ST1100 Fuel Pit Cock Problem / Or is it?

Friends,

I have an ST1100 1997.

Recently converted to a K & N Air Filter and this began a series of problems, problems I need your input to resolve.

When I throttle on... The K & N allows the engine to breath a much deeper breath and I feel it in the lower RPMS. I am great until the 4000-5000 rpm range then throttle lag, if I roll off throttle then I can slowly throttle to higher speeds but it is slow and does not feel right.

The problem did not exist with the stock air filter, and I may need to go back to oem if I can not work out the problems.

So then some random research tells me that I either need to do one of two things:

1.) Time to re jet the carbs, buy the kit and do it.... My Honda guy quoted me a $350 to rejet. I am not techo savvy but that sounds like a rip,... for $40 I can go back to the OEM air filter. The rejet kit is about $100.

2.) A little issue about the fuel pitcock diaphragm... I found a ditti that says if the little diaphragm is broken, has a crack or is worn that the fuel does not flow right. This article seems to mirror my problem and I have found a $20 diaphram kit on-line... Honda does not sale the kit only the pitcock assembly for $125.

So if you have experience on this let me know.... Has anyone out there had to replace a pitcock diaphragm? I have only found one article on it but it almost nails my problem.


What would be your next step???

Oh one more question, should the fuel pitcock drip fuel out of the bottom, for any reason? I was changing my fuel filter and wanted to check for leaks before retupperising and the little pitcock was dripping fuel? It was coming out of the little hole that actually looks like it was design to drain fuel or release / take in air? Any thoughts here, if the pitcock is leaking would that mean that I do have a bad diaphragm?

Update, on Sunday, I went back to check the bike and the fuel drip issue was self resolved... Some how I must have backed fuel into the pitcock when we changed out the fuel filter.

Still need some help on the fuel pitcock issue?

Anyone else have the K & N issue? I have the foam cover on the K & N...

James

James,
It doesn't cost a penny to bypass the petcock and see if that is the problem. Just unhook the line going in, and attatch it to the filter. Just takes a couple of minutes to do. Give it a try. If that's the problem, you can either rebuild it, or leave it bypassed like many of us have done.

I'm thinking you are getting too much air into the engine and need a rejet. I'd suggest you leave that to the pros as it may have to be done several times to get it right. Make sure they do it on a dyno if they are doing it. Or just go back to the stock filter.....

Good luck!

Speedracer612 said:

Update, on Sunday, I went back to check the bike and the fuel drip issue was self resolved... Some how I must have backed fuel into the pitcock when we changed out the fuel filter.
Still need some help on the fuel pitcock issue?
Anyone else have the K & N issue? I have the foam cover on the K & N...
James

Click to expand...

Hi James,

Take the foam off the K&N. It's not supposed to be used on ST1100s. And because you've made a change to your fuel/air delivery system, you have to do a carb sync.

Keep an eye on the Auto Fuel Valve (vac operated fuel petcock). If the K&N fix doesn't change the current drivability issues, then bypass the Auto Fuel Valve and see if that does it. It still may be the/a problem. You may not always see evidence of leaking, although I'd expect that you'd probably still have a raw gas smell.

HTH Good luck and please keep us poSTed.

Regards, John [98K miles w/ST1100 K&N air filter, WITHOUT a foam cover]

Re: ST1100 Fuel Petcock... Permanently Bypassing?

Just thought I'd add something to the discussion about bypassing the Auto Fuel Valve for everyone's consideration. From my archives, here's an old poST to the ST-Riders LiST by a STrider whose opinions I highly respect:

----------------------
Subj: Re: [ST-Riders] Auto Fuel Valve
From Bob Peloquin, ... [STOC #3445]:

Scott Finn, ... [STOC 4752], asked:

> At the risk of sounding like a complete idiot, "What is the downside of
> simply taking this thing off and putting it on the shelf for good?" ....
> It seems to me that it would almost be like having a bike with a manual
> valve and never turning it off. I've heard arguments on both sides of that
> one as well.

Since the EPA mandated sealed fuel system came into play, the ST's
fuel tank can contain considerable pressure or a small amount of
vacuum due to temperature changes when parked. Both of these
conditions do bad things to carbs. Pressure can force fuel past the
carbs' needle valves, overflowing into the cylinder and possibly
causing hydraulic lock with severe engine damage. Vacuum can suck gas
and air back through the carb feed hoses and make the bike hard to
start after an extended period. I experienced hard starting with
extended cranking after my vacuum valve failed and was bypassed.

The vacuum shutoff valve was added to the bike to prevent these
problems. You wanna eliminate the valve - fine. Put in a manual fuel
valve in that location to replace it or remove the gas cap when
parked. You could also drill out the pressure/vacuum doohicky in your
gas cap and you'll have no problems. Otherwise, leave the fuel system
design to the Japanese IMHO.

Bob Peloquin
---------------------------

I agree with Bob. BTW, I also believe that the ST1100's Secondary Air Supply System (aka: PAIR valves) should not be removed. JMNSHO, of course.

Regards, John

+1 on the problem being the foam cover on the K&N. This has been documented numerous times. It's way too restrictive. The fact that K&N includes this cover makes me wonder what they are thinking or if they ever bothered to test this filter set up in an ST1100. I don't believe that filter model fits any other motorcycles. Maybe they felt the filter element without the cover wasn't adequately filtering particles out of the air?

If it were me, I'd put an OEM filter back in and GO RIDE!

Re: ST1100 Fuel Petcock Problem / Or is it?

Seems to me this thread should be on the ST1100 Tech Board. JMO

Re: ST1100 Fuel Petcock Problem / Or is it?

STGhOOST said:

Seems to me this thread should be on the ST1100 Tech Board. JMO

Click to expand...

I think you might be correct...

OKay Troups,

Here is a summary of what happened.... After taking off for TexSTOC, I had a long day... It took me three tanks of gas to get to Arkansas. Then on top of that, the throttle lag got worse. ON Saturday morning, I headed for the Honda shop in Fort Smith, they were no help, but they referred me to another shop. After pulling off the tupperware it was evident that the little EPA valve was leaking about 2/3's of all the gas. It also was not supplying enough fuel at the top side of the throttle. I by-passed the the valve and pulled the K & N Foam cover on the air throttle and all power was back, all throttle was back and the bike was running good. As a precaution I felt it best to head home, So I doubled back on the Talimena Trail, what a rush!

Thanks to all that supplied their time and input this was a great trip even though I did not get to have dinner with the Crowd.

Glad to hear its all better now.

The Talamina is definitely a kick! Joe led me on that one... just beautiful.

Mark

STill Fiddlin said:

I just R&R'd one of those vacuum switch/petcock gizmos on my bike because I had ordered the rebuild kit as a precaution (and am killing time waiting for new rear wheel dampers...). It's a pretty simple procedure. In my case, it was a waste of money, because the existing diaphragms, even at 90K were fine.

Click to expand...

If this diphragm is anything like the fuel pressure regulators that GM uses one of the possible causes for the failure is running fuel that is mixed with Ethanol. Ethanol can deteriorate rubber and cause leaks like this. Some states mandate the use od Ethanol. For instance in MN all gas for road use has to contain at least 10% Ethanol and is many times refered to as E-10. I typically buy gas that is only for off-road use at one of the local gas stations. It is 91 octaine non-oxegenated fuel. Becuase it is non-oxegenated (No Ethanol) it is technically illegal to use in vehicles in MN but it is the only 91 octane fuel that the gas station sells. As a side note because gas has more BTUs then Ethanol I can tell the difference performance wise. With my ST if I run normal E-10 91 oct and go wide open throttle it takes off just fine. If I do the same with non-oxegenated 91 octaine I can feel the front wheel come off the ground. Same road, same amount of throttle and same air temps. Sure that isn't a dyno reading but it does say something.

So if your area sells ethanol in your gas try and find some pumps that are non-oxegenated. This will give you better performance and may prevent this problem with the leaking diaphragm.

How does a st1100 run with a leaking petcock? I have a hit and miss problem with mine. It acts like it is starting to run out of gas at highway speeds and normally when the tank gets down. The first time I filled it up with gas and replaced my fuel filter. I had it stall on me again yesterday. I got it restarted and ran a little rough. Then it cleared up. If the pet cock is leaking is there a way to bypass it so I can go on the moonshine run. I do not have time to wait for parts? My mileage is down to 41mpg last tank compared to my average 50mpg.

Changing the air filter won't affect the sync. If the sync was good before the filter change, it will be good after.

Take that foam ring and throw it in the trash. You are starving the engine of air at higher rpms by using it. K&N did NOT use a foam filter ring filter over the main filter for many, many years. For some very strange reason, they are not including the foam ring. They say they've tested it with the ST. I say bull****. Every single person who has bought a K&N with the foam ring and usd it with their ST has had the same problem you describe. And every person who had that problem and removed the foam ring solved the problem. (Makes you kinda wonder why they added it if they're filter is so good to begin with.)

Anyway, throw the foam ring in the trash and go out and ride. No rejetting is necessary.

brian99stpegs said:

How does a st1100 run with a leaking petcock? I have a hit and miss problem with mine. It acts like it is starting to run out of gas at highway speeds and normally when the tank gets down. The first time I filled it up with gas and replaced my fuel filter. I had it stall on me again yesterday. I got it restarted and ran a little rough. Then it cleared up. If the pet cock is leaking is there a way to bypass it so I can go on the moonshine run. I do not have time to wait for parts? My mileage is down to 41mpg last tank compared to my average 50mpg.

Click to expand...

It's very easy to by-pass the fuel valve. Just remove it and reconnect the hoses. It's self evident once you have a look at it. You could have a failing fuel pump too. Read this sometime: http://home.insightbb.com/~mmartin36/FPDiagnostics.htm

STill Fiddlin said:

I just R&R'd one of those vacuum switch/petcock gizmos on my bike because I had ordered the rebuild kit as a precaution (and am killing time waiting for new rear wheel dampers...). It's a pretty simple procedure. In my case, it was a waste of money, because the existing diaphragms, even at 90K were fine.

Click to expand...

I wish I knew what kills these things. Mine is still working at 165k miles.

Don't know either. But mine died at around 45,000 miles. A nice semi-circular split in the diaphram. I was surprised the bike would run.

hawkeyeST said:

I wish I knew what kills these things. Mine is still working at 165k miles.

Click to expand...

How about this? Is anybody with a failed fuel valve also in the habit of using any type of fuel additive or carburetor cleaner? I never put anything in mine except what comes from the pump.