Thoughts - 1983 GS550E Stalls When Stopping

[MacGyver]

Still Stalls on Command (aggressive stop)

The bike was re-assembled last night, no missing parts, no extra parts. The bike started right up and ran as expected for a bench tuned carb set. I took it for a ride and it still will stall on an aggressive stop, even just pushing the bike forward while idling and yanking hard on the brake will kill the engine right away. As usual, it runs great at speed and the throttle response is noticeably better now.

I am hoping now that all the major variables have been addressed to the best of my ability, a proper balance and idle pilot screw adjustment may just cure this, but I am doubtful at this point. I hope to meet up with my friend who has a balancer rig this weekend if possible.

[MacGyver]

Eureka! I hope...

Last night I tried to balance the carburetors again after reading in the service manual that the recommended RPM for the procedure is 1750, not 1100 as I was aiming for previously. Before doing so, I pulled the plugs and noticed that 1 & 2 were carbon fouled - too rich - no surprise there. I know something is not quite right with carb #1. I get the engine balanced at 1750, but I am still hearing the odd pop from the exhaust, still to rich on carb #1.

Logic tells me that something is creating a rich mixture, hmmm...

OK, the starter plunger creates a rich mixture, let's check that again. Some previous owner had put silicone around the plunger cap. Let's check that and while were at it, swap the two and see if the problem moves from carb #1 to #2. There is a rubber sheath that covers the end of the cable as it goes into the cap. Initially I thought this was a heat shield to protect the cable from the engine. Currently the sheath slides and moves freely along the cable, but there are traces of some long ago dried out adhesive on the cable. While the proper assembly has been lost over the years, I decided to silicone this in position agains the cap and seal it to the cap. Once that was done and the engine restarted - Eureka! The engine was running completely different. My balance was completely off now and my homemade manometer (yardstick, tubing, stick-tack, and ATF) fluid got sucked out towards carb #1 faster than I could adjust or kill the engine.

Oh well, the sunlight is fading so I'll balance roughly and try again tomorrow when the fluid has reset itself. Now I suspect that the rubber sheath on the plunger cable should be held under the seal that is on the top of the plastic plunger cap. We will see how my silicone seal repair works for now, but I think replacement caps are in order, should be less than $10 each.

This is testimony to the others that have gone before me and proclaimed - Eliminate Air Leaks! Unfortunately for us BSW30SS twinned carburetor owners, most of those red flags are aimed at the intake boots as the rest of the carb banks out there use a very different starter/choke system that would not be subject to air leaks.

A final note before I get back to work, after this starter/choke cable swap and sealing, carburetor #1 now started responding to pilot screw adjustments and seemed happiest somewhere around the 2-2.5 turns out range, just like carburetor #2. I hope my next post will be a happy problem solved post. Thanks again to all those who helped me get this far.

[Calvin Blackmore]

Last night I tried to balance the carburetors again after reading in the service manual that the recommended RPM for the procedure is 1750, not 1100 as I was aiming for previously. Before doing so, I pulled the plugs and noticed that 1 & 2 were carbon fouled - too rich - no surprise there. I know something is not quite right with carb #1. I get the engine balanced at 1750, but I am still hearing the odd pop from the exhaust, still to rich on carb #1.

Logic tells me that something is creating a rich mixture, hmmm...

OK, the starter plunger creates a rich mixture, let's check that again. Some previous owner had put silicone around the plunger cap. Let's check that and while were at it, swap the two and see if the problem moves from carb #1 to #2. There is a rubber sheath that covers the end of the cable as it goes into the cap. Initially I thought this was a heat shield to protect the cable from the engine. Currently the sheath slides and moves freely along the cable, but there are traces of some long ago dried out adhesive on the cable. While the proper assembly has been lost over the years, I decided to silicone this in position agains the cap and seal it to the cap. Once that was done and the engine restarted - Eureka! The engine was running completely different. My balance was completely off now and my homemade manometer (yardstick, tubing, stick-tack, and ATF) fluid got sucked out towards carb #1 faster than I could adjust or kill the engine.

Oh well, the sunlight is fading so I'll balance roughly and try again tomorrow when the fluid has reset itself. Now I suspect that the rubber sheath on the plunger cable should be held under the seal that is on the top of the plastic plunger cap. We will see how my silicone seal repair works for now, but I think replacement caps are in order, should be less than $10 each.

This is testimony to the others that have gone before me and proclaimed - Eliminate Air Leaks! Unfortunately for us BSW30SS twinned carburetor owners, most of those red flags are aimed at the intake boots as the rest of the carb banks out there use a very different starter/choke system that would not be subject to air leaks.

A final note before I get back to work, after this starter/choke cable swap and sealing, carburetor #1 now started responding to pilot screw adjustments and seemed happiest somewhere around the 2-2.5 turns out range, just like carburetor #2. I hope my next post will be a happy problem solved post. Thanks again to all those who helped me get this far.

Fromwhat I see those tiny tubes are there toprotect the cable formt he heat of the engine....

I had a great deal of trouble with the "choke" unitl i removed and fully liubricated the cable....

provided the plungeers fully seat there should be no air leak but if the plungers are not evenly seating as might occur with one sides cable sticking......then gosh your totally unbalanced.

your tenacity is quite astounding its good to see folks go as far as you have.

[twiggy2cents]

wow i need to try this, i am always rich on 1 and 2. i am going nuts over it, i even put a diff set of carbs on it!

[MacGyver]

Starter Air Leak? No. Plunger Stuck? Yes.

I was back at it again last night and got things balanced, again. I started playing with the idle mixture screws and low and behold carburetor #2 was now not responding to any input. I pulled apart the starter/choke plungers and this time removed the plungers from the cable and dropped them into the carbs. One dropped into place smoothly and the other stuck half way down carb #2. I swapped them and the good one still dropped into place no problem, the bad one would drop into place on carb #1, but only in a certain rotated position. Anything else and it would stick.

New plunger, caps, and holders are being ordered. In the mean time, I'll leave the bad plunger off the cable and in running position in the carb. I'll start the bike with just one carb 'choked' for the time being.

I ran out of time to test and balance this temporary setup. We will see on Thursday how things work out.

[Calvin Blackmore]

I was back at it again last night and got things balanced, again. I started playing with the idle mixture screws and low and behold carburetor #2 was now not responding to any input. I pulled apart the starter/choke plungers and this time removed the plungers from the cable and dropped them into the carbs. One dropped into place smoothly and the other stuck half way down carb #2. I swapped them and the good one still dropped into place no problem, the bad one would drop into place on carb #1, but only in a certain rotated position. Anything else and it would stick.

New plunger, caps, and holders are being ordered. In the mean time, I'll leave the bad plunger off the cable and in running position in the carb. I'll start the bike with just one carb 'choked' for the time being.

I ran out of time to test and balance this temporary setup. We will see on Thursday how things work out.

Does the brass have nasty striations cut into it?
I polishedmine with brasso and they moved very niucely in the bores

springs would alos need to be in good shape..

[MacGyver]

I have ordered some new plungers, caps, and plugs, but in the meantime I'll try your suggestion. No, there isn't any obvious mark on the plunger but since this was the one part I didn't dip when I did my rebuild, perhaps there is some thin layer of varnish hiding. I'll get some brass polish and give it a try.

[MacGyver]

Fixed It! Woohoo!

Finally got it! I disconnected plunger #1 from the cable and pressed it into the seat. #2 was left connected as normal so starting the bike when cold is not as smooth as it should be, but that is a small price to pay. I was able to balance the carburetors properly and the idle is now nice and smooth. The quick test of pushing the bike will idling and hitting the front brake hard failed to stall it. That put a smile on my face. I quickly got my gear on and went for a test ride. I pulled out of the back alley and stopped hard in front of the girlfriend who was unloading some stuff from the car. The engine kept running! There were smiles on both of our faces now.

The engine did stall a couple of times on the ride, but not during braking or at stops. When slowing down to make a turn, as in clutch in and closing the throttle quickly produced a stall a couple of times. That is a minor inconvenience compared to the engine dying any time one brakes hard.

I am awaiting PartShark.com to process my order for caps, holders and plungers. I'll likely pick up some brass polish and see what I can do in the mean time with the existing plunger.

Now on to building up the girlfriends experience and confidence so we can enjoy some serious ride time together.

Thanks yet again for all the help and I hope this guides someone else in the right direction.

[MelodicMetalGod]

Finally got it! I disconnected plunger #1 from the cable and pressed it into the seat. #2 was left connected as normal so starting the bike when cold is not as smooth as it should be, but that is a small price to pay. I was able to balance the carburetors properly and the idle is now nice and smooth. The quick test of pushing the bike will idling and hitting the front brake hard failed to stall it. That put a smile on my face. I quickly got my gear on and went for a test ride. I pulled out of the back alley and stopped hard in front of the girlfriend who was unloading some stuff from the car. The engine kept running! There were smiles on both of our faces now.

The engine did stall a couple of times on the ride, but not during braking or at stops. When slowing down to make a turn, as in clutch in and closing the throttle quickly produced a stall a couple of times. That is a minor inconvenience compared to the engine dying any time one brakes hard.

I am awaiting PartShark.com to process my order for caps, holders and plungers. I'll likely pick up some brass polish and see what I can do in the mean time with the existing plunger.

Now on to building up the girlfriends experience and confidence so we can enjoy some serious ride time together.

Thanks yet again for all the help and I hope this guides someone else in the right direction.

Wow...congrats!!!!

I've been watching your ordeal b/c I've been very interested in the what the cause might be. However, it sounds to me as if you're saying the cause was a choke plunger that wasn't closing/stuck open. If that's correct, I'm not understanding how that relates to braking as the trigger for the stalling...? Unless it's simply the idea that under hard braking you're also simultaneously snapping the throttle closed and that's what's actually causing the stall due to the choke still being open.

Does that sound about right?

[MacGyver]

Hi Melodic,

I can't say exactly what was happening as I am no educated expert. My hypothesis is that the starter plunger being stuck out about 1/8-1/4" was causing a rich mixture imbalance and creating a somewhat instable idle. The stalling during a sharp decrease in forward momentum (aka braking), was likely due to the design of these carburetors having the starter jet located at the front of the floats and the sloshing forward of gas during braking flooded the engine with gas and caused the stall. That's my story and I am sticking to it.

We have been busy since I completed the tune up and the girlfriend hasn't had a chance to ride the GS yet. I can't wait to see her smile when she starts enjoying the ride rather than struggling with it.

[MacGyver]

Follow Up...

Well it has been almost two months since my last update. I am happy to say that the GS is running very well now. It will still stall the odd time if you clutch in and let off on the throttle quickly when cruising above around 5k rpm. That is a minor inconvenience and has been reported by other owners so perhaps it is a quirk of this vintage. A little throttle or leaving the clutch out seems to take care of that inconvenience.

I picked up a ColorTune kit and tuned the idle mixture preset screws. One carb liked both screws around 2.75 turns out and the other was closer to 3.5 turns out. The bike idles great now around 1100-1200 rpm. Cold starts are immediate and effortless with the choke on just past the horn button (about 3/4), warm starts usually need a bit of throttle. The set up is all stock (except for possibly the idle air jets - specs say 35 but these are 40) and it always ran fine with any throttle. Now at idle the plugs are looking good as well. I have confirmed that the stalling behaviour we observed before was directly related to the starter plunger. With the choke on, arresting any forward movement with the brakes will stall the engine. Initial culprit found, many more dealt with!

The compression on #2 after the valve adjustment is now up around 120 psi, matching 1 & 4. Cylinder #3 does seem a bit low, but I'll likely check it after riding another 1000 km or so as it may just have been a bad read.

The girlfriend commented that the bike is much more responsive now. Before all the work, twists of the throttle were a bit sluggish to respond. Now the GS has a spirited nature in line with my fuel injected V-Strom. The unfortunate part is now that the bike is ready, the girlfriends confidence and desire is not. In the end it is her fear of the environment that may cause her to remain a passenger, not a driver.

Thanks yet again to all who offered advice along the way. I have learnt so much and the carburetor is no longer a mysterious black (silver?) box to me. I have also discovered how much fun a light, spirited, little GS550E can be compared to my dual-sport and adventure-tourer mainstays. Perhaps this GS will find a permanent home in our stable, or as planned, it will go on to another rider in Spring, time will tell.

[MelodicMetalGod]

Congrats on gettin' it sorted and ride-able!

Obviously, something is still off if simply braking with the clutch in and the throttle off (that's how I do it EVERY time ) causes a stall now and then, even with the choke on.

Best of luck and enjoy the ride!

[Calvin Blackmore]

Congrats on gettin' it sorted and ride-able!

Obviously, something is still off if simply braking with the clutch in and the throttle off (that's how I do it EVERY time ) causes a stall now and then, even with the choke on.

Best of luck and enjoy the ride!

OMG engine braking?
ewww
I always keep my revs up clutch in
prolly doin it wrong though



the whole process that you went through was wonderfully presented to us all and demythed the siamesed carbs for all.

I am getting a new OEM seals for my forks if Bikebandit pulls it together after two delays and would like to be able to express in pictures for the rebuild what you have achieved in words for your carb problem.

Oh and I will give you 50 thats right 50 Canbadain dollars to the girl with the....no wait for the bike........mebbe 60 if my pogey comes in soon.