Just a little lesson

[Guest]

First off i would like to say hello to everyone here. Iv'e been on here for a while but I forgot to say hi, HI!
So anyway, I just recently went through my carbs on my 77 gs550 and got everything all cleaned up and assembled and it fired right up after the very first bump of the starter. Well I know I needed to do a sync on them before anything but don't have the adapters here and cant get them till I get back. I did a bench sync on them and did have any issues there. Now on to the puzzling part for me. I noticed that I had one colder pipe on number 1. I followed everyone's advice on swapping wires, checking float levels, making sure carbs where clean, checking valves, compression, leak down and got no where. The funny part was that I couldn't achieve a idle change with the pilot on that one carb. Which is why I cleaned them so many times. The only thing I couldn't check was the if the carbs where synced. I made a stupid ASSumption that the bench sync would get me in the ball park, WRONG. I did read somewhere on here once that the bench sync should be done but only to get into the ball park. Still good advice. The last thing I thought about was maybe the sync is off and adjusted #1 slide again while it was running to open it up to let in more fuel maybe. Well wouldn't you know it the SOB took right off firing on all 4 and purring like a kitten. So while I still have to do my final sync I did manage to learn a valuable lesson, don't rule out the fact that the bench sync is going to be right every time. Anyway just thought I would put that out there for anyone who might be having issues similar to mine.

[tkent02]

Very good lesson learned. What the synch does is compensate the carbs for differences in the engine cylinders, if one has lightly lower compression or something else a little off you are making it run more evenly, make all cylinders weak and strong do an equal share of the work.

You can somewhat tell how well it is synched by raising the idle with the big speed screw underneath, and pulling one spark plug at a time while it idles. If they all drop about the same amount of RPM it is fairly even. With twins you can get it really close this way, with a four cylinder not so much, but it will tell you how far off you are.

Find someone near you with a set of manometers, it will run a lot nicer.

[Rob S.]

You can somewhat tell how well it is synched by raising the idle with the big speed screw underneath, and pulling one spark plug at a time while it idles. If they all drop about the same amount of RPM it is fairly even.

I like that. Makes sense to me.

[cyberwolph]

Hadn't thought about the plug thing, that make perfect sense. The reason I thought of it being out is because I remember telling myself it looked funny the the screw to adjust it was almost flush with the jam nut. Dang slide was bottomed out in there. I was going to make my own manometer but I need one that's a little more portable than a 2x6 as I have a buddy that is going need his done too. Thanks again for the plug tip.

[tkent02]

Just buy a cheap set, or better yet buy a good one and charge your buds a few bucks to let them use it with you supervising.

The Morgan Carbtune is really worth the money.

If you want to buy my old one let me know.

[cyberwolph]

Thats the one I am going to get. Thanks for the offer too.

[Nessism]

Humm, so you are suggesting the Suzuki factory service manual that tells you to vacuum sync the carbs is right? Who would have thought? Makes one wonder what other maintenance suggested by the manual people are skipping? Valve adjust maybe?

[tkent02]

Pretty much the whole damned book in most cases from what I've seen.

[cyberwolph]

I think its a matter of having the stuff to do it properly and they assume it doesn't HAVE to be done.

[Grimly]

I think its a matter of having the stuff to do it properly and they assume it doesn't HAVE to be done.

Probably something to do with the almost maintenance-free nature of cars for the past couple of decades. A helluva lot of cars led a neglected life (and many garages compounded it by cutting corners) and mechanically ignorant owners (and their friends /offspring/relatives) tended to assume everything was like that now. Thirty year old Suzukis, although tough old birds, do need some fettling from time to time.

[wildeye]

hi my bike is doing the same ,and a little back firing, till it warms up then it fine , guess I need to do same ,??

tom PM me with info on your old Carbtune , thanks

[P.V_FINLAND]

Had same problem in my bike 4 carb had no idle and had back fire ..i did what you and opened little carb 4 and it started working...Thnx for tip

[cyberwolph]

You bet, glad it worked out.