Running

[Mickly]

Has anyone experienced this and found a solution?

 

My new to me 2016 KTM 350 EXC-F (single cylinder 4stroke with fuel injection) has developed an issue:

 It starts with no issue
It rides with no issue
But !! After about 2 to 3 miles it starts spluttering, loses power and grinds to a halt as if running out of fuel despite having plenty of fuel in the tank, after about 30 seconds at the road side it starts & idles but a few hundred yards up the road it does it all over again, ad nauseum until I get home - luckily not far.

So far I have:

Checked and cleaned the battery terminals & where the earth strap attaches to the chassis.

Checked and cleaned all the connectors stuffed behind the headlamp.

Checked and cleaned the inline filter within the quick release tank fuel pipe connector.

Removed the tank and checked that the in-tank fuel pump is working with no splits or cracks in the hoses or filter.

It had a new injector just before I got it ( receipt and old one provided )

The in tank filter looks ok but I’ve ordered another one to fit while it’s all apart.

The next course of action would be to  purchase a fuel pressure measuring kit to see if it falls when the bike grinds to a halt.
Oh I’ve checked the tank breather as well

 

Any more ( sensible ) ideas?

Edited December 21, 2024 by Mickly
Stuff

[Simon Davey]

Sounds like the demise of the spark plug. 

They nearly always show failure once hot. 

The only way to be sure, is to replace it. At least then it's discounted if its not the fault. 

Edited December 21, 2024 by Simon Davey

[Mickly]

43 minutes ago, Simon Davey said:

Sounds like the demise of the spark plug. 

They nearly always show failure once hot. 

The only way to be sure, is to replace it. At least then it's discounted if its not the fault. 

Oh, forgot to say it’s got a new plug

but thanks

[Mississippi Bullfrog]

Crank sensor failure comes to mind. It's a magnet and if the coil develops a crack it opens up when hot, then closes again as it cools down. 

 

 

[Mickly]

42 minutes ago, Mississippi Bullfrog said:

Crank sensor failure comes to mind. It's a magnet and if the coil develops a crack it opens up when hot, then closes again as it cools down. 

 

 

Thanks for the suggestion

Would it cool and close over 30 seconds?

I’ll look up on how to test it

[Hairsy]

I’d suggest trying to hook up to the diagnostics port. If it’s an intermittent sensor (which it could be) then there should be a logged fault.

 

Also, can you just let the bike warm up at home to recreate the problem? If so, wait for the problem and then check for spark.

[Yorky]

Check the fuel line connections if you've had the tank off or been working in that area recently.

[Mickly]

2 hours ago, Hairsy said:

I’d suggest trying to hook up to the diagnostics port. If it’s an intermittent sensor (which it could be) then there should be a logged fault.

 

Also, can you just let the bike warm up at home to recreate the problem? If so, wait for the problem and then check for spark.

Thanks, this is a good idea, I have an OBD2 reader and would just need to purchase an adapter to plug into the bikes diagnostics port.

I have discovered that the bike itself will show up any issues with a series of flashes of the FI light, this comes on when you hit the starter and goes off as it should do.

I’ll return to this once I’ve got the new fuel filter and buttoned it all up.

[RideWithStyles]

Yea sounds like something is being vacuumed (pulled) to block it, when stopped it slowly releases the pressure (movement) and can start again.

so change or check fueling - pump, internal filters, pipes.

oil filters have been known to do something similar, if its an old or cheap filter that prolapses.

[Fender1515]

Does the engine have the same symptoms if you run it stationary?

[Mickly]

30 minutes ago, Fender1515 said:

Does the engine have the same symptoms if you run it stationary?

 Not totally sure, although when it grinds to a halt it will start and idle.

[Mickly]

50 minutes ago, RideWithStyles said:

Yea sounds like something is being vacuumed (pulled) to block it, when stopped it slowly releases the pressure (movement) and can start again.

so change or check fueling - pump, internal filters, pipes.

oil filters have been known to do something similar, if its an old or cheap filter that prolapses.

It has got a none OEM fuel filter in the tank, that although clean(ish) does look like it’s got a dislodged filament, I’ve got a proper one on order.

[Mickly]

On 22/12/2024 at 08:54, Hairsy said:

I’d suggest trying to hook up to the diagnostics port. If it’s an intermittent sensor (which it could be) then there should be a logged fault.

 

Also, can you just let the bike warm up at home to recreate the problem? If so, wait for the problem and then check for spark.

I really hope it’s not the crank position sensor as I found out that it’s routed behind the cam chain guide / tensioner & that needs to come out to fit a new sensor

Edited December 23, 2024 by Mickly

[Fender1515]

38 minutes ago, Mickly said:

 Not totally sure, although when it grinds to a halt it will start and idle.

Can you try running stationary, leave at tick over until it reaches norm temp and fans comes on, if it still runs ok, wind it up till it reaches red temp and keep i there for a min or two and see if it still runs OK. Apologise to your neighbours after! 

[Copycat73]

i`m gonna call fuel pump .. i was warned about my 701 .. basically the brushes wear out on the motor and blacken the filter with charcoal .. so i replaced it for a brushless motor.. 

[Mickly]

The new filter turned up on Xmas Eve, but I wasn’t brave/stupid enough to try and sneak to the garage to work on it until today:

Here is the new OEM Mahle filter next to the one installed.

 

When I picked up the complete assembly a bit of black crap fell out of it and I could hear more rattling around when I gently shook it, this wasn’t apparent when it was wet with fuel, but now it’s dried out.

Decided to remove the fuel pump from its housing to investigate further.

Looks like we maybe have a winner - I’ll get a new pump & strainer on order, just need to decide if it’ll be a cheap AliExpress job or a much more expensive one with a lifetime guarantee.

[Mississippi Bullfrog]

2 hours ago, Mickly said:

The new filter turned up on Xmas Eve, but I wasn’t brave/stupid enough to try and sneak to the garage to work on it until today:

Here is the new OEM Mahle filter next to the one installed.

 

When I picked up the complete assembly a bit of black crap fell out of it and I could hear more rattling around when I gently shook it, this wasn’t apparent when it was wet with fuel, but now it’s dried out.

Decided to remove the fuel pump from its housing to investigate further.

Looks like we maybe have a winner - I’ll get a new pump & strainer on order, just need to decide if it’ll be a cheap AliExpress job or a much more expensive one with a lifetime guarantee.

Ye gods...how did it get into that state?

 

Be good if its an easy fix. 

[Mickly]

1 hour ago, Mississippi Bullfrog said:

Ye gods...how did it get into that state?

 

Be good if its an easy fix. 

No idea how it got so bad, it was off road for a year before I got it, maybe it was stored with very little fuel in it allowing it to rust.

Its got a filter ‘sock’ in the filler neck to stop rubbish going into the tank when you fill up but dunno how long that’s been in place.

[Mickly]

So I coughed up £90 for a new Quantum pump and strainer, fitting was a nightmare but I’ll spare the details except all the connectors fell off the end of the wires as soon as they were touched.

Just got back from about a 5mile run on KT, no stuttering issues at all, even feels like it’s found more gee gees, involuntary 2nd gear wheelie off the throttle

So hopefully it’s now all sorted

 

[Simon Davey]

That's a flippin' good start to the year. 

Well done that man.