happen if the arm's bent or the pivot's sticking, or the needle valve seat is worn or grubby. Some models of bikes are also notorious for misbehaving when leaned over on the sidestand.

Thanks for clearing up about the jet needle.

I just took the bottom off the carbs to have a better look at the needle valves and the seats. The needle valves look fine to me - identical condition to a set of new needles I installed on the carbs on the CB650. The seats however look worn/dirty. I sprayed them with some cleaner and scrubbed them the best I could but it doesn't seem to have made difference to how they look. The right hand one looks a fair bit worse than the left hand one which is in line with only the right cylinder flooding with fuel.

Still doesn't account for the volume of fuel that is getting past though. I'll take the fuel pump apart and make sure that is all kosher, otherwise it will have to be the tap that is the problem - but then the tap hasn't been leaking while I've had it off the bike...

[Rodney007]

hope you get it sorted bro.... ring up those carb dudes in the city!

[R6_kid]

hope you get it sorted bro.... ring up those carb dudes in the city!

I'm gonna hit up treads this arvo and price up some new valve seats... they are $13.95USD so hopefully shouldn't be too expensive to get locally. I've used Auckland Carburettor Specialists before - didn't help much at the time, though it wasn't really their fault.

Update: took the fuel pump apart - looks like it's pneumatic, wasn't expecting that. All seals and diaphragms are in good condition.

[imdying]

R6_kid, dumb question time... but are you quite sure you know what the needle and seat, and float, are, as opposed to the main needle and jet? Odd question I know, but some of your text is a little odd.

[R6_kid]

The float is the plastic thing filled with air which floats when fuel enters the float bowl, this in turn raises the float needle into the seat - setting the level of fuel in the float bowl.

The main needle is what is lifted up and down by the slide/diaphragm to allow fuel mixture to enter the venturi.

[imdying]

Ok, that's cool... so you can see how fuel gets from the tank, and into the carb, and thus what must be leaking?

Have you setup a carb on the bench with a measured fuel supply, or something similar?

[kwaka_crasher]

I wasn't meaning the float valve needle, I was meaning the Jet Needle.

As someone has already said, this has no effect on fuel getting into the engine when the crank isn't turning i.e. there is no vacuum.

[kwaka_crasher]

So to repeat & clarify what I said before, the only way for fuel to enter the intake and thus the cylinders while not running is through a float valve that is either leaking when closed or not closing. The float bowl overflows out through the lowest jet.

[imdying]

FCRs don't have a bowl overflow outlet? (well duh, sounds like obviously not, but I thought I'd ask)

[george formby]

I'm gonna hit up treads this arvo and price up some new valve seats... they are $13.95USD so hopefully shouldn't be too expensive to get locally. I've used Auckland Carburettor Specialists before - didn't help much at the time, though it wasn't really their fault.

Update: took the fuel pump apart - looks like it's pneumatic, wasn't expecting that. All seals and diaphragms are in good condition.

Keep me posted how you go. At some point I will have to do the same thing.

[george formby]

Google JBX Tech pages, you may be able to download the workshop manual for your TRX.

[jonbuoy]

You can test the seats off the bike - either with fuel in the lines or by blowing gently down the fuel line to each of the carbs - when you lift the float up you'll feel it block off the air. There must be two problems - 1: floats not shutting off the fuel supply and 2: shutoff not working on the fuel supply to the carbs themselves when the engine is off.

[R6_kid]

I'll test the seats after my exam on Tuesday, in the meantime the inline tap seems to be doing it's job.

I have just noticed that there was no hose clip where the fuel supply from the tank goes to the fuel pump, and there wasn't much of a seal between the hose and the fitting (read: it was leaking slowly). Could air leaking in through here release the vacuum on the tap and therefore allow the fuel to flow?

[kwaka_crasher]

I have just noticed that there was no hose clip where the fuel supply from the tank goes to the fuel pump, and there wasn't much of a seal between the hose and the fitting (read: it was leaking slowly). Could air leaking in through here release the vacuum on the tap and therefore allow the fuel to flow?

No. Vacuum OPENS the fuel tap, not closes.

[mud boy]

blah blah blah blah blah blah
i agree:yes:

[R6_kid]

Just skimming some of my olds threads. In the end I fitted an inline fuel filter and the issue went away. From memory the internal filter on the fuel tap was toast so I went with the easy fix and just put an $8 fuel filter in the line from the tap to the carbs.