Got it rebuilt...now having idle woes...

[Mickey85]

I got the bike rebuilt, and added some shorty mufflers, primarily for a price point. I went up a jet size on the mains and primaries to compensate. I put it all back together, and now when it's cold, it'll idle on the choke OK, and occasionally run a high RPM until it gets a bit of heat in it, then calms down to 700ish RPM. When relatively warmed up, it doesn't stay idling on any of the 3 choke settings.

The bike starts immediately, even after sitting all night, and doesn't appear to have vacuum leaks having shot it with starting fluid. I rebuilt both carbs and the petcock, and fuel appears to be flowing relatively well when on the "run" setting.


Any ideas? Should I go back to the original jets to see if that helps situations? The bike is completely stock except for the new jets and mufflers.

 

[Greasey Fingers]

Maybe check you don't have the tip of an idle screw snapped off in your carbs?

 

[Mickey85]

Didn't see anything when I rebuilt it. I didn't pull the carbs apart, although I suspect perhaps a float may be sticking...would that give me the results I'm seeing?

 

[xschris]

What year/model is the bikes? When you rebuild a clean carbs you need to FULLY take them apart and clean/replace parts Make sure everything is adjusted to spec and sync the carbs with a manometer. If the bike is idling low I would try to turn up the idle with the idle screw on the carbs If that don't help take a look at the plugs and see if they are wet or black. If so the bike is too rich.

 

[Mickey85]

It's an '81. I did fully take the carbs apart, but didn't separate them or mess with the throttle linkage. The bike hasn't been on the road since '87, and before that was serviced at the dealership - I decided that given its history, the carbs would be synced enough to deal with and really didn't want to go to the extra time and hassle if I could get away with it. I also didn't mess with the idle, as it (again) is original. The first time the carbs have been apart was when I pulled them apart a couple weeks ago.

I pulled the plugs and they were black, indicating either a bad ignition or rich fuel. I pulled the plug caps (wires have been replaced), and they were reading a resistance of 9.1ish ohms on one, and 7.4ish on the other. While that seemed to be the problem, since I haven't been able to get to the dealer today to see about a new pair, I replaced the jets in the carbs with the original ones. Now it will only idle on full choke, and then at 3500 RPM. When I put it to half choke, it idles, but craps out when I even look at the throttle, and putters out when I put the choke all the way in.

At this point, I think my plan of action is going to be replacing the spark plug boots and installing the richer jets again to see if that does it. If not, F-it. I'm taking it to the dealer and they can figure it out. I'm a car guy - ain't nobody got time for fiddly bits like synchronizing carbs and such.

 

[xschris]

What are the idle mix screws set at? I would try 3 turns out and if that don't help go 4 but no more. If it will only run with the choke it's lean.

 

[Mickey85]

So, it's lean, but it's funking up the plugs and painting the mufflers greasy black...

The idle mix screws are exactly where the factory put them in 1981.

 

[xschris]

If they are still capped from the factory you will have to remove them to get the bike running right. Since you have changed the mufflers to a non-factory setup the bike will need to be tuned for it. Have you set the valves on the bike yet? I know you have not touched the linkage for the carbs but you will still have to sync them. Another thing to check with a bike that has sat that long is compression. Greasy black may be oil. Make sure the oil is not over filled. With the bike on it's center stand check the level.

 

[Mickey85]

Valves have been set, oil and filter have been changed and are sitting at 2.2 qt, right in the middle of the sight glass. Compression is around 160 for both cylinders. When I got it, I pulled the plugs and fogged the cylinders with PB blaster, then did a slow "kick start" spin a few times to make sure the pistons weren't sticking.


I'll pull the carbs again today, replace the richer jets, and adjust out the mix screws. We'll see where that leads us.

BTW, when it does smoke (usually on deceleration), it's grey smoke, not blue, and doesn't have any burning oil smell. I realize that's not a very scientific way to do it...

 

[XSLeo]

You mentioned in your first post "it would settle down to 700ish rpms." If your trying to idle at 700 rpms, that's too low. Try setting it at 1000-1200 rpms.
Leo

 

[Mickey85]

It wasn't my plan to get it that low. I doubt that's the final idle speed once I get it sorted out.

 

[Mickey85]

Success!

I replaced the richer jets and pulled out the idle screws. I discovered that they were about 3-1/4 turns out from the factory, I set them at 4. Now it idles well.

Is it a normal thing for it to die if you pull the choke out while it's warm?

Also took it on it's first ride. Seems to do well, and with the glasspacks, it's obnoxiously loud. Shook like a dog crapping peach seeds, but my thinking is that it's due to flat spotted tires after being parked for 25+ years, as both of the wheels run *almost* true.

I also need to adjust the clutch, as it engages way too late, and seems to be very on/off. That could just be that it needs to be ridden a while to loosen it up again, but I want to adjust the cable so that it engages more at about the halfway mark, instead of all the way out.

It certainly is a different experience from riding the Buell...Hilariously fun, and in a different way.

 

[Under Dog]

Quickly clarify for me - you replaced the richer jets (with what?) or your replaced with richer jets?

 

[Mickey85]

I replaced the stock ones with richer ones.

I went with 45 pilots and 137.5 mains.

 

[levdir]

The clutch on this bike just generally tends to engage late, but it's never a bad idea to adjust it.

 

[Mickey85]

Welp. Now I've discovered that it doesn't want to idle at normal idle. I had that problem, then cranked the stop down to 1500 RPM. Now, a few hours later, I crank it over without the choke, and it gets to 3000 RPM and stays there. That indicates to me that it's lean...do I pull the idle mix screws out further? I've already got them out 4 turns...

 

[xschris]

4 is the max with them. What do the plugs look like? You may have pulled some junk in the carbs. I would try syncing the carbs with a manometer.

 

[Mickey85]

Fired it up again, idles at 1250. Something's sticking...and I'm not going to sweat it. For now at least.