Thoughts on slightly wandering idle

[Phil]

After riding a bit, basically 1/2 mile or longer and then coming to a stop the bike will idle somewhere around 2k. If it stays idling it will make its way down to the 1.3k point or so and seem to stay there.

Any thoughts on why this might be happening? I don't appear to have any intake leaks. The carbs are clean with new boot o rings. The only carb related item that I haven't done was vacuum sync the carbs. I attempted to bench sync them and they appeared close.

Would the carbs being out of sync cause this to happen? It otherwise is running quite well with what appears to be very good power throughout the throttle.

Could over oiling the air filter cause this to happen as well?

 

[Nessism]

Vacuum sync is mandatory...as is valve adjustment. You are just guessing at the reason until you verify all the basic maintenance is complete. You might want to read the Newbie Mistakes thread linked in my signature.

Where are the pilot mixture screws set? They should be somewhere between 2.5 and 3 turns out as a starting point.

 

[Phil]

They are set at 2 turns out. The issue I have with setting them with the highest idle method is that the idle will increase to appoint and then it will plateau for awhile and then start to dip as you keep turning out the screw. At this point I have them set to where it begins to plateau.

What are the symptoms of out of sync carbs? I have seen a ton of references to vacuum syncing but not much mention of how out of sync carbs behave.

Vacuum sync is mandatory...as is valve adjustment. You are just guessing at the reason until you verify all the basic maintenance is complete. You might want to read the Newbie Mistakes thread linked in my signature.

Where are the pilot mixture screws set? They should be somewhere between 2.5 and 3 turns out as a starting point.

 

[Nessism]

They are set at 2 turns out. The issue I have with setting them with the highest idle method is that the idle will increase to appoint and then it will plateau for awhile and then start to dip as you keep turning out the screw. At this point I have them set to where it begins to plateau.

What are the symptoms of out of sync carbs? I have seen a ton of references to vacuum syncing but not much mention of how out of sync carbs behave.

I'd try 2.5 turns and see if that helps. Also, a poor vacuum sync can cause a wondering idle, and out of spec valve adjustment will cause all kinds of running symptoms and burn up the engine too. Like mentioned already, it's best to perform all the basic maintenance items first, then work on running problems if any remain. Maintenance is about avoiding problems, not fixing them after the fact so please don't wait until the bike falters before taking care of common tasks.

 

[tom203]

This is how it goes, fix one thing and discover more problems! Intake leaks are not always obvious- tiny bit of air bypassing carbs can fool you. Valves that aren't fully closed at right time can be bad news. Who knows what PO did or didn't do. Like Mr Nessism said, you need to catch up on maintenance. Nice day, so get some riding in- more issues are bound to surface as you put some hours on bike. I'd check charging system out ASAP, cuz this is a common failure point that can leave you stranded without much warning.

 

[Phil]

Well I decided to suck it up and just ordered the Morgan Carbtune. I also ordered a valve cover gasket so I can check the valve clearances. Hopefully synced carbs and valves in proper clearance will solve all of life's troubles.

Vacuum sync is mandatory...as is valve adjustment. You are just guessing at the reason until you verify all the basic maintenance is complete. You might want to read the Newbie Mistakes thread linked in my signature.

Where are the pilot mixture screws set? They should be somewhere between 2.5 and 3 turns out as a starting point.

 

[Phil]

Luckily, for me, not the PO, the charging system left him stranded in NH and had it dealt with at that time (he even posted on this forum asking for advice while he was stranded). He ended up replacing the stator and the R/R. I think it was basically the only thing the he had done with the bike.

Once everything I ordered shows up I will get on the valves and then the syncing and hopefully that will be it for idling issues. I also ordered a set of brake pads. The ones on it weren't at the wear indicators, but they didn't look to be in very good shape. Very scored and had little bits of material missing from the surface. They also just looked very old.

Yeah I plan on riding it some more. I have only ridden it about 100 miles and I haven't wandered to far because I don't 100% trust it at this point.

This is how it goes, fix one thing and discover more problems! Intake leaks are not always obvious- tiny bit of air bypassing carbs can fool you. Valves that aren't fully closed at right time can be bad news. Who knows what PO did or didn't do. Like Mr Nessism said, you need to catch up on maintenance. Nice day, so get some riding in- more issues are bound to surface as you put some hours on bike. I'd check charging system out ASAP, cuz this is a common failure point that can leave you stranded without much warning.

 

[Nessism]

Make sure you redo the charging system wiring to eliminate the headlamp loop and strengthen the R/R grounding. It's critical to do items like this if you want the bike to be reliable.

Good luck

 

[tom203]

Morgan carbtune!!! you'll find new friends quickly!
You need to inspect/test the charging system- some of the aftermarket R/R's are inferior and PO might have done a quickee and dumped it on you! the connections are always suspect. Recall that first you measure valve clearances and then locate needed shims- I have some buried somewhere.
Enjoy

 

[Guest]

My idle wanders a little with similar symptoms to yours, but I'm pretty sure it's because the carbs are too rich. I sync'd them a while back with the Carbtune Pro, and I definitely have no intake leaks (brand new intake boots and K&N pods).

It's probably partly also because I had to up the idle a little to help it stall less when stopping at lights after riding in traffic at low throttle openings.

I also have issues setting my mixture screws at the moment but that seems to confirm my too rich issue. The one use of my Colortune so far was to use them to set the mixture screws. I almost couldn't get them lean but I could easily get them rich, so I've left them about 2.5 turns out for the moment.

I *really really* need to find a way to get some time with my Colortune. I've learnt to ride around it for now but it's not nice on the clutch having to ride it so much when it bogs off idle

 

[Phil]

I ended up testing the stator and it tested out ok. The headlamp loop was easy to eliminate. I need to follow up with the ground for the R/R because I didn't have time to unbolt the seat and figure out where the existing one was actually going.

Just out of curiosity, is it normal for the RPM's to increase when the stator is fully disconnected from the R/R?

Unfortunately I don't have a multimeter with a diode test setting so I can't specifically test the R/R. The one on the bike appears to be a fairly new looking stock 5 wire unit.

Across the battery it measured 13 volts at idle, and it didn't budge when the RPM's were at 4k. Though the meter I have only resolves to 1 volt.

Getting in there and actually looking at the wiring did make me realize that I could clean it up some. It's on my to do list on some rainy weekend.

Make sure you redo the charging system wiring to eliminate the headlamp loop and strengthen the R/R grounding. It's critical to do items like this if you want the bike to be reliable.

Good luck

 

[Phil]

Is it running rich because of a jetting issue? Mine system is completely stock. The wandering of the idle seems to only be +/- 500 rpms's. As it get completely warmed up it seems to find its way to 2k...sometimes it will come back down, sometimes it just likes to stay at 2k. If it just siting in the driveway idling, without actually being ridden, it will stay pretty much under 1.5k.

It's not much of an issue actually riding it, its really just annoying that I can't get it to completely behave.

My idle wanders a little with similar symptoms to yours, but I'm pretty sure it's because the carbs are too rich. I sync'd them a while back with the Carbtune Pro, and I definitely have no intake leaks (brand new intake boots and K&N pods).

It's probably partly also because I had to up the idle a little to help it stall less when stopping at lights after riding in traffic at low throttle openings.

I also have issues setting my mixture screws at the moment but that seems to confirm my too rich issue. The one use of my Colortune so far was to use them to set the mixture screws. I almost couldn't get them lean but I could easily get them rich, so I've left them about 2.5 turns out for the moment.

I *really really* need to find a way to get some time with my Colortune. I've learnt to ride around it for now but it's not nice on the clutch having to ride it so much when it bogs off idle

 

[tom203]

It's not much of an issue actually riding it, its really just annoying that I can't get it to completely behave.

Still sounds like a minor air leak- it doesn't take much.
13 volts charging output at high idle is OK- you need a better meter and posplayr quick tests to check overall system.Checking the ground wire from R/R to battery negative is a must, otherwise the R/R might have trouble figuring out battery's needs. There should be about 1.5 to 2.5 volt rise as rpms go up off low idle. At least you seem to be charging OK. so enjoy this weather.
When the stator is completely disconnected, it's not producing any load, so it ain't putting any load on motor- rpms might climb slightly

 

[Guest]

Yeah my too rich issue is purely my fault. I initially made the mistake of trying to tune from the pilots up instead of mains down, and I also didn't realise it wasn't fully warmed up so thought it was leaner than it was. That resulted in my mains being 8 sizes up and my needles are one notch up but I went back to stock pilots.

Unfortunately that's about the only time I've had to get noisy/smelly time in the garage, so hopefully I can get some more of that time before too much longer and get stuck in with the Colortune.

One thing with your idle... you should be setting it at around 1100RPM once she's warmed up completely.

If you have the idle set too high that may screw things up a little...

 

[Phil]

If its a small air leak then it's going to be pain to track down because it doesn't seem to happen until the engine is quite warm. I drove around the neighborhood last evening for about 10 minutes and it didn't creep up. I guess the plan is to check the valves, sync the carbs and then assess the situation at that point.

It might be related, but the bike isn't liking to start with the choke on. It only seemed to recently start with this issue. With the choke about half on it will start but barely hold 1k rpms. If I touch the choke in either direction it will usually just die. After maybe a couple minutes I can turn the choke off and it will run. It used to start well with the choke.

The only thing I have really changed on the bike is a new air filter. I put in an OEM one a couple weeks ago. Would over oiling it cause something like this to happen? I think I will unbolt the seat and try to dry it out more. Then I can check on the R/R ground at the same time.

Still sounds like a minor air leak- it doesn't take much.
13 volts charging output at high idle is OK- you need a better meter and posplayr quick tests to check overall system.Checking the ground wire from R/R to battery negative is a must, otherwise the R/R might have trouble figuring out battery's needs. There should be about 1.5 to 2.5 volt rise as rpms go up off low idle. At least you seem to be charging OK. so enjoy this weather.
When the stator is completely disconnected, it's not producing any load, so it ain't putting any load on motor- rpms might climb slightly

 

[Guest]

Over oiling can make it run rich, you shouldn't be able to squeeze any oil out, it should basically just be damp.

 

[tom203]

maybe you mentioned this already, but............. have you disturbed the carb boots to cylinder head? Those o-rings might be calling for attention- they need to be temp resistant- ordinary hardware store ones won't survive long. PO might have been in there already. 80 degrees inland- just like august, but lake temp is 55 degrees !

 

[Phil]

The o-rings on the boots are brand new. They came from the guy on here along with all the carb o-rings. I got out and rode about 90 miles. The bike did great. The idle still wandered but it was pretty random. Sometimes when I came to a stop it would idle perfectly fine, sometimes it would be about 2k. Sometimes when it idled at 2k there would be slight clunk sound and then it would idle normally. I have no idea what that was about.

maybe you mentioned this already, but............. have you disturbed the carb boots to cylinder head? Those o-rings might be calling for attention- they need to be temp resistant- ordinary hardware store ones won't survive long. PO might have been in there already. 80 degrees inland- just like august, but lake temp is 55 degrees !

 

[sicnarf442]

I *really really* need to find a way to get some time with my Colortune. I've learnt to ride around it for now but it's not nice on the clutch having to ride it so much when it bogs off idle

Pete, Let us know how the Colortune works for you. I've read that a limitation is that you can only use it to indicate conditions at idle. At higher rpm's the bike needs to be on a dynamometer to reproduce engine under riding conditions.

Francis
Austin, Texas
1980 GS450S

 

[tom203]

Hooray for "bike did great" -a reward for your efforts. The clunk sound is odd- other than clutch that is; when you do valve clearances, check how cam tensioner works to make sure its happy.