JohnnyL's 1980 GS550L Cafe Build

[JohnnyL]

Got a link to the catch can? Looks better than my setup...

https://www.amazon.com/gp/product/B00514BR5C/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

 

[JohnnyL]

Ok carb experts. Please come out of the woodwork and offer me your suggestions.

The bike needs to be choked for a couple of minutes before it will idle without it. I warmed the bike up for a few minutes and it idles nicely at about 1200 RPM. You can hear pops coming from the exhaust. Every once and awhile, a carb will pop and backfire. Whop the throttle and it revs up to 5-6000 nicely but is slow to return to idle and when it does, it drops below idle and nearly dies. I've tried getting the revs above 6000 and it doesn't seem to want to go. Like a fuel starvation problem?

Current main is at 100(stock 92.5). Current pilot is at 42.5(stock 40). Air screws are one turn out(tried 2 turns and 3 turns also. Doesn't seem to make much difference). I'm running high quality pods. I haven't messed with the needle height. The exhaust is a reverse cone quieter muffler so it has a baffle in it. In other words...it's not open. For the hell of it, and I don't know if this tells anything, I put an infrared thermo on the exhaust manifolds. Cylinder 1 reads 579 degrees, Cylinder 2 reads 517 degrees, Cylinder 3 reads 503 degrees and cylinder four reads 475 degrees. I don't know how accurate this harbour freight thermo is either.

I'm open to suggestions. Tuning carbs is my least favorite thing to do and I'm just not very good at it. I really wish I could just give it to someone and say call me when it's running great. I also understand it is difficult to tune a bike without actually taking it for a test ride. That's just not an option here with the weather the way it is plus I don't have a seat. It seems like I should be able to get it close to running right sitting still. It seems close to running right. I just don't possess the know how to know how to make it perfect. Someone that knows carbs should be able to diagnose this pretty quickly I would think.

 

[Cipher]

Buy a front fender and an exhaust gas analyzer.

But seriously I doubt the infra red is coping well with a textured wrapped exhaust pipe. Likely causing more confusion to use it than putting it aside.

Also holy hell what is the size of the intake port on the oem airbox? Them pods have a massive surface area. I just got some new filters for the Kbike and you can breath through em with 0 impediment whereas my old 550 element was highly resistant to being blown clean with compressed air.

 

[JohnnyL]

Buy a front fender and an exhaust gas analyzer.

But seriously I doubt the infra red is coping well with a textured wrapped exhaust pipe. Likely causing more confusion to use it than putting it aside.

Also holy hell what is the size of the intake port on the oem airbox? Them pods have a massive surface area. I just got some new filters for the Kbike and you can breath through em with 0 impediment whereas my old 550 element was highly resistant to being blown clean with compressed air.

i have a front fender on. It just wasn?t on when I took that photo.

I wasn?t shooting the header wrap with the infrared. I was shooting behind the exhaust flange where the pipe comes out of the head.

Your point to the surface area of the pods?

 

[Cipher]

i have a front fender on. It just wasn’t on when I took that photo.

I wasn’t shooting the header wrap with the infrared. I was shooting behind the exhaust flange where the pipe comes out of the head.

Your point to the surface area of the pods?

Point is there is a greatly reduced restriction on airflow meaning youre likely jetted far too lean even three increments over stock.

Call me crazy then try 110s with no other mods.

 

[Cipher]

Those are nice filters I looked em up on the makers url. They looked to be well oiled on the pics there.
Are yours oiled? it hard to tell. Might just be the lighting but they look whitish and clean.

 

[Steve]

I can't fully the support the number, but I agree with needing a bit more main jet.

I will also suggest going back to the stock pilot jet.

Jetting depends on air flow. The reason you need bigger main jets is because you have removed the stock airbox, which is a bit of a restriction on air flow at, and near, full throttle. At anything less than full throttle, your throttle butterflies are the restrictions, not the airbox, so air flow is pretty much unchanged. It is usually good to raise the needle a bit to allow a bit more transition to the richer jets, but air flow at idle is virtually unchanged, so no need to change the pilot jets.

Go back to the stock 40s and turn the MIXTURE* (not 'air') screws out three full turns to start with. After the bike warms up a bit, turn each one in slowly, listening for a rise or drop in engine speed. If it rises, keep going. When it drops, stop, back up 1/4 turn, move to the next screw. After you have done them all, do them again, but only back out 1/8 turn. See if you have crisp throttle response and return to idle. Of course, this should be done AFTER a valve adjustment and a vacuum carb sync. You need to ensure that each cylinder is getting the same amount of air so that you know that your adjustments are fuel-related.

* I use the term "mixture" screw because it controls a pre-set mixture, not just air. Suzuki's official term for them is PILOT screw. It is important to know that turning them OUT will richen the overall pilot mixture, turning them IN will lean the overall pilot mixture.

This is just <my> opinion. I'm probably wrong, and somebody will be sure to point it out. :-\\\

.

 

[bwringer]

Thanks for the input, Steve!

I've been helping with this as I can, but I'm a bit lost with carburetion on modified bikes; I've always been in the "stock is best" camp, but that's not an option here.

Thus far, we haven't been able to find any solid jetting/adjustment info whatsoever from anyone who's actually running pods on a CV carb 550. Surely there's one out there...?

 

[JohnnyL]

I can't fully the support the number, but I agree with needing a bit more main jet.

I will also suggest going back to the stock pilot jet.

Jetting depends on air flow. The reason you need bigger main jets is because you have removed the stock airbox, which is a bit of a restriction on air flow at, and near, full throttle. At anything less than full throttle, your throttle butterflies are the restrictions, not the airbox, so air flow is pretty much unchanged. It is usually good to raise the needle a bit to allow a bit more transition to the richer jets, but air flow at idle is virtually unchanged, so no need to change the pilot jets.

Go back to the stock 40s and turn the MIXTURE* (not 'air') screws out three full turns to start with. After the bike warms up a bit, turn each one in slowly, listening for a rise or drop in engine speed. If it rises, keep going. When it drops, stop, back up 1/4 turn, move to the next screw. After you have done them all, do them again, but only back out 1/8 turn. See if you have crisp throttle response and return to idle. Of course, this should be done AFTER a valve adjustment and a vacuum carb sync. You need to ensure that each cylinder is getting the same amount of air so that you know that your adjustments are fuel-related.

* I use the term "mixture" screw because it controls a pre-set mixture, not just air. Suzuki's official term for them is PILOT screw. It is important to know that turning them OUT will richen the overall pilot mixture, turning them IN will lean the overall pilot mixture.

This is just <my> opinion. I'm probably wrong, and somebody will be sure to point it out. :-\\\

.

Thank you Steve! Everything you said makes a lot of sense. Brian is coming over today with his carb sync tool and long reach snap ring pliers. We will change out the pilot jet back to stock. I only have the 92.5, 100 and 117.5 mains so I will probably put the 117.5 mains in for now and order some 110s and maybe some sizes in-between.

I'm a little confused what the "mixture" screw is. Is this what I know as the "air screw"? The little screw on the top of the carb? This one:

 

[Steve]

Yep, your "air screw" actually controls a MIXTURE, that is the screw that Suzuki calls a "pilot" screw.

I am out of town right now, but have a few jets at home that I might be able to send you for experimentation. Should be home Monday evening, will check my inventory on Tuesday.

.

 

[JohnnyL]

Ok. Brian just left. He brought his nifty electronic meter that also measures EMF(I think). We could probably ghost hunt with it. LOL. The bike was giving off a tremendous amount of noise(Maybe Brian can explain this better). Brian then checked my Dyna ignition wires for resistance and shielding they had none. Apparently they're supposed to have some? Anyway....the spark plug wires were giving off so much interference that they were throwing off all sorts of things. The gauge on the bike would blink and we hooked up a timing light to watch the light pattern and it was inconsistent therefore throwing off the spark. This would cause backfire in the carbs and exhaust. Crazy shyte!

I'm off to Napa now to get some new crimps for spark plug wire. I have this cool fabric spark plug wire that matches my wiring loom that we checked for shielding and it does have it. I will be trying these on the bike and see how it runs then. I might not get to it today though because the family is going to see Birds of Prey at 2:45. I'll keep you all posted. This is crazy stuff.

 

[Grimly]

I can't see clearly on that last pic of the bike in the yard, whether you have resistor plug caps or not. If you don't, you'll have to use resistor plugs, although for all I know you may already have done that.

The resistors in the HT leads (or caps, or plugs) keep the RF interference way down, compared to non-resistored leads, caps, plugs. Non-resistored HT circuits cause mayhem to onboard electronics.
You only need to put the resistance in one place - lead, cap or plug, not more than one, else all you do is rob spark energy.

I'm in the same boat - got a set of ultra-nifty plug leads with factory caps that I was loathe to chop off, so I fitted resistor plugs, namely BR8ES, which have an inbuilt 5Kohm resistor.
Actually, I regard it as a good thing, because resistor plug caps often get ignored and forgotten about for far too long, whereas now I get a new set of resistors every plug change.

 

[JohnnyL]

I can't see clearly on that last pic of the bike in the yard, whether you have resistor plug caps or not. If you don't, you'll have to use resistor plugs, although for all I know you may already have done that.

The resistors in the HT leads (or caps, or plugs) keep the RF interference way down, compared to non-resistored leads, caps, plugs. Non-resistored HT circuits cause mayhem to onboard electronics.
You only need to put the resistance in one place - lead, cap or plug, not more than one, else all you do is rob spark energy.

I'm in the same boat - got a set of ultra-nifty plug leads with factory caps that I was loathe to chop off, so I fitted resistor plugs, namely BR8ES, which have an inbuilt 5Kohm resistor.
Actually, I regard it as a good thing, because resistor plug caps often get ignored and forgotten about for far too long, whereas now I get a new set of resistors every plug change.

These are the Dyna spark plug wires I used. https://www.z1enterprises.com/dyna-ignition-wires-7mm-copper-core-red.html They are indeed non-supression core. I ended up changing the spark plug wires to these: https://brillman.com/product/7-8mm-cotton-braid-spark-plug-wire/ This didn't fix the problem. Still getting RF interference by means of mis-firing and gauge interference when the tachometer is connected. After emailing with Brian last night, we realized that the chassis doesn't have a direct ground connection to the chassis. We did put in a direct ground cable to the engine but not the frame. I don't know if this is the problem but this is the next thing I will try. I am going to make up a ground cable and connect directly from battery negative to the chassis.

This is driving me nuts. The mis-firing seems to only be happening on cylinders 1 & 4 and not 2 & 3. I might start the bike and video the timing light in slow motion to see if there is any sort of pattern to the mis-fire. I also will probably run down to Napa and see if they have the BR8ES resistor plugs.

 

[JohnnyL]

Amazingly....the NGK BR8ES plugs smoothed out the ignition. No more backfiring through the pipe or carbs. The bike sits there and purrs like a kitten. I'm still getting some sort of feedback through the RPM signal wire though. The RPM signal wire is attached to the output side of one of the coils. This causes the LCD data on the screen to flicker/pulsate. I don't know if some sort of RPM signal filter will help with this or not. I have emailed Acewell and am waiting for a response to this issue. The good news is that the bike is idling well and now I believe I can move on to jetting the carbs.

 

[Spyder]

A solid frame ground is essential to everything getting proper voltage. I can't be sure this will solve ALL of your woes, but I'll bet it will be your coil and spark issue. Either way, it is a necessity. I don't think your plug wires were an issue.

I don't think you will be too far out with the #117 jets. You will need to raise your needles, and like Steve said, start at 2.5-3 turns out on the mixture screws, and fine tune from there.

 

[Grimly]

This might be all you need for the tacho signal - it's probably spiky and dirty.
https://www.glowshiftdirect.com/tachometer-signal-filter/

 

[JohnnyL]

This might be all you need for the tacho signal - it's probably spiky and dirty.
https://www.glowshiftdirect.com/tachometer-signal-filter/

Yep! I was looking at the same one. However, I spoke too soon when I said the problem was solved. I went to restart the bike and the damn thing started backfiring again. Only through carbs 1 & 4 and the exhaust. Here's what I've done to try to zero in on the problem:

1. Removed Dyna coils and put OEM coils and wires back on. Still misfiring on 1 & 4
2. Checked connections where Dyna ignition connects to coils. Still misfiring on 1 & 4
3. Disconnected the battery and ran off of another battery. Still backfiring on 1 & 4
4. Disconnected the stator and ran off of another battery. Still backfiring on 1 & 4
5. Disconnected everything(lights, gauges, etc.) from the M-Unit except the ignition. Still backfiring on 1 & 4

Mind you, dynamic timing has been done and at idle, the light is right on the F mark on the timing advancer. It idles good minus the popping through the carbs and exhaust. I put the timing light on a black surface and just watched the light flash pattern on 1 & 4. Steady flash and then skips a flash every once awhile(hence backfire). 2 & 3 have a steady flash with no skipping.

I'm running out of things to try. Any suggestions? Anyone? I'm about to call an exorcist.

 

[JohnnyL]

I think I zero'd in on the problem. The Dyna ignition requires a spacer to be installed on the timing advance magnet. I originally had the spacer installed but noticed that I couldn't freely advance the cam(it was too tight) so I took it off. But it seemed like there was too much movement of the cam allowing it to maybe miss a spark. I ended up milling the spacer down by about 30 thousandths and now it fits nicely. The backfiring seems to be gone but I'm not sure that it is firing at all on 1 & 4. I have spark at those spark plugs but the exhaust temp on 1 & 4 was 200 while the exhaust temp at 2 & 3 was 400. Something is wrong. Timing is dead on. Bike idles nicely with no backfiring or popping but it just doesn't sound right. It idles for a little bit and then dies. And as soon as I grab the throttle, it boggs like it's only running on two cylinders.

 

[Grimly]

Assuming a good 12V feed to the ignitors... make sure with a meter.
To rule out a weak coil, swap the coils over.
If the fault doesn't follow the coil, suspicion falls on the ignitor. Not unknown for these Dyna ignitors to fail not long out of the box and lead to much head-scratching. Dyna are well aware of this and replace them quickly.

 

[JohnnyL]

Update to where I am right now.

1. I currently have the OEM coils and plug wires on the bike.
2. I have checked all voltages at the coils. All good.
3. I have switched the coils from right to left. Still burping and farting on 1 & 4
4. I have checked the timing dynamically and still see a skipped spark every once and awhile on 1 & 4.

I have diagnosed the bike as having atrial fibrillation. The next stop is with a cardiologist.

In all seriousness, I can only think that the problem lies with the Dyna ignition. I have ordered a new one though Z1 and will slap it on when I receive it. If it solves the problem, I will return the defective one for a refund. I have also ordered some tools to allow me to sync the carbs. I ordered a Morgan Carbtune, a pair of Motion Pro long nose snap ring pliers to allow me to raise the needle height and a carb adjustment tool for syncing the carbs(screwdriver/wrench). I also ordered an adjustable RPM signal filter from KOSO North america and some 107.5 and 110 main jets. I'm hoping the RPM signal filter will clean up the signal coming from the coils to the gauge and stop the blinking.

I'm really hoping the poltergeist in this bike is the Dyna ignition being defective. I can't move onto tuning this bike until I figure out why it's missing a spark on 1 & 4. Once that is figured out, I can move onto syncing the carbs and tweaking the jets and needle heights.

Ugh.....