Why so many C10s have fuel problems.

[smithr]

As some of you know I have had this on my mind for a while. I have a theory I would like to put out there and see what others think. Here is as simple and short as I can make it. The amount of fuel left in the lines past the petcock is so small the heat of the engine evaporates it when you stop the bike. This lets the float needles drop open a bit and the fuel level is left just about right at the needle valve opening area. As more fuel evaporates as the bike sits it leaves varnish on the needle valve(or float hinge) and sooner then later the valve will not seat well. I have tried to do some testing on how much fuel it takes to refill and re-seat the floats the next day after you stop from a normal temp ride. Funny it is just about how much fuel is left in the lines of the stock system. With the petcock valve working normal then no new fuel is allowed in and so you have air and fuel mixing at the needle valve and float hinge area. Most times this goes unnoticed until the petcock fails or the needle seals so bad that you notice rich running problems. Simple prevention might be as easy as turning the petcock to prime for a few seconds the next day after a ride if you think the bike is going to sit for a few days. Each time I do this you can hear the air rush into the tank as the bowls refill. I think once you fill the tubes and bowls it should sit better for a few weeks before enough fuel can evaporate to let the needles drop again. So what do you egg spurts think? Photos[/url]

 

[crisp]

I have not had this problem with my bike, 70K + miles so don't know it I need the solution. If this a problem I have luckily avoided your solution certainly seems simple and easy to try. My only problem would be remembering. What was this topic again? - on the trailing edge of technology

 

[jaxrider]

Bob, I have ridden 200k miles on everything from RD400's to ZZR1200's including a 1997 C10 and never had this problem. My carbs have ever only had problems from rust, water or sand. The needles have never gotten varnished though I have bought used carbs for bikes that sat and the carbs were not functioning due to gas sitting in them and then turning to goo. My C10 only had problems idling due to find dirt in the carbs, which came out when I drained the float bowls. Maybe that's because I usually use a little bit of the enrichment circuit when starting cold and this extra fuel carries it over until the engine runs a few seconds and the vacuum petcock opens for more fuel to flow. I also try to buy brand-name gas such as Shell or Exxon or BP when riding. We have "Kangaroo" here and also "Gate" which both work fine in my bikes (ZZR1200, Katana 600 and Intruder 1500LC). I use them when its' not convenient to use the brand names, but usually hit the brand names at least half the time. This may be related to the quality of additives in the gas. David in Jax COG# 7898 NE FL AAD & COG Vendor www.dreamjobresumes.com preparing resumes for COG members and friends I ride a KAWASAKI ZZR1200 - Euro http://www.motorbikestoday.com/reviews/Articles/ZZR1200.htm US http://www.motorcyclistonline.com/roadtests/2002_kawasaki_zzr1200/index.html

 

[Brett0769]

Unflagged stores can carry anybody's gas, it's a matter of what the distributor has available. So you might have picked up Exxon additives from the Kangaroo or BP or anyone else. Flagged stores though only carry the formula of their patron, so if you're looking for consistency that's the way to go.

 

[dpreach007]

my cousin is a merchant marine who used to work on tankers that shipped gasoline between texas and florida. He told me that when we think one gas is better than the other (like BP or Exxon or whatever mom and pop gas station) is not true. He told me gas is gas. Any enrichment with additives comes at the pump. He said he experienced the same gas being pumped from all the tankers would all come from the same refineries and go into the differently labeled tankers. but it is all the same gas 98 Windsor Green Connie "Nicodemus" 17k COG #8566 AMA #1084059 CDA #0308

 

[slybonesjesse]

Well for all those who say they have never had this problem, I would like to ask how do you know? I will up front agree that you have never had a problem in that you were never stranded, the bike always started, it always ran fine, never hydrolocked, never had a problem that was traced back to this, etc. Yes I agree. I have never had any of these problems either. But ..... Here are two observations of mine. 1. My Connie as a fuel filter. And one of the things I have noticed is: If I stop and only for an hour or two the fuel filter is always full. But if I stop for the day the fuel filter will be empty. Where did that fuel go? Obviously the petcock is not leaking. But if the floats always shut off and there is no evaporation where does it go? Why is that not filled up. 2. At a recent NWCOG wrench session two sets of SISF Jet Kits were installed. One of the things Colin showed us on a set of open carbs was how rough feeling the float needles are. These carbs were from perfectly good running bikes that started and ran well. And make it to the wrench session with no problems, etc. But when the carbs were removed and the movement of the float needles was examined you could actually feel that it was NOT nice and smooth. To the point that one of the steps performed during the installation of the Jet Kit, not part of the instructions, was to remove the needles and clean out the passage way. The Jet kit installers took the extra bit of time to make it all nice and smooth again. So... Yes I got my first M/C and RD350 way back when I was 14. And I too can say I have ridden all these years and never had this problem, as in I have never had hydrolock, never gotten stuck, never had the bike run like crap that was directly traced to this, bla bla bla.... But.... I think there is some merit to his thought. Its not complely out of wack. I saw this first hand that those needles do not work perfectly smooth and there is varnish/something in there causing this. And with a little cleaning it was all smooth again. So I dont believe it was part of the carb housing itself. 2003 Concours, 56K COG #6953 IBA 28004 http://home.comcast.net/~slybones/Concours/connieMain.htm

 

[jaxrider]

Hmmm.... Maybe some fine valve grinding compound on the float needles? Mine had rubber tips on them which might be the reason I never had the problem. I was also scared spitless of hydro-lock and put on the manual petcock conversion so maybe I never had a problem because I turned the gas on before starting, and didn't have to crank it to get the vacuum to pull and let the fuel flow? David in Jax COG# 7898 NE FL AAD & COG Vendor www.dreamjobresumes.com preparing resumes for COG members and friends I ride a KAWASAKI ZZR1200 - Euro http://www.motorbikestoday.com/reviews/Articles/ZZR1200.htm US http://www.motorcyclistonline.com/roadtests/2002_kawasaki_zzr1200/index.html

 

[smithr]

Well most of us that use our bikes weekly will never see this problem. We are a minority among Concours owners I would bet. Most sit for weeks. I am not sure it is the needles that are fouling and making them leak. Like I hint to it could be the float and its hinge. I have seen this before. So some of you that have had many carbs apart what causes the needle valve not to seal most times? Photos[/url]

 

[MAN OF BLUES]

I suppose I have hads carbs off about as many times as Bubba, and have never found the fuel line empty or low any time I have disconnected it from the petcock. It unfortunatly for me, due to the mess, always dumps gas,... whether it sat overnight, or for 3 weeks. This tells me the "event' you are seeing is not on every bike, and might be a symptom of another problem, like a leaky vacume diphragm or seal in the petcock which allows the drainage. A fingertip on the straw theory, to make it simple. as for why the needles get dorky, well when they sit in there with gas, and the pressure exerted on that annular ring of the tip to the orifice, the actual pressure in that contact area is extraordanary relative to the contact area. Thats why it seals. This same pressure will creat a "dent" and in some cases cause a "cold flow" of the softened rubber creating a "lump" on that delicate surface. Way back when the earth was cooling, Mikuni breathers utilized polished steel meedle valves, sealing against a brass orifice, and it worked very well, I think the compound of the polymers used in the tips today varies from manufacturer to manufacturer, and even between batches. Combined with fuel additives that have become so common here for folks to use in lieu of actually servicing a dirty carb, attacks of this polymer become more suspect. Smoothing the 4 ribs on the shaft of the needle each time it is removed also aids in it moving unrestricted.