At my wits end....need guidance...fuel air? igniter? IDK!

[drejal]

Okay...here's the long and short of it.

Current setup :
1979 GS550 L
Intake - Pods (cheap ones), with new intake o-rings. Carbs cleaned, new o-rings installed. (had them apart yesterday and verified clean jets and passages). 102.5 mains, and larger pilot jets as well (forgive me, I don't remember what size, but I do know they are larger than stock) pilot circuit functions well, as judged by plug chops.

Exhaust - modified stock exhaust, at some point a PO removed most of the "guts" in the pipes, so they are almost straight pipes save for what looks like the stock baffle still intact about 1 foot up inside the pipe.

Ignition - Dyna S electronic.


The problem: Engine pulls strongly up until about the 5k range, stumbles slightly, and gets progressively worse until it hits a wall at the 7k mark. At WOT, engine stumbles/gurgles?/ popping noise from exhaust. Will not go past 8k mark at all.

What I have done so far:

Coil relay mod - had 9.5v at coils, now getting 11.8v. When installing mod, I cleaned up connections and repaired poor wiring from PO.

Jet needle - at first I thought this to be a lean condition, so last night I raised the needle...it was at 2nd notch from bottom, I moved it to the bottom notch. Problem got worse, it hit the wall at about 6k - 6.5k. So, thinking I mis-diagnosed a rich condition as lean, today I moved the clip up two notches from it's "original" position. Now 2nd notch from top. Still worse, will rev to about 6k if I give it a little "choke/enrichening" lever, without choke it won't rev. So I'm thinking moving the clip up 2 notches was too big a step.

Here's the rub.....the night I performed the coil mod, I took the bike out and it ran clear up to the redline STRONG, and would have gone farther if I'd tried. The next morning, I took it out for a couple hours and it ran well, but was hitting the "7k wall".


I've spent the last week or so doing searches here in the forum, searching elsewhere....to no avail, it seems. Similar threads I've read have lead to different air/fuel problems or timing or the igniter. At this point, I'm stumped, frustrated, and my wife told me I have to take a break!!!!

If anyone would kindly guide me in the right direction....ask me anything I may have left out, I'll supply whatever info may help. I just want it to run like it did the night of the coil mod again!

I'm going to go play disc golf, and take my frustrations out on some trees! Perhaps when I get back I'll be in the mood to start wrenching again. Thanks for any help...

edit....
I wasn't sure exactly which heading to post this under, I took a stab at the "performance/tuning/mod" since my ride has had mods done to intake/exhaust/coils/etc.. my apologies if I'm in the wrong area. Feel free to move this thread if I'm in the wrong spot!

[gs road racer]

First is the stumbling in midrange at partial throttle or wfo? Did it run well before this? If it's at partial opening what happens at wfo?Always go back to the start and see what you did. A larger main affects everything above idle I would have left the stock pilot in and the needle position as well to start. I don't know what the stock mains were it doesn't list them on bikebandit.. I'm thinking they were probably 95? 97.5?. The choke comment makes me think it's too lean... more info please Reread again check all the things you did associated with the coil changes.Check spark on all four.

[gearhead13]

What was the stock main jet size?
My stock jet was 107.5 and with pods and 4-1 I needed to go to a 127.5 or so. Thats 8 jet sizes over stock with pods vs airbox.

[Octain]

<<<< (had them apart yesterday and verified clean jets and passages).>>>>

From this quote it seems that you didnt dip the carbs and all parts?
It VERY important that you do this. They may look clean but that dont mean they're clean. Its a cheap and very easy task. Although a bit tedious still easy.

Trust me, ya need to do this.
Then we can figure out if there is a jetting problem.

[drejal]

stock mains are 80's for the 550. carbs are VM22SS

stumbling in midrange is at partial throttle, begins popping/backfiring? at wfo. Before the coil mod, there was a problem at cruising speeds, where it would begin to hesitate when held steady around 4k. after coil mod, that problem cleared up for about 3 rides. It seems like I correct one problem, and the bike runs fine for a few rides, then something else.

I read the VM carb rebuild guide and followed as well as I could. there is a note that says the vm carbs without the o-rings on the fuel fittings shouldn't be separated if possible, because it leads to problems after the seal is broken. --- well, lucky me, I have those fuel fittings. So no, I haven't done the full dip yet.

[GregT]

Some of the symptoms you report could be coils on the way out - a good run after the relay mod in the cool of the evening followed by progressively worsening breakdown under load could point this way.
Have you checked coil & leads ohms ? What's the spark like in open air and how far will it jump off the bare end of the lead ?

Greg T

[drejal]

Some of the symptoms you report could be coils on the way out - a good run after the relay mod in the cool of the evening followed by progressively worsening breakdown under load could point this way.
Have you checked coil & leads ohms ? What's the spark like in open air and how far will it jump off the bare end of the lead ?

Greg T

ok....I'll give that a check tonight and in the morning. I've printed out the "ignition troubleshooting" page that's linked on basscliff's site, and I'll go through all that.

one other thing.....they say the only stupid question is the one that is not asked, so I have a couple "simple" questions.

1. sigh.....where exactly is the igniter located? I think it's the only component I don't know the location of.

2. the other question.....is the "signal generator" the same thing as the dyna s pickups that have replaced the old points/condenser? Just making sure I've got that one straight.

thanks for pointing me in a different direction. I'll report back with my findings.

Andre

[gearhead13]

ok....I'll give that a check tonight and in the morning. I've printed out the "ignition troubleshooting" page that's linked on basscliff's site, and I'll go through all that.

one other thing.....they say the only stupid question is the one that is not asked, so I have a couple "simple" questions.

1. sigh.....where exactly is the igniter located? I think it's the only component I don't know the location of.

2. the other question.....is the "signal generator" the same thing as the dyna s pickups that have replaced the old points/condenser? Just making sure I've got that one straight.

thanks for pointing me in a different direction. I'll report back with my findings.

Andre

Your bike is pre-1980 so there is no stock ignitor, your dyna s replaced the points. The pickup and ignitor from a 1980 and newer is replaced by the dyna s which is fully contained behind the right side cover.

[drejal]

which would explain why I haven't found the ignitor! thank you

should make troubleshooting the ignition a little easier. will be getting started as soon as I have some coffee in me.

thanks all!

[Octain]

Dip those carbs! Its a four or five day process so get to it!!

If you dont, you'll never know and may end up running in circles for a very long time.

Trust me dude, been there done that!

[greg78gs750]

+1 on dipping the carbs. dont let the fuel tubes scare you off. there are replacement tubes available, but they are a bit pricey. if you are really worried about yours, give em a couple wraps of teflon tape before you install them....worked on mine, no leaks 3 years on.

also, you have a lot of changes going on at once, pods, exhaust, jetting, ignition, etc.....dont be surprised if it takes a while to get it straightened out. just be patient and thorough.

greg

[drejal]

Some of the symptoms you report could be coils on the way out - a good run after the relay mod in the cool of the evening followed by progressively worsening breakdown under load could point this way.
Have you checked coil & leads ohms ? What's the spark like in open air and how far will it jump off the bare end of the lead ?

Greg T

so....for the coils, the primary windings are both reading about 3.5 ohms, within spec as I understand it. However the secondary (from plug lead to plug lead) is reading about 15k on each coil. The guide I printed out was for the gs1000, and it mentions the coils should be about 40K or so. Are the coils for the 550 that much less resistance? The spark will jump about a quarter inch from the bare leads to the plugs.

for the carb dipping.....ok. you've beaten me into submission. my next trip to the auto parts store will be for the can of carb dip, and teflon tape. If that's what it takes to get it to run like I know it can!

[drejal]

just an update in case anyone follows this thread in the future...

carbs are dipped, and bench synched.

Found the source of the problem. While the cabs were soaking, I was able to troubleshoot the wiring a bit, and found that after I did the coil relay mod, one of the connections coming from the dyna pickups had come loose, and possibly was shorting to the frame. Now that the connections are proper, it's running strong again. Revs all the way to the red.

Thanks for all the help everyone!

[Octain]

Awesome!
Glad you got it sorted.