Bad Fuel Precipitates Back Fire and Idle hunt - - Excellence in Motion
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post #1 of 7 (permalink) Old Jan 15th, 2020, 3:48 am Thread Starter
Join Date: Dec 2019
Posts: 11
Bad Fuel Precipitates Back Fire and Idle hunt

Greetings and Salutations to all!

Now that my beloved 2008 K1200S is with me in the Kingdom of Thailand: I was happy as a clam and living the dream, until I stopped at a Shell station and have had backfiring and idle hunting ever since. Woe is me.

Shortly after uncrating my K12S, I put 2 liters of 95 octane gasoline from a PTT fuel station, the bike was running, no purring like a big Cat at all speeds for about 150 kilometers....

Stopped at a Shell fuel station on Rama 9, and could not find any octane rated pump. They had shell supreme, shell super....blah blah blah....and after being adamant with the attendant in Thai language that I needed Benzine 95, I'm pretty sure it ended up being gasahol 95.

Within 2 minutes of leaving the station, the nightmare began..... Bang, Pow, burp burp Bang bang and a Stall or 2 as I limped her to my office about a kilometer away.

The next day, I had my crew completely siphon the tank out, and refill with 95 Gasoline and add fuel injector cleaner.

I'm about half way through the tank of fuel now, but still have backfire issues (less severe) at low speed and Idle.

It seems I may have to pull the tank and air box.

Would some one chime in and give me a direction of interest to specifically investigate or inspect while tank and airbox are apart?

Thanks in advance, I should have her apart by next week.

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post #2 of 7 (permalink) Old Jan 25th, 2020, 5:27 pm
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Join Date: Sep 2008
Location: Honolulu, HI, USA
Posts: 153
I'm a K13 guy with years of experience on two K100RS. To the extent your fuel system is similar: although "your crew" emptied the tank, there's still (bad) gas in the fuel lines from pump, filter, injectors, and back through fuel pressure regulator to tank. You may have to run a while to circulate this out. Suggest fill, run, siphon into a clear container to see if there is water in the fuel. Or you can fill a liter, run, siphon and discard a couple times.

It's also possible the filter is effed up with water and/or dirt, and that you'll have to replace it.

It is also faintly possible that fuel isn't your problem at all. Check your main ground wire for good clean connection at both ends.

A hunting idle is generally a sign of an intake leak, make sure your intake path is free of cracks in rubber bits.
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post #3 of 7 (permalink) Old Feb 4th, 2020, 5:11 am Thread Starter
Join Date: Dec 2019
Posts: 11
ALOHA, Howzit brah? I lived in Ewa Beach for six years.... what a great Island chain! Easy to get lost in Volcano chain in Maui....

Any how..... great advise, as I'm still trying to digest it all. I hooked up a GPS digital harness and while running the wires, discovered a few things....

Its dirty down the snorkels, and the throttle bodies are a bit oily... I used an inspection mirror and a flash light for a preliminary looksy.

I will be pulling the tank, airbox and related items and following a few (if not all) of your suggestions.

I also finally recieved my genuine service manual and it mentions " time change items" ... one of thses being the secondary air valve or what's known in K bike talk as an SLS valve.

Expensive little buggars, at 100usd but the repair/service manual clearly states 25k time change.

Thanks for chiming in, were on the same page as the fill, burn 1/2, and drain.... I did not stop to think of looking at the fuel through a glass container.... great call and MAHALO!

I'll update next week.

Sawasdee Khrap.

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post #4 of 7 (permalink) Old Feb 7th, 2020, 5:18 am Thread Starter
Join Date: Dec 2019
Posts: 11
Today, My staff and I, removed the components to access the Fuel Tank and Air Box. fairly painless and uneventful.

Upon inspection of Fuel and Fuel Tank: No discrepancies noticed as way of water balls or globules in Tank.. We did find a few shiney metal flakes and some rusted particles residing at the bottom. But nothing earth shattering to write home about or anyone here.

We did attempt to remove the Fuel Outlet and take a little peak inside what looks like a prime area for sediments or water contamination to hide, but just became to tired to bring up the repair manual and check.

Tomorrow we will continue and report.

Pictures of progress in the meantime.
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post #5 of 7 (permalink) Old Feb 12th, 2020, 9:54 pm Thread Starter
Join Date: Dec 2019
Posts: 11
Greeting and Salutaions!

We are moving along with the K1200S..... beginning to get the feeling its something very simple, it's just not presenting itself just yet.

After pulling the Fuel Tank, Cleaning it, and inspecting it: we decided to upgrade the Fuel Quick Disconnect to the stainless steel\Chrome plated Brass for both the Male and the Female. Nothing noteable was found in the tank.

We did ponder what the big white plastic unit was on the backside of the access panel, which some operator\owners call :"The Invisible Filter". We searched through the Parts Catalouge and the Service and Repair Manuals to no avail. The Unit is integral to the Fuel Tank Access Plate and we did find some Microbiological growth in that component. A gray whitish smelly sustance that we removed with some fuel injector cleaner for Toyota.

The nest step is to pull the Silence, also known as the Air Box. We do not have the niffty cutting tool from BMW, nor any replacement clamps to re-attach and install the Airbox.

All lines were visually checked and no cracks were found. But as the problem was probably precipitated by the poor operation after the bad gasahol incident.....its looking more like a small sense line, canister, or missing plug somewhere in the idle control system.

Until Next time..... Everyone please enjoy the Ride for me!
Capt howdy likes this.
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post #6 of 7 (permalink) Old Apr 29th, 2020, 4:49 am Thread Starter
Join Date: Dec 2019
Posts: 11
Follow Up to Idle Hunt and Afterfiring

Gosh Darnit.... what is with this server Jumping up and down?

I just lost several Paragraphs..... So Down and Dirty as I'm being Spammed?

Removed Clamps to Air Intake Box, found 1/2 cup of motor Oil in Bottem of Box. Secondary Airvalve stilll operated when 12Volts Applied. Step Motor Stuck closed and used carb Cleaner. Cleaned Box, re-assembled and re-installed.

Pictures Attached.

Thats it for Now!

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post #7 of 7 (permalink) Old May 1st, 2020, 9:49 am
Join Date: Jun 2015
Location: Raleigh, NC, USA
Posts: 12
My 08 K12GT has overflow from oil tank connects to airbox: If bike allowed to lay down for any time at all oil will run to airbox, if oil tank is overfilled some oil will go to airbox. Any oil go into your bike with the Shell fuel?
dedmnhd is offline  

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