Fuel leak when the engine is running only?

Afan said:
Since the fuel leaks only when motorcycle is working and it turns on without problems I think shut off valve shouldn't be a problem, right?
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Possibly . . . but it will be easy to see if that is where the leak is, so check it well before digging into the carbs. There are also a myriad of small hoses from there that feed all the carbs, so a thorough inspection of what you can see, with the air filter housing removed, is also in order.

Good luck tomorrow.
 
Late chiming in here... checking the vacuum fuel shut off valve would be the first thing to check. Very simple, remove the four screws from the back plate and inspect the diaphragm. Replacement diaphragm kits are available $35. A new valve from mother Honda is over $100.
 
Bush said:
you should also replace the "elbows" and the o-rings inside them, which mount the hoses to the head.
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+1 Bush!

Afan:
If you can wait for delivery of the Al elbows and the o-rings I would do both elbows if you have to remove the carbs. If you find you don't have to remove the carbs you'll have the elbows when (not if) one of them fails.
 
Bush: Pair system was on before then. I've got a '93 ST1100 USA model with 112k miles on it with the pair system still intact.

As far as finding the problem, first order of business would be to take off the fairing and dummy tank and then run it to see where it's leaking from.
If it's the vacuum cut-off valve it's an easy fix to by-pass it.
 
Mark said:
If you can wait for delivery of the Al elbows and the o-rings I would do both elbows if you have to remove the carbs. If you find you don't have to remove the carbs you'll have the elbows when (not if) one of them fails.
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That's true. Good idea. Thanks.
 
The secondary air supply system with air injection control valves (aka: PAIR) was installed on all USA ST1100s. It's a passive system that does not affect performance. I have not seen a documented failure of these valves.

+1 on just removing enough tupperware to ID the source while the engine is running. No need to disassemble the auto fuel valve initially. If the leak is as bad as it sounds you should see fuel running out of the weep hole on the bottom of the valve 'in situ.'

If I was not currently immobilized recovering from sinus surgery, I'd bomb over to help diagnose (assuming free room and board). :)

John
via iPhone 4S
 
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John OoSTerhuis said:
The secondary air supply system with air injection control valves (aka: PAIR) was installed on all USA ST1100s. It's a passive system that does not affect performance. I have not seen a documented failure of these valves.

+1 on just removing enough tupperware to ID the source while the engine is running. No need to disassemble the auto fuel valve initially. If the leak is as bad as it sounds you should see fuel running out of the weep hole on the bottom of the valve 'in situ.'

If I was not currently immobilized recovering from sinus surgery, I'd bomb over to help diagnose (assuming free room and board). :)

John
via iPhone 4S
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Now THERE"S an offer the OP might want to consider . . . . if he could wait long enough for you to get better.:D

John, so ALL years of all USA ST1100's from day 1 came with the PAIR system? I thought it was just California models at first, moving on to all models, Canada included sometime later. Now I'm not even sure when the Canadian models started with PAIR, as my '96 is not so equipped.
 
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John OoSTerhuis said:
It's a passive system that does not affect performance.
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There rumours that plugging the system gives a gain of ~2HP...
I have not seen a documented failure of these valves.
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The '94 I'd refurbed had one with defective diaphragm, causing a vacuum leak... that was the first time I'd ever seen one failing, they seem quite reliable...
 
So... My friend was here today and he took the carb out. That was a fight! :D

And look how my sub-filter (or what was the name) looks like.

20150416_202336.jpg

:D

So... Where ti order new one?
 
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And looks like rubber gasket on one of float bowls is damaged. We put some gas in the carb to see where is the leak and - nothing close to dripping I had before. Although, on one of float bowls started accumulating a drop of gas.
So, is THIS the right set?
 
We didn't took the carb apart but it looks like something need to be cleaned. I don't know if/when previous owner cleaned the carb recently? So, I was thinking, to speed up the whole process, to take it to Garvis Honda dealer/shop to clean it and replace the float bowl gaskets. How much I can expect to pay for the service? The friend of mine is kinda busy so to wait on him it could take a several weeks to do it. But, also, if it's to expensive I would rather wait :)
 
Mark said:
+1 Bush!

Afan:
If you can wait for delivery of the Al elbows and the o-rings I would do both elbows if you have to remove the carbs. If you find you don't have to remove the carbs you'll have the elbows when (not if) one of them fails.
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I see there so many elbows and o-rings... :-(
Could you please put a link and/or image of the elbows and o-rings you're referring to? Thanks.
 
John OoSTerhuis said:
+1 on just removing enough tupperware to ID the source while the engine is running. No need to disassemble the auto fuel valve initially. If the leak is as bad as it sounds you should see fuel running out of the weep hole on the bottom of the valve 'in situ.'
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We tried 2 times to figure out, with running engine, and he saw where it si but could say WHAT it is. So we decided to remove the carb.

John OoSTerhuis said:
If I was not currently immobilized recovering from sinus surgery, I'd bomb over to help diagnose (assuming free room and board). :)

John
via iPhone 4S
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That would be great!!! Actually, even if we fix it, we can meet each other so you can take a look at the bike and suggest what (is next) to do. I believe there is still plenty of old parts ready to be replaced. :D
 
Afan said:
And look how my sub-filter (or what was the name) looks like.

So... Where ti order new one?
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Several folks have used a foam filter from a lawn mower engine, cut to size. Easy to find at a local hardware store or garden equipment shop.
 
Afan said:
Is this ok for my 1998 ST1100? How 'bout the price?
http://www.siriusconinc.com/pro-detail.php?pid=&product_id=3089
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An IMHO reasonable priced source for carb rep-kits and other items is NRP...
Fuel tap repair kits:
http://www.nrp-carbs.co.uk/shop/index.php?route=product/product&path=42&product_id=2967
(I had a K&L rep kit here which did not fit at all (bad MFG, diaphragm was oval), the NRP set did fit totally precise)
carb diaphragms:
http://www.nrp-carbs.co.uk/shop/index.php?route=product/product&manufacturer_id=22&product_id=835
 
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