GS550ES Running Quality Questions

[strawboss]

Hello All,

I just put a thread in the GS owners section to introduce myself. I have been doing some reading on the site, but am wondering if anybody has any other suggestions for me while working on my 1984 GS550ES. Here goes my story.

At the end of last year my bike quite running one day when I was about a mile from home. I pushed it home and left it sit a few hours and it started again, but wasn?t running right. After a few minutes it died again with no spark. Anyway, it ended up being a bad signal generator coil. I ebayed a used one, checked the resistance measurements which checked good, installed it and my bike ran again with new plugs. However when driving it, it was hesitating under moderated loads. It would run WOT pretty good, idle good, and cruise pretty good, but hesitated and missed mostly in 5th and 6th gear when accelerating from 1/8 throttle. Then I noticed the airbox drain would drip about a half-dollar sized amount of fuel on the ground when I parked it on the side stand. After the initial drips there was nothing else if left over night on the ON or RES petcock position.

So I removed the BSW carbs to clean them and check things out. I also removed the new plugs and inspected them. The two LH side plugs (LH carb) had a slight black ring around the base whereas the two RH plugs (RH carb) were clean and looked good. Also, in the process I found out the airbox had warped and wasn?t sealing against the air filter anymore. The carbs had some contamination in them. I diassemmbled and cleaned the carbs with spray brake cleaner and blew out all the passages with compressed air. I did not remove the fuel screws because I have done that before on other GS?s and it was a pain. My idle quality is also good so I didn?t think they would be a problem. I did not soak the carbs because I didn?t want to disassemble the rack and have the crossover tube o-ring leak again (I replaced them a few years back). I checked the needle and seat seal, and the o-ring by hooking up a vacuum gauge to the fuel inlet barb and checking the leakdown with the needles just sitting in the seats with the bottom of the carbs up. The RH side had a small amount of leakdown ? about 2-3 inHG in a minute. If you put light pressure on the needle it didn?t leak at all. Other carbs where I found the needles would cause running problems usually leak down completely within seconds. The LH needle was good with no leakdown. These needles were new Suzuki parts about 5 years ago.

So I double check the float settings and adjusted the LH side a little so that they were both in the middle of the Clymer manual tolerance which I think was 20.5 mm without the gasket. I checked the slide diaphragms and reassembled the carbs. There was a little bit of varnish in the LH choke plunger orifice that I cleaned with brake cleaner and Yamaha carb cleaner as best I could. I checked function of the choke plungers both sides and they seemed to be fine. So back on the carbs went. I added foam to the airfilter so it sealed and away I went. I also checked the ignition system and coil connections and put dielectric grease on the terminals.

Well, my fuel mileage is down to about 38 MPG from the usual 42 MPG. Plus it still drips some fuel from the airbox drain only just after I shut it off. Sometimes a few drops, sometimes a three inch circle worth. Yesterday when I got home from work, I left the bike running on the center stand for about five minutes and no fuel dripped. I left it on the center stand for about 15 minutes and not one drop. I put it on the side stand and about 5 drops fell. I wonder if the fuel is blow-back from the carb or is it from to high of float level/leakage. It does run better after the carb cleaning, but it still misses during moderate acceleration mostly in 5th and 6th gear under load. I am trying to get through the information posted here, but there is a lot of stuff. Here is a list of things I have thought about, but haven?t done yet.

- I haven?t check compression or done a leakdown test yet.
- Need to check plugs again and see what they look like.
- I haven?t changed the intake o-rings.
- When I changed the needles, I think I reused the o-rings. However I was thinking my vacuum check would prove they were OK.
- The petcock does not let fuel run in the ON or RES position ? only the prime.
- No fuel drips from the petcock pulse line plug when the tank is on the bench and hoses are disconnected.
- I haven?t checked timing since the signal generator assy change because it isn?t easily adjustable, but I should probably do this.
- I haven?t tried to take a ?live? reading on fuel level, but I could probably do this fairly easily using the float bowl drain screw holes.
- I wonder if the LH side choke plunger isn?t sealing completely. Does anybody know if this is a common problem? What is the best way to test this? I might just switch the plungers from side to side and see what happens. Would this cause the carbs to spray back gas into the airbox??

It seems like it almost has to be a fuel level problems, but I don?t know what else to do since the needles didn?t leak down. The petcock and diaphragm seem to be good since it doesn?t leak with the hoses disconnect and the tank pretty full of fuel.

Anybody have any suggestions or see that I am missing something?

Thanks much,

Ryan Zahn

p.s. sorry for the typos........... :?

 

[GQROD]

Sounds like the petcock is the first problem to check before rebuilding the carbs again, granted tearing them down and going through every single orifice is the safe way to do it, and definetly check the float heights, with the petcock constantly throwing fuel there , there won't be any place for the fuel to get out except through the carbs and into the airbox, mine had a similiar problem but my pertcock is fine, my float heights were NOT within specs so i reset them. Hope this helps. ps o-rings are cheap insurance against future problems there is somone on this site which sells them inexpensively.

 

[Guest]

Yup, bad petcock is dumping fuel in your crankcase.

 

[strawboss]

Thanks for the info guys.

I don't think the petcock is bad because it doesn't leak fuel in the on or res position and there is no leakage past the vacuum line port. I didn't get a chance to look at it anymore this weekend. Hopefully I find some time in the next few days.

Later,

Ryan

 

[strawboss]

Update

Update

Hello All,

Just wanted to post update. So far I wired in relay to get good voltage to coils. I had a 2 to 2.5 volt drop from battery to coils. The voltage drop occured in the key switch. I wired the relay into the fuse block so that the coils, signals, and headlights all got good power. It helped with overall running and light quality. However I still have the fuel dripping from the airbox drain, but not as much. I have been trying to take live reading of the fuel levels in the bowls by draining them fuel into a cup and then using a Maximizer syringe to check the volume. Looks like the RH side has a higher level than the LH. Also, does anybody know where to get stock jet needles and needle jets. Looks like they have been discountinued from Suzuki. I have two needles with worn sections in the mid to upper part of the needle. The plating is gone and the bare aluminum is now showing. No major step wear or anything, but something I think should be replaced.

Got to run and get the Banshee running for a trip this weekend. Will post any updates when I figure this thing out..........

 

[MelodicMetalGod]

Also, does anybody know where to get stock jet needles and needle jets.

Me? I've got a set of "the weird carbs" that I could let go. Let me know if you're interested.

Best of luck!

 

[p_s]

I believe the airbox drain should be plugged as well. At least it is on my GS550ES and it makes sense to me that it should be.

 

[strawboss]

Jet Needles

Jet Needles

Hello All,

I am still tinkering with my bike trying to get it to run top notch. I drive it every day to work, but I still don't think it runs as good as it used to. Anyway, after closely examining the carb, I have one jet needle that is pretty worn in the upper section. The "gold" anodizing or coating is gone and the bare aluminum is showing underneath. This section is probably about 2-3 mm long. Another needle has a spot about the size of the end of a pen with similar wear. The other two needles look good. I would like to replace the two worn needles but you can't get them from Suzuki anymore.

I looked at Sudco's website and they don't list a 5C70 needle on their page. What are my options now? I could get a DynoJet kit, but don't feel like spending $125 for some brass. I can't find a chart that explains what a 5C70 needles is so that I could try to cross reference a similar needle that is current available. I am familiar with Keihin needles from Banshee tuning, but don't understand the Mikuni needles yet. I have a chart for 6 series needles that explains them, but nothing for 5 series needles.

The other day I lowered the needles about 0.027 with washers and it seems to run better. Before this change the bike had a sputter that would be very bad after a full throttle roll on while running 60 MPH in top gear (verified it is rich with choke operation and plug color). The tach is around 5k at 60, but can say for sure since the tach operation at cruise speed has been erratic for years. After I lowered the needles is seems to be better but still occurs at a higher RPM and throttle position. I am starting to think my mains are too rich, but they are stock as is the rest of the bike. I can see that the needles are worn in which I can justify changing needle height, but the mains should be good from factory calibration. I also examined the needle jets and they seem to look good with no major wear. You can see where the needle slides up and down in them with polishing, but no evidence of grooving or wear.

This brings up another question. I have a friend who has an old Honda three wheeler that used to foul plugs. He messed with it for a while, rebuilt carb, etc, etc. Never got it 100%. He ended up replacing the main jet with a stock size replace and wham, the thing runs like a million bucks. Is it possible for a brass main jet to wear over time?

Any help and/or thoughts are appreciated.

Later,

Ryan

 

[Calvin Blackmore]

all mechanical things are subject to wear.
yes the jet could get out of spec over time
or some previous owner used hard metal to probe its orifice and mucked it up.

 

[strawboss]

all mechanical things are subject to wear.
yes the jet could get out of spec over time
or some previous owner used hard metal to probe its orifice and mucked it up.

Yup Calvin - no doubt about mechanical things wearing over time, no way around it.

A main jet is not subject to any metal interfacing (like the needle jet) only fuel flow. I am just trying to understand that fuel flow would actually wear brass. I guess it is like water running down a river - erosion.

I don't think the main jets have been "molested" ever. I have owned the bike since 7k miles and have only had the carbs apart once (up until now) to replace needles and seats. Seems like the main jet should take longer than 33k miles to wear which is the current mileage on my bike.

 

[Calvin Blackmore]

assuming your neeldes are worn in the same place as mine are then it is possible that they caould bottom out on the mains.

do the needles have any wear on the tips or just at the point they enter the emulsion tube?

hell spend 20 bucks and put in new pilot and mains at least youw ill now what its not

 

[strawboss]

No wear at the tips, just up near the clip where they slide in and out of the emulsion tube for probably 90% of their life.

Yup, I think I should just get some new stock size replacement jets and make sure everything is at least to stock specs.

 

[strawboss]

Needles

Needles

Anybody know where to get replacment needles or the other information I requested my previous post?

 

[Guest]

Get a Dynojet kit.
Have you tried motorcyclecarbs.com? A bit pricey but they have alot!

 

[strawboss]

Found the problem

Found the problem

Hello All,

Good news and bad news. I finally figured out what is wrong with my GS. Learned a lesson too. Never forget the basics. I was on my way to checking the valve lash tonight when I decided to run a compression test:

Cylinder 1 = 62 psi
Cylinder 2 = 110 psi
Cylinder 3 = 130 psi
Cylinder 4 = 115 psi

Service manual says 115 is service limit. You can see it in the plugs too when you look at them. Cylinder 3 plug is the cleanest, but they are all carboned some. Bike still starts good and runs ok, until you try to accelerate at higher speeds in higher gears. It all makes sense. I believe the culperate was the leaking air filter seal due the airbox warping. I fixed it this spring, but it must have been too late. I haven't had the carbs off in years or change the filter in quite a while, so I am not sure how long it has been running this way.

Not sure what do with it now. Bike is still in good shape, but I am not sure I feel like sticking the time or money into it to freshen up the top end. Where do you stop and start? Pistons, valves, valve seats, etc. Might be time to put old blue to rest...............

Looks like you can get oversize OE pistons. About $100 with rings list. Haven't found aftermarket yet. Wiseco doesn't show anything in their catalog. Need to do some research, investigating, and thinking. :-k

Have a good night all,

Ryan

 

[ryonker]

Did you check the compression with a hot engine? And with the throttle wide open?

Service manual says to warm up engine to operating temps. Shut off, then do the compression check. Also, throttle should be held wide open.

A major cause of low numbers (other than the above) is also your valve clearances. When clearances are off, compression will drop.

Good Luck!

 

[strawboss]

Did you check the compression with a hot engine? And with the throttle wide open?

Service manual says to warm up engine to operating temps. Shut off, then do the compression check. Also, throttle should be held wide open.

A major cause of low numbers (other than the above) is also your valve clearances. When clearances are off, compression will drop.

Good Luck!

ryonker,

The engine was cold, but I did hold the throttle open. I checked the valve lash on cylinder one, to make sure it wasn't holding the valves open, and the valve lash was good. I can believe the engine being hot or cold could make a few pounds difference, but not the drastic amounts I am seeing on my engine. I think I may have some badly worn rings. The engine doesn't use any oil, but the compression ring must be worn.

Thanks for the info.

Ryan

 

[Guest]

Drop a little oil into the cylinder and see if the compression numbers rise.

 

[ryonker]

Where in Wisconsin do you live?

Rick

 

[strawboss]

Updaet

Updaet

Chef & Rick,

Sorry for the delay. Been working on my car a little - too many projects going on. After Saturday morning when I made my reply I started thinking about the WOT while doing the compression test. I started doubting myself about holding the throttle open when I played things back in my mind. I know that WOT is the usual procedure for a compression test, but I wasn't 100% sure I actually did - more focused on pressing the start button and not frying myself with spark plug voltage!!! So I proceded to adjust the valves since I had the valve cover off already. I found a couple a little tight around 0.002" and a few about 0.006". The weren't terriible, but I set them all between 0.003-0.005". I forgot what a tedious pain that is!! ;-)

After I reinstalled the head cover I re-did my compression test with my Mac compression gauge and the engine warmed up. I got 125 psi on 1, 2, and 3, and 130 on 4. I repeated the test a couple of times and got the close to the same readings. These are a little low according to the OE spec, but are above the 115 psi minimum in my Clymer.

So, thanks for the heads up and making me think about my procedure! The bike still ran the same this morning. It starts up and idles great. It cruises good, but doesn't like to take a lot of throttle while running higher speeds around 50-60 MPH (approx 5k RPM in 6th gear). Lowering the needles seemed to help, and if you don't crack it WOT you can get it to accelerate decent, but you have to modulate the throttle just right or you will feel a decrease and stumble when you twist too far. I think I should mark my throttle from closed to open in 1/4 throttle increments so I can determine if this is consistent or always happens a the same spot. I would think if it is always at 3/4 or more throttle, the bike needs a smaller main. However I know the 1 needles needs to be replaced for sure and one other needle is not too far from it. I changed a needle or two on Polaris quads and once they wear through the gold coating the machines just run fat at "normal" throttle positions -foul plugs and run like crap. So I guess I should get that DynoJet kit ordered since I can't find stock or other replacement needles. Plus I will get mains to play with.

While I was working on my bike I checked the resistance of the coils. Primary was 4 ohms on both and secondary was 34.5 and 34.7 ohms. I did the relay mod so the coils are getting a good strong 12+ voltage signal. Valves are set, intakes are good, intake o-rings are new (thanks Robert Barr!) I checked the plug caps and wires for arcing one night in the garage with the lights off - didn't see any. My plug caps are original yet, but they look OK. Suzuki is crazy at 14 bucks each for replacements. Anybody know the part number for replacement NGK caps?? Petcock is working properly. Float height is 1 mm higher than stock at 21.5 mm (fuel level lower). Diaphragms look good. No exhaust leaks. Air filter is clean and sealing properly (now). Not sure what else to do other than start jetting.

I should probably do a plug chop at WOT sometime. I need to get some new plugs so that I get a good reading. I just am hesitant to change stuff from stock since the bike is all stock yet: airbox, exhaust, air filter, etc.

Any advice is appreciated. This community is great and I am glad that I found it!!

Rick, I live outside of Lomira, WI which is south of Fond du Lac and North of Milwaukee just off Hwy 41.

Later,

Ryan