[Seft]

Float needles are not sealing. Needle seats are dirty/scored, float height is incorrect, needles are warn or float(s) are hanging up. It should not matter if you are on prime, res or run unless your carbs aren't functioning properly. It is a good safety measure not to leave the petcock in prime as bypassed fuel will make it into the oil.

Thanks for the advice, so the float needles and seats were all replaced when I cleaned everything up, it's done literally 15 miles with them so I'll start with the float heights and check the condition of the needles and seats to be sure they're ok. I'll double check where I'm measuring the float height with the service manual too, wondering if I measured at the edge of the float not the centre which would be higher. If they're letting too much much fuel in does that suggest they could be too high or too low in terms of measurement?

How can I test if the floats are 'hanging' with the carbs off, is there a simple check I can do?

I presume I need to drain the oil and change the filter before running everything again but will draining as you would for a normal oil change be sufficient or will I need to do something to get absolutely everything out? In terms of quantity oil was to the F line and fuel took that level to the top of the inspection window.

Will get everything back in bits tomorrow, it was only two short rides but they were bloody good fun, hopefully there'll be more soon

[ZookRick]

You can try pulling the bowls off, and blowing in the fuel inlet holding the floats up to see if you can get any air through. Did you use all new o-rings in the carbs? There is an oring that seals the seats to the carb body.

[Kreylyn]

Sit the carbs on the bench, in a catch pan. Hook up the fuel source, above them... if you see fuel leaking out somewhere, that will point to which cylinder if only ... is having the problem.

A faster way to help narrow it down... fill the carbs with fluid till they stop or very slowly allow flow... then blow on the fuel line. The problem spot will bubble (if you can't see it, you can hear it... ) to let you know there is an issue with sealing flow. Should help narrow it down as well.

Krey

[Seft]

You can try pulling the bowls off, and blowing in the fuel inlet holding the floats up to see if you can get any air through. Did you use all new o-rings in the carbs? There is an oring that seals the seats to the carb body.

Thanks, will give it a go. Replaced all the o-rings including ones for the seats.

Sit the carbs on the bench, in a catch pan. Hook up the fuel source, above them... if you see fuel leaking out somewhere, that will point to which cylinder if only ... is having the problem.

A faster way to help narrow it down... fill the carbs with fluid till they stop or very slowly allow flow... then blow on the fuel line. The problem spot will bubble (if you can't see it, you can hear it... ) to let you know there is an issue with sealing flow. Should help narrow it down as well.

Krey

Cheers, I'll get them off the bike again later and see what's going on. If I blow down the fuel line after they've taken on what fuel the will, if everything's working normally I presume the air would just vent down the tubes normally sitting over the air box wil no other sound?

Also if there something I can use to neutralise the fuel so I can mix it with sand and bin it safely at all?

Also I'm not convinced that it was the starter clutch cover starting to leak oil, looks like it came from higher up, there's a drip at the bottom of the rubber seat between carb one and the engine. Gonna clean it all up a lot as there is a lot of what looks to be old oil and grime about the place so too hard to pin point it.

[Kreylyn]

Thanks, will give it a go. Replaced all the o-rings including ones for the seats.


Cheers, I'll get them off the bike again later and see what's going on. If I blow down the fuel line after they've taken on what fuel the will, if everything's working normally I presume the air would just vent down the tubes normally sitting over the air box wil no other sound?

Also if there something I can use to neutralise the fuel so I can mix it with sand and bin it safely at all?

Also I'm not convinced that it was the starter clutch cover starting to leak oil, looks like it came from higher up, there's a drip at the bottom of the rubber seat between carb one and the engine. Gonna clean it all up a lot as there is a lot of what looks to be old oil and grime about the place so too hard to pin point it.

So the flow of anything is ... into the fuel line to the T fitting where it splits. Then it flows through a port to the float needle seat. If the needle is not seated, flow will pass through and into the bowl area. Above the bowl area is open with a vent port at the top (the other Ts higher up).

So what should happen when the floats hit full is the float needle should seal off. That means nothing should be able to move through. Air or fuel or liquid should be stopped.

Blowing on the fuel line with the carbs full should result in nothing moving though the line. If something moves... any at all... it's not sealing and that's an issue.

Fuel thinned oil will leak from all kinds of places where oil would not normally leak. Clean things up, fix the carb leak, change the oil... will probably find no more leak at all.

Krey

[Seft]

So the flow of anything is ... into the fuel line to the T fitting where it splits. Then it flows through a port to the float needle seat. If the needle is not seated, flow will pass through and into the bowl area. Above the bowl area is open with a vent port at the top (the other Ts higher up).

So what should happen when the floats hit full is the float needle should seal off. That means nothing should be able to move through. Air or fuel or liquid should be stopped.

Blowing on the fuel line with the carbs full should result in nothing moving though the line. If something moves... any at all... it's not sealing and that's an issue.

Fuel thinned oil will leak from all kinds of places where oil would not normally leak. Clean things up, fix the carb leak, change the oil... will probably find no more leak at all.

Krey

Thanks Krey, will get them off the bike now and give this a go, just need to find something to sit them on that I can catch fuel in. I've given everything I can reach a good clean so far and can carry that on once I get some more parts cleaner so hoping you're right about the oil.

Edit: Do I need to replace the oil filter too, will the petrol have damaged it etc?

[Seft]

So with regard to float height the service manual, Suzuki one, not Haynes says to measure like this:

https://imgur.com/gallery/TxUHM

but I measured with the calipers perpendicular to the mating surface of the bowl, would this be sufficiently out to cause the extra fuel flow?

[Kreylyn]

So with regard to float height the service manual, Suzuki one, not Haynes says to measure like this:

https://imgur.com/gallery/TxUHM

but I measured with the calipers perpendicular to the mating surface of the bowl, would this be sufficiently out to cause the extra fuel flow?

I'd doubt it would really make much of a difference in final position (measure, but when off and checking see if there is a diff).

No, you don't need to replace the filter. Fuel will not have done much anything to it. What little mix of fuel it would hold will evaporate out through the crank case vent.

Krey

[Seft]

I'd doubt it would really make much of a difference in final position (measure, but when off and checking see if there is a diff).

No, you don't need to replace the filter. Fuel will not have done much anything to it. What little mix of fuel it would hold will evaporate out through the crank case vent.

Krey

So I tested filling the bowls from gravity fed tank then disconnected and blew down the fuel pipe, no air went in, no bubbling, no fuel came out.

I measured the float heights, as per diagram above, as the bottom of the float is curved as you suggested there's no difference. They're all about 13.2mm except for number 3 which was at 14.3 ish. Now this is odd as I'd have thought if it were going to let too much fuel it the height would need to be lower as the higher the float height the sooner the fuel flow would be shut off as that float would activate sooner wouldn't it? Stumped as to how this could be the cause?

[Kreylyn]

So I tested filling the bowls from gravity fed tank then disconnected and blew down the fuel pipe, no air went in, no bubbling, no fuel came out.

I measured the float heights, as per diagram above, as the bottom of the float is curved as you suggested there's no difference. They're all about 13.2mm except for number 3 which was at 14.3 ish. Now this is odd as I'd have thought if it were going to let too much fuel it the height would need to be lower as the higher the float height the sooner the fuel flow would be shut off as that float would activate sooner wouldn't it? Stumped as to how this could be the cause?

That was measuring them with out compressing the springs on the float needles right? 2002 600 carbs?

Have a check on the o'rings are not pinched/ rough for each of the seats too. Fuel could leak around those if that is the case.

I'd still suggest a leave them sit to see if they leak. It may be something a little slower that the blow test isn't going to show.

Krey

[Seft]

That was measuring them with out compressing the springs on the float needles right? 2002 600 carbs?

Have a check on the o'rings are not pinched/ rough for each of the seats too. Fuel could leak around those if that is the case.

I'd still suggest a leave them sit to see if they leak. It may be something a little slower that the blow test isn't going to show.

Krey

Yeh, so I held them vertically and then just rocked them back until the floats rested on the needle springs without pressing them in then measured the height.

Yes, they're 2002 on a UK 600, spec says 13mm +/- 0.5mm.

I'll leave then to sit hooked up to fuel later today, are we talking leaving them for hours here?

If that shows nothing I'll dismantle further and check the seals and needle valves closely including the valve seat seal you mentioned. I'll lower the one float to spec too.

If the pilot screw was turned out excessively could that cause this problem, at 2.5 turns out at the moment?

[Kreylyn]

Yeh, so I held them vertically and then just rocked them back until the floats rested on the needle springs without pressing them in then measured the height.

Yes, they're 2002 on a UK 600, spec says 13mm +/- 0.5mm.

I'll leave then to sit hooked up to fuel later today, are we talking leaving them for hours here?

If that shows nothing I'll dismantle further and check the seals and needle valves closely including the valve seat seal you mentioned. I'll lower the one float to spec too.

If the pilot screw was turned out excessively could that cause this problem, at 2.5 turns out at the moment?

I don't see that the a/f screw would cause the issue, but 2.5 does sound a little far out for a UK spec bike. Normally I would expect those to be in the 1.5 range (A lot different jetting than here in US). Google "drop down method" for tuning the a/f screws for a simple method that will tell you exactly what they need to be for your bike.

I'd expect a max of 24 hours, but more than 1-2 for making sure they don't leak.

Now, depending on how weather is... you could have a situation on occasion where really hot days + engine heat will cause the fuel in the gas tank to boil. Add to that a blocked or partially blocked vent, and you could have a situation where the fuel flow PSI is much higher on a temp basis... and that could force past a float needle. I'm not expecting that to be a high possibility, but it's something to understand is possible (or similiar situation) to know that perhaps there isn't a real serious issue, and it could have been a one off. The US CA model bikes with the pair system for example, have been known to fill the charcoal canister with fuel that then gets pumped into the system and overly richen the carbs because the boil issue.

Krey

[Seft]

I don't see that the a/f screw would cause the issue, but 2.5 does sound a little far out for a UK spec bike. Normally I would expect those to be in the 1.5 range (A lot different jetting than here in US). Google "drop down method" for tuning the a/f screws for a simple method that will tell you exactly what they need to be for your bike.

I'd expect a max of 24 hours, but more than 1-2 for making sure they don't leak.

Now, depending on how weather is... you could have a situation on occasion where really hot days + engine heat will cause the fuel in the gas tank to boil. Add to that a blocked or partially blocked vent, and you could have a situation where the fuel flow PSI is much higher on a temp basis... and that could force past a float needle. I'm not expecting that to be a high possibility, but it's something to understand is possible (or similiar situation) to know that perhaps there isn't a real serious issue, and it could have been a one off. The US CA model bikes with the pair system for example, have been known to fill the charcoal canister with fuel that then gets pumped into the system and overly richen the carbs because the boil issue.

Krey

2.5 was the spec from the Haynes manual, will have a look at the method you mention and change this regardless of everything else. Need to find somewhere to set the fuel feed and carbs up that I can leave where it's out the way and well vented. Garage isn't good for ventilation. Interesting you mention weather, it has been hot here but hot for the UK is likely way off the US concept of hot. However, back to the poorly vented garage where the bike lives it does get unpleasantly hot the bike would have been heated over the day along with the fuel and it was hot when I went out but I'm sceptical that it could have been hot enough to boil the fuel. That said the bike was hot for a long time after riding, though I put this down to there being an excess of fuel/oil in the engine with more pressure so the cooler wouldn't have been as efficient. Anyway, plan of action now is:

1. Reduce carb 3 incorrect float height to nearer 13mm
2. Set up fuel and carbs and see if they leak when left for up to a day leaving everything undisturbed
3. If they don't leak, rock slowly in the corner banging my head on something
4. Take out the valve seats and check condition of the valve seat o-rings and needle valve tips
3. If fine put everything back together, check float heights after installing again
4. Check A/F mix setting Edit: Looking at drop down method I'd need to do this with the carbs on the bike, I don't have any way to adjust the screws while carbs are on the bike especially with a hot engine, will have to create some kind of Frankenstein screwdriver as Ž£45 for this is a bit steep https://www.carbtune.com/bevel.html and I can't find any seemingly good alternatives
5. Replace oil
6. Test everything again on a cooler day
7. Hope that it's a random overheating problem.

Is it worth using some gasket adhesive on the mounts to the engine and the air box just the maximise the chance of there being no vacuum leaks? Have some black Suzuki bond stuff that I used on the valve cover gasket and over the join on the surface for the sig gen cover.

As always, thanks for your support with this, really is appreciated, hoping I'll have some cash left at the end of this to chip in to support the site a bit too!

[Kreylyn]

2.5 was the spec from the Haynes manual, will have a look at the method you mention and change this regardless of everything else. Need to find somewhere to set the fuel feed and carbs up that I can leave where it's out the way and well vented. Garage isn't good for ventilation. Interesting you mention weather, it has been hot here but hot for the UK is likely way off the US concept of hot. However, back to the poorly vented garage where the bike lives it does get unpleasantly hot the bike would have been heated over the day along with the fuel and it was hot when I went out but I'm sceptical that it could have been hot enough to boil the fuel. That said the bike was hot for a long time after riding, though I put this down to there being an excess of fuel/oil in the engine with more pressure so the cooler wouldn't have been as efficient. Anyway, plan of action now is:

1. Reduce carb 3 incorrect float height to nearer 13mm
2. Set up fuel and carbs and see if they leak when left for up to a day leaving everything undisturbed
3. If they don't leak, rock slowly in the corner banging my head on something
4. Take out the valve seats and check condition of the valve seat o-rings and needle valve tips
3. If fine put everything back together, check float heights after installing again
4. Check A/F mix setting Edit: Looking at drop down method I'd need to do this with the carbs on the bike, I don't have any way to adjust the screws while carbs are on the bike especially with a hot engine, will have to create some kind of Frankenstein screwdriver as Ž£45 for this is a bit steep https://www.carbtune.com/bevel.html and I can't find any seemingly good alternatives
5. Replace oil
6. Test everything again on a cooler day
7. Hope that it's a random overheating problem.

Is it worth using some gasket adhesive on the mounts to the engine and the air box just the maximise the chance of there being no vacuum leaks? Have some black Suzuki bond stuff that I used on the valve cover gasket and over the join on the surface for the sig gen cover.

As always, thanks for your support with this, really is appreciated, hoping I'll have some cash left at the end of this to chip in to support the site a bit too!

Little bit cheaper... https://www.amazon.co.uk/d/Automotiv...ngle+carb+tool

Or something else may be similar in option. The one you linked would function a little easier/smoother, but that is a big price diff.

Gas can boil as low as 40c depending on pressure. Surprise. I know I was once I found that out.

Krey

[Seft]

Ok clearly I've forgotten some physics here, as low as 40 makes that perfectly plausible, will do other tests all the same though. Looking at reviews the carb tine driver seems to be well thought of with near zero play so might be the way to go...hmmm...would be easier if I could think of another use for it to justify the price though!