Topic: Premium fuel left me stranded

[zenocchio]

I just want to express my frustration and hopefully picking your brain with my latest issue.

this morning on my way to work I stopped and refueled at a Shell gas station as I was on reserve.
For the first time ever I filled with premium gas, 91, normally i am using 87.
The bike is a cb500 running velocity stacks, well tuned. I never had an issue with it.

I rebuild the carbs last summer, and cleaned the fuel filter a month ago.

The bike was running poorly, I had to open fully the choke to have it going, but only for few hundred meters. I finally got to another gas station and dump 95% of the gas out and refilled with 87.

the bike started right up, was ok for a couple of km, but then I had to start playing again with the choke and eventually died for low battery.

What did I messed up? Can just a higher octane fuel ruin my morning like that?
the best part is that i had my wife in the back! she is been soo good, not complaining even when we had to take the bus to get to work one hour late!

[TwoTired]

Also certain not a 91 octane issue.  Most probably is a fuel contamination issue.  Doesn't take much to plug the pilot jets as they are only 0.016 " on diameter.

Switch to reserve and you supply fuel from the bottom of the tank...where are the big particles settle.

Check the fuel screens and sediment bowl.  Check the tank for rust.   Flush the pilots jets and the carb bowls.

The bike needs clean fuel.  Some stations can provide dirty fuel, expecting your filter to clean it.

[Jerry Rxman Griffin aka MuthaF'er]

Fuel from the bottom of the tank with water maybe.

[SOHC4 Cafe Racer Fan]

It was not likely the higher octane fuel.  I sometimes run a cap of Seafoam and/or some octane boost with no negative effects.  It may have been some muck at the bottom of your tank sucked in by the reserve valve.

[zenocchio]

Thanks guys. So removing the bowls & the three jets and clean them should help?

[madmtnmotors]

Thanks guys. So removing the bowls & the three jets and clean them should help?

and filter

[zenocchio]

Good, i love to work on my bike at the side of the street!

[zenocchio]

Ps. This is the troublemaker

[goldarrow]

Very likely pilot jets clogged as twotired mentioned above

[zenocchio]

Which one is the pilot jet? Can someone point it out on the diagram?
Will I be able to access it without removing the carbs?

[flybox1]

#32
also clean the emulsion tube (long tube #3 , remove pressure clip and main jet)

[TwoTired]

The pilot jets are next to the big casting stem protruding into the middle of the carb bowl. 

When you remove the bowls look a the bottom of it for sediment.  That would be the smoking gun.

Almost certainly, the only thing you need to clean is the pilot jet in each carb, or just the carb corresponding to the coolest exhaust pipe.
Yes, I've encounter this very problem.  You don't even have to remove the carbs if you have the proper size/length screwdrivers.

Warning, don't put the death grip on tightening the pilot jets when reinstalling.  They will snap off with too much torque.

You can also strip threads when reinstalling the bowl screws, too.  Just be gentile but firm.  It's old, you know. 

[zenocchio]

The pilot jets are next to the big casting stem protruding into the middle of the carb bowl. 

When you remove the bowls look a the bottom of it for sediment.  That would be the smoking gun.

Almost certainly, the only thing you need to clean is the pilot jet in each carb, or just the carb corresponding to the coolest exhaust pipe.
Yes, I've encounter this very problem.  You don't even have to remove the carbs if you have the proper size/length screwdrivers.

Warning, don't put the death grip on tightening the pilot jets when reinstalling.  They will snap off with too much torque.

You can also strip threads when reinstalling the bowl screws, too.  Just be gentile but firm.  It's old, you know. 

Thanks! That is very helpful!

[SOHC4 Cafe Racer Fan]

As a safeguard, you may also want to install a fuel filter in the line between the petcock and the carburetors.  There are higher volume clear glass ones, which will show if any debris is flowing from your tank.

[zenocchio]

As a safeguard, you may also want to install a fuel filter in the line between the petcock and the carburetors.  There are higher volume clear glass ones, which will show if any debris is flowing from your tank.

That is a good idea, and I have one with me as a spare.

[TwoTired]

If your stock filter is working, you don't need an inline.  How many times must you filter fuel;  2, 3, 7, 10 times?

Also, there are fuel line issues.  The gravity fed system needs a constant grade drop to feed properly.  Line loops can cause feed issues with air trapped within.  There is very little room to insert an extra and redundant filter anyway.

Also, if/when a filter collects particles, it flows less, causing yet other issues, overheating and loss of power at higher speeds.  So, you must now add filters to your routine maintenance/replacement schedule.

Make the stock one work as it should.  Problem solved.  Then for your model, only the sediment bowl is addressed on a regular maintenance cycle.

[madmtnmotors]

Make the stock one work as it should.  Problem solved.  Then for your model, only the sediment bowl is addressed on a regular maintenance cycle.

+1

[zenocchio]

Yesterday it took me a good hour to sort the bike and getting it home,
I have cleaned the tank petcock  filter, that was fine, it had a small amount of debris.
I then open the bowl of the #4 carb, little to none there, but the jet had one hole clogged.
put it back together, i realized that one of my fuel lines had a kink in it. this line feeds carbs 3-4 while the longer one goes to 1-2. I have a cb750 tank, and probably a cb500 petcock. Having the tap on the right side and very little clearance bent my line. I will have to cut a shorter lone and install it. the two tank outlet, are supposed to deliver the same fuel flow or one is dedicated to the reserve?
Anyway, long story short,
the bike runs perfectly now.
thanks to all of you!

[SOHC4 Cafe Racer Fan]

Yesterday it took me a good hour to sort the bike and getting it home,
I have cleaned the tank petcock  filter, that was fine, it had a small amount of debris.
I then open the bowl of the #4 carb, little to none there, but the jet had one hole clogged.
put it back together, i realized that one of my fuel lines had a kink in it. this line feeds carbs 3-4 while the longer one goes to 1-2. I have a cb750 tank, and probably a cb500 petcock. Having the tap on the right side and very little clearance bent my line. I will have to cut a shorter lone and install it. the two tank outlet, are supposed to deliver the same fuel flow or one is dedicated to the reserve?
Anyway, long story short,
the bike runs perfectly now.
thanks to all of you!

Sweet!

[madmtnmotors]

Glad to hear you're back in business.

I have solved problems with just a visual inspection many times. Reminds me of a car broke down on the side of the road one weekend morning as I left to run errands. There were a number of people milling about so I figured they had it under control. THREE HOURS LATER, on my way back home the car is still there with a now dejected looking, smaller group of people there. I stopped to see if I could help, and after gathering the basic info "it will crank but won't start, and I just did a tune up!" I had them crank it over while I watched/listened under the hood. As the starter cranked the engine over I noticed the distributor cap rocking back and forth.     

I instructed the driver to stop cranking, snapped the distributor cap clips firmly into their correct position (gotta love the clips, no tools needed!), told him to "try it now" 

Fired right up and they were on their way (gone in sixty seconds!). 

Of course they couldn't leave without the compulsory "what did you do!?" Felt bad having to explain the purpose of the distributor cap retaining clips to the guy that did the tune up. I'm sure he received more than one "you dumb a$$" for that one...