Topic: CB350f Airbox linked to hanging idle?

[jetthugo]

Rookie question but could a warped air box be linked to a hanging idle?

[flybox1]

That sure looks like it might be the source of leaks....
Do as Calj mentioned, and listen for rpm changes.

[jetthugo]

Thanks for the response guys. I went to the local PepBoys and picked up some Carb cleaner to see if there are any vacuum leaks. All seems good and idles around 1,200 (not warmed up, but just turned on). But when I spray carb cleaner on this part of the image, the bike stalls. So I'm guessing that this IS the issue?

[Scott S]

 I wouldn't think so, because that goes into the plenum, right? Therefore, all four carbs are getting the same air. If it was one of the boots from the manifold to the head, yes.

[Scott S]

 But you should still fix that. If nothing else, you're getting unfiltered air.

[jetthugo]

But you should still fix that. If nothing else, you're getting unfiltered air.

I was able to get a used and "good condition" air box for $30 on eBay so that should be on its way.

Issues I see are:

1. Checked the spark plugs and the have dry carbon buildup so I'm suspecting it's running too rich.
2. Idle Set Screw may be off. Anyway to set it back to a "original" position?

[Scott S]

 The main idle screw?
 You can remove the rack and lower or raise the slides until you get the set screw to the correct position. Bottom out the slides and try resetting it. You'll have to sync the carbs again.

 Do you have aftermarket jets? Repop pilot jets are sometimes too short and can cause a hanging idle.

[jetthugo]

The main idle screw?
 You can remove the rack and lower or raise the slides until you get the set screw to the correct position. Bottom out the slides and try resetting it. You'll have to sync the carbs again.

 Do you have aftermarket jets? Repop pilot jets are sometimes too short and can cause a hanging idle.

On Friday I switched out the handle bars to stock ones. After doing so, I rode around for about 5 minutes and everything seemed smooth and idle was at 1,200. I started messing with the main idle screw and it's pretty wacked out now. Does the bike need to be warmed up before I start messing with the main idle screw? I read that as I turn it, give it about 30 seconds for it to react to the change. Is this right?


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[Scott S]

 If the bike was tuned correctly and carbs were synced, changing the bars shouldn't have done anything.
 Set the idle with the bike fully warm.

[jetthugo]

If the bike was tuned correctly and carbs were synced, changing the bars shouldn't have done anything.
 Set the idle with the bike fully warm.

Yea I had just synced the carbs and got everything right about 2 weeks ago. I'll play around with the main idle and see what happens


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[333]

I am constantly messing around with the idle screw until it warms up on my 350F.

[flybox1]

350F carbs have a fast idle cam built in to the choke lever.  Once you get your bike to operating temps, adjust your idle at the idle screw.   From here, you should NOT need to adjust it, even with cold starts.
If youre having to play with it to get your bike started, your idle mixture is incorrect.
Adjust your air screws until an idle plug chop gets you LIGHT brown plug insulators. 

[jetthugo]

Well, I adjusted the idle to where it needs to be and all seems to be running good. I did notice this high pitch sound coming from the side that was not there prior....


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[flybox1]

ensure you have the correct air screw setting now that youve decreased the air supply into the carbs.
if youve done all of the recommended tune ups, please complete a vacuum sync.  it will quiet the engine down immensely.

[jetthugo]

ensure you have the correct air screw setting now that youve decreased the air supply into the carbs.
if youve done all of the recommended tune ups, please complete a vacuum sync.  it will quiet the engine down immensely.

I just vacuum synced the bike about 2 weeks ago with the carb synchronizer, do I need to do it again?

[jetthugo]

I just vacuum synced the bike about 2 weeks ago with the carb synchronizer, do I need to do it again?

Yes, because you had a major leak when you did it. Now that you've fixed the leak, re-synch them. Bet they're off well and good.

Ok, so I'll re-sync. So let me get these steps right so that I don't screw it up again.

1. Correct my airscrews (4 of them). Increase them to the right until they are snug. Then decrease by 7/8 of a turn. (I'm guessing IN is clockwise, and OUT counterclockwise?)

2. Then do my vacuum carb sync

3. Celebrate!

(BTW, this image is the airscrew correct?)

[Scott S]

 Adjust the valves, set the timing and points and warm the engine.  The sync the carbs.

[jetthugo]

Adjust the valves, set the timing and points and warm the engine.  The sync the carbs.

When you say "valves" you mean the 4 airscrews right? At 7/8th turn?

[Retro Rocket]

Adjust the valves, set the timing and points and warm the engine.  The sync the carbs.

When you say "valves" you mean the 4 airscrews right? At 7/8th turn?

  NO, the inlet and exhaust valves in the head...Thanks for the laugh...

[jetthugo]

Adjust the valves, set the timing and points and warm the engine.  The sync the carbs.

When you say "valves" you mean the 4 airscrews right? At 7/8th turn?

  NO, the inlet and exhaust valves in the head...Thanks for the laugh...

Oh man, now I'm lost. Can't you tell I'm a noob 
I have no idea what these things are. I'm searching for valve adjustments on YouTube but it's for a twin CB350...

[flybox1]

+1 to the above
The 3000mi tune up items covers everything, as calj mentioned, and all the steps can be done by you.
The vacuum sync is the last piece in a line of necessary tune-up items for a proper running bike.