Can't get rich enough

Help. This year I dug into my 550 Maxim, and I can't get rid of my white plugs.


Carbs - pulled them off the bike and broke them down. Found a broken float pillar, bought some Mikuni carb bodies off eBay and replaced this body. Soaked in carb cleaner, blew out passages with compressed air and carb cleaner, installed new o-rings, throttle shaft seals, and float bowl gaskets. Replaced a chewed-up pilot jet and three seized float needles. The jets looked to be the right sizes. Set the float levels, shooting for +/- 1 mm but a couple might have been within 2 mm... it's a bit hard to measure. Clunk test passed. Reassembled. Bench synced.

Compression test (before valve adjustment) - 145 to 155 on all cylinders.

Valve clearance - removed (and refinished!) valve cover, re-shimmed, all within spec except #2 exhaust which is 0.13mm. I had this shim out to read its size, but after replacing and ordering new shims I haven't been able to get this one out again--the bucket won't spin anymore, so something is wrong here--but the clearance measurement was close so I proceeded to reinstall everything and try tuning.

Installed new intake manifolds and gaskets, torquing to specs. Carb-to-airbox boots were in great shape.

With everything back together today, I scrubbed my YICS port out, installed the YICS tool, balanced with a Morgan Carbtune (stainless rods), colortuned and found I needed to be about 5.5 to 6 turns out to get some yellow/orange color (I had previously set these about 3.5 turns out for some test drives). When a cylinder was done I'd remove the colortune plug and installed a new spark plug. Finally pulled the YICS tool, reinstalled the tank and seat.

After all this, I went for a 30 minute test drive. The engine seemed to be revving smoother after the YICS tool/Carbtune sync. I didn't notice any hesitation. Drove around town for a while then hit the kill switch and pulled in the clutch on my block and coasted into the driveway. The plugs are all bone white, like new. Engine seemed hot.

What could I be missing?
- Doesn't seem like it could be an air leak. If so, where would it be? Seems like I replaced everything that could have been suspect.
- I suppose the PO could have drilled out some jets (could you tell by looking closely?)
- The air filter looked fine and everything is stock (airbox/exhaust). But the exhaust seems a little loud, could the PO have pulled the baffles? I had the right muffler off to adjust the rear brake earlier and I looked through it... looked like there is a pipe with some kind of bend that runs through the muffler, but I could see daylight from one end to the other. There are also a couple rust holes near the collector/muffler junction where I can feel exhaust gases. Could less restriction in the exhaust cause a lean condition?

I'm struggling here...

 

PS - Seems harder to start after the colortuning, like I need to hit the start button with my opposite hand and rev the throttle a little more. But then I get a decent idle once it's started. After the bike cooled off I tried again and the idle was a little 'lopey' or rough until it warmed up for a minute. When I first cleaned the carbs it seemed to start right up with some choke.

Maybe I just really misread the colortune? This was at idle, about 1000-1100 RPM.

I suppose I can do the propane test for air leaks, dig into that #2 exhaust and get ALL my valves in spec, pull the carbs again and check/replace all the jets. Not sure what to do about the exhaust though, if that's even a problem.

 

Bro, I feel your pain. We're like bike blood-brothers or something.

My problems seemed to start when I swapped my shims (all too tight!). Got new ones installed and I couldn't get rich either, scary hot motor and crankcase. How are your carb boots? barely hanging on or covering the hole nicely?

 

Bike blood-brothers, I like that. I feel the bond!

Carb boots looked really good, thick rubber, cleaned up nicely with some Pine-Sol and they grip the airbox nicely. What's your approach? Carb attack?

 

Sound like a plan!

Did you set the floats "wet" or dry? Be sure to confirm float levels using the "clear tube" method with gas.

When using the colortune, you don't want to be solidly IN the yellow/orange range, you want to see it then go back just until it's nice and blue again.

Be sure you're not being fooled by the plugs. The bikes that run the 12mm plug (550/600, X models) tend to produce a rather clean looking insulator; you need to read the "flame ring" and electrode. Also keep a brand new plug handy as a comparison-- what may appear to be completely white plugs may not actually be once compared to a "virgin."

If the idle has begun "loping" then something's not sync'ed, or tweaking mixtures threw your sync off a tad.

 

Set the floats wet with a clear tube.

On the Colortune, I dialed out until I finally saw yellow/orange, then dialed it back into the blue. There seemed to be a huge range of blue. I'm guessing most of it was whitish-blue indicating lean. I'll see if I can post pics of the plugs.

I kept the carbtune on while I was tweaking mixtures and readjusted sync after. Not sure why it because hard to start/rough initial idle. Maybe I set the mixtures wrong. Is 5-6 turns out ridiculous? How many turns out can you be before the mixture screw spring is no longer compressed?

 

I've heard 5 - 6 means you need the next size jet. Should be something like 3/4 to 3 turns out to achieve the correct setting. If the bikes stock I would change throttle shaft seals and manifold boot gaskets, and silicone the insides of the manifolds (I didn't read the whole thread above).

'The leaner blue won't work throught the RPM range and you need the borderline richness to feed the beast when rev'd from idleing

 

Yeah, sorry yamaman, I was wordy. New throttle shaft seals and manifold boot gaskets. No leaks that I can find with a (unlit) propane torch. But.. the engine doesn't seem to bog down when I tried to cover the airbox inlet, either; it wasn't a perfect seal, just my two fingers side-by-side over the top, but it seemed to have no effect.

I was thinking about the exhaust system some more, and it seems like the condition of the exhaust would have little effect on the mixture because the carbs never "see" the backpressure (or lack of backpressure) if your valves are sealing right. The cylinder/valves should isolate intake from exhaust, right?

 

As I understand it, the backpressure as you say, has no influence on the actual mixture itself. It does however influence the way the mixture, once in the cylinder, burns. An unrestricted exhaust flow creates a lean burn which will need to be compensated by a richer mixture.
I could be way off base here though, so don't take my word for it!

 

Any luck Chaz? It does sound like we're having the same issue and after my shim change I'm lean as heck too. I'm considering getting new jets but will wait and see how she runs after i try the new carb components...

 

Nothing conclusive. Started it yesterday with the CarbTune installed and the sync was right on (with and without YICS tool installed). Pulled a plug and it was dark and wet. I re-colortuned and still find myself 5-6 turns out. Need to do another plug chop to see where things really lie.

Also need to dig into that darn #2 exhaust valve and get that in spec for clearance. Think I'll have to pull the cam. Can anyone tell me if the buckets are supposed to lift right out?

I couldn't find a leak with propane. Will also need to pull the carbs and double-check the jets/float levels. This may have to wait until next weekend.

 

Delete please, I just remembered that he already cleaned his YICS passage...

 

The bucket should lift right out, there is nothing retaining them.

 

Can someone confirm this?

On one of my cylinders, when I colortuned I unscrewed the richnes screw until the screw was loose, the colour changed, but not to full yellow, just a bright blue, the rest are 5 or 6 turns out to get the right blue.

I live at an altitude of 500m, which should give me a richer mix (less oxygen), not leaner.

If I need new jets, where can I get them from? I was thinking of getting a stage 3 kit anyhow, Dynojet? Someone else? (I heard the dynoet needles can wear quickly??)

 

Get a Rubber Syringe from a Pharmacy



Use straight SeaFoam and Flush-out the Pilot Jet Passage.
Remove the Pilot Jet and Flush the Passage by inserting the Nozzle-end of the Bubble Syringe into the Pilot AIR Jet.

Flush the AIR Jet opening down through the Pilot FUEL Jet opening with the FUEL Jet removed.

Flush the Pilot AIR Jet through the Pilot Mixture Passage with the Pilot Mix Screw, Spring, Washer and O-ring removed with your finger blocking the Pilot FUEL Jet orifice.

Power Flush the whole Passage with a strong flushing of the passages by flushing from the Pilot FUEL Jet orifice through the system.

If ... THIS ... doesn't help with the Lean condition, ... AND --> ALL your Jets are the right size and in the right places, ... then bumping-up a Pilot Jet Size and Tweaking with a Larger Pilot FUEL Jet is next.

 

Thabks Rick..

My wife is a nurse, I'll get her to get me one of those.. LoL.. i think their other use is for enima's! (Sounds about right)

They don't sell Seafoam in Europe as far as I can tell, or at least, not in my part of Europe.. I take it that a general carb cleaner will have the same effect?

The bike does exhibit less power than I would expect in the lower rev range, so I wouldn't be surprised if the tubes leading to the jet were gummed, they were the only part I couldn't clean when I was working on it.

 

Do you recall removing the Center Main Nozzles? Long, brass, tubes with an hour-glass look about them, ... with rows of tiny Metering holes drilled through it?

We refer to those tubes as Emulsion Tubes.
They, let outside AIR up through the Center Tube which both draws-up Petrol and atomizes the Petrol rising up the Tube,

There are as many as 20 small holes drilled in that tube and each needs to be clean as a whistle to assure the Engine makes its best Power.

They are released by removing the Main FUEL Jet and Washer exposing the bottom of the Tube which you press of tap lightly upon to send it out the topside of the carbie.

 

Yes. I took those out and gave them a good bath in carb cleaner, all the little holes were clear when I put it back, I think there were either 14 or 18 of them (pairs of 3 and 4 or pairs of 4 and 5).

What I did notice was that behind the pilot jet there was something else brass which I couldn't get out. I assumed that was the same thing for the pilot jet but figured it wasn't supposed to be removed, I didn't want to force it and make things worse. I assume that this is what squirting carb cleaner down the pilot air jet hole will clean?

 

Would exhaust leaks cause lean running? I know people have said they need to re-jet after installing an aftermarket 4-to-1 exhaust. I do have some small holes in my collector/mufflers.

 

not really. depends on how bad they are. put it this way, if you ran open headers you would need to rejet. you're talking about a problem that May cause a lean condition whereas open headers would require rejetting cause you did something on purpose. You can't rejet for your problem, so if the holes are big enough and its running lean you'll have to fix them. Just look at the plugs and you'll know if it's safe or not.