KrZy8 Stumble off Idle

[dcarver]

KrZy8 has developed a pretty significant stumble off idle, but not all the time! Seems more prevalent when hot.

significant stumble off idle

as in I've stalled it several times now, once placing me in a less than ideal traffic situation.

Several summers ago, she ran very bad, even quit running all together at the Yosemite run Tyler put on. KrZy8 died at park entrance. After cooling down, she started and I made it back to hotel.

Quick diagnosis, fixed what I thought was fuel cap problem (not venting) then rode with PanMan and Niehart and Loud Jeff IIRC.

Of course, PanMan put on a freaking goat trail a KLR 650 wouldn't even like, it was hot and slow going.. and KrZy8 was throwing conniption fits. I rode ahead of the pack at a slightly faster pace to provide more cooling and even coasted downhill when possible.

Reading the mighty FJR forum, all indications were that the TPS was heat soaking and failing, sending the ECU into fuel mixture crisis.

Replaced said TPS with new. All has been good till now. Symptom is ONLY right off idle!

Facts

• Did valve adjustment about 5k ago, she ran freaking GREAT until nowNew plugs, filters, heavy maintenance
• New TPS. I didn't get the EXACT TPS numbers per the book, IIRC they were off by about 5 or so. Will check again later.

[*]35 - 47 mpg which is normal data for KrZy8 depending upon rider friskiness, weather, and fuel.
[*]Only run top-grade fuel. Chevron regular.
Plan of Action

• Check air box for mice activity
• Check compression
• Do Leak Down test
• Get TPS numbers
• Replace injectors. I have 4 matched spare injectors at the ready. They were the '2nd' best set of 4 as worked on by RC Engineering.
• Take KrZy8 out back and shoot the *****!

So, before doing all this thought I'd post up and see what all of y'all think the POA should be.

Any ideas, oh great collective?

This bike HAS to make 250k miles before I either part her out or shoot her or whatever!

Thanks in Advance,

dcarver

 

[RossKean]

I assume no error codes in evidence?

Sometimes a MAP sensor will cause some grief but should throw an error 14. (line to sensor can get plugged with goo)

https://www.fjrforum.com/forum//index.php/topic/170314-fault-code-14-gen-ii-solved/

Can't imagine it is your injectors unless you have been messing with JB Weld in your fuel system again - any chance 100% of the crud was not removed?

I expect blocked air filter would be more in evidence at higher rpm and greater engine loads than just off idle.

Definitely check the TPS.

What is idle RPM?

Fuel pressure regulator?

Hope it isn't a compression issue.

Good luck!

 

[dcarver]

I assume no error codes in evidence?No error codes.

Sometimes a MAP sensor will cause some grief but should throw an error 14. (line to sensor can get plugged with goo)

https://www.fjrforum.com/forum//index.php/topic/170314-fault-code-14-gen-ii-solved/

Good call. I just happen to have 3 FI Rails as spares. Just might swap a sensor and see what happens!

Can't imagine it is your injectors unless you have been messing with JB Weld in your fuel system again - any chance 100% of the crud was not removed?

Crossed my mind too. But I have, guessing, 20-30k miles on bike since then? Replacing injectors is ez-pz as compared to removing fuel rail.

I expect blocked air filter would be more in evidence at higher rpm and greater engine loads than just off idle.

Good thought. Hmm. And it runs great out of the 'off idle' zone. So probably a waste of time. But easy to check!

Definitely check the TPS.

I remember IonBeam riding with a Fluke 87 strapped to the tank watching the voltage. I have VDC datalogger I could use...

What is idle RPM?

​All my bikes that I can adjust have high idle RPM, 1500 to 1700. It saves a lot of grief and dumping..

Fuel pressure regulator?

No clue where it is, what is, how it works, nothing. Original fuel pump... hmmm. Another great lead from the RossKean!

Hope it isn't a compression issue.

Me too. My 'new' engine is now a 'very used' engine!

Good luck!

Thanks Ross!

 

[Brodie]

Don

Just for kicks, try removing KrZy8s California charcoal canister from the plumbing, and dont forget to cap the port off the air box. Perhaps the hot stumble is from an enriched mix from the dump valve venting the charcoal at that critical moment.

Just a passing thought.

Brodie

 

[mcatrophy]

Agree with Brodie that it could be your charcoal canister. I had an occasion when I believe mine caused a significant problem moving from rest (I posted about it here). Only happened to me the once, but then it's rare to get California temperatures here.

Didn't block mine off for two reasons, they are threatening us with exhaust emission testing on bikes, and it's rare to get California temperatures here.

 

[kenporider]

It sounds like you may need to replace the TPS again. Mine did the same thing--stumbling just off idle from a full stop with no other symptoms-- when two separate TPS's failed on me within two years.

 

[RossKean]

Agree with Brodie that it could be your charcoal canister. I had an occasion when I believe mine caused a significant problem moving from rest (I posted about it here). Only happened to me the once, but then it's rare to get California temperatures here.
Didn't block mine off for two reasons, they are threatening us with exhaust emission testing on bikes, and it's rare to get California temperatures here.

IIRC, the canister was removed (or bypassed) from that bike some years ago. Seems to me that its removal and subsequent operation of the bike on dusty roads without an airbox port being blocked might have been one contributing factor to the demise of the original motor. (I think that was one of the theories.)

Or maybe I am mis-remembering - sometimes happens in my old age!

In any case, the charcoal canister problem usually rears its ugly head for a relatively short period of time after a heat soak - i.e. after parking in the sun for an hour or two. Not while riding. Carver has had that bike for a looong time and this is a relatively recent phenomenon so I'm sure that he would recognize that for what it is. (Not like he was new to the bike or local climate conditions.) Unless something has messed up with that plumbing, this being a canister issue isn't a possibility, IMHO.

One thing I didn't mention in my original reply is the possibility of a tank venting problem. Check to see if the stumble disappears when you open the gas cap. Is there a "woosh" of inrushing air to fill a vacuum? More with a full tank or near empty?

I believe that the Gen I and Gen III+ have had more issues with TPS failures than Gen II. I certainly wouldn't discount that possibility (especially in a bike with this many miles) and would definitely make very sure that it is set correctly in terms of range.

 

[BanjoBoy]

I always run Water Wetter w/ anti freeze. Obviously not a cure for your problem, butt dropping the temp a few degrees never hurts. Besides, it's pink!

 

[dcarver]

Agree with Brodie that it could be your charcoal canister. I had an occasion when I believe mine caused a significant problem moving from rest (I posted about it here). Only happened to me the once, but then it's rare to get California temperatures here.
Didn't block mine off for two reasons, they are threatening us with exhaust emission testing on bikes, and it's rare to get California temperatures here.

IIRC, the canister was removed (or bypassed) from that bike some years ago. Seems to me that its removal and subsequent operation of the bike on dusty roads without an airbox port being blocked might have been one contributing factor to the demise of the original motor. (I think that was one of the theories.) Or maybe I am mis-remembering - sometimes happens in my old age! ​You remember correctly! No canister since ~2007 and the deer strike.

In any case, the charcoal canister problem usually rears its ugly head for a relatively short period of time after a heat soak - i.e. after parking in the sun for an hour or two. Not while riding. Carver has had that bike for a looong time and this is a relatively recent phenomenon so I'm sure that he would recognize that for what it is. (Not like he was new to the bike or local climate conditions.) Unless something has messed up with that plumbing, this being a canister issue isn't a possibility, IMHO.
One thing I didn't mention in my original reply is the possibility of a tank venting problem. Check to see if the stumble disappears when you open the gas cap. Is there a "woosh" of inrushing air to fill a vacuum? More with a full tank or near empty? ​Good idea. I have never heard a woosh sound. But then again I normally don't gas the main tank at the pump, rather backfill from the Aux tank. Don't have to remove tank bag that way.

I believe that the Gen I and Gen III+ have had more issues with TPS failures than Gen II. I certainly wouldn't discount that possibility (especially in a bike with this many miles) and would definitely make very sure that it is set correctly in terms of range.

Really hope it's not TPS. It's a PITA to remove install without taking fuel rail off.

Thanks for all the good advice!

 

[Hudson]

Don, I think KrZy8 needs its own technical forum

 

[TellurideFJR]

damn stumble

 

[HIGHLANDER]

Don, I think KrZy8 needs its own technical forum

My vote is plan F( and DC knows this )

Take it out back and shoot the *****.

 

[FJR Flyer]

Just a thought, have you checked the sync? Long shot.

 

[RossKean]

Just a thought, have you checked the sync? Long shot.

Can't imagine that a TBS could be off that much, especially since he runs his idle well above 1000 rpm! Also, Don just finished a MAJOR maintenance cycle on the bike and it has been running well for several thousand miles since.

That said, there is a possibility that he has lost a rubber nipple covering a synch port or has developed a major leak elsewhere in the vacuum system. Aftermarket cruise control vacuum canister maybe? One more thing to check, I guess. Hope he finds a smoking gun!

 

[dcarver]

I'll be getting after it tomorrow. Today was 'check the retirement dollars status' day.

Gonna trim the spending, for sure.

 

[bigjohnsd]

If you were with us, like you should be, you wouldn't be worried about this niggling problem! JSNS

 

[Hudson]

I'll be getting after it tomorrow. Today was 'check the retirement dollars status' day.
Gonna trim the spending, for sure.

So this is probably the wrong time to say I might be putting the KTM up for sale?

 

[FJRay]

I'll be getting after it tomorrow. Today was 'check the retirement dollars status' day.
Gonna trim the spending, for sure.

So this is probably the wrong time to say I might be putting the KTM up for sale?

I'll swap you a real nice KZ1300 for it. Only operated on three miles of dirt road by an old retired guy.

 

[escapefjrtist]

DC: I'll be getting after it tomorrow. Today was 'check the retirement dollars status' day.

Gonna trim the spending, for sure.

Hudson: So this is probably the wrong time to say I might be putting the KTM up for sale?

That's just mean Hudson!

~G