1982 550 LTD #2 cylinder issue

One bench sync objective is leaving enough thread on the thumb screw adjuster to enable later ability to reduce idle rpm incident to performing the engine-running sync.
If the middle thread position is unworkable, just leave "some" thread available to later reduce the idle speed.

Consider -- later performing the engine-running sync typically requires lowering the slides via the thumb screw idle adjustment (along with the individual slide adjustments and pilot screw adjustments also being made). All toward achieving the best (lowest and smoothest and steadiest) idle with balanced vacuum among the carbs (which equates to equal performance among the cylinders).

Imo, it's virtually impossible to properly sync with idle far exceeding normal idle rpm. Hence, completion of engine-running sync is frustrated if needing to reduce idle speed, but can't do so due to running out of thread on the idle adjustment screw.

Good Fortune!

Hey Lou and Patton,
I got time to pull my 550 carbs and take a peek at what was going on in there... So, all 4 slides are very close to one another (just eyeballing). I took the throttle return spring off and pulled open the throttle and all 4 slides are allowed to go past the top of the throat of the carb on the engine side. I didn't measure it, but I'd say each one is about the thickness of a popsicle higher than the top of the carb throat. Would this be enough to cause my WOT throttle issues?

Also, I was looking at the spark plugs... They all look kinda rich. Odd thing is some of the electrodes have a yellowish substance on them...kinda crusty crap. Any ideas?

If possible, a video would make things easier to diagnose.

Get yourself the service manual for your bike, it will save you lots of headaches, time, and $$$.

I like the slides to stop about 1mm above the engine/small side. Never had any problems with this.

Have you done a WOT plug chop? WOT at low rpm means LOTS of fuel input, where as at high rpm, not so much. Where in rpm band are you using WOT and what happens in other rpm bands?

GL.

apbling wrote:

Also, I was looking at the spark plugs... They all look kinda rich. Odd thing is some of the electrodes have a yellowish substance on them...kinda crusty crap. Any ideas?

The yellowish crap is usually from rotten fuel additives that can contain lead, or a nasty oil additive that leaks past the valve seals and causes issues. Dont use any fuel additives on a regular basis, they are only ok once in a while, and NEVER use oil additives ever, no matter what anybody says. Just use a good brand name, designed for motorcycle - oil.

I really dont like to "read" plugs, as i find them to be notoriously useless in many cases. you can experiment to find out if you need leaner or richer jets. Pull the air filter - if performance perks up considerably, then youare deffinately too rich, and should change to smaller jets/lower your needles.
Try riding with the choke engaged. If it perks up then, you are too lean and should use larger jets/raise your needles.

GL.

A video of the carbs or a video of my riding the bike WOT?
It's been a while since I tried, but I want to say it was at higher RPM's. I do have the manual for my bike. They don't talk about diassembing the carbs and setting WOT throttle and such.

apbling wrote:

Hey Lou and Patton,
I got time to pull my 550 carbs and take a peek at what was going on in there... So, all 4 slides are very close to one another (just eyeballing). I took the throttle return spring off and pulled open the throttle and all 4 slides are allowed to go past the top of the throat of the carb on the engine side. I didn't measure it, but I'd say each one is about the thickness of a popsicle higher than the top of the carb throat. Would this be enough to cause my WOT throttle issues?

Hard to say. If it's too rich to begin with, this extra 1/16" may make it bog a little. It would show some black smoke at WOT. I'd correct it and see what happens. If the jetting is lean, this would actually help correct the WOT mixture.

In order to determine if the jetting is proper, though, you need it stop flush otherwise you can't use WOT to assess the main jets.

Before I discovered the throttle was opening too far, I thought I had a rich main, but everything just short of WOT was showing lean on the AFR gauge. When I corrected the stop I could see may main was too small. Corrected the main and everything was good.

In some cases, though, it may actually prove useful to have it go past full to richen it up at WOT. Maybe to correct a needle profile etc. Or just to have insurance against being lean. As Teknine said, plug reading is hard to use especially when it's close. (Obviously if it's way off, the plugs will tell you.)

Also like Teknine says, the AFR ratio changes with RPM at any given throttle position. When you are in the power range of the throttle (greater than about 1/4 or 1/2) you want the AFR to sweep through the 12 range as the RPMs increase. But this means it ends up around 13. You can get this just right with an O2 sensor, but I don't think you'll ever be that precise with reading plugs. In this case, going past full would be good insurance.

apbling wrote:

Also, I was looking at the spark plugs... They all look kinda rich. Odd thing is some of the electrodes have a yellowish substance on them...kinda crusty crap. Any ideas?

Sounds like some foreign material other than gasoline. Maybe carb cleaner was burning in there? Haven't really seen that before.

Can you post a photo?

Thanks guys. I'll try to get a picture. For some reason my camera has issues focusing on the plug and wants to focus on the background...

Anyway, since the bike is stock jetting, pipes and intakes, the jets shouldn't be wrong, right? Plus I haven't touched the needle positions.

I'll just set the WOT to be flush, adjust my pilots AFR screws, say a little prayer and see what happens. I'm thinking I might have the pilots a little rich since my plugs look kinda sooty. Then again, I did just have the whole top end apart and used a good amount of oil to assemble it and haven't run it much since, so maybe alot of the crap is still burning off.

Those bikes were somewhat lean to begin with. It's possible that dealers knew this and set it up to get a little more fuel at WOT. If everything is stock, I wouldn't worry about a slightly richer WOT. That said, it shouldn't hurt to set it up flush either. Both ways would probably be ok.

Weak coils can show up problems at WOT because at WOT you have the most mixture in the cylinder and the spark has the hardest time to jump under those conditions. It's possible the WOT problem is the coil geting weak, or even the igniter for that matter.

Sorry I don't remember the exact details on your bike, but are you using new plugs (before the yellow crud showed up) and do they have the normal gap? Larger gaps will also create the type of misfires a weak coils or igniters might create.

Yep, I have new plugs. Stock coils and igniter, but newer caps and wires. They are gapped correctly. It could be the coils, but I have a sneaking suspicion it is the WOT throttle adjustments. Because:

1. Before I holed the piston, I could go WOT, but I just had lean issues.
2. After I got the motor all put back together, I found the badly clogged #4 pilot circuit. (I holed #2 piston) At this point I know I tried WOT and no issues. I took apart the carbs and separated everything to try and do the lemon juice boil. Ever since then WOT issues shown up.

I think I may have a float a little too high on one of the carbs and that coupled with the slightly higher WOT maybe is causing my issues... I hope

I just wish I knew which cylinder is missing at WOT.

apbling wrote:

...wish I knew which cylinder is missing at WOT.

One method could be throttle chop during the missing, then read the plugs.

Good Fortune!

Can you replicate the WOT problem while it's on the center stand? I used to use an exhaust gas analyzer by putting the bike on the center stand, then in sixth gear go WOT with the rear brake dragging a bit. You only do it about 1 or 2 seconds. Only do it once, then you have to wait at least 10 minutes for the brake to cool down.

If you can do that, you can put a timing light on one wire at a time and see if there is one not firing.

You could also do the chop Patton suggested, using this method, and inspect the plugs to see if one has fuel on it, or if one is noticably whiter.

I'm not sure if I can replicate the WOT issue on the stand... I would need to drag the wheel I think. Maybe there is some other way without using the brake?

It's definitely a throttle position issue though, not RPM related.

I think I like your timing light method. I'm not too good at reading plugs, so I don't know if the plug chop would do much for me. I have a good feeling that once I get my fuel service levels dialed in, verfiy clean carbs (again) and get the WOT set along with the pilots, things will be good. *crosses fingers*

BTW, I got one of those colortunes... hoping that this might also enlighten me a bit to whats going on at WOT.