Bike cuts out after revving

[kickaha]

Hello,

Have a K5 that is stalling/enging cutting out, after revving.

At idle, it seems to be ok, sitting at around 1500, but after revving it, it drops below that, sits at 1000-1300, sputters and cuts out (while in neutral, 1st with clutch in etc).

Happened first time about a couple weeks ago, after fueling at a Sainsbury's. Thought it might be bad fuel, but the station claimed they didnt have any other such complaints that day.

Removed the fuel, added new fuel with some Seafoam, and bike ran like new.

A couple weeks later, and the same problem is back now, and got stuck far from home so called RAC. They did a hard reset, but no joy and "suspect fuel issue".

Any thoughts?

And while I appreciate its hard to diagnose something remotely like this, would anyone have any recommened mechanics in the south west london area?

Many thanks in advance.

[admin]

One thing to rule out is a blocked breather in the fuel cap. Easy to check, just open the cap and see if anything changes. I'm also wondering if the fuel pump has picked up some debris.

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[mister c]

Is the bike stored outside? I had an issue where the tank drain tube was blocked which allowed rain to make its way into the fuel causing issues on my gen 1 bike. Could be worth draining the tank again, but into a container to see if you have any water in your fuel. The water is heavier, so sits at the bottom

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[kickaha]

thanks for the quick replies, much appreciated.

John - tried it (running without fuel cap), and bike still cuts out after revving engine. i get plenty of pops from exhaust suggesting (by my novice thinking), that the bike runs rich more than lean.

mister c - dont know if my K5 has tank drain tube, but happy to check. looking into it. will drain tank again as suggested, but might not be a few days, so will get back to you with results.

[mister c]

Originally Posted by kickaha

thanks for the quick replies, much appreciated.

John - tried it (running without fuel cap), and bike still cuts out after revving engine. i get plenty of pops from exhaust suggesting (by my novice thinking), that the bike runs rich more than lean.

mister c - dont know if my K5 has tank drain tube, but happy to check. looking into it. will drain tank again as suggested, but might not be a few days, so will get back to you with results.

This hole has a pipe that goes inside your tank & should exit at the rear. They sometimes get blocked, or the rubber drain hose that's attached to it gets crimped which then allows water to build up around the filler, then drops into the fuel tank. I'm not saying that's the issue, but could be worth investigating.IMG_20240109_062827.jpg

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[Seeker]

Originally Posted by kickaha

i get plenty of pops from exhaust suggesting (by my novice thinking), that the bike runs rich more than lean

popping on the overrun is caused by a lean mixture, usually an intake air leak but (less often) an exhaust leak.

Do your secondary throttle butterflies do their start up dance?

https://www.youtube.com/watch?v=2dkXIIf7U20

[Bibio]

another cause could be the battery is past its best or the terminals on the RR connector. this sound the same symptoms i had and it turned out to be the RR connector.

[kickaha]

[QUOTE=mister c;3142757]This hole has a pipe that goes inside your tank & should exit at the rear. They sometimes get blocked, or the rubber drain hose that's attached to it gets crimped which then allows water to build up around the filler, then drops into the fuel tank. I'm not saying that's the issue, but could be worth investigating.Attachment 16931

thank you mister cc, it seems ok (i think), but havent checked the hose beyond just checking the opening. what does worry me, is the appearance of light rust around the fuel intake, which I'm looking into. Will have to drain tank and clean it.

[kickaha]

Originally Posted by Bibio

another cause could be the battery is past its best or the terminals on the RR connector. this sound the same symptoms i had and it turned out to be the RR connector.

Thanks Bibio, have checked battery and voltages are:
12.54 when off
11.98 when ignition is on
drops to low of 8 or 9 when starting up and runs at 14.4

seems ok, i think...perhaps too high when running? or too low when kicking over?

[kickaha]

Originally Posted by Seeker

popping on the overrun is caused by a lean mixture, usually an intake air leak but (less often) an exhaust leak.

Do your secondary throttle butterflies do their start up dance?

https://www.youtube.com/watch?v=2dkXIIf7U20

Cheers Seeker. Here's a vid of the attempted dance of the butterflies. Doesn't look as impressive as those in your vid, so perhaps that's indication of the issue I'm experiencing...

https://www.youtube.com/watch?v=1Nui5QjOEO8