[steelcap]

The Bike
<BR>
<BR>2006 Thruxton. Airbox replaced with K&Ns.Jets = 150/42. TORs AI removed, Cal emissions removed. 7 months old 10500miles (running with no problem for first 10000miles)
<BR>
<BR>
<BR>The Problem.
<BR>About 4 weeks ago bike started coughing and spluttering at cruising speed. Thought it was a tank of bad gas (been to a different gas station). Drained tank. Continued to cough and splutter, usually after about 10-15 miles riding. Idles fine when it happens, but gently rolling on the throttle increases revs til about 2500rpm then revs just drop quickly to about 2000rpm and fluctuate between 2000 and 25000. If I leave the bike to cool a bit (10-15 mins) It's back to normal. At first I could continue the rest of my commute (another 15 miles), but it has gotten to the stage that it's happening every 2 or 3 miles after the initial time on a ride.
<BR>
<BR>Yesterday I drained the tank completely again. Pulled the carbs and checked and cleaned everything - appears to be fine. I installed new spark plugs and a new fuel line. Re checked fuel filters and checked all electrical connections.
<BR>
<BR>It happened again this morning on the ride to work.
<BR>
<BR>Has anyone else experienced this? Any suggestion?
<BR>
<BR>Could it be a problem with ignition coil/leads?

[ This message was edited by: steelcap on 2007-01-22 11:44 ]

 

[alfacliff]

how about pulling the fuel line and blowing through the sock filter in the tank? there is a fine mesh filter built on the top of the petcock that can get plugged up with bad gas, rust, varnish and such. if it is pulgged, you will have to drain the tank and remove the petcock to clean it.
cliff

 

[steelcap]

I pulled the petcock yesterday while the tank was empty and checked the filters - both were fine. I ran some clean gas through them (backwards) to make sure though.

 

[grayghost]

Hey Steelcap,

If you've ruled out a gas delivery issue (which it sounds like you have, as well as a gas cap venting issue (or pinched or kinked fuel line, I think the next logical place to investigate would be spark/ignition.

You may want to park the bike in a darkened garage with the exhaust properly vented-pointed outside (OBVIOUSLY DO NOT RUN THE BIKE WITH THE GARAGE DOOR CLOSED) and take a mister bottle with water and carefully spray the mist on the spark plug cap, spark plug lead and see if there is any arcing from a crack in the lead. This can cause the symptoms you are describing. Carefully examine the leads for ozone cracks etc.

Failing that I would likely go with an after market quality set of wires as found on the www.newthruxton web site, install them, and test again.

Good luck. Let us know how you make out

 

[Iceseven]

Try what Cliff said about the tank filter and if that doesn't help then it could possibly a bad coil, had the same problems you mentioned over a period of time and checked everything over and over again, finally took it in to the dealer and they switched coils and that was the problem.

 

[steelcap]

Thanks Greyghost, I'll give that a try this evening.

 

[AVMECH]

I had a similar problem after doing the airbox removal. After about 10 min at cruise would cut out and couldn't maintain 60, Sputtered out after 2nd gear at high revs. I set fuel floats to 16mm, one less than the factory 17 but still within the +/- 1 in the manual. No problems since. Also, 150 main seems a little high. I'm running 138/42 TOR's one shim and it runs great. The 150 would suck that bowl down even quicker than a 138. How long since airbox removal?

 

[sweatmachine]

FYI I run 155s on mine, I think I could even go to 160s and it runs guuureat!

 

[AVMECH]

yeah, I've been thinking of trying 145 to see what happens. I have yet to hear of anyone having a float issue like mine, but I swear, it solved the problem. mabey something to try before spending money on a coil.

 

[steelcap]

On 2007-01-22 18:17, AVMECH wrote:
I had a similar problem after doing the airbox removal. After about 10 min at cruise would cut out and couldn't maintain 60, Sputtered out after 2nd gear at high revs. I set fuel floats to 16mm, one less than the factory 17 but still within the +/- 1 in the manual. No problems since. Also, 150 main seems a little high. I'm running 138/42 TOR's one shim and it runs great. The 150 would suck that bowl down even quicker than a 138. How long since airbox removal?

Airbox was removed at about 650 miles - same time as TORs installed and AI removed. So it's been running great for 9000+ miles.

I'm just in the middle of checking the carb mounting boots for a vacuum leak - just about the last thing on the air/fuel side of things.

I checked the float height yesterday and it was 16mm, so I left it at that.

Also the engine temp definately has something to do with it. I let it cool for 2 hours then took it for a spin. After 1.5 miles it started doing it again. I limped homespluttering and coughing. It was still acting up in the garage. I left it for an hour, didn't touch a thing and it fired right up and revved with no problem.

Once I've checked the carb mount I'll ride it round the neighborhood and see what happens after a mile or so.


Thanks to everyone for the help and advice so far.

 

[boboso]

Steelcap, saw your psot over at BIR forum as well. I think someone there mentioned the vacumm caps on the carb and manifold. Sometimes they fall off etc (loose, cracked) and this has been reported by some to cause a similar issue.

Good luck!

 

[RedBird]

Your problem sounds like ignition to me, and I can only think of two things that could cause this: The coil or the igniter--I would replace the coil first since it costs much less.

You mentioned checking the fuel filters--did you check the small inline filter in the top of the "T" connection between the carbs. The fuel line goes from the petcock to the "T" and then to each carb--the small screen filter is inside the "T" connection.

Larry

 

[CAPTDON]

Sounds like a clogged / crimped fuel vent to me? Just a thought? :???:

 

[bonnieblackinfl]

I'm with 'bird, it's sounds like the ignition system; Coil, crank sensor, or ignitor.

Change your fuel filter to a clear glass, Mr Gasket automotive type. It let's you see what the status of fuel to the carbs is.

Greg

 

[steelcap]

Just for future reference - first the dealer replaced the ignition coil and although it improved the situation slightly, it didn't cure it. This week I had the pick-up coil replaced and so far (after 150 miles) it seems to have fixed it.

Thanks to everyone for their advice/suggestions and hopefully this will help someone in the future with this problem

 

[stu]

Thanks for telling us the cause. A lot of times you never hear what the problem turned out to be.