Mikunis won't idle down

Hey Dave,

I just got done taking the valve cover off and verifying that the cams are set right , so its back to the carbs. I put the 120 pilots in and now it hovers about 4 grand so I presume I'm gettin there.

Ed

This may just be a shot in the dark and asking a dumb question, but you mentioned in an earlier post that you noticed the slides returning back after you close the throttle because you had the air filters off to verify this. Are you running no air filter when you are having the racing idle? Would maybe having air filters on make this situation better or more manageable? I remember one time I left mine off to verify my slides were returning and it ran like complete crapola.

I appreciate the the idea on the air cleaners, but yes I've had them both on and off. I used to own a kz400, and if I tryed running it without the stock air box connected it did the same thing so you are spot on. Whats slayed me, and why I started this thread was the hovering after you crack the throttle and supposedly idled it back down, I've never had that happen before. I expect the cams and porting done to the head , are what have thrown the idle circuit so far out of whack( effected the signal strength). While I have the cam cover off I'm going to measure the cam lobes to see exactly what I have in there.Been lucky so far this season , I've only missed 2 or 3 days good riding so far.

Ed

Godfrey wrote: ...hovering after you crack the throttle and supposedly idled it back down....

Possible causes of failure to idle back down include:

Air leak from wherever;

Improper carb sync;

Pilot circuit adjusted too lean;

Pilot circuit being too lean for whatever reason;

Sticking timing advancer;

Throttle cable maladjustment;

Defective throttle cable.

Above list isn't exclusive.

Good Fortune!

Had some time today, and had the carbs off, bench synced them and checked the float levels ( sorry don't have the fixture for the fluid level), both were off. checked the plugs and they were black. Beings I found I needed to sync the slides and set the floats I put the 17.5 pilot jets in to start over. Its still didn't cure it, but at least the plugs aren't black.

Ed

34mm is a lot of carb for that bike. they will run fine but u will find a lack of bottom and and loads of top end. just like that motor was built for.
big cams are not likely your problem.

rs34 carb pilot screws are only adjustable from 1/8th to 1/2 turn. what level did u set the floats at ? they should be at 17mm. do a clear tube float level test when u get it back together. a bench sync is good enough to get u going.

www.sudco.com/Carburetor/SudcoMikuniCatalog.pdf

yes I set them at 17 mm exactly with a set of digital calipers, the bowls don't have the proper fixtures to do the float height with a tube, not sure how I would accomplish that.

Ed

here we go again, see if this makes any sense to any of you.I disassembed the pilot system again today and cleaned it as thoroughly as I know how. In going thru and thinking this thru I realized that i have probably been turning the idle screw and slides a bit more then 1/4 the way open. The engine barely lopes along at 1000 rpm and if I don't try to get it to run smoother or faster, I can crack the throttle open, and it returns and doesn't hover; but there is not enough rpm to let it recover and stay idleing.What i think I may have been doing is in raising the slides , I was getting into the needle and needle jet to get my fuel and air. I expect because of the cams, and the porting the signal strength at idle is not as great as stock, and the pilot air jet is not allowing enough air in to allow a smooth steady idle, without getting into the next circuit or the needle and needle jet. Your thoughts on a larger pilot air jet and matching pilot jet to bring the idle circuit into a usable rpm range please?

Ed

No offense, but I think you're over your head with this. You should at least know how to jet/adjust a carb if you are going to own any sort of modified engine. You might want to start with something stock so you can learn via the factory service manual.

None taken, most stock carbs , have fixed air bleeds, at least the ones I've seen, and then theres a big difference between working with cv's and this. Granted this is the first time , I've worked with tuning these carbs, and dealing with longer duration cams in a bike, gotta learn somehow. I was quite pleased, being able to take the stock 650 from 40 to 50 mpg with just carb work and no gearing changes, but thats another story. Ty for your input Kidkawie and the rest of you as well.

Godfrey wrote: here we go again, see if this makes any sense to any of you.I disassembed the pilot system again today and cleaned it as thoroughly as I know how. In going thru and thinking this thru I realized that i have probably been turning the idle screw and slides a bit more then 1/4 the way open. The engine barely lopes along at 1000 rpm and if I don't try to get it to run smoother or faster, I can crack the throttle open, and it returns and doesn't hover; but there is not enough rpm to let it recover and stay idleing.What i think I may have been doing is in raising the slides , I was getting into the needle and needle jet to get my fuel and air.

*** I expect because of the cams, and the porting the signal strength at idle is not as great as stock, and the pilot air jet is not allowing enough air in to allow a smooth steady idle,

without getting into the next circuit or the needle and needle jet. Your thoughts on a larger pilot air jet and matching pilot jet to bring the idle circuit into a usable rpm range please?

Ed

Kidkawie, how can u read this and think he doesnt know anything about carbs ???

Godfrey, your assesment is right , but there is enough signal for u to get this bike to idle properly. u may just need to idle at a slightly higher rpm.

will it idle better if u adjust the idle rpm screw up (raise the slides)?
try removing the pods and see if it helps, or adding choke, . see wich way it WANTS to go , rich or lean.

the most common way to do the tube meathod of checking the fuel level, is to drill, and tap a spare drain plug then screw in a 1/4" threaded hose barb. or just drill a spare cap and wedge in a rubber plug with a hole in it, then squeese a tube into the hole.

Thanks Mark, , no worries , I'm still around, takin my time trying to think this thru; removed inspected and reinstalled /sealed the rubber manifolds; the problem still persists.
Bought a sudco mikuni tuning manual off e bay, should be here tomorrow or Friday. Yes it idles better at a higher rpm, even 1200, it'll recover till you get up to operating temp, then it won't idle down again. The choke kills it dead right now. 2 things, seems weird to me, but oldkawman recommends buying 115 pilot jets and installing them before ever putting a set of RS carbs on, even with porting and a borekit ( they come stock with 117.5), and from a suzuki forum it was suggested that for smaller displacement engines, RS carbs like restriction aka an airbox.

Ed