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Author Topic: Idling wild, and bogs opening throttle  (Read 2672 times)

boggy

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Idling wild, and bogs opening throttle
« on: September 17, 2012, 05:50:03 PM »
I had a rich bog last year that I tuned with some jets, needle positions.  I've run great all season, commuting daily, never touched my idle.  I know I was still running a bit rich but within reason.  Roughly even temps between 70-80F.  Ran it for hours on last Sunday and commuted fine Mon-Thurs.  Idled perfect/kicked first kick all season.  Really even throttle and power up and down the RPMs.

I dialed my air screw 1/4 turn to lean it out as in the past few weeks prior I've noticed quite a bit of backfiring (more than usual).  Because my throttle-needle in in the highest (or lowest?) position when I lean out my air screw, I can not lower my idle speed as I'm at the extreme of the idle screw so it was idling a little high.  That was the first thing I noticed about 2 weeks ago but again, it was running really solid, daily. 

Tried kicking last week on way home from work after a fine morning commute and I fouled a plug.  It wouldn't kick and when I pulled it, it smelled like gas, pretty sooty.  New plug started right up but the bike was running really bad.  Sounded like it was missing firing or something but I got it home.

Sunday morning I put in a new plug, and it kicked right up but as soon as I went to give it gas, it wanted to flub-out on me.  Like it was choking on gas maybe.  Or not getting enough.  Not sure.  So I drained the float bowl but that didn't help.  Neither did cleaning the fuel filter.  Sooty plug again.

Now it will kick over, and the idle will be wild.  It'll race, then it'll settle down.  If I give it gas it sounds really raspy, some snapping-popping at times, but past 1/4 throttle it wants to give out on me.  Then it'll stall out and won't kick over for a little while.  This is in neutral.  If I put it in gear and try to go it'll feel like it's getting gas, then not.  Forward-pull, forward-pull, then nothing, then pull, then nothing.  Lurching forward.  Dialing the air-screw does not help.

I'm a complete loss.  I spent so much of last year dialing in the carb and like I said, for months now it's been running GREAT.  No wild temperature swings.  Just a really quick onset of this issue.  My first thought is I'm way to rich, but WHY would I be SO rich all of a sudden after months and months of no issues?  That makes me hesitate to mess with any jetting right now. 

I'm ready for some ideas.  Let me know what you think.

Thanks/Boggy
« Last Edit: September 17, 2012, 05:54:34 PM by boggy »
2007 AVL
2006 DRZ400SM

barenekd

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Re: Idling wild, and bogs opening throttle
« Reply #1 on: September 17, 2012, 06:51:07 PM »
It could be a few things, a sunken float, or leaking float needle would be my first places to look as it sounds like you are way too rich. Is your needle at its lowest or highest setting? it's hard to tell from your description.
Bare
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boggy

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Re: Idling wild, and bogs opening throttle
« Reply #2 on: September 17, 2012, 08:31:22 PM »
I had to search back in some threads - Needle is in the top notch, so at it's lowest point.  Last year I had to adjust the height of my float bowl which was bogging out and set it to 19mm (I believe) as was recommended by everyone with a PWK 30mm flat-slide.

Wondering how my float could change since then. Perhaps it's stuck.
2007 AVL
2006 DRZ400SM

ace.cafe

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Re: Idling wild, and bogs opening throttle
« Reply #3 on: September 17, 2012, 08:37:13 PM »
I'm betting that the rubber hose between the carb and the manifold has some kind of air leak in it. A tear, or a pinhole, or some failure that's letting air in.
What's happening to your bike is a classic symptom of that hose getting a hole in it.
The fuel with the ethanol in it eats that rubber away, and then it leaks air, and the engine runs bad, if it even runs at all after that happens.
It can be a sporadic thing too, if the air leak is small and sometimes it seals and sometimes it doesn't.

* I just saw you have the PWK 30, and I don't know if that uses the hose connector or not. If it doesn't, then disregard the above.
« Last Edit: September 17, 2012, 08:41:18 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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boggy

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Re: Idling wild, and bogs opening throttle
« Reply #4 on: September 17, 2012, 09:05:52 PM »
Ace,
Yah, PWK is carb body right to engine.  Metal to metal, gasket in between.  Possible leak there maybe?  What about my fuel line from my petcock to the carb?
« Last Edit: September 17, 2012, 09:10:09 PM by boggy »
2007 AVL
2006 DRZ400SM

ace.cafe

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Re: Idling wild, and bogs opening throttle
« Reply #5 on: September 17, 2012, 10:04:15 PM »
It's hard to say. It could be a lot of things.
Probably the best thing to do is yank off the whole intake system and check it out thoroughly, clean it, and use new gaskets when you put it back on.
Drain some gas out of the tank to be sure that there's no water laying in the bottom of the fuel tank, causing problems.
Clean the petcock and fuel line to be be sure it is flowing a decent amount.
Give the whole carb a good disassembly and cleaning, and make sure all passages are clear and clean and that the float level is good.

Check the air filter for flow, and there shouldn't be much left unturned after that.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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boggy

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Re: Idling wild, and bogs opening throttle
« Reply #6 on: September 17, 2012, 10:26:09 PM »
OK, thanks for the list Ace.  Hopefully just a sticky float bowl or something.

2007 AVL
2006 DRZ400SM

Arizoni

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Re: Idling wild, and bogs opening throttle
« Reply #7 on: September 17, 2012, 10:46:33 PM »
While you have the carb off, check the flatness of the mounting flange using a piece of glass or a good steel straight edge.

I've seen the "ears" on some carbs bent leaving the bolts tight but a pronounced gap between them where the air passage is.
With a flat gasket in place, the carb can look tightly mounted but still have a bad leak into the engines inlet duct.
Jim
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barenekd

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Re: Idling wild, and bogs opening throttle
« Reply #8 on: September 17, 2012, 11:29:21 PM »
Floats can change. If it's a metal one, they can develop leaks at the solder joints. If it's foam, they can get a leak in the outer skin and absorb gas. I've had it happen personally in both types, and seen it on several others. It's fairly rare, but it's become one of the first things I look at.
Bare
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boggy

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Re: Idling wild, and bogs opening throttle
« Reply #9 on: September 18, 2012, 01:00:50 AM »
I'll check for both of these things.  Thanks guys.
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2006 DRZ400SM

Bill Harris

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Re: Idling wild, and bogs opening throttle
« Reply #10 on: September 19, 2012, 07:01:13 PM »
boggy,

On your PWK 30mm flat-slide carb flange there is a grove for a 'O' ring, ensure the 'O' ring is in good shape and seated in this grove, I use a heavy weight grease to hold the 'O' ring in place, this 'O' ring can slip out of it's grove when mounting the carb and cause a leak.  Also check the gasket that goes between the carb and 'O' ring, and the intake manifold on the head.  If the 'O' ring or gasket are not in go shape or the 'O' ring has slipped when mounting the carb, it will give you some of the symptoms you are having.  Just a thought.   Good luck with your project.

Check this web sight out:
http://www.lowbrowcustoms.com/tech/pdf-files/jrc-flatside-carburetor-install-guide.pdf

Cheers,
Bill       
« Last Edit: September 19, 2012, 08:28:28 PM by Bill Harris »

boggy

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Re: Idling wild, and bogs opening throttle
« Reply #11 on: September 19, 2012, 08:25:46 PM »
I'll check that out too.  I believe the last time I had the carb off (last Fall) I put on a new gasket and o-ring but I'll have to double check, and give them a good once/twice-over.  I'll have to pick up some grease as well.  Just on the o-ring or on the gasket too?

(Getting to this next week).

Thanks Bill.
2007 AVL
2006 DRZ400SM

Bill Harris

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Re: Idling wild, and bogs opening throttle
« Reply #12 on: September 19, 2012, 08:35:07 PM »
boggy,

Use grease just on the 'O' ring.

Check this web sight out:
http://www.lowbrowcustoms.com/tech/pdf-files/jrc-flatside-carburetor-install-guide.pdf

Cheers,
Bill
 

boggy

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Re: Idling wild, and bogs opening throttle
« Reply #13 on: September 20, 2012, 12:34:25 AM »
Thanks Bill. Hey, while I have your attention:
When I bought my AVL second hand, it came with the PWK.  On the opposite side of the idle-screw is a hole that I have highlighted in the attached image.  It was sealed with epoxy when I received the bike.  When I first started getting my rich bog, I thought the epoxy might have a hole in it so I removed it and put in an extra idle-screw and screwed it in tight.  It didn't fix anything but as my carb was running great all year I've not taken it out.  Do you have that hole plugged on your PWK? Or is it wide open?  It's open in this pic.

Thanks. Boggy
2007 AVL
2006 DRZ400SM

Bill Harris

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Re: Idling wild, and bogs opening throttle
« Reply #14 on: September 20, 2012, 02:37:47 AM »
Thanks Bill. Hey, while I have your attention:
When I bought my AVL second hand, it came with the PWK.  On the opposite side of the idle-screw is a hole that I have highlighted in the attached image.  It was sealed with epoxy when I received the bike.  When I first started getting my rich bog, I thought the epoxy might have a hole in it so I removed it and put in an extra idle-screw and screwed it in tight.  It didn't fix anything but as my carb was running great all year I've not taken it out.  Do you have that hole plugged on your PWK? Or is it wide open?  It's open in this pic.

Thanks. Boggy

boggy,

At that location my PWK has a small brass screw in the hole.

Cheers,
Bill
« Last Edit: September 20, 2012, 02:53:22 AM by Bill Harris »