problem idling during warmup

[chuck hahn]

Either a broke ring or stuck rings. try putting a few ounces of a 50/50 mix of acetone and ATF in the cylinder and let it soak a few days. This concoction eats carbon and anything else making a ring stick. Start it outside till the smoking goes away and then do another check on that cylinder. If its like it should your good to go..if not I would think about a broke ring.

[BigD_83]

Given that you mentioned pulling the plug wire off #4 didn't affect the idle, I would have expected to see that low compression number on #4 cylinder, not #2...

[DimitriT]

Where are the pilots screws set? How is the air cleaner?

The 550's are jetted lean from new. My old 550T took 3.5 turn on the pilot screws otherwise the idle would hang. You also need to have the carbs vacuum synced otherwise the idle won't be stable.

You know I can't really tell where the pilots fuel screws are set because I used the max-idle/rpm-drop method to set them.

I did get around to cleaning and re-oiling the foam filter. Lots of junk came out. The thing is with those foam filters the dirt get embedded deep in the foam and gets stuck in there. So if you don't clean it well you are not really cleaning it. I got a bowl of kerosene and really worked it all out this time. Messy job. I should just replace it next year. I clean it about once every 10k miles, btw.

[cowboyup3371]

You can find out by gently turning them in until lightly seated counting as you do then backing them out that same number.

[chuck hahn]

And I would also recheck the valve clearances on that low cyclinder to eliminate a valve leaking pressure past it.

[Nessism]

Set the pilot screws at 3.5 turns and vacuum sync the carbs. You can tweak the pilot screws a little from this starting point but I wouldn't get too far off this baseline without good reason.

This said, if #2 truly has such poor compression you have a major problem. No way out other than to pull the head and cylinder and fix what's broke.

[chuck hahn]

I would recheck the valves on that jug and do the soak first. This will eliminate the two most obvious things BEFORE tearing it down. Now if the reading stay the same ..or shows very little improvement..then yes its tear down time.

Check the obvious before jumping into what may or may not be necessary.

[DimitriT]

Well.. one strip down later and the compression readings are now:

#1 135
#2 120
#3 120
#4 120

This was right after the head went one when it was cold so there might
have been a little oil left over after reassembly.

The bike runs alot smoother now and there's at least 20% more power.

But it looks like the one month is was sitting didn't agree with it.

I was about to do a carb sync and I hooked up an external tank. Two minutes
later I discover a puddle of gas under the bike. Looks like a float is now sticky.

I managed to get the carbs synced and the bike runs really smooth but there's
a hang up when I run it at about half throttle and then let it up for a few seconds
and then apply throttle again.

Also I noticed that the idle fine tuning screw bottoms out before I can set the
right richness for #4.

This all tells me there still a sticky float or a float valve that's not closing right.

I think I'll need to pull the carbs again and this time I will clean the jets and
figure out what's up with #4.

I have this tool to help check the float height now.