Mikuni Two-Barrel BS30 carburetors

[first timer]

Call it what you will. You might call it a baffle. But there's a cage you wrap the fiberglass around in the V&H pipe.

Not all pipes have facilites for packing. If you need a famous example of a "packing-less" pipe, look at dynomax mufflers. Or if you need examples more close to home, the stock pipes are all about baffles, not about packing to absorb sound.

These are some good tips. I wish I had an O2 sensor, if I did I'd be much closer to having my 83 running in tip top shape. ;-)

FirstTimer jinxed me. he said I shoudl clean my pilots. Then the bike wouldn't start. I parked the bike last night, and when I came to it in the morning, there was a puddle around the kickstand. Skreemer had mentioned that I was leaking oil.

It wasn't oil. Looks like one of the float valves in my carb isn't sealing quite right. So all the gas that's in the line from the tank to the carb dribbles out onto the ground. *shakes head* And the reason why it looked like oil? It washed the oil off the base of the back of the crankcase.

SO... Dem carbs need to come apart, the mixture screw covers drilled out, and I need to order some jets. :-) (not many.. I happen to have most of these.... *shakes head*)

your just lazy, any new old bike owner first thing they should do, in this order: (let me get on my soapbox) change the oil and filter, check the air filter, change the plugs, and thoughly clean the carbs before even riding it. there is no excuse not to, with all the tutorial we have posted here on the issue. (i'm stepping off my soap box now). p.s i still love yeah nerobro.

about the baffel, if you want to do a home brew job to make one, you can go buy one of those heavy gauge wire mesh office trash cans. cut it up and roll it up then wrap it in some exhaust grade fiber glass (most bike shops should have some) should kind look like this crude drawing )====(. or you can get a cheap oil auto oil filter the size of you megaphone, drill some holes in the end, then jam it into the maga phone screw side facing out. you may want to pop rivet it to the megaphone but it should quite it down. and like i said these are home brew (ie rat bike)

[550ERAT]

hey there. i have a 83 550e. (blue/white). i found a brand new set of carbs but they are from a 85 550. my carbs have the numbers 43410 on them, the new carbs have 43610. the set up looks the same. does anyone know if these will work on my bike. the price also seems right ($150.00). with new boots too. oh yeah, they are from a 550L if that helps

[Nerobro]

Yes, they'll fit. But why do you need new carbs?

[550ERAT]

for some reason i cannot get my carbs "right" even had a m/c guy work on them, they were so gummed up he had to use a jewelers bit to clean the jets. i don't know what else to do. i figured it was a decent price so , why not? i am stuck!!!!!

[Nerobro]

spend $30 and replace all the jets. If you used a "bit" of any sort, you're probally running stupidly rich right now.

What are the symptoms?

[txironhead]

No matter how gummed up they were, a couple of days soaking in carb dip should have cleaned them good as new. You NEVER use anything hard to clean jets. I've always used fishing line or a toothpick with great results. I normally soak the bodies and jets overnight, spray them off with aerosol carb cleaner or an air gun, then go over them with several sharp toothpicks to make sure it's clean. If it's not, back in the dip.

If he used a bit on the carb bodies, they're probably shot. If he had soaked them long enough they wouldn't have had a problem. If he didn't, I agree that you're probably going to have to buy new jets because you'll never get them balanced or calibrated with oversize jet holes. There's a fine science to jets (as I'm becoming painfully aware with my own carbs) and soft brass is easily damaged.

[550ERAT]

are all of the rebuild parts avail for these carbs thru the dealer? including gaskets, o-rings etc... i don't know if jets alone will do the trick. The carb bodies were not damaged, only the jets were touched with the bit. As far as symptoms, hard starting, poor accell, if it ever stops raining, I will try to take it for another spin. I am not afraid to work on them myself, just don't want to screw them up. Stock is fine with me (it's just for buzzin round town) So, as of tight now, save the $150, spend $30-40 and see what happens? sound right? I appreciate all the input.

[Nerobro]

YOu should replace the o-rings that are behind the carb boots. But those are the only o-rings you shoudl "need' to replace. You should pull out the mixture screws so you can clean them. That will require a drill though.

The jets, and the four aforementioned o-rings are available through a dealer.

[distraction628]

bits

If you used jewels bits or jet bits of the same size and did it right then there shouldn't be a problem. All my jets are measured with the bit's I have never messed one up so far but I now people have. Like I said be carefull if you do drill jets. Always clean with soft something frist, bits are for the jets that are so bad and you don't have the time or money in your back pocket to spend at the moment. Just my 2 cents. I will buy jets 99% time but I still check there size with my bits, start with the next size down and never force them. just set them in if they fall thru go to the next till one doesn't.

[550ERAT]

what about the o-rings on the end of the jets or mixture screws? those avail from the dealer? again, thans for all the help.

[Nerobro]

There are no o-rings on the jets. The o-rings on the mixture screws are typically ok.

[550ERAT]

ok, i am probably gona tackle tghe rebuild/clean myself. There is a link on the home page to a carb cleaning section. It shows a 4 carb set up. Will these 2 bbl carbs be similar in their construction or are they completely different beasts?

[Thomas Kenny]

Erat, I just finished rebuilding a spare set of Mikuni two-barrel carbs for my 1984 GS550ES that I bought off of Ebay. Get a gallon can of carb cleaner from NAPA or another autoparts store. Tear down your carbs and lay aside all rubber and plastic parts. Remove all jets, the float and needle and seat. The pilot jets are along side each other in small deep holes. Be careful that you use a screwdrive that is the right size for these jets and that you do not force them. I bought an aerosol can of penetrating oil and sprayed down all part that needed to be unscrewed and let them sit overnight before removing. One of my carbs did not have the float bowl drain screw in it and it was pretty rusty inside. The carb cleaner did the trick. Let me know if you have any more questions and how your rebuild goes. I am sure that I have forgotten something but this was my first rebuild and these carbs are not really that complicated.

Have Fun, Tom

Put the carbs in the cleaner one at a time for about 3 days each. Pull them out and wash them off in warm water and then blow out all of the orifices well with compressed air.

[Thomas Kenny]

Well I got my spark issue fixed. I bought four new NGK caps and a used coil from Ebay. I'll get the good ones later Distraction :-). Any way after several attempts with an overhead gas bottle and my vacumm line to the tank plugged, it finally started farting and then started to where it would run slowly although with an occasional backfire. I noticed that my boot between the head and carb was loose as I saw some exhaust gases coming out around the boot when I got a backfire. I tightened up the boot strap, and put my K&N filter in and the airbox cover. The engine starts and will idle but labors up to about 2500 RPM and then acts like it is running out of gas. I got quite a bit of water coming out of my airbox drain line and then it stopped. I started messing with the low speed air jets and they seem to be all over the place although when fully closed on one cylinder at idle the engine dies. All exhaust headers are hot. I just installed a Vance and Hines 4 into 1 pipe on the bike and nothing else. I haven't jetter yet but based on your past experience I am going to get a set of 105's and 110's and start with the 105's. I am just confused because I rode the bike for about 5 miles after installing the pipe and it ran well, just lean when I opened the throttle. I am hoping I haven't burned any valves. Speaking of valve I adjusted them all to .004. Any suggestions as to what I should try. My Signal Generator and Igniter unit check OK.??? Thanks all

[Thomas Kenny]

I put on the other coil that came with the set from Ebay and I have good spark at all plugs. However now I am running on three and I hear a tapping in the area of Number 3 cylinder under the cover. I did a compression check on 3 since the header is now cool and I got 50 lbs with a warm engine and I was getting 125 cold after the valve adjustment last week on all four cylinders. Perhaps my valve adjustment that I did last week is way out of whack on 3, or I have a badly burned valve? I will pull the valve cover off next weekend (only today to work on it) and check for a loose adjuster or a broken spring or???? Plug is sooty black. I hope I don't have a holed piston!!!