Stumped by a damn bing!

Hey y’all, haven’t posted on here in forever but here I am! I have a Ktm Foxi with an e50, 14mm bing and 65cc airisal kit. I’ve had this thing for almost a decade and it’s always been suspiciously reliable.

Lately its been acting up and I’m stumped. It will start but as soon as the rpms get up it dies on me. Sometimes if I let off the gas if will still idle. It very much feels like it is starved for fuel. Last time it died I went ahead and pulled the float bowl. There was a little bit of gas in there but it definitely was not full. Here’s where I’m confused:

1. The carb is clean all passageways aren’t clogged when.

2. The banjo fitting is definitely lined up correctly for max flow

3. I can see fuel in the line and it flows freely from the petcock if I pull the line.

4. The float height looks good. I bought a new one and threw it in just in case mine was bad, problem persists

5. It ran well for years with the current set up/jetting (I think jet is a 78)

I’m stumped. I’m hoping I’ve just been away from peds for too long and am missing something obvious. Any help is appreciated!

Re: Stumped by a damn bing!

Richard Eberline /

gas tank cap or bubbles in fuel line.

Re: Stumped by a damn bing!

There is a tiny little thimble looking filter in the banjo bolt, it doesn't need to be lined up to anything. Also the banjo spigot nipple thingy can corrode closed, I had that happen a few years ago and messed me up.

If you want to test it, leave the bowl off and install everything else as normal, see if gas pisses out.

If you are stuck running ethanol gas, start adding some stabil marine in there.

Re: Stumped by a damn bing!

Graham: I pulled the filter out of the banjo and the passage way is looking good in the banjo but good thinking! Gas is flowing.

I’m wondering now if an air leak is causing my carb to loose vacuum. Gaskets are definitely ready to be replaced but I’m not sure that would effect the flow so drastically? (edited)

Re: Stumped by a damn bing!

roots to wings /

If it's not what Graham said, meaning there aren't any snots in your banjo, banjo thimble, or the hole the fuel goes into the bowl thru, or snots in your jet, or chunks in your fuel filter, I'd be thinking condenser or points and timing.

Re: Stumped by a damn bing!

^bingo^air leak change out your crank seals, search for air leaks. You can test by enrichening your mix with extra gas, choking with your thumb, or tickling the tickler on your float bowl.

I know its a pain removing installing carb but adjusting the float to have a correct amount of fuel level is important.

Re: Stumped by a damn bing!

I'm betting it is less to do with the float itself but the float needle may be sticking and not letting fuel flow properly into the carb while riding at speed. But it trickles down and refills the bowl by the time you can get it all off to check. With a bing and fuel delivery issues it is the first thing I check and replace.

Re: Stumped by a damn bing!

roots to wings /

I was working on a new bike this morning and my float level was just a little off and combined with a slightly roached float needle causing the carb not to fill. I agree to make sure the bowl is filling

Re: Stumped by a damn bing!

I end up going over to a sha. But that is not exactly going to be an easy swap or straight forward tuning either. I just end up having better luck with my sha setups than my bing setups. They are two completely different animals tho.

Re: Stumped by a damn bing!

just thought I'd let y'all know it was a bad condenser once again! I need to pick up a spare vw condenser to keep on hand. Thanks for all the help :-)

Re: Stumped by a damn bing!

roots to wings /

I have one right now that will run great for 20 mins and then mawww out at wot and cut out. If I lay off the throttle it will come back. I replaced my condenser and it’s still doing it and getting worse. Maybe my new condenser is junk, but I think I have an air leak once the entire engine is warmed up which means new gaskets seals, and bottom and bottom end rebuild. Curious to hear more about your symptoms

Re: Stumped by a damn bing!

Roots. Check the carb float needle. Clean the jet area out really well. And if the needle head is bloated or warped in any way you will want to replace it.

The float can get stuck and not open fully and run the bowl dry at WOT. When off the gas it has time to refill the bowl enough to keep the bike running.

Re: Stumped by a damn bing!

roots to wings /

Thanks man. It’s done this with two different carbs and I replaced the condenser. I am about to rebuild it so how fully I can get on the other side of this. Does it only when hot at wot.

Re: Stumped by a damn bing!

Roots to wings, I’m in the same boat! I thought I was all clear but once things get real hot like go top speed for a few miles my ped dies. It kinda starts to struggle more and more til it just stops and needs to chill for a few before it can start. Longer I wait the better it runs.

I think I’m overheating due to air leaks! It appears my techno circuit pipe is leaking where it mounts. Got some new gaskets coming in the mail and am gonna grind some fins a little for a better fit this weekend in hopes that I can make this thing road worthy again. Let me know if you solve your problem.

Re: Stumped by a damn bing!

Worthman,

Same thing as roots. Clean your carb.

The only thing that will overheat and stop these bikes is the condenser on them. If that is good then you are running out of fuel from your carb and causing you bike to die.

If your bike overheats it will seize, not just die.

Re: Stumped by a damn bing!

Richard Eberline /

I once had a petcock, that the fuel flowed so slow, that has your same scenario. Worked slightly better on reserve. Also back to my original post gas cap, not venting.

Re: Stumped by a damn bing!

I did check the cap and it appears to be venting (I can spray air through it) also pulling it off doesn’t change anything. Gonna go ahead and pull the petcock this weekend and check again to see if the float needle is sticking. Thanks for all the ideas y’all

Re: Stumped by a damn bing!

roots to wings /

Todays test. Installed 2nd new condenser and checked head and gaskets. I didn't get 50 feet past the end of my driveway. Walk of shame back up the driveway. Turns out my atomizer had vibrated so loose as to almost have dropped in the bowl. Checked the rest of the carb (always clean the jet) and tightened everything up and ripped at wot for 15 mins without issue. Longer test needed to see what happens when engine is warm on long run before I drop it for the rebuild. Proper position of petcock filter? I assume at same angle as tank rather than touching the top or bottom of tank inside. Also want to test 51 slide with the idle hole. Setup is Bing 15, 15, 2.17, 78, #1, clipped third from top, br6hs, metal mesh, mlm cali, 14x40. 42-43 mph top speed. I know it will go faster (but don't care to as forks and bottom end are untouched) with 16x40 or even 16x45 but clutch needs tuning (xstiff springs) and might need a new bell for proper bottom end. I love the sound and top end of the mlm cali, but the estoril hits harder, is more torquey, and has better bottom and mid range overall, but 2-3 mph slower up top. Have to try estoril again without rattling atomizer. Note that the both the estoril and cali pipe flanges had to be ground down fairly significantly to connect to Airsal exhaust port.

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