Lean mixture, screws 6 turns out already

Chacal has a great little screwdriver that is captive for the idle screws. I bought one and once I saw it I was glad I got it. It's just about impossible to mess up a screw using it.
I visited my local small engine repair shop and asked if he had any small fuel tanks laying around (not new) that i could use for adjusting float levels, and later syncing the carbs. He directed me to the back yard junk motor pile. In 30 seconds i spotted a Briggs&Stratton engine that had a 1/2 gallon tank and a fuel shutoff valve on the bottom. I scored that for 5 bucks. Now I just need to clean it out and set it up with some fuel line.
Use only screwdrivers in good condition, and buy a few cans of carb cleaner. I used Berkabile Gum Cutter on tough spots. It's not hard, just time consuming.

 

Wow what fun I had tonight with the shims! Here's what happened this has got to be new.

There were 6 I needed to pull out and record. All four intakes and the two outboard exhausts.

When installing the shim tool I discovered that both the exhaust side bolt threads were partially stripped-luckily it was only the first few threads. I used some PB and was able fix em, but it slowed the process.

5 out of 6 shims came out pretty easily (wish I had hemostats though), ..but the #4 intake shim would not come out. After almost an hour, I was in full on curse mode, mostly swearing at the bastard who must have put JB weld on the shim-Finally it came out after 6 small tools went at it. This shim was so old that there was no number to read, not even a remnant. It was being kept in by some fatigue on the metal (looked like symmetrical swirls) that had sort of bonded with the bucket. I ended up scraping a little damage into the area around the bucket trying to get it to break loose-hoping it won't be an issue. It's not in the area where the bucket actually seats but right around the area-I guess I could try and sand it down but I would worry about the shavings more than the little scrapes.

To try and determine the size of the worn out shim I laid it on a perfectly flat surface and using a magnifying glass w/bright light compared it to 285mm and 275mm shims. It appeared to be a 280mm, but can't be 100% sure.

God I hope the carbs are not this much of a pia. This valve adjustment is not a hard job unless this sort of stuff happens. Clearly these valves either haven't been done recently or were done incompletely. The shims I pulled were E1-270mm, I1-290, I2-285, I3-285, E4-275, I4-unknown?

Does anyone know if those numbers look like originals? Since the valves tighten over time those seem like pretty large shims.

Pulling the carbs next-Pray for me.

 

There is absolutely no way to tell if those are the original shims or not; the originally-installed shims varied all over the place.

Don't guess at the one you can't read. Either invest $12~$15 in a cheap digital caliper (worth every cent) and "read" it; or take it to a local garage, machine shop, the auto parts store, or even your neighbor--- anyone who might own a micrometer.

OR- Swap it with one you can read, re-measure, and then shim based on your "new" clearance.

Dude, you've gotta quit chewing up metal. All of this stuff requires a gentle hand. As long as you didn't damage the head enough to prevent the bucket from moving (and rotating) freely, you're OK, don't worry about sanding it.

Be sure to dip the new shims in clean motor oil upon installation; and be sure they seat fully. Sometimes it takes a bit of a "push" because the oil acts as a cushion, but they gotta be oiled.

 

Right did that (used shim I could read) and it was a 280, because putting in a 275 took it from .10 to .15. clearance. I won't be putting back any of the old shims. The scrapes are on the "beach" around where the bucket seats "shoreline" so at least 1/8" away from the bucket. It rotates freely. Believe me for the first 40 minutes on that shim I was gentle, but it just wouldn't budge (like it was welded to the bucket). I tried moving the notch into 4 different positions (180, 160, 200, 210 degrees away from the shim tool. And repositioned the shim tool at least twice at 180 and 200 degrees. It finally came out at 160 degrees, even then it took getting underneath with a blade to get it to nose up and then many pries with a repeatedly cleaned sharp small flatblade to get it to pop (Nothing at all like the other 5 they just popped up).

I really do need to ride today but... :-(. Never before have I seen the value of having more than one bike, NOW I get it.

 

I use a tiny flat-bladed screwdriver (the smallest screwdriver that comes in Craftsman sets) to pop the shims up, and my trusty hemos to lift them out.

You can get by with only one bike; but to do that you have to have gone through it completely first, so that it's like having a NEW 30-year old bike.

However, maintenance still needs to be performed. I did a mid-season valve adjustment this past summer; but since it had been put in spec 5000 miles before, I only needed to re-shim one valve. And it didn't take me off the road. When you check again 5K from now, you'll probably have a lot less work to do.

That being said, it doesn't hurt to have an operational spare or two.

 

I'm the PO. While I appreciate the "trust no PO" rule (I follow it too), I went through those carbs like a DI was going to check them. I followed the rebuild guide here and was paranoid about having to do the job twice. I went through every orifice with everything including welding tip cleaners. I verified every passage with carb cleaner. The sliders were squeaky clean and drop just like they should. Every consumable part was replaced. I was so careful about the bench sync that the bike took very little adjustment to sync them. I tested each cylinder with a Colortune plug. When I was done, I used it for daily commutes and took it to Deal's Gap for some small bike entertainment this summer. It ran like a top the whole time.

I admit it was the first time I'd rebuilt a carb since by Accord in 1990 and the first time I'd rebuilt a multi-carb assembly, but it was running great. When I sold it, the only issue I was aware of was that the charging system seemed to have an issue. I just ran out of time and needed to sell.

I'm open to questions and I don't take the assumptions personally. 8)

Thanks!

 

Yamatoman, welcome! The thing that has me scared about your carb work is the "I went through every orifice with everything including welding tip cleaners" part. Welding tip cleaners are not designed for this application. They can and do remove material from the tiny little passages, thereby changing the flow rate of the circuit.
Also, I went through my carbs the first time before I found the write-up on here. So, the float bowls didn't get the proper care. Bike ran, but not great. Second time through I had a better idea of what these carbs specifically need, so they got a proper cleaning. Ran better, but still not excellent. Third time through them I used parts from the proper source (Len) and actually got everything sealed that needed to be. Also, still found more little bits that escaped the first two cleanings.

What I'm trying to say is that you may have done an excellent job, but these carbs with their microscopic little passages need perfection. Not good, not excellent, not wow-that-took-forever-it-must-be-clean; they need spotless shiny surgical clean.
You may have had it at that point, but if the mixture screws where at 6+ turns out then the carbs are damaged.
Once they are cleaned to that level, they are easy to adjust. (Now, the V4 Honda Magna carbs...those are a PITA!!!)

Now that my carbs are CLEAN, my bike fires right up and purrs like a tiger. Runs like one too! Or maybe a gazelle....you get the idea.

 

I doubt they're damaged; I just don't think they're truly clean. They're Mikunis and have the tiniest passages it's possible to drill into metal.

No offense, but my original diagnosis still stands; besides getting the valves in spec (necessary for vacuum sync) I still think the carbs are plugged somewhere. If not, then it is possible that they were damaged by the use of tools that removed more than just crud.

Again, no offense, but I don't trust float levels until I see them for myself; you simply can't go by what someone else did, no matter how accurately it was supposedly done. It won't take ANY "doing" if the floats ARE set correctly; it wouldn't hurt to double check.

 

I totally get what you're saying. Is it possible I missed something? Sure. Did I damage anything? I seriously doubt it. The one thing i am is careful with things that cost if I break them. I don't bubba things.

I bought this bike to take a break from another project. Cleaning the carbs was both a learning process and something fun to do, so no step was rushed and all of he parts came from chacal. It would have been nice to have someoneone available to grade me though.

MercuryMan is always welcome in my garage. I'm back to wrenching on my RoadStar now, but my girls miss Maxine.

 

I had someone send me a rack of Mik's he couldn't get to respond to any kind of fine tuning.
After looking at the Jets IN the Carbs, using a Jewelers Magnifying Glass, we found the WRONG Jets, ... all-over the place.
We wound-up ordering New Jets from Len.

The Sizes of the Jets are engraved on each Jet.
You might as well double-check to be sure you aren't a victim of hacked-together Carbs built just to make a bike start, ... to hear it run.

 

Just to throw my two cents in you are having the same problem I had a few weeks ago. My problem was the caps on the vacuum tubes, you know the ones you use to do a vac sync, were not sealing properly. The air leak could not be detected even with propane. BUT as soon as I changed them ALL my carbs where rich so I had to reset them. Before that she ran really good but the engine heat was enough to case them to warm up and leak. And the rubber did not seam to be hard at all. But it was enough to cause a leak.
Just my two cents.

 

Thanks Groundhugger, I haven't checked those caps because they look brand new, but I will now. It's interesting that this all started during the first time the bike had a chance to really get hot. I was stuck in Bikes, Blues, & Barbeque traffic on Dixon Street in Fayetteville for about 15minutes and the problems cropped up then. Prior the longest the bike ran without good air was ~1minute (red light). So maybe the heat caused a little leak up there. I have been busy but will be back working on it tomorrow, will replace those caps and see what happens.

 

As these Bikes age ... the O-ring between the Manifold and Head loses resilience.

Replacing them and tightening the Manifolds is a risk due to the SOFT Steel Cap Screws fastening the Manifolds which seize and break all too easily.

Sealing the back-side of the Manifold to the Head with a BEAD of Sealant "Smooched" into the joint will prevent breaking-off a fastener and the related Horror-show getting a seized fragment extracted.

 

So did my ROCK HARD ones. It's really quite phenomenal, they look nice and spiffy-new, while in fact they become absolutely rock hard. As in, can't even "squish" 'em with a pair of pliers.

 

Update and no good news :-(

Valves are done-within specs. Pulled carbs and didn't see anything wrong/dirty. Of course I am no expert on these Mikuni's. I didn't break the rack, so can't say I saw everything but what I did inspect looked the same from carb to carb and it all looked really clean. I suppose breaking the rack is next.

Put it all back together and problems remain. 3&4's pipes are getting hot and will change the idle with adjustment of pilot screw. 1&2 are not as hot and it seems like #2 changes idle just a bit, but nothing on #1. Unlike before, Idle wants to hang, won't return quickly and once it does it wants to idle around 1000 or eventually just dies.

Just to recap. Ignition system totally in spec. Plugs new and good. Replaced manifold caps (to be sure) and no vacuum leaks anywhere. Carbs passed clunk test, float levels are right, no varnish, no blockage, o-rings are new.

Also just to add to the fun. Replaced brake lines but the screws on master are totally stripped. The choke cable broke at the lever (was not abused just slacked and it broke!) and that screw is stripped-cable can be replaced w/o removing screw (small +). The screws on the ignition cover were stripped as well, but I got them off with an impact driver and replaced them with allen bolts.

I want to say thank you to everyone for your input and help. Unfortunately I am out of money, out of time (college is taking all my free time), out of patience, out of ideas. What is really depressing is that I got this bike to save money commuting to school and that hasn't worked out too well. I am back to spending $60 per week in gas and have now dropped every spare penny I had into the bike and its going nowhere. My plans are to pull the carbs again (time willing) and see if I missed anything. But whatever I find will have to be free to fix at this point. Maybe next year I will have the Maxim up and running. Right now it seems like I made a mistake.

Once again thanks to all for trying to help me. I will update if anything changes but for now...Houston we have a problem!

BTW- I have a great big SUV for sale if anybody is interested. Plenty of power and predictable gas mileage.

 

Maybe when you pull the carbs next time take a real close look at your manifolds. I noticed on one of mine this weekend that there was rubber separation from the vacuum tube sticking out of the top. I smeared it with high temp RTV, and FINALLY installed my new vacuum caps from Chacal. My idle went rich on me, and smoothed a little more from what it was. More tuning to do...

I'm tempted to change my manifolds. Has anyone tried loosening them while the engine is hot (and the aluminum expanded) with sucess and not breaking a bolt?

 

You can't just look at the carbs.

You need to "field strip" them http://xjbikes.com/Forums/viewtopic/t=31061.html and then shoot carb cleaner through all the tiny passages to be sure they're all truly open. A lot of those little passages aren't straight, you can't tell anything by just looking at them. Your symptoms still point to a blocked passageway or wonky float. All you need more of at this point is patience.

Re: changing manifolds on a 550. We're lucky--- none of our (intake) bolt holes go all the way through, so the chances of breakage are somewhat reduced. When you're ready to try: Get some Kroil: http://www.kanolabs.com/google/ and soak the bolts/manifold joints for about a week prior.

 

I have Kroil... Good stuff but it stinks!!!
My carbs slip into the manifolds easy. I'm thinking they are shot. Cracked up pretty good and probably just time to get rid of them...

 

Thanks bigFitz. I did have them apart but I didn't go the whole nine yards. After looking through the multitudes of carb info here, and checking everything else off the list that it could be. I have come to the conclusion that you have identified my problem. What kept me from going the "whole nine" was time, impatience and the fact that it ran so good before. I now believe that it was on the verge of having issues (or something caused issues to develop) and sure enough they cropped up or crapped up might be a better term. One thing-since 1&2 are down are you thinking that they both have a blocked passageway?

I'm not giving up so next - cleaning up garage and creating work space to go the field strip route. I only wish there was a part II to your Mikuni post, a step by step of rare Mikuni BS28 carb rebirth! I understand what to look for with respect to "not clean," but how will I know if any of those little parts have been damaged/changed enough to cause my issues. What's your opinion about using SeaFoam as a cleaner/dip, then finishing with carb cleaner and compressed air?

Wish me luck and patience and hopefully I won't have to ask too many boneheaded questions.

 

Why risk dipping these Carbs when they'll clean-up quite nicely just being exposed to Carb Spray and hand cleaning.

Prop the Bowls level.
Shoot some cleaner into them.
Put the Float Valve, Pin and Jets in the Bowl to soak before you do them.

If you have a Varnish Stain that is almost bullet-proof, ... then you dip.
But, then you'll likely need Shaft Seals.

For Mikuni Carbs you should be able to SCRUB the Parts, ... by hand.
Get a Hard Toothbrush.
ScotchBrite Pad
Pipe Cleaners (White, long - - Craft store.)
Bubble Ear Syringe -- Power Flushes passages.
Q-Tips
Time.