Timing, smoke, carburetor adjustments....I may need help

[jmcgill89]

Well,

I'm near the end of my rope with the GT550. Last week, I took the tank off and used the dial indicator to set the timing. My first clue as to something being wrong was the fact that for each set of points, I had to fiddle with the points gap to even get the timing halfway proper. If I run with the stock Suzuki points gap in the manual, I could NEVER get it close on the timing....they were all opening way too far before TDC.

When I got it somewhat close, I put it back together and started her up....it runs, and the smoke has abated somewhat in the right hand cylinder, but the left and center have taken up the slack, so to speak. I took the plugs out again yesterday, and now my right plug, instead of being a dark chocolate color with oil on it, is now a dryish light tan color. So, obviously something I did there changed something.

When running, it just seems "off" in some way....when I'm accelerating, it's wanting to "four cycle" unless I hit a sweet spot on the throttle....when I'm going down hill and lay off the gas, it wants to "surge"...feels like the compression surge I used to get on an old moped.

I'm sure I'm just off in one way or another...maybe I need new points, maybe the float levels in the carbs are bad....I'm nearly at a loss, though. If I knew of a professional around here, I'd pay gladly, just to have someone knowledgable take a look at the old girl.

[tz375]

It was OK but not perfect and you set the timing and it's not as good suggests that the timing is still not quite right.

Start with the set of points that is fixed to the plate (left cylinder IIRC) and get the gap right and then swing the hole plate to get it timed spot on. Then gap (12 - 16 thou) and time the other pair.

Double check how you are reading that dial gauge. They are easy to misread, as several people on this board have found out already. Timing is 3.37mm according teh book in front of me, but check that to be sure. Plugs are vertical, so no need to adjust for spark plug angle like you do on a 750.

[jmcgill89]

I'm sure I probably misread the gauge, but it's not in mm....it's in inches, so I had to convert.

I guess I should find one in mm.

I'm going to get a new set of points....that's for sure.

[Coyote]

Excuse me tz, but your post is somewhat misleading. You gap ALL the points before setting the timing. Then that's a done deal. Then you adjust the points to open at the correct time.
A thou indicator is fine. 3.37mm x .03937 = . 1326 rounded to .133 BTDC. That's where the points should 'break'. You start with the left set that is fixed to the plate by rotating the plate to get the 'break' point to occur at .133 before top dead center. Then the plate is cinched down and not moved again. The center and right have their own adjusting screws to set the break point.
If you are confused, find top dead center rotating in a clockwise direction and set your zero there. Rotate counter clockwise about 300 thou, then come forward to .133 before the zero you set. That's where the points should open. Always go in a clockwise direction to double check your setting. Points have a terrible habit of moving when you tighten them down.
If you don't own a timing light, beg, borrow, steal or rent one. It's an indispensable item. When you are done with the indicator. hook the timing light loop around the left plug wire and fire up the bike. Off the mark? It always is for me. If you are nimble and not shaky handed like this old man, you can actually set them to perfection with the engine running.

[tz375]

Chris,
Agree that it's probably better to set all the points first but I don't think it makes any difference to the process. The point I was trying to make was that he needs to get the left cylinder timed correctly before timing the other two.

My interpretation of his story was that he had to tweak all three sets of points gaps in order to get any of them "right". That didn't sound right to me.

[jmcgill89]

To be perfectly honest....I'm surprised it didn't blow up on me for the bad timing job I did. These motors are surprisingly resilient given their age.

I found a video on the internet about "How to read a dial indicator"...and it was eye-opening to say the least

It seems, I've got the timing adjusted to about 10% as advanced as it should be....it's basically firing at TDC now with fouled up gaps. It's set at about 10 thousandths BTDC right now.....ugh.

In short, I'm a moron.

I'm going to do it all over again this afternoon (static timing).

Oh, and I was using my volt meter instead of a timing light.

[smoketriples]

[quote="jmcgill89"]To be perfectly honest....I'm surprised it didn't blow up on me for the bad timing job I did. These motors are surprisingly resilient given their age.

Too far advanced and it would have. Retarded is less of an issue. I did a GT550 by timing light only, and made it ten miles before holing a piston. Don't know the reason but timing to factory plate by light made it very far advanced.

My 750 on the other hand, did by dial gauge and then by light and both were dead on.

e

[H2RICK]

Gents, I've always used the factory marks on the "propellor" on my 550 to set my timing. I have an old ohmmeter that has a 50 ohm scale on it and that has served me for 30+ years on ALL my points ignition bikes.
I have, on occasion, used my dial gauge and/or my timing light as double checks too, however my most consistent results performance-wise come from the stock marks with the ohmmeter.
My .02 worth.....

[jmcgill89]

I think I finally have the timing adjusted somewhat correctly. I first got the points right, and then used the dial indicator for the best approximation I could get, it's not perfect still, but it's a start. It idles and starts MUCH better than it did before.

I took it out on a quick 6 mile ride and cruised at about 4500 rpms....after it warmed, the smoke cleared up somewhat....at stop lights it was barely noticable. I'm hoping to start getting the oil burned out of the pipes with some longer rides soon.

[tz375]

That's great news and you used Coyote's approach which is good. He and Rick really know how to make these bikes work well.

The "propeller" is a good way to time them if you know for sure that the marks are in the right place. On both GT750 motors I rebuilt, there was a lot of slack/play between the propeller and pin, so it doesn't work for me. I'm guessing that the way they came from the factory was closer to where it should be and they knew how to account for that slack.