Need a little help with carb issues....

[Anonymous]

'81 GS750. Bike now starts and idles fine. The problem is it runs well until about 4-4500 rpm when it seems a bit sluggish from there on up with a bit of popping above 6500 rpm. Plugs show a faint white so I suspect a bit lean. My question is this, can I adjust for this lean condition by moving the clips on the needles and if so do I move up or down?

Also, could the ignition play a part in this? This bike sometime in it's life had been converted to points. Everything seems fine.


I just wanna ride!!!!!

[earlfor]

Re: Need a little help with carb issues....

I would:

Check points gap and timing.

If/when that is correct, put guages on it and check vacuum levels and carb balance. You should show at least 10 in Hg at 1200 rpm.

Earl

'81 GS750. Bike now starts and idles fine. The problem is it runs well until about 4-4500 rpm when it seems a bit sluggish from there on up with a bit of popping above 6500 rpm. Plugs show a faint white so I suspect a bit lean. My question is this, can I adjust for this lean condition by moving the clips on the needles and if so do I move up or down?

Also, could the ignition play a part in this? This bike sometime in it's life had been converted to points. Everything seems fine.


I just wanna ride!!!!!

[Anonymous]

I don't have a manual (about to close a deal on a factory one) so I did a little web searching and come up with a few specs.

Point gap = .018 and mine are set at such.

Ignition timing = 17 degrees BTDC. This is where I need a bit of help. How does one check the timing on this bike? Do I need a special timing light or can I use a multi-cylinder automotive type? Also which plug is it timed off of? (Man I hate being ignorant. Why can't turning wrenches come as easy as slingin paint!))

After having checked the point gap I fiddled around with the ignition plate setting it at different positions and taking a short spin. Rotating the plate clockwise (retatrding?) seemed to help correct the sluggish feeling I was gretting at 4-4500 rpm. It is just now it acts like it cuts in and out somewhat over 6500 rpm and will not climb much over 6500-7000 rpm in fifth gear (about 70-75 mph if I remeber correctly).

I also need to get a carb synchronizer so I can set the carbs when all comes in line.

I guess it is one step at a time. They're baby steps but at least I am moving forward!

Thanks for the help!

[earlfor]

OK then, your bike was manufactured with an electronic ignition, consequently, there is no manual or factory specs for points ignition setup for your bike. The points gap you will need to set to is .014
Here is the sequence you will need for setting the points gap and timing your bike. All you will need is a continuity light. That can be any 12 bulb in a socket with two wires and an alligator clip on each wire so you can connect it.

You will need to do a static (non running) timing first. You can use a timing light once this part is completed and the bike will run.



I've posted this in answer to others needing the same info, but it seems easier to just copy and paste it for you rather than make you search tech pages to find it. Being new, you may not be able to find it. :-)

(NOTE........I wrote this for someone that was replacing their points, so just dont do the replacement part.........but DO read everything because some parts of the replacement proceedure are needed for points setup.)

Here's the proceedure for setting gap and timing. The points are located under the round cover on the right end of the crankcase/crankshaft.

The round 6" plate that both sets of points are mounted on (breaker
plate) is held in place by three screws located at 12, 4 and 8 oclock.
Loosen the 3 screws on the breaker plate. Note that the screw at 12
oclock is in a slot. Rotate the breaker plate until the 12 oclock screw
is centered in the slot. Tighten the three screws.

We will replace the left side set of points first (located at 9 oclock
position) These are the points for cylinders 1 and 4.

Take a 19 mm wrench and rotate crankshaft until points are at widest
gap. Unscrew hold down screw on pointset and remove points. Note the
white wire that goes to the pointset and the placement of the insulator.
The insulator must be correct or the points will be grounded out and
will not work. Put the new points onto the breaker plate, set the gap to
14 thousandths, and lightly tighten the hold down screw. Install white wire.
Rotate crankshaft once again with 19mm wrench until points are at widest
gap. Check that widest gap remains at 14 thousandths. Adjust and
retighten holddown screw if needed.

Rotate crankshaft until rightside points are at widest gap (for
cylinders 2 and 3) Remove old points and install new points and set gap
at 14 thousandths. Note insulators on black wire installation. Rotate
crankshaft with 19 mm wrench again stopping at widest gap. Recheck gap
as you did with the left pointset. Adjust and retighten hold down screw
on points if needed.

THE ABOVE COVERS SETTING THE POINTS GAPS




Next is the timing:

Timing for cylinders 1 and 4 (the left set of points)....................
With 19 mm wrench, rotate crankshaft while looking through the timing
window and align the mark that looks like |F1 with the timing mark on
the engine case.
(the line (|) preceeding F1 is the mark |F1

******NOTE**** It appears some models use the notation |F1 and some used the notation F1| In either case, you set to the mark ( | )





note: some bikes will have a stationary timing mark on the engine case
and some will have a mark on a stationary timing plate that can be seen
through the timing window)

Connect a continuity lights wire lead/clip to the white wire clip on the
left pointset. Clamp continuity light probe tip to ground on the bike or
battery negative terminal.

Turn ignition switch to on (do not attempt to start bike, just switch
ignition to on)

The continuity light should be on.

Loosen the three screws on the breaker plate located at 12, 4 and 8
oclock. Rotate breaker plate until continuity light just flickers out.
Retighten the 12, 4, and 8 oclock screws on the breaker plate.

Unclip continuity lead from left pointset.



For the Right pointset
Rotate crankshaft with wrench until you see the timing mark F2| become
aligned with the stationary timing mark on the engine case.
Connect continuity light lead to black wire on right pointset.
The ignition should be switched on and the continuity light should be on.

The right pointset is mounted to a breaker half plate.
You will see that you can loosen the mounting screws on this breaker
half plate and this will allow you to move the right pointset. This will
adjust the timing without changing the points gap. When you rotated the
complete breaker plate for the left pointset to get the continuity light
to flicker out, thats what you did. You adjusted the timing on cylinders
1 and 4 without changing the gap on their pointset.
Unfortunately, the whole breaker plate being rotated moves BOTH sets of
points, so that is why you must set the left side first and that is why
the right side is mounted on its own independent half breaker plate.
SOoooooo.... Smile Loosen the breaker half plate on the right side and
rotate as needed to cause the continuity light to just flicker out.
Tighten the half plate back down when satisfied with the adjustment. Smile

Remove continuity light and HOPEFULLY, start bike.


Earl





[quote="cozee"]I don't have a manual (about to close a deal on a factory one) so I did a little web searching and come up with a few specs.

Point gap = .018 and mine are set at such.

Ignition timing =

[Anonymous]

Thanks Earl!

Ooo, .004" out on the points. Little buggers staying open too long. Setting the timing sounds simple enough. I will get to work this afternoon.

Would you leave the points in or reinstall the electronic ignition? I have a parts bike with a good electronic system in it. If the electronic is the way to go I think I will wait till winter as long as I can get the bugs worked out of the bike for now. I wanna ride!!

[earlfor]

I would leave the points in it for now. They are simple, cheap, easy to set and dependable. Its also something you can fix if they for some reason get out of "whack". :-) I bought a Dyna S for my 750 almost 3 years ago. The points are so little trouble and so dependable, I still have the points in the 750. Just never felt any need to change tothe electronic ignition. I get about 20,000 miles on a set of points and they cost $8.
Not a bad deal at all. :-)

Earl

Thanks Earl!

Ooo, .004" out on the points. Little buggers staying open too long. Setting the timing sounds simple enough. I will get to work this afternoon.

Would you leave the points in or reinstall the electronic ignition? I have a parts bike with a good electronic system in it. If the electronic is the way to go I think I will wait till winter as long as I can get the bugs worked out of the bike for now. I wanna ride!!

[earlfor]

Just an additional bit of info..........
Some bikes were manufactured with non adjustable electronic ignitions.
Consequently, there may not be a timing mark on the crankcase for you to align the F1| or the F2| with. If this turns out to tbe the situation, if you look at the breaker plate and its three hold down screws, the top screw is located at the 12 oclock position. The timing mark on the engine case is located at 11:55 (uhhhh, i'm not sure whether that is am or pm though) :-) :-) That will be about 1/16" to the left of the left edge of the 12 oclock breaker plate hold down bolt/screw.

Earl

Would you leave the points in or reinstall the electronic ignition? I have a parts bike with a good electronic system in it. If the electronic is the way to go I think I will wait till winter as long as I can get the bugs worked out of the bike for now. I wanna ride!!

[Anonymous]

I was kinda wondering about a crankcase timing mark and whether or not it was present since this bike originally had an electronic ignition. I haven't had the chance to get out to the garage yet so thanks for the added info.

Do I have to account for Daylight Savings??!!! LOL!!!!

Just an additional bit of info..........
Some bikes were manufactured with non adjustable electronic ignitions.
Consequently, there may not be a timing mark on the crankcase for you to align the F1| or the F2| with. If this turns out to tbe the situation, if you look at the breaker plate and its three hold down screws, the top screw is located at the 12 oclock position. The timing mark on the engine case is located at 11:55 (uhhhh, i'm not sure whether that is am or pm though) :-) :-) That will be about 1/16" to the left of the left edge of the 12 oclock breaker plate hold down bolt/screw.

Earl

Would you leave the points in or reinstall the electronic ignition? I have a parts bike with a good electronic system in it. If the electronic is the way to go I think I will wait till winter as long as I can get the bugs worked out of the bike for now. I wanna ride!!

[earlfor]

:-) :-) :-)

Earl

[quote="cozee"]
Do I have to account for Daylight Savings??!!! LOL!!!!

[Anonymous]

timing

nope but you have to allow for time zones

[Anonymous]

nope but you have to allow for time zones

I said to heck with tryin to figure it out and simply called the Hippy Dippy weatherman to see what time is is in Burbank!!!!

Now getting back to regularly scheduled programming, I went through the explained process of setting the points and the timing. It sure does run a lot better now!! Still a bit sluggish on top end but it has set for a few years and is 20 plus years old.

I've put 80+ miles on it already this evening by going for 10-15 mile rides. It seems to run better and stronger with each ride. I won't be able to work on it anymore till next weekend but in the mean time I am going to order a carb synchronizer and my manual should be here by Thursday.

Thanks again Earl!!!! Once I get this bike mechanically sound then I will start on the 700ES. I hope you will be ready!! LOL!!!

[earlfor]

heh heh :-)

Earl

Thanks again Earl!!!! Once I get this bike mechanically sound then I will start on the 700ES. I hope you will be ready!! LOL!!!

[Anonymous]

Earl, based on this piece of your directions, does it matter which way you rotate to get the light to flicker off? P.S. I have a GS550 that has elec. ignition and mounted a Dyna S instead, so I am trying to set the timing for the Dyna S now.

"Loosen the three screws on the breaker plate located at 12, 4 and 8
oclock. Rotate breaker plate until continuity light just flickers out.
Retighten the 12, 4, and 8 oclock screws on the breaker plate."

[earlfor]

Yes, it matters. You want the light to flicker off when rotating the breaker plate counter clockwise. The light flickering off will indicate the sensor comin up on time. If you were going in the opposite direction, it would indicate its past time and we all know time goes by so slowly and time can mean so much.
Are you still............uhhh, maybe we shouldnt go there. :-)

The answer is counterclockwise. :-) and that all I'm going to say for now. :-)

(the rotational direction of the breaker plate only makes a slight difference and will not cause the bike to not run acceptably)

Earl

Earl, based on this piece of your directions, does it matter which way you rotate to get the light to flicker off? P.S. I have a GS550 that has elec. ignition and mounted a Dyna S instead, so I am trying to set the timing for the Dyna S now.

"Loosen the three screws on the breaker plate located at 12, 4 and 8
oclock. Rotate breaker plate until continuity light just flickers out.
Retighten the 12, 4, and 8 oclock screws on the breaker plate."

[Detman101]

Okay, so we always rotate the breaker plate "CounterClockwiwe" until the continuity light flickers out....right?

Just making sure before I attempt this.
:?

Dm of mD