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carb rebuild update

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Guest

Guest
I dunked the carbs and got them all cleaned out last week, and this weekend I got them all put together, assembled into their rack, and adjusted. They're ready to put back on the bike. I also got the manifolds back on with their new orings and stainless screws.

I probably won't have a chance to put it back together and try starting until next weekend. Will post again to let you all know what happens Wish me luck!

These things are not easy to work on. Thanks to everyone who offered advice and suggestions. Don't know if I could have done it without your help. I'd probably never figure out how to adjust the throttle slides on my own...

Debby
 
Good luck debby, keep us posted. I know you'll get it going strong :)
 
I got it all put back together today with the unipods. Pressed the starter button and it fired right up! It 's running much better than before. Has a nice smooth 1200 rpm idle. No backfiring, surging, or fouling plugs. The only adjustment I've made so far is the idle speed screw. All other settings, and the jetting, are stock. I think our mile-high altitude helps compensate for the leaning-out effect of the pods.

I might need to go up a size on the main jets. At higher throttle and rpm, feels a bit lean maybe. Hesitates a bit when shifting gears and getting back on the throttle. Runs fine at lower throttle settings though. I looked at a couple of the plugs - one looked a bit lean, the other a bit rich. It definitely needs a carb sync. Will have to do that before I can draw any conclusions about jetting. Time to place another web order for the mercury stix...

I also installed a new clutch cable (big improvement!) and replaced the cowhorn bars with some standard-types. The new bars came from a Kawasaki H1. I figure they should be good for a few extra HP :)

Debby
 
Hmm. I did a longer test ride and have to postpone the champagne. Around town it's fine but out on the highway, with more throttle and load, it's not fine. Way too lean from about half throttle on up. The more load/throttle the worse it gets. So it definitely needs richer mains. And a richer needle position or richer needle jets or...

The pods are such a simple clean solution. I really like them. And they make carb access so much easier. But I might be needing a lot of carb access to get the tuning right. Or (I hate to say) I could spend a couple of hours getting the stock boot back in there and quite likely be done with the whole carb ordeal. Oh the irony!

If I do keep the pods, does anyone have any suggestions on jetting changes? I'm at 5000 ft elevation...

Debby
 
The jetting must be chanded for the pods. Correct me if I'm wrong, your motor is stock except for the pods, right? What brand of pods? Uni's?
Here's what I would do if you've got the patience regarding re-jetting and want to try using Mikuni jets and the stock needles (instead of a Dynojet kit) which is not designed for a stock exhaust anyway.
With your elevation in mind, try 3 full sizes up on your mains. Raise the needles 2 positions by lowering the needle clip 2 positions, or grooves. Turn your pilot screws (underneath) out 1/4 turn more than where they were stock. Turn the side air screws 1 3/4 out. Foam air filters need to be oiled. Gap your plugs.
If you're sure the carbs are clean, the ignition is timed correctly, and your valve clearances are reasonably within range, do a good manual carb sinc' and then sinc' them with a vacuum tool. Turn the slides up with the idle screwknob enough to allow an idle. Put a fan or two on the motor and warm it up. Adjust the side air screws for the highest rpm you can achieve and re-set the idle to about 1100 rpm using the idle screwknob. Now connect the vacuum tool and get the levels within 1 cm of each other. I like to set them at 3500 rpm.
My jetting suggestions are just that, suggestions. You may have to re-adjust the needles/mains/pilots. If you move the needles, you MUST re-sinc' every time. Good luck. :)
 
Wow, that much? You're probably right though, it's really lean. As you guessed, the bike is otherwise stock, including the exhaust. The pods are unis and I did oil them (I grew up around dirt bikes so I know about that :)

Thought I'd try ordering some jets and take a shot at it. Would have to take the carbs off anyway to get the stock boot back in. That stock system must *really* be restrictive. Kind of like running a 10k race breathing thru a straw! Hmm, wonder how much improvement a pipe would make. The bike is not exactly overendowed in the hp department. Don't want to get into that right now though.

According to their website, dynojet doesn't offer anything for my bike. So I have to do it the hard way. I think the end results will be worth it but I'm afraid I might be messing with the bike all summer. Will probably get it right just when the snow starts flying :(

Debby
 
It's not that the stock air system is extremely restrictive, it's that the complete fuel / air system is so sensitive. It's not like changing the intake on a small block chevy engine. If you go back to the stock intake system, you probably won't need larger main jets. If you stick with the pods, try to get a few sets around the size Keith suggested, otherwise you might be ordering and changing well into the riding season.
 
Remember, a full size in Mikuni jets is 5. A half size, or step, is 2.5
So if you have #80 stock mains, try #95. Also, don't forget the needle adjustments. You spend the most time riding while on the needle circuit. The needles must be set correctly to avoid a lean/overheating motor.
I believe the jetting suggestions I gave you will at least get you in the ballpark, (I hope spot-on) but jetting can be a lot of trial and error. That's where the patience comes in.
Just don't do as a lot of people do and throw in some larger mains and consider the bike re-jetted.
 
Well, I gave up on the pods and decided to put the stock airbox back on. Considering that I have the stock exhaust, all that grief just didn't seem worth it. Only took an hour or so to get that airboot shoved back in place.

Bike runs great now! Smooth and quiet with a nice idle. WAY better than it ran before the carb rebuild. And I haven't even sync'd them. It's really fun to ride now that everything is working properly :)

Regarding pods, my conclusion is that they just aren't worthwhile unless you plan to install a performance exhaust. Then they're a must. Does anyone want a nice set of unipods? Pre-oiled, ready to go. Email me, I'll cut you a great deal ;)

Debby
77 GS550B
 
You're fortunate the lesson you learned was relatively cheap. While jetting isn't rocket science it does take a lot of patience and the desire to tinker for maybe years to come. I sometimes regret installing a stage 3 kit and pods. While my bike does run just fine it took a lot of time getting it right and it is more sensitive to temp changes. Actually the performance gain is noticeable for awhile at first and then you just get used to it. I installed mine back in '86 and now it almost seems like it's stock... but it sure don't sound like it.
 
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