WTF - gas issue? what's going on here? anybody have the same issues?

was getting ready for a ride tuesday with my riding buddy Jeff (73 Mk1). i was low on gas, and needed to fill up. the 74 started OK, but ran like crap - seemed like an ignition problem. got to the gas station and told Jeff i didn't know if a ride today was going to happen since i seem to be having issues. anyway, filled up the bike with fresh non-E, and it immediately ran normal. obviously a fuel problem - low on gas and i'm guessing, one or both cylinders starving for gas. fast forward to yesterday. i pulled my tank to swap out the petcocks - had a (main) leaker - mine were not the best quality, but i did have a new set of BAP's (BTW vast improvement over OE style repro's). dumped in about 2 gallons of gas - again, bike started OK, but had the same running like crap issue. not as bad as tuesday, but still running bad. went out for a quick ride, and after about 5 minutes, bike was running normal. so my question, what's going on here, and has anyone else experienced this problem? the only thing i can figure is i had some air trapped in the fine mesh petcock filters. possible explanation? i've run with low gas before and even ran out of gas twice and never experienced this before? also, i'm thinking the reserve petcock did not have a filter from the factory - correct? both sets of replacements have filters. would that have anything to do with it?

Air trapped in the mesh is highly unlikely.

At first I thought ‘blocked cap vent hole’ but your later explanations don’t seem to support that.

Are you sure it’s not just cold? Without a decent cold start circuit, Amal’s can often make a bike run like crap until it’s warmed up. A problem that is amplified if your pilot jets are too small or partially blocked, as the engine will be lean anyway, thus much worse when cold.

I would drain all the gas out into a clear jar, look for water at the bottom.
Jaydee

Fast Eddie said:

Air trapped in the mesh is highly unlikely.

At first I thought ‘blocked cap vent hole’ but your later explanations don’t seem to support that.

Are you sure it’s not just cold? Without a decent cold start circuit, Amal’s can often make a bike run like crap until it’s warmed up. A problem that is amplified if your pilot jets are too small or partially blocked, as the engine will be lean anyway, thus much worse when cold.

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thought of that, but still in the mid 70's here in florida. i agree, cold engine might cause the problem, but bike was sufficeintly warm by the time i got to the gas station. only ran normal after fill-up.

jaydee75 said:

I would drain all the gas out into a clear jar, look for water at the bottom.
Jaydee

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good point - i did wash down the bike and gave it a good rinse before tuesday's ride. living close to the ocean, fighting rust is an ongoing battle. i was pretty careful about over-rinsing the tank. when i drained the tank to install the new petcocks, didn't notice any water in the gas, although, wasn't looking for it either. originally, the problem went away after a fill-up - puzzled....

You never take off in a recip airplane without pullling the drains and LOOKING at what you get. Water being the big worry.
Washing a bike in warm weather can get water into the system easily. Condensation. Drain your carb bowels regularly and
right after you ride so they sit dry.
Im laughing at 70 degree wx. It rarely reaches that even in summer where I am. :-(

I wouldn't say "obviously a fuel problem" meaning only fuel delivery problem. The miss also sounds like it also corresponds with the bike's temperature which could be an air leak that seals up when the bike gets hot. I had exactly the opposite happen. I guess that I over tightened a manifold allen screw and cracked the manifold. The crack was invisible to the eye, but when the bike warmed up it sucked just enough air to cause a miss on one side... Granted, my issue came after warm up, not prior to it...

So, maybe check the tightness of your manifold allen screws, and spray carb cleaner on the intake track when the bike is cold and idling poorly. If the spray causes a stumble maybe it's an air leak somewhere...

update - started the bike this AM and went for quick ride - everything's seems normal, SOooooo, i have no friggin idea WTF's going on - ????? maybe i did have a residual amount of water in the tank and low fuel level kicked things up. who knows????? sure do like those new petcocks though.... thanks for the replies.

Drop you carb bowls. My bet is you may have picked up some fine debris from your tank that settled into the carb. You may have cleared it out by running the bike but there is a chance there still might be some. I had a fine layer of rust form in my tank during my rebuild, found it covering my main jet after about 100 miles. Cleaned my tank with Evaporust, cleaned my carbs real good. Problem gone.

Blame the old petcocks...

You said you'd washed bike prior. Any chance water got trapped in the HT leads off the coils or at plugs? I typically run some dielectric/silicone grease on inner lead boots to help keep them sealed.

Old stale fuel, modern fuels go off not like the old leaded fuels of old, have had the same issues with my older Thruxton ran great one day and the next day ran like crap then the next day wouldn't even fire up, drained the fuel and add fresh fuel and fired straight up, normal unleaded fuel goes off after a few weeks to about 3 months, hi octane fuel will last a lot longer, I always fill up at busy fuel stations as tanks get filled up more often, I have also got bad fuel from fuel stations and when it does go off its like you have ignition problems and E10 fuel well that's another story but I never use E10.

Ashley

I get trash gas sometimes at the pump making the old motor behave like it's coming apart ( intermittent missing, etc. ) followed by hard starts and then no start. I've finally reached the point where if something doesn't happen right I drain the tank and carbs (perhaps blow some air through after removing the bowls) then add fresh fuel rather than beat myself up chasing a ghost. 99% of the time it was the fuel going sour..... You can smell the difference.

jaydee75 said:

I would drain all the gas out into a clear jar, look for water at the bottom.
Jaydee

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Game show buzzer. The ONLY benefit to E10 fuel is it keeps the fuel system clear of (normal amounts of condensate) water.

concours said:

Game show buzzer. The ONLY benefit to E10 fuel is it keeps the fuel system clear of (normal amounts of condensate) water.

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Yes, but... It comes with the penalty that the "absorbed" water is available to corrode anything that the fuel comes/stays in contact with.

This is a political subject. A response from the Arab oil embargo situation way back when , but it stayed with us.
Pure gas is what our bikes ask for and require. There are threads about where and what to buy on this forum. Plus you always vote with your money , enjoy.

just to clear things up, fresh non-ethenol, 89 octane in the tank. still running OK.

Kinda funny, we used to add gas drier (ethanol) to our fuel. Now we complain because it's already there!

FWIW, I've never had any trouble with "normal" (up to 10%) ethanol mix and have never made any attempt to avoid it. I just buy gas at whatever station is handy when I need it. Yes, it goes off relatively quickly compared to "old" gas formulations. For storage purposes, I add some Stabil and have stored cars/motos for up to 7 months with it and, in every case, they start right up as if they had been running yesterday. IMO, the issue concerns ethanol fuel that is left "standing" untreated in the tank for extended periods - though not really sure what "extended periods" might be. After winter and back in "normal" operation, our stored cars and motos may sit for 2-3 weeks between drives in the summer and none of them have any problem with ethanol gas. Related - my Commando's FG fastback tank (from Burton Bike Bits) as been unaffected and has been on the bike since '08.

OTOH if you do nothing as far as stabilization over the winter if the vehicle isn't operated, I have seen untreated ethanol/gas end up so totally clogging carburetors that they had to be removed and aggressively cleaned before they would function again!

E10 is no trouble.... (these bikes) except for long term storage. My 850 just sat for a month, (with pump E10 gas) started first kick & ran great. Stabil & a dash of 2-stroke rust preventative will carry through to March

I'm draining this year... The mower and Goldwing will eat anything so it won't go to waste. It'll be like candy at the movies to the wing as it sours a bit.