Topic: Stumbling when returning to idle

[CarbonK]

Washer goes in between the spring and o-ring so the spring doesn't cut the o-ring.

Alright cool, I ordered the missing parts earlier today. Here's hoping this will alleviate some of the issue.

[bochnak]

Usually a dip in idle after a quick rev is indication of a rich condition.

[CarbonK]

Ok, I got the missing washers and o-rings on. Should I put the carbs back in the bike and start it up to see if that fixed the problem?

[DaveBarbier]

So you know if that alone fixes the issue you can do just one thing at a time like putting the IMS's back with proper o-rings and such, but it would be good to put your needles in the proper position while they're out. You'll need to sync again.

The needles can be removed and adjusted while the carbs are on the bike, though. Takes a little fiddling but it beats taking the carbs off again since you've got the stock airbox.

I'd wait to see what Fly and others say. I would change needle position as well as the IMS fix.

[CarbonK]

So you know if that alone fixes the issue you can do just one thing at a time like putting the IMS's back with proper o-rings and such, but it would be good to put your needles in the proper position while they're out. You'll need to sync again.

The needles can be removed and adjusted while the carbs are on the bike, though. Takes a little fiddling but it beats taking the carbs off again since you've got the stock airbox.

I'd wait to see what Fly and others say. I would change needle position as well as the IMS fix.

Needles effect 1/4 throttle and up right? After I get equal plug readings at idle I'll assess the rich condition going on. I don't have the stock air box.

[DaveBarbier]

So you know if that alone fixes the issue you can do just one thing at a time like putting the IMS's back with proper o-rings and such, but it would be good to put your needles in the proper position while they're out. You'll need to sync again.

The needles can be removed and adjusted while the carbs are on the bike, though. Takes a little fiddling but it beats taking the carbs off again since you've got the stock airbox.

I'd wait to see what Fly and others say. I would change needle position as well as the IMS fix.

Needles effect 1/4 throttle and up right? After I get equal plug readings at idle I'll assess the rich condition going on. I don't have the stock air box.

My mistake, I was getting confused with another post.

[CarbonK]

After getting the missing washers and o rings in I put the carbs back on the bike and let it idle for a few minutes. Still getting the same results, I'm gonna check for vaccume leaks around the first carb rubbers. I'm really hoping for one because I'm running out of ideas. I attached a better pic of my plugs.

[bochnak]

You need to find out what is going on with leftmost plug/cylinder (I'm assuming it's #1?)

With it running, take a spray bottle full of water and spray each header tube. The water should sizzle off at the same rate on each tube. Looks like you are not getting fuel to that cylinder or it's not firing for some reason. An IR gun works even better.

Check for vacuum leaks.

Can you post a video of it running?

[CarbonK]

Here's a little update. I did a few things before testing it at idle again. I know it's best to make one change at a time but I was frustrated with taking the carbs off and pulling the spark plugs everytime. I cut back the wire and switched #1 spark plug boot with #4, checled valve lash, replaced the aftermarket 42 slow jets with keihin ones, and synced the carbs.

Also, there are two holes at the opening of each carb, I'm assuming these are air jets? Well I overlooked those when cleaning the carbs but this time I made sure they weren't clogged up. I reused the cleanest spark plugs I could find, mostly ones that were in cylinder #1 from previous idle tests.I fired the bike up and let it idle, pulled the spark plugs and they're all light gray/tan. I will try this test one more time with new spark plugs because I feel as though the used ones compromised the results. I suspect it's running lean on idle.

Maybe clogged air jets fouled plugs 2,3, and 4 and my carbs have too small a slow jet which causes the lean condition in cylinder 1? I don't think aftermarket slow jets could be the culprit because I remember switching them around between the lean cylinder and one of the rich cylinders and getting the same plug reading.

[CarbonK]

Got all the plugs looking good at idle now, I have yet to test out my original "revs going way low when returning to idle" problem. I know its tough finding a baseline carb tune for the PD carbs when you messed with the intake and exhaust but if anyone is interested my settings are as follows.

Steel Dragon V Stacks with the mesh screen in them
Mac 4 into 1 exhaust cut right before the can
PD46C carbs
45 slow jet
110 main jet
Needle 2nd from the top
IMS 2.5 turns out

Givin' out my thanks to all who helped me out trying to diagnose my issue.

[DaveBarbier]

Nice, glad you're on your way! But you said IMS is 2.5 turns out, are they all the same or have tuned them for highest idle speed?

Do you have pictures of your float heights? And I couldn't find where you said you synced the carbs. That's done, right?

[CarbonK]

Nice, glad you're on your way! But you said IMS is 2.5 turns out, are they all the same or have tuned them for highest idle speed?

Do you have pictures of your float heights? And I couldn't find where you said you synced the carbs. That's done, right?

I turned them all out until the plugs were an equal brown. How do I adjust for highest idle speed? I do this with the engine on?

I don't have any pictures of my float height, I usually use a buddy's phone to take pictures since my phone no longer focuses leaving all the pictures blurry. He isn't around right now. To set the height I followed your instructions I've seen in another thread with the piece of paper cut to 4mm. The carbs were synced 3 days ago but this was before I put bigger slow jets in and adjusted the IMS.

[flybox1]

Nice, glad you're on your way! But you said IMS is 2.5 turns out, are they all the same or have tuned them for highest idle speed?

Do you have pictures of your float heights? And I couldn't find where you said you synced the carbs. That's done, right?

I turned them all out until the plugs were an equal brown. How do I adjust for highest idle speed? I do this with the engine on?

No, you did this correctly.  IMS are adjusted based on plug color(A/F mixture) not idle speed.
Can YOUR ears properly tune A/F mixture inside a carb?
Idle speed is not an appropriate way to measure proper A/F mixture.
Plug color, or dyno sniffer.

[DaveBarbier]

Nice, glad you're on your way! But you said IMS is 2.5 turns out, are they all the same or have tuned them for highest idle speed?

Do you have pictures of your float heights? And I couldn't find where you said you synced the carbs. That's done, right?

I turned them all out until the plugs were an equal brown. How do I adjust for highest idle speed? I do this with the engine on?

No, you did this correctly.  IMS are adjusted based on plug color(A/F mixture) not idle speed.
Can YOUR ears properly tune A/F mixture inside a carb?
Idle speed is not an appropriate way to measure proper A/F mixture.
Plug color, or dyno sniffer.

I was about to type that you should do what Flybox suggests, haha. Plug color is better, but the manual does say to adjust for highest idle speed from what I remember.

Any update on whether or not your idle issue is gone?

[CarbonK]

Any update on whether or not your idle issue is gone?

Problem still persists. Didn't even make it around the block. Shifted from second back down to first and the bike gradually went down in revs and died while I got off the gas, pulled the clutch, and was coming to a stop.

[flybox1]

Turn your idle up so it doesnt die. . .

[CarbonK]

Turns out my idle issue was caused by fouling plugs.

[flybox1]

What did you do to keep them from fouling?

[CarbonK]

What did you do to keep them from fouling?

I really had to play with the IMS for a few days. I'd get em to where all the plugs were a light brown at idle but for some reason after I left the bike for a day or two they'd all go black again after starting it up with fresh plugs but I've finally got them dialed in, all light brown everyday at idle. At the end of a 30 minute ride I found the plugs were fouled again so I suspect my main jet/needle is too rich. Seeing as though my needles are already on the second clip position from the top I ordered a couple smaller sized main jets. I'm gonna test them out and raise/lower the needle accordingly.