'02 B12 Issue with Carbs and Ivan Kit

[Ronin]

So for various reasons it has taken me a year plus to try and get my moto back in working order but I have gotten to the point of stumped on getting it ready for the road and turn to the experts for help.  Here's the deal:

I have a Yoshi pipe, Ivan’s jet kit (stage 3 I guess, it’s with the 112.5 main jets, Ivan instructed modified air box, no snorkel, clips on the needles are in the suggested #2 or #3 position (can’t remember which since it’s been a few years) and the tapered needles) 4 turns on the pilot screw, PAIR system removed and blocked off, and stock pilot jet.  At cold start the engine will turn over on the first crank and work its way up to “standard” idle which I have set at around 1250 1300rpm.  It will run at idle fine while I get on my gear.  I go out and drive through the neighborhood for 10-20 minutes to allow the engine to warm up (there's a circuit where I just have to slow down and not stop).  It runs fine through all rpm’s while tooling around the neighborhood and then when I stop at our garage and let it sit at idle for a few minutes it slowly starts idling down and dies.  When I say idle down I mean it will, over a span of 10-20 seconds, idle from 1200 to 1000 to 700 to 500 to 200(not exact numbers but round-about) and die.  When I try to start it up again I have to crank on it multiple times open the throttle about an 1/8th of a turn and then will it finally start.  But it will sit at idle for a few minutes and die again.

Do I need bigger pilot jets, do I need to place the ½ step shims, do I need to raise the needle clips so the needle sits higher at idle?  I’m thinking the problem is the pilot jet but I’m not sure.  And from what I have read on the board it looks like it might be the pilot jets since death is occurring at idle while warm.  If it was loping or not getting enough fuel at higher rpm’s I would lean towards needle position, dunno though. I am trying to be systematic about the diagnosis but which turn do I take to get to the next diagnostic step?   

[mosquito]

Dunno if any of this will be applicable for you, but I've been using the info from Factory Pro: http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

Above 3K RPM my bike was running fine, but it just wouldn't idle with similar symptoms. Release the throttle & come to a stop and it slowly went down to idle speed and then in less than 30 s, gradually slow down and die.  I'd been having to continually blip it, or leave it choked a hair so it would idle fast for every stop light.  Mine wouldn't idle hot or cold though.

After doing lots of cleaning and adjusting I finally took the carbs off again yesterday and managed to get all of the idle jets out; one of them had been torn up by a PO.  I carefully cleaned all of them and measured / set all of float heights.  Previously I'd eye-balled them with a ruler and a couple were off.  Now it's idling fine, just need to adjust the floats again 'cause I'd set them too rich.

[Ronin]

I had forgotten about the factory pro page.  Thanks for the reminder.  Now I have a few items I can check without making major changes in the setup.  Thanks mosquito.

Yeah, I checked float bowel heights and set them to Ivan's recommended measurements when I put the Ivan kit on and I am pretty sure the PO didn't make carb changes cause the factory screws were in place and the brass plugs were there too but I might be wrong.  I've also cleaned the carbs twice with carb cleaner and compressed air and initially it ran better but it still had the same idle issue which made me think something was wrong with the fuel as in the tank was throwing particles into the fuel but I ruled that out with an in-line fuel filter which I have since removed because I thought it might be the problem but now I know it's not but I am leaving it off to lower the numbers of potential issues until the problem is solved.

Matt

[Ronin]

So here is the resolution for those that may reference this post in the future.

I called up Ivan's shop and talked with him about my problem and without missing a beat he diagnosed the problem.  He said (and I am paraphrasing), "since the 2001-2002 Bandit's are oil burners your getting oil vapors back into the air box at idle since you have the crankcase breather tube hooked up to the airbox.  And when you are sitting at idle the vapors build up and choke off the carbs.  And when you open the throttle up a little it clears out the airbox".  He continued to tell me to unhook the crankcase breather tube from the breather on top of the valve cover and cruise around for awhile and come to a stop like I usually do and if it starts blowing out puffs of white smoke then you have your diagnosis.  He said, if this is the problem, then put a filter on the end of the crankcase breather and block off the airbox hole.

So I went home, cruised around with the hose off, got the engine nice and warm, set at idle in the garage and it ran fine.  Just as an experiment I put the hose back onto the breather and guess what, it started to die, so I pulled the hose off and it quickly recovered itself back to normal idle operation.  So problem solved and one satisfied Rockland County Motorcycle customer.   

[mosquito]

Vewwy interesstink.  For me my problem came back after about 500 miles and I'm almost certain I'm burning oil.

Thanks!

[Ronin]

That's what I was thinking when he told me the fix.  I knew mine burned a little oil but the engine doesn't burn enough to create any puffs of white smoke so I never really worried about it, until now.

He also told me that if I really liked the bike and wanted to keep it it'd be a great idea to bore it out to a 1216 and drop some JE pistons in there.  He indicated that it would help the oil burning prob.

Matt