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**petelardo** · 06-29-2007, 06:01 AM

I think you're on the right track here...

Stock carbs are NOTORIOUSLY lean, due to EPA requirements; your results indicate that your carbs ARE too lean. You DIDN'T tell us which type of air filter you're using... one of the things we need to know is this: Are you using a STOCK air filter, shown here:

http://images.powersportsnetwork.com/fiche/images/Suzuki/1985/Motorcycles/2114_13.gif

OR, are you using an aftermarket filter? If so, please identify it for us. This isn't a MAJOR detail, but the more we know, the more likely someone can help to point you in the right direction on this... If you're using an aftermarket air filter, is it a (cotton) gauze filter, or a (foam /synthetic) rubber filter? Does the filter require oiling before use? If so, did you use the recommended air filter oil, or a substitute? It DOES make a difference, so please fill in those blanks for us, and let's see if we can help you make some progress here.

Other than wanting to know which air filter you're using, it seems to me that you're on the right track here, but I URGE you NOT to shim the needles until AFTER you know the effects of swapping those main jets. I suspect that the mixture will be a little too fat once you install the new mains, so RESIST THE URGE to shim the needles... yes, I realize WHY you want to do it, but I have to advise against it. If you were at sealevel, and your son was ONLY going to ride at sealevel, you MIGHT get away with shimming the needles at the same time, but it would STILL be the wrong approach... the cardinal rule will ALWAYS be, make only ONE change at a time! OK, so you already know that, but there's no telling who will read this in the future...

NOW, recite the mantra: ONE CHANGE AT A TIME! ONE CHANGE AT A TIME! ONE CHANGE AT A TIME! OK, follow that with some deep breathing; if you EVER get tempted to make wholesale changes to your carbs, refer to the mantra, OK?

I like your approach on the rejetting situation; reusing the two existing #97.5 mains for the outside cylinders means you'll only need to buy two new mains (the #105s) for the inside cylinders...

Swap those mains, IGNORE the pilots AND the needles, and let us know what you learn... if the bike won't start AT ALL, or if the plugs foul quickly, switch the jets one size smaller; install 95s and 102.5s...

Make sure the rider has extra plugs, and the tools to change them with, unless you have a way to haul the bike home. The rider has to be prepared to have the engine die suddenly, at the worst possible moment, but, you already know that. I'm simply trying to make it obvious to anyone else who is tempted to do this that an experienced rider should do these tests...

BTW, set the various mixture screws to the middle of the range; that should be about 1 1/2 to 2 full turns out from lightly seated. You only need to ballpark those settings for now, so setting them at mid-range of travel should do the trick...

Best of luck to you and your son; keep us posted...

**hikermikem** · 06-29-2007, 06:40 AM

Thanks for the response. She's running a stock airbox with an OEM paper air filter which does not require oiling, lid is on.

I'll try to resist the overwhelming urge to make, as you said. "wholesale changes." I'll post my results when I get the new jets & have an opportunity to do some tests.

Thanks again for assuring me I'm on the right track. Of course I'd feel better if someone out there with the same bike has encountered the same issues.

BTW - I'm in CT, where the elevation is less than 1000 ft.

**hikermikem** · 06-29-2007, 09:22 AM

Forgot to mention...

I'm running the stock "4-2" exhaust, but it appears the PO had drilled 3, equispaced, 5mm dia holes around the outlet port plate at the tail end of ONE of the exhaust pipes. The other one has no additional holes adjacent to the outlet port.

I can only assume they were looking to either reduce the exhaust backpressure (on only one side?), or make it sound "meaner." Either way, bad idea in my humble opinion.

I'm thinking of putting in 3 sheet metal screws to block the holes, and if that works, my buddy has a welder & I believe I can barter his services for a 6 pack!

Also, a couple of additional questions:

1) Since I've already vac synced the carbs as they currently are, will I need to re-sync after plugging the holes

2) Will I then need to re-sync each time I change jets?

Thanks again for any advice.

Mike

**Calvin Blackmore** · 06-29-2007, 09:56 AM

Did the bike have #90 jets on it?
My exhaust and jets are for canada and were OEM supplied as 97.5 and 105.

But my exhaust has no EPA stamp on it like your likely does in an obscure spot.

I wonder if they would have had different exhausts and jets for California in your modle year and if the PO changed exhausts.

I know you checked and cleaned you carbs are the diaphragms OK as in visually inspected? I have no means of checking the vacuum but both side on my bike make an enourmous suction sound whne the slides are manually pushed open.

I had one go once wiht a tiny pinhole it was small and the carb worked but not in synch with the other side with a good diaphraghm. made life nasty.

I suppose the synching would have made this evident or does it only account for flow at WOT?

**hikermikem** · 06-29-2007, 11:40 AM

The bike is totally stock, came with 90 & 97.5 jets. I assume the exhaust is stock also (except for the extra holes I mentioned in an earlier post!).

This is in Connecticut, not California. I've seen the CA carb on several of the parts listings sites (flatout, bikebandit) and you're correct - those are jetted a bit different to comply with the CA EPA crap I supose.

RJ · 06-29-2007, 09:51 PM

That "pop" that your son heard sounds like it may have damaged something in the carbs. I would be very hesitant to think that as the bike was running well then all of a sudden you need to re-jet the carbs. Yes it's true that stock carbs are set on the lean side. I do not believe this is what you are dealing with. Possible dislodged piece of crap plugged something up. You may have soaked the carbs to clean them but if you did not blow compressed air through all of the small orifices after soaking you may still have a clogged passage. Also I would recommend soaking in pure gasoline versus parts cleaner. Much more dangerous in terms of fire hazards and such but what better solvent than the juice that left the gum in the carbs in the first place.

**hikermikem** · 06-29-2007, 10:22 PM

I did the 24 hr carb dip followed by compressed air & 2 additional cans of spray carb cleaner, then more compressed air. I also used a small dia wire to poke & probe as many passages as i could get into.

However, with that said, it's possible some sludge may still be clogging a passage, but I don't think it's that likely (but you never know).

I never heard or rode this bike before the "bang" and this being my son's 1st bike, I gotta believe he doesn't really know what "running OK" really means. As I mentioned, there were several additional items I fixed that as stand-alones, would have made the bike run poorly (bad petcock, bad coil, valves out of adjustment, bad intake o-rings). I don't know how the bike COULD have run OK, considering these issues.

Anyway, thanks for the suggestions - I'm hoping someone can tell me what jets work well in their GS550L.

Mike

**KEITH KRAUSE** · 06-30-2007, 09:27 PM

The most common reason for the bang is unburned fuel collecting in the exhaust header and at some point it finally ignites. Could be carb related or weak spark related. If it isn't still happening I suppose you can focus on the lack of power under load and some popping at high revs in neutral.
I know some models come a little lean from the factory but they aren't so lean that you can blame your problems on the stock jetting...as long as you've checked and IT IS stock. Generally, a little richer at the mixture screws will be enough for general riding around.
If your problems are carb related, you have to notice at what throttle position the problems are at. Each jetting circuit controls certain throttle positions. If a bike pops at 1/3 throttle when revving, it's not the main jets fault because you aren't even using the main jet yet. Mark the throttle housing and grip if it helps and tell us at what throttle position(s) the problem is noticable and when it begins and/or ends.
Usually, a bike that revs in neutral but won't accelerate well under load is fuel starved, but it can also be starved for air. However, you also have some popping which is difficult to diagnose without hearing it/riding it. Popping can also be electrical related.
You say you've checked every electrical component and replaced a coil.
The carbs are clean and synched, etc.
The petcock is good and all lines are new.
The air filter is good.
Compression is good.
But the bike only starts and idles well. Seems like somethings been missed.
If I had the bike here I'd probably do some basic checks first, even if you seem to have things covered.
First would be a quick electrical check. What kind of voltage is the RR putting out at various rpm as required by the factory? If good, what does the spark look like at each plug? If good, can you put a timing gun on the timing marks and check the advancer action? If good timing and advancing correctly AND NOT INTERMITTENT or jumping around, that should prove a good, steady spark and correct voltage at all times. Just trying to tell if the higher rpm popping and lack of power are spark related. If good...
I'd probably check for air flow next. Air box seal condition and look for any obstructions in the housing first. The CV's won't tolerate problems with housing leaks. Also check for positive carb bowl venting. Fuel starvation will occur if any lines or passages aren't completely clear to breath. I'd also check gas cap venting. If all good...
The above are pretty easy and obviously basic checks. If it is carb related or fuel flow related, and considering all the things you say are checked such as clean carbs, good o-rings, fuel level in each bowl, new petcock, etc, all I can think of (at the moment) is to check the tank for any rust/dirt particles that could quickly foul your new petcock screen and possibly enter the carb passages and float valve area. I assume you're not using a fuel filter and the fuel/vacuum line is the correct diameter and neither are kinked or routed incorrectly.

**thewiz** · 06-30-2007, 09:38 PM

Keith, as usual, made a great list of all the items you need to check. DO NOT overlook the cleaning, I am mean really good, on the gas cap vent. My 1000 had the same symptoms as yours, cleaned out the vent and she purrs now. Fuel starvation. Maybe not your answer but easy to do. I like those kind!

**hikermikem** · 06-30-2007, 11:04 PM

Keith - thanks for taking the time to comment. I appreciate your "back-to-basics" approach. I will certainly do a double check of the electrical components, although I'm not exactly sure how to check for a quality spark at the plugs.

Wiz - I will also check the fuel cap vent too, I haven't done so yet, thanks.

I am somewhat embarassed however

. I was messing with her today I found a good size hole in the exhaust system, located underneath the frame in the tube that connects the left 2 pipes to the right 2 pipes.

Although I knew the exhaust was fairly loud, up 'til now I hadn't really looked at at closely. There's quite a bit of exhaust blowing out this hole, so I would guess this might be a lot of the problem.

The good news is I have another GS550 "parts" bike (1985 GS550E), and tomorrow I plan on switching out the pipes (both are 4-2 stock pipes, although the E model is connected a bit different according to the fiche view on Flatoutmotorcycles. Another plus is the my parts bike also has an oil cooler, so I may as well bring that over too.

I have a question regarding the cooler though, my L model (no cooler) has an oil pressure switch in the filter cap. The E model doesn't have the pressure switch in the cap, but has a cooler. Is there any reason why I would need to remove the existing pressure switch when I add in the oil cooler? I was planning on just leaving it there.

I'll report back tomorrow (I hope) on how things went after the pipe switch.

**hikermikem** · 07-01-2007, 10:22 PM

Update after more checking... still lousy

OK, here's the latest status after performing more troubleshooting.

(For reference, I haven't changed the jetting or needles yet)

As Keith suggested, I tried to investigate the spark plug wires & such. I do not know how to check the actual spark, but I did dis-assemble the spark plug caps & found a fair amount of corrosion within the inner workings (springs, stud, connector). Cleaned up nicely with a wire brush.

I also completely dis-assembled & cleaned the gas cap insides with carb cleaner & a wire. It was very gumed up & doubtful it was venting much.

THEN, I figured, OK Mike, you have finally found the problem. Warmed her up and took a ride - performed pretty much as before, much to my dismay. Left me on the side of the road a couple of times too, as it died when I was giving it full throttle up hill.

I did notice something that happens very sporatic however. Every now & then it seems to "catch", and she takes off like a rocket. It only last for a second or so, then back to stumbling & popping. I don't know if it's fuel or ignition related, but it's frustrating to glimpse her potentional ever so briefly.

So here I am again asking, NO, BEGGING for help. What do I do now?

All suggestions welcome!!

Disappointed Mike

**KEITH KRAUSE** · 07-02-2007, 10:34 PM

OK. I assume the other pipe was put on so there's no holes in the exhaust to aggravate things?
It's very difficult to tell from your description if it's electrical or fuel or air flow related. It always is actually.
From the abrupt way it "clears up but only for a second", it sounds electrical to me. But it's a fine line not being able to ride the bike myself.
You say the electrical system checked out but I'm wondering. Have you seen the "Stator Papers" here? I'm concerned about your spark and at different rpm. You need to test at various rpm and see what voltages you have at the stator and RR. Obviously, a good battery and clean connections throughout are necessary to tell if any problems are related to specific parts. I also asked about putting a timing gun on your marks and seeing if your timing is advancing and holding steady at full advance. As for spark quality, the first thing is to make sure you have a bluish/white spark during simple hand cranking and with each plug grounded to the head. An orange spark isn't acceptable. The timing gun should show intermittent spark if there is some. There are of course further tests if you have a manual to show you what your ignitor and other parts should be doing in various conditions.
Does the bike try to clear itself at a certain moment, meaning throttle position or rpm? If this is fuel/air related, what happens under IDENTICAL re-test conditions if you remove the air filter (lid still on)? Where are the mixture screws set now? Should be approx' 1 1/2 turns out on a totally stock bike. What do the plugs look like? Good, bad, uniform? Do the plug reads change between a minimal throttle chop test and a high speed run at true 1/2 throttle? I know high speed testing is dangerous, but if you can coax the bike to do it, it may help us find the problem. What speed will the bike achieve? Any oil burning or any other symptoms?
After reading about the crusty plug caps, it seems to me there's probably other basic maintanance items to check before blaming jetting or whatever. I know it's work, but all basics must be done before you can really troubleshoot parts. Clean filter, carbs, carbs floats adjusted, no intake leaks, valve clearances, clean electrical connections, good battery, proper venting.....a lot of stuff.

**hikermikem** · 07-03-2007, 10:10 AM

Thanks again for your opinion Keith,

I'm backtracking now as time permits - I have to let this bike sit a while, hope to be able to get back at it later this week.

No, the "E" model stock pipes will NOT fit on my "L" model. (Trust me, I tried to persuade them for a couple of hrs last night). Not enough room under the frame, too tight. My friend has a welder & I will coax him into trying to patch the original pipes.

I haven't touched the jets, left it stock (mains: 1/4 - 90, 2/3 - 97.5; pilots 37.5))

As i said before, this bike is a bit of an odd duck - little differences here & there: same power plants & electronics, but the frames, suspensions, brakes, etc... are different between the two. Learning as I go.

I'm very confident that the non-electrical stuff I've addressed (carbs, valves, o-rings, airbox checks, fuel/vac lines, petcock, etc...) is in fine shape. As I stated before, I've "fixed" so many things on this bike that I wonder how it ran at all before, let alone ran "well" as my son proclaims. I'm chalking that up to his inexperience with ANYTHING mechanical.

I'm starting to concentrate on the electrical system now - I agree that based on the "catching for second" symptom, it sounds like an electrical issue. I was going to switch ignitors between the two bikes, but the E bike's ignitor is toast - I bench tested it & it was DOA.

I pulled the plugs from my last "ride" (hard to say what throttle position these represent - the bike wouldn't go & actually died twice while i was trying to wind it out at full throttle) and #1 was a bit rich, #4 was perfect. Plugs #2 & #3 were VERY white - this is the coil I switched in from the E bike, it bench tested OK, but I don't think it's working. The original 2/3 coil failed the bench test, that's why I replaced it in the first place. The original L ignitor bench tested OK.

I checked my R/R at the battery - voltage seems OK when running: approx 13.5 - 14.5V. i didn't go crazy checking, just wanted to make sure it wasn't excessively high, & was in fact charging. Not sure I know how to check it further. It does appear the R/R is not stock however, as compared to the one on the E bike. Mine is a little black box, the E one is looks like a mini-ignitor, metallic with fins. I don't appear to have any battery issues though (new this year) but who knows, hasn't really had an oppotunity to fail yet.

I did order two new coils from Z1, and I'm thinking of installing a Dyna S ignition too, although Dynatek doesn't list one for this bike. Researching that is todays task - all the stuff from Dynatek is for older "points" bikes, & I'm not yet too savy with this stuff. Guess I need to take an Ignition 101 class! I will read the stator papers, but somehow I thought that issue was for older electonic systems.

I'll keep you posted as to my progress, any other info or suggestions you may have are more than welcome.

I am getting rather dismayed & frustrated with my lack of real progress here.

regards, mike

**LeeGS550E** · 07-03-2007, 10:59 AM

I have done the Dyna S on our later model 550's. I'm running it right now. The problem with this is the timing advance that you get from the earlier mechanical advance units doesn't match that required by our later 16 valve engines. I'm not convinced that I'm getting great performance out of it. Timing it becomes a bit of a compromise because (iirc) the the 16v requires more advance than the 8 v engines. I did not, however, search for the GS model with the best match for timing specs before I bought a mech. advance of ebay. The one I ended up using was from a 650 I believe. Don't get me wrong - putting the Dyna S on there allowed me to get an otherwise dead bike back on the road without trying to find a used, expensive, untrustworthy ignitor unit on ebay. My original ignitor did not pass the resistance tests spec'd in the FSM. I would be 100% sure if I were you that the ignition system is failing. I put a timing light on mine and found that the spark was jumping all over the place, then did the ignitor test from the FSM.

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Can U stand another question about re-jetting, PLEASE!

Can U stand another question about re-jetting, PLEASE!

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