Help, Gas coming out of Airbox?

[mikubuilder]

well, I know for a fact that 79 carbs will not accept bowls from any later carbs because of position of brass enrichment tube as well as a little nib in a bottom of a bowl meant to hold down rubber plug for pilot tower in transition carbs....(DAMHIK )

[DGXSER]

First fo all - Congrats Unicorn on getting the beast properly running!!!!


Having now configured a set of 78-79 carbs, and worked on several of the 80 and 81 variety, I have found the following;

The diaphram tops are interchangable, I have MNS tops on my 78-79 carbs right now.

The float bowls from 78-79 are NOT interchangable to the 80-81. That brass nipple is off. Otherwise they do fit, and no, bending the brass tube over to get the bowl on does not work (friggin idiot POs). It will look like it is right, but the bowl will never seal. I have had no problem putting 80 or 81 bowls on either year carbs.

All of the itnernal jets are interchangable (Sorry Motot, but I have had no problems with K&L kits. But you do have to get them from a reliable source that knows the differences in the pilot jet styles.) Not saying you can jet them wrong, just that they all will screw in the holes correctly. You do jet for the carb not the bike.

The slides are not interchangable.

[motoman]

First fo all - Congrats Unicorn on getting the beast properly running!!!!


Having now configured a set of 78-79 carbs, and worked on several of the 80 and 81 variety, I have found the following;

The diaphram tops are interchangable, I have MNS tops on my 78-79 carbs right now.

The float bowls from 78-79 are NOT interchangable to the 80-81. That brass nipple is off. Otherwise they do fit, and no, bending the brass tube over to get the bowl on does not work (friggin idiot POs). It will look like it is right, but the bowl will never seal. I have had no problem putting 80 or 81 bowls on either year carbs.

All of the itnernal jets are interchangable (Sorry Motot, but I have had no problems with K&L kits. But you do have to get them from a reliable source that knows the differences in the pilot jet styles.) Not saying you can jet them wrong, just that they all will screw in the holes correctly. You do jet for the carb not the bike.

The slides are not interchangable.

Jetting brands interchangable, true enough, but are NOT the same as equivelent Mikuni jets. Mikunis are designated by whatever flow rating they use. Aftermarket, who knows. If you still don't believe me, take a large Mikuni jet, whatever size, and compare hole size with an equivalent K&L jet. BTDT and also found substansual differenences between a 185 small Mikuni(air jet) and K&L same size designation air jet. The K&L air jet in a 185 is equivalent to approx. a 210 air jet in Mikuni. Also, internal underside of aftermarket jets are cut at a slight different angle. Doesn't surprise me, as identical the same, there would be copyright infringements I'm sure. I can tell you from experience in both cases that the Mikunis jetted with ALL mikuni jetting, and correctly jetted, their smoothness from idle on up come close to my STeed or a Wing without so much as a hiccup, even with the stock 30+yr.old ignition. Hotter coils and Irids will just mask an already existing jetting issue. Those are just the facts, but it's your bike and your choice.

[DGXSER]

Jetting brands interchangable, true enough, but are NOT the same as equivelent Mikuni jets. Mikunis are designated by whatever flow rating they use. Aftermarket, who knows. If you still don't believe me, take a large Mikuni jet, whatever size, and compare hole size with an equivalent K&L jet. BTDT and also found substansual differenences between a 185 small Mikuni(air jet) and K&L same size designation air jet. The K&L air jet in a 185 is equivalent to approx. a 210 air jet in Mikuni. Also, internal underside of aftermarket jets are cut at a slight different angle. Doesn't surprise me, as identical the same, there would be Copyright infringements I'm sure. I can tell you from experience in both cases that the Mikunis jetted with ALL mikuni jetting, and correctly jetted, their smoothness from idle on up come close to my STeed or a Wing without so much as a hiccup, even with the stock 30+yr.old ignition. Hotter coils and Irids will just mask an already existing jetting issue. Those are just the facts, but it's your bike and your choice.

One day when I am feeling energetic, and have some extra cash laying around, I will invest in all Mikuni jets to replace the K&Ls I have in the carbs now. Mains and pilot jets anyway, I believe my air jets are Mikuni. The rest are all stock. Just to see for myself what difference I can tell.

[LEVVIN]

Just going back to the fuel flooding out of carb bell mouths and into crankcase again for a moment...

I got fed up with this happening to my '80 xs1100 hardtail trike, ( started" life as a police highway patrol bike your side of the pond in San Diego)
so I ditched the vacuum tap and fitted a nice reliable manual tap.

Except I have the collective memory of a goldfish and a dead badger.

I kept forgetting to turn off the tap and remember one day an Asda (Walmart) assistant running up to me and sheepishly saying ' you look like a biker...', yeah, I'm 6' 1' 23stone, bald with a beard and wearing a leather waistcoat covered in patches....

'Is that your blue trike outside, cos if it is there's a big pool of petrol around it and someone has called the fire brigade just in case!'

Oops.

So, after yet another roadside strip down of carbs,( I'm an expert at stripping and rebuilding carbs with nothing more than a leather man tool and some swearing...)

I decided I needed some foolproof method of shutting down the fuel automatically, but more reliable than vac taps.

And I did.

After searching flea bay, I found the ideal unobtrusive solution.

A 12v fuel shutoff solenoid designed for LPG conversions.

A nice little unit, fully insulated, hose tails for 6mm rubber hose either side and operated by a 12v wire I've rigged to the off side of the ignition switch.

Works faultlessly and even though, with new needles, seats and floats, I STILL get overflow issues, especially after switching to reserve fuel, AND I have a good quality fuel filter,

At least I don't get unattended fuel floods anymore.

Lev

[unicorncomputer]

While I finally tracked my issue down to be leaky petcocks, I have just ordered a Pingel Vacuum Fuel Valve since the OCTY is missing on my 79 special.

There is another thread on here about using a 12v shutoff valve I was just reading yesterday, but I had already ordered the Pingel valve.

Steve

Just going back to the fuel flooding out of carb bell mouths and into crankcase again for a moment...

I got fed up with this happening to my '80 xs1100 hardtail trike, ( started" life as a police highway patrol bike your side of the pond in San Diego)
so I ditched the vacuum tap and fitted a nice reliable manual tap.

Except I have the collective memory of a goldfish and a dead badger.

I kept forgetting to turn off the tap and remember one day an Asda (Walmart) assistant running up to me and sheepishly saying ' you look like a biker...', yeah, I'm 6' 1' 23stone, bald with a beard and wearing a leather waistcoat covered in patches....

'Is that your blue trike outside, cos if it is there's a big pool of petrol around it and someone has called the fire brigade just in case!'

Oops.

So, after yet another roadside strip down of carbs,( I'm an expert at stripping and rebuilding carbs with nothing more than a leather man tool and some swearing...)

I decided I needed some foolproof method of shutting down the fuel automatically, but more reliable than vac taps.

And I did.

After searching flea bay, I found the ideal unobtrusive solution.

A 12v fuel shutoff solenoid designed for LPG conversions.

A nice little unit, fully insulated, hose tails for 6mm rubber hose either side and operated by a 12v wire I've rigged to the off side of the ignition switch.

Works faultlessly and even though, with new needles, seats and floats, I STILL get overflow issues, especially after switching to reserve fuel, AND I have a good quality fuel filter,

At least I don't get unattended fuel floods anymore.

Lev

[XSLuigi]

Just going back to the fuel flooding out of carb bell mouths and into crankcase again for a moment...

Lev

Ok so I just had this same issue. Just got the bike a few weeks ago. last week i put it to PRIME and started it for a minute before I left town... and I forgot to switch over to ON. came home after the weekend, fuel pool under the bike!!!

Sooo, I freaked, came on here, read a bunch of stuff and put my petcocks to on. As far as I could tell the overflowing stopped (its been a few days and she is finally not making new puddles) Took a bit but from what I could see the air box filled up and was slowly draining out the bottom (sounds common)

Now to my BIG question.... has anyone actually had this cause fuel flowing into the crank case, and HOW??? I pulled the oil fill cap and I didn't see any signs of oil contamination, so I think im good. But again, how would gas make its way into the crank case on a 4 stroke???

[WMarshy]

Ok so I just had this same issue. Just got the bike a few weeks ago. last week i put it to PRIME and started it for a minute before I left town... and I forgot to switch over to ON. came home after the weekend, fuel pool under the bike!!!

Sooo, I freaked, came on here, read a bunch of stuff and put my petcocks to on. As far as I could tell the overflowing stopped (its been a few days and she is finally not making new puddles) Took a bit but from what I could see the air box filled up and was slowly draining out the bottom (sounds common)

Now to my BIG question.... has anyone actually had this cause fuel flowing into the crank case, and HOW??? I pulled the oil fill cap and I didn't see any signs of oil contamination, so I think im good. But again, how would gas make its way into the crank case on a 4 stroke???

Its quite simple really, because you float needles are leaking past their seats it allows fuel out the back or front of the carb mouth depending on path of least resistance. When is flows out the engine side of the carbs it will leak past the valve seats and into the cylinder where it makes it past the rings and collects in the oil.

Depending on the amount of leakage and how level the bike is sitting its possible all the leakage is draining out the back of the carb and into the air box and all over the engine case. You have the bike on the center stand and be on a perfectly lever surface for run towards the air box or have the front tire elevated from level.

[XSLuigi]

That sounds feasible, I can't imagine the quantity of fuel required to fill up the head to the point of valve saturation.

I had my bike on the side stand, garage floor has a bit of a grade to it so the front would have been higher than normal.

I'm thinkin an oil change is in order as I am uber paranoid lol

[natemoen]

That sounds feasible, I can't imagine the quantity of fuel required to fill up the head to the point of valve saturation.

I had my bike on the side stand, garage floor has a bit of a grade to it so the front would have been higher than normal.

I'm thinkin an oil change is in order as I am uber paranoid lol

When in doubt, change it out! The cost of spun bearing is so much more that 3 quarts of oil. Fix the carbs, and change the oil!

[WMarshy]

That sounds feasible, I can't imagine the quantity of fuel required to fill up the head to the point of valve saturation.

I had my bike on the side stand, garage floor has a bit of a grade to it so the front would have been higher than normal.

I'm thinkin an oil change is in order as I am uber paranoid lol

Im not sure what you mean by valve saturation... just remember, one intake valve is always open if not two partially depending where the crank position is. Then throw in the fact that these bike typically have a few miles on them and may not have 100% leak tight seats and it doesn't take much to allow gas to pass into the cylinder even with the valve closed.

You should be paranoid, enough gas in you crank case will cause damage to your bearings if you run it with diluted oil. A little bit wont hurt but how do you quantify "a little bit"? Did you see a noticeable increase in your oil level?

My first experience with this issue was a headache so say the least. I filled my tank up then parked it for about 4 days because of rain. Came out and started the bike and noticed it was smoking excessively. Looked down and saw what looked like oil pouring out of my air box. About half a gallon of gas leaked into my crank case. When I started the bike the pressure in the case forced the oil/gas mix up the crank vent hose and into the mouth of the carbs via the little U shaped tubes in the air box. I ended up cleaning the carbs twice because I didnt realize all the gas in the crank after the first time. Luckily it didnt damage anything and I learned a valuable lesson in carb cleaning.

Since then I decided to modify my petcocks to add an off position and just shut them off when the bike sits.

http://www.xs11.com/forum/showthread...ht=petcock+mod

[XSLuigi]

I was talking about enough gas to pour out the carb bowls out to fill up the airbox, and back into the cylinder head. The angle of all that would make me think you would need a good amount of gas to do that.

But yeah regardless guys you both said it, I'm def not gunna turn that sucker over without some fresh oil. Glad I noticed this before I tried to. Oil looks a bit dark anyway and its a new bike, there are no reasons not too.

The oil level actually looks a bit low to me. Again, just the fact that I am a new owner of this bike is enough to do that service. Are these filters readily available at most places or am I gunna have to go order from the Yami dealer? I usually use bike bandit for the random oem stuff, never order oil filters from them though haha

[Rasputin]

I was talking about enough gas to pour out the carb bowls out to fill up the airbox, and back into the cylinder head.

It wont go to both the airbox and the engine. It will take the path of least resistance. If it flows to the airbox then the front is higher than the rear. If it finds it way into the engine then the carbs leak towards the engine and then flow thru an open valve. Usually this happens when the rear of the bike is higher (on centre stand is one way). It will not always happen this way as when you stop an engine that particular valve is not always open on the offending carb. Some days it is and the fuel will run into the engine.
Always pays to be safe than sorry so I agree you should change it out if in doubt.

[WMarshy]

I was talking about enough gas to pour out the carb bowls out to fill up the airbox, and back into the cylinder head. The angle of all that would make me think you would need a good amount of gas to do that.

But yeah regardless guys you both said it, I'm def not gunna turn that sucker over without some fresh oil. Glad I noticed this before I tried to. Oil looks a bit dark anyway and its a new bike, there are no reasons not too.

The oil level actually looks a bit low to me. Again, just the fact that I am a new owner of this bike is enough to do that service. Are these filters readily available at most places or am I gunna have to go order from the Yami dealer? I usually use bike bandit for the random oem stuff, never order oil filters from them though haha

Actually you dont need a lot, the carbs sit almost horizontal when on the center stand on a level surface, just slightly bias to the rear. If the front wheel was ~2" lower than the center stand then it would be enough slope forward to make the gas run into the engine.

Filters:
Autozone: SP2
Napa: 4933
STP: SMO-2
O'Reillys Auto:
Wix 24933
Fram CH6002

[XSLuigi]

sounds like this is relatively common, didnt look if it was already but maybe sticky??? just sayin.