Exhaust Full of Fuel...Driving me nuts now!

[rider4life]

Everytime i go to start my bike its flooded. The left carb fills the cylinder and exhaust with fuel. Must of poured out a litre of fuel out the exhaust this morning. I've already replaced the needle and seats. plus set the float heights. Still does it. Any ideas? On the verge of selling it soon.

[mikee]

New fuel tap and leaky float valves , park it on a paddock stand


If it's any consolation they all do it to some extent


Mike

[looey]

Even if your petrol tap is letting fuel past in the off position and your needle valve is also leaking, the fuel should be finding its way down the float bowl overflow tube and out the back/bottom of the float bowl.

I'd be making sure that's not bloacked first, so the worst case until you get it fixed will be petrol dripping on the floor and not filling the engine ?.

[rider4life]

So i took the pipes off the tap and it leaks out on the off position. I have just fitted new float valves and seats as it used to leak out the overflows. That solved the problem but now it fills up the left cylinder with fuel. Make's it near impossible to start.

[horace]

Sounds like a new fuel tap then , it will always fill the left cylinder the way the pipes are plumbed to the carbs.

[steve h]

Is the float valve seat gasket OK?

[looey]

I still stay whatever is leaking past it should be coming out the carb overflow, not filling the engine !.

Have you double checked the overflow outlet is not blocked ?.

I did have a bike some time ago that I couldn't stop the petrol tap leaking past when in the off position, so I just made a couple of stubs of petrol pipe with plugs in the end and stuck them on the tap when I was't using it.

[mikee]

I recently fitted a new tap to my 4lo
it would leak in the off position , but wouldn't flow properly when on , bike wouldn't start easily and wouldn't run properly , fuel starvation and flooding , best of both worlds

I agree with looey tho the floats should shut the fuel off , didn't on mine for some reason
anyway its leaking on the other side now dispite a rebuild kit

the joys

mike

[mikee]

Possibly , will try that

Mike

[ngordoncrosby]

Also try when starting it to do it as slowly as possible with no throttle,like every good two stroke as long as there is a spark and a bit of fuel ,it will go...

[mikee]

then it sprays petroil all over wifeys car

lol

[rider4life]

To be fair the tank is kinda rusty inside but it has inline fuel filters that look clean. I had the carbs sonic cleaned. then complete rebuild kit. Still have the same problems but they change day to day lol. I might get the tank modified to tank a different type of tap worst case. I agree with looey though. If the float was dodgy it should leak from the overflow not fill up the engine. Maybe i ditch the originality and go with a new set of carbs something more modern. No point being original if i can't ride it

[farmboy]

I had a problem much like yours on my rebuild bike. Had it running on an aux tank when I built it waiting for the paintwork to return, the aux tank had a tap on it, bike started perfect even when left a week or more.
Had main tank re fitted with its old fuel tap , much same problem , although not as bad.
left overnight would not start , plugs dripping wet and spat fuel out od pipes foe first few mins. Messed around for a few days with it, same flooded out every time come to start even with tap at 'off'.
So after running it up to temp and fine i parked it up overnight, but first removed the two pipes from the tap , then used a bit of scrap hose to loop the two outlets from the tap, so acting as a plug.
Next day fe fit pipes , bike start first kick runs fine.

I also then run 2 short hoses from the tap into a bottle overnight , sure enough with the tap 'off' still had fuel in the bottle.
So i have ordered a new tap , going to fit it later today as its raining maybe.

My bike never leaked out of the overflow from the float, it has new float needles too. Guess it just works up through the main jet slow and runs down to the reed valves into the crankcase.
I will se how mine works with a new geniune £££ tap and let you know. I have been pulling off the pipes and looping the tap for tha last few weeks I have been runnng around on it, went out yesterday (sat pm) sunny here ! re fitted pipes , started 2 nd kick.

[rider4life]

Thanks for the reply. let me know how it goes. I'm gonna fit a new tap anyway. but when it was going well started first or second kick. now the left cylinder just gets flooded

[rider4life]

Just took the tank off and removed the fuel tap. The whole tap is packed with grit. it's like sandblasting grit. fuel was full of grit particles. tank is sounds like it has grit inside and its also rusty inside. Hope it hasent wrecked the bores. Gotta get it cleaned out and sealed.

[nige]

Had same problem with mine when left it in the man cave for 2 weeks with the tap turned on. Seems like a common problem when the bike is on the side stand. The overflows on my carbs are not blocked but when the bike is on side stand overflowing fuel finds its way into the crank not the carb overflow. Mine resulted in an engine rebuild as fuel sitting in the crank cases shot the crank seals.. I now turn the fuel off and if leaving bike for while put it on the paddock stand as have removed the centre stand.

[shane250]

Remove the tank
Remove the tap and put a plastic bag over the top and refit.
Fill tank with vinegar
Leave for a few days
get tooth brush rub where possible
Drain tank into washing up bowl thro filler
Filter back into tank thro t shirt and funnel
Repeat until no rust is left and inner tank like new.
Strip tap completely and make sure it's assembled right and shuts off.
Wash tank out straight away with water and dry quick to neautralize vinegar
Fill with 2 stroke mix .
When leaving bike I turn tap off and leave the bike running a couple of minutes but don't drain the carbs completely.
First kick every time for me...

[rider4life]

Doing it at the moment using the electrolysis technique. seems to be working well. can i get away with not sealing the tank as its not as bad as i thought. Might try vinegar aswell. where can i get it cheap?

[mikee]

Aldi /lidl for cheap vinegar

Tho it's not dear from asdas

Mike

[rider4life]

Normal vinegar or white?

[horace]

90p for two litres in morrisons.

[shane250]

Aug 11, 2014 22:21:05 GMT 1 rider4life said:

Normal vinegar or white?

Any

[muttsnuts]

once you have cleaned your tank out, rather than mucking about with neutralisers etc, I just fill the tnak with a gallon of Diesel and swill it about for a good few minutes, then drain it off into a container until I need it again for the same purpose.

HTH

[rider4life]

thanks for that mutts. I was reading around for what to do after this. when i drain the rust water out to fill with new stuff it flash rusts after a few mins

[rider4life]

Today i removed the carbs for the 4th time. thought this time i would take the reeds out. Crankcase is full of fuel as pictured. put some 2 stroke oil down there and swished it around to keep the bearings lubed. I'm guessing the reeds should not have any gaps they are both like that. Hopefully after i clean the carbs out for the 4th time with a new tap and inline filters i should be good to go.

[steven]

Hi,

I fitted two new repair kits to my fuel taps and pressure tested them to two psi when I was pressure testing my fuel tanks.
Even with the repair kits fitted, I could not get the fuel taps to seal properly, and it always leaked from the pipe going to the left hand carb.
It doesnt leak much, but Im not out on my LC as much as I would like, and it does stand for a while sometimes.
I always pull the petrol pipes off, and fit these two blanked off pipes to the tank if Im leaving it any more than a day or so.
When I return home on it after being out on it, I usualy turn the fuel tap off approx 100 yards form the house and then fit these two blanked off pipes before I put it to its bed.
One piece of pipe linked between the two pipes on the tap would do the same job.
I dont think its too desirable to have your crank case full of petrol as it must wash any oil off the bearings,and it cant be too good for the crank case seals or the labarinth seal, but as Im not posative about that, I just ensure that the crank case does not fill with petrol by fitting the two blanked off pipes.

I have heard different opinions about reeds, some folk say that a gap is not a problem, as at 10 thousand RPM, the reeds open and close so many thousand times a second or something like that.
Other say they must seal properly.
I am of the opinion that they must seal properly, and I devised a test for them which I called the "quack" test !

I bought fibre reed also, but could not get them to seal, and they kept failing the quack test.
I spent a few MONTHS trying to get a set of reeds that sealed properly, in the end I bought origonal yamaha reed petals which are approx £10 each petal and are/were still available from Yamaha.
I bought several sets of reed blocks from evilbay, and was even lapping in the rubber face on very fine wet and dry on a glass plate in an attempt to get the new petals to seal properly.
After a while I eventualy managed to make up a perfect set of reeds/reed blocks that sealed properly.

To test them I blew threw the opening on the reed block and if a rasping or "quacking" noise was heard, I decided that they were sealing properly.
Holing them up to the light, or shining a torch in them also showed if there were any chinks of light coming through, but the quacking/rasping test was my prefered method.
Be aware that there are a couple of revisions on reed petals, but if you order new petals from Yamaha, you will obviousely get the latest revision.
You will also find that air cooled RD reed blocks are the same as LC ones, but Im not too well versed on air cooled stuff.
Brand new reed block assemblys complete with reeds and stops etc are/were still available from Yamaha last year, at a cost of approx £100 each.

HTH
steven.

[steven]

Hi,
After another look at your pics of your reeds......the gasket is fitted to the wrong face.
The gasket should be fitted on the front face of the reed block assembly, looks like your gasket has been fitted to the rear?
Also looks like you have oem or genuine pistons?, as I dont see any tangs, or evidence of their removal ?
steven.

[rider4life]

Thanks for the reply steven. I see what you mean about the gaskets. I bought the bike off a old guy as a road going project and the ammount of problems i'm finding is crazy. I removed the reed petals and sat them in hot water then bent them. they sit alot better now. carbs all cleaned again and its back up and running. tank off at the moment my dad lost the fuel tap screws somehow. I also drained all that fuel in the crankcase and threw some 2 stroke oil down there.

Thinking of running a couple of these www.ebay.co.uk/itm/181230493788?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

[shane250]

Aug 15, 2014 16:20:43 GMT 1 rider4life said:

Thanks for the reply steven. I see what you mean about the gaskets. I bought the bike off a old guy as a road going project and the ammount of problems i'm finding is crazy. I removed the reed petals and sat them in hot water then bent them. they sit alot better now. carbs all cleaned again and its back up and running. tank off at the moment my dad lost the fuel tap screws somehow. I also drained all that fuel in the crankcase and threw some 2 stroke oil down there.

Thinking of running a couple of these www.ebay.co.uk/itm/181230493788?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Just get your tap to not leak they dont if they are right.If you cant, get another but often its because they havnt been cleaned out right or assembled properly of course the tank needs to be clean.The last thing you want is a restricted fuel supply,or it is if you want to use it properly 

[badger69]

Hi I'm having same problem, petrol all over my new built garage floor, so I've just bought a front paddock stand to keep it level, hope no more waisted fuel, I'm a total beginner in doing my own work on my lc , my brother used to do it all for me, but he was killed out on his bike 20 years ago, So when my exhausts are full of petrol do I need to remove them, or is it ok to start and push out the fuel that way, also how do I check if the crank case has fuel in it, and last question, the 2 blanking pipes I know one would be for the tap to left carb, what about second one, and can someone show me exactly where I fit fuel filters to save any muck getting into my engine, sorry for these silly questions, but we all have to start somewhere, all help with thanks.