2006 GS500F - Starting/Choke/Idling problem - PROBLEM SOLVED !!!

[bval]

Final Solution:

Well, I guess it's confessional time and time to give the prize to  . . . . Ben2go!

The confessional part is that I didn't really understand what "little o-rings" Ben2go was referring to. There are several in a carb, on the needle holder and the pilot screws, plus the ones between the carb body and diaphram cover, which Ben2go was referring to. However, these o-rings magically disappeared before I even knew they were there, so I thought the ones I saw on the needle holder were the ones he was referring to. They must have stuck to the cover and fell off before I saw them, so I didn't even know they were there.

Kudos to all those who kept thinking vacuum leak, because that's really what was happening with those O-rings missing. When the carbs were cold, the metal would have contracted leaving a gap at that spot. When the carbs were warmer, the metal would expand and the gap would become smaller and affect the problem less.

I finally discovered it when considering raising the needles a bit, even though I was still convinced it was a vacuum leak but couldn't find the leak. I noticed the recess where the o-rings go and started to wonder what they were for. When I pulled up the online fiche, it was staring me in the face - number 40 - an o-ring that lined up exactly with that spot. Not having any o-rings small enough on hand, I improvised by cutting two small rings off the end of an alligator clip insulator that fit exactly. When I installed them, Presto Mondo! The bike fired right up, stayed about 1500 rpm for about 3 seconds, then shot up to 4000 rpm as it always did. When I backed off the choke lever, the revs dropped to about 2000 rpm and held steady.

Thanks guys . . . as always you've been a great help and I should have asked for clarification on the o-rings you were referring to Ben2go.

Cheers -  - Bval



I've been reading a number of posts lately relating to starting problems with GS500F's that seem to be related to carburation. I have a problem I've not been able to fix for weeks and it seems to be getting worse.

Here are the symptoms:

Choke doesn't work well. It tries to fire once, then I can try all ll I like, it won't fire. I have to bump start it every morning now and once started, it won't rev up to 4000rpm unless I rev the engine about a half a dozen times. Even then it only sits at about 3000rpm and won't go higher. When I try to adjust the choke down at all after a short time, it slows right down to 1000 - 900rpm and can easily die unless I rev it again and try to adjust the choke higher. Once I get it to a point where it will keep running (about 2 minutes), I can't take the choke off for about 10 minutes of riding or it will die once I stop for a stoplight or something. After 10 minutes, it still takes a long time (another 10 minutes) to reach the point where it will rev at 1200 - 1300 rpm which is where the idle speed screw is set to.

Once fully warmed up, it seems to run okay, (but I'm guessing it could be running better yet). Sometimes I notice a faint fuel smell when I stop the bike, but no obvious leakage. Float height seems okay using the "tube" method to check it, but it could be a bit on the high side (slightly above the gasket). I wonder how all of a sudden that might happen when there is no dirt in the carbs to cause needle seat problems. Both carbs are the same height when I check them and I can't imagine the metal tab would bend.

Stuff I've done:

I've been though pretty much everything I can think of. Even had the carbs off, twice now. Nothing appears to be out of whack and I can back-blow air through the fuel and air passages. Can't find any vacuum leaks. Hose connections all match those in the service manual. Choke starter plunger and cable seem to be working as they should. Vacuum canister, PAIR vavle, selenoid and one-way valve all okay. Saw some posts about a plugged carb (bowl) vent hose, but mine seems clear. I can draw air through it no problem whether the tank is on or off, so I don't think it's being pinched either. Valves are about mid-range on specs. (a skosh under .002 inches - easy to move bucket - estimate it's about .040 -.045 mm) If there was a vent problem on the tank, I'd expect that there would be a problem under full throttle too, unless it's only affecting the start/low speed. However, why would it not do the same thing with the bike warmed up?

If this sounds familiar to anyone, I'd really appreciate some help. I have a K&N filter (not installed yet) and a carb re-jet kit on the way. I'm hoping in the process of re-jetting I might resolve the problem. When I rejet, I'm planning on completely and carefully cleaning all the stages of the carb just to be sure. I think it would be better to fix the problem before making rejet changes.

[ben2go]

It does sound a little like a vacuum leak.The carbs could be out of balance.Have you checked the intake boots?Fouled plugs can do some crazy things.Are they producing a bright blue spark?Have you disassembled the petcocks and checked them?The one in the tank has a screen that could be blocked.The frame mounted one could have a bad vacuum diaphram.That could cause an internal vacuum leak and suck excess fuel into the engine.Use this to check your plugs. http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html When you took the tops off the carbs(black plastic lids) did you put the little tiny O-rings back in?That can cause the diaphrams to act crazy.

[bval]

Well, guess there were a few other things I've done that I forgot to mention: 

- carb balance is spot on - (I suspect this would also affect running throughout acceleration, but mid to high seems fine)
- bike's only got 26,000km on it, but I've inspected the boots anyway they look like new
- I sprayed WD-40 all over the carb while the bike was running (to check for vacuum probs), no effect
- found a couple questionable vacuum connections and secured those, no effect
- plugs are new - when recently removed they did show minor signs of lean mixture, but nothing dramatic - bike also runs fine when warm,  no misfiring
- inside of tank looks like the inside of an autoclave - spotless and so is the filter
- fuel flow from all petcocks is heathy and starting/running bike on Prime has no effect, so I'm not thinking petcock diaphram probs-
- it's been quite a while since I had the tops off the carbs, so I can't recall the little orange O-rings you're referring to, so when I do the rejet, I'll definitely pay attention to that, but there were no "spare parts" left over..lol
- both the regular paper air filter and K&N (with stock jet reducing adapter) have excellent air flow and changing them around has no effect

Here are a few more tidbits:

Bike is usually stored in a semi-heated garage, but lately has been under cover outside at about 36-40 degree F temps. I did notice starting/idling problems before I started leaving it outside overnight, but it's definitely been getting worse. I've got it back indoors tonight to see if it makes any difference to starting in the morning. When I start it at the end of my work day after being in a semi-heated underground garage for 8 hours, it starts fine, but still has the idling problem.

I've been all over the vacuum hose system, boots, diaphram covers, etc., and can't find anything that seems to be leaking vacuum.

I'm really starting to suspect a clog in the "Slow System" and/or the "Starter System" (as they're described in service manual) I've checked them but not meticulously. As I said, air seems to be able to be blown backwards through the key passages that lead to the throttle body. Given that it fires when bump started, my theory is that just enough air and gas are sucked in to the engine by virtue of the engine being forced over at higher revs than a starter can provide. Once it kicks in, it's drawing some fuel, but not enough to get the revs up to 4000rpm or idle very well. Once it starts warming up, fuel can evaporate more easily, and if there is a clog, more fuel or air may be getting by the clog as the metal expands. Given that I'm only 5 days from rejetting, I think I'll wait until the kit comes before I pull it all apart again, but I'll be meticulous in making sure all air and fuel passages are clear, particularly in the slow/starting systems.

[bval]

Well . . . temperature is definitely a factor.

Last night I kept the bike in the partially-heated garage and it started right away this morning. Temperature in the garage was about 65 F. But, still experiencing poor idling conditions after startup. When using the choke, the idle is not smooth and doesn't jump up to 4000rpm quickly as it used to. Still sits about 3000rpm and creeps up to about 3800rpm and no higher. When I knock it back after a minute or so, it has a difficult time maintaining a steady idle and wanders a lot. With the choke still partially on while riding and coming to a stop, it drops to about 900rpm and tries to stall.

It does warm up faster (probably because it started out warmer), but as it's only about 40deg F out, the temperature never seems to reach full unless I'm in stop and go traffic. That's the only time it idles properly. By the way, I'm using AMSoil Synthetic 10w40.

Still seems to point to problems with the Start/Slow Systems in the carb to me. I'm sure it's quite lean from the factory as well, but hopefully a rejet will take care of that.

[510]

I noticed the same thing with my '05. At night, if it gets below 45 degrees, starting in the morning tends to be a bit difficult. During the summer, when it doesn't drop below 60, starting is almost instant.

Since you seem really on top of the maintenance, and there's nothing wrong with the carbs or leaky hoses, I wouldn't worry too much about it. Like all carbureated and air-cooled bikes, the GS tends to be kinda cold blooded, and in cold weather, getting it to even start can be annoying. Getting it to proper idle temperature might take a while too, since the entire engine block, which has cooled down to the ambient temperature, acts like a heatsink.

[bval]

Thanks for the feedback on your experiences with your '05. I think you make some good points. I was starting to come to similar conclusions by trial and error, so seeing your comments helps confirm it.

I'm doing the rejet anyway because I have a K&N drop-in filter and I'd like to get a little more kick out the bike if I can. Most experienced guys I talk to suggest a rejet even on a stock configuration just because it's usually quite lean from the factory, which doesn't help.

I'm getting rid of the stuff that's preventing me from keeping the bike in the garage in this weather, so at least starting shouldn't be a problem anymore. Hopefully with the rejet it will richen things up a bit and might improve the whole choke and warmup situation as well as the response. Making sure the carbs are really clean and ensuring all passages are clear should help too.

[GS500F-K8]

.

[bval]

Solution: Dynojet rejet kit

Well, I installed my Dynojet rejet kit and everything seems to be running fine now. Bike starts fine, idles fine and runs fine. I'm using a drop-in K&N filter with stock exhaust. The jet kit was easy to install and I didn't need to do any fiddling other than tweaking the mixture screws a bit. Even got rid of a flat spot around 6000 - 7000 rpm.

The only thing I noticed that was odd was a slight black coating on the tip of one of the mixture screws that looked a bit like oil from the crankcase vent pipe. It wiped off easily and did not seem to be causing a blockage.

I think the real problem is that these bikes are tweaked very lean from the factory and it doesn't take much to throw it off.

[bucks1605]

Solution: Dynojet rejet kit

Well, I installed my Dynojet rejet kit and everything seems to be running fine now. Bike starts fine, idles fine and runs fine. I'm using a drop-in K&N filter with stock exhaust. The jet kit was easy to install and I didn't need to do any fiddling other than tweaking the mixture screws a bit. Even got rid of a flat spot around 6000 - 7000 rpm.

The only thing I noticed that was odd was a slight black coating on the tip of one of the mixture screws that looked a bit like oil from the crankcase vent pipe. It wiped off easily and did not seem to be causing a blockage.

I think the real problem is that these bikes are tweaked very lean from the factory and it doesn't take much to throw it off.

It's good to hear at least someone got their DJ kit to work properly. I've yet to achieve that with mine, it's close, but not perfect.

[bval]

It's running fine in relation to how badly it was running before, but I may find it still needs some tweaking as I get used to it. I'm thinking it may still be a little slow on draw when rolling on the throttle, but it does accelerate nicely throughout the range.

What's your setup for filter and exhaust?

[bucks1605]

I'm running the K&N lunchbox and a full yoshimura system

[bval]

Well, as luck would have it, (bad luck that is) my problem going away was only temporary. It worked fine for a couple of days after the carbs were pulled and replaced with the DJ kit, then has been progressively getting worse to the point where it's not starting again and more than once a day. It used to just happen in the morning.

It bump starts fine, sometimes backfires when trying to use the starter (which is usually an indication of lean condition) and sometimes will start if I pump the choke lever and wait a bit. Given that the DJ kit does not affect the starting or idle circuits, I'm suspecting that something in the starting circuit of the carb is causing the problem. Probably something partially blocking the fuel and/or air passages from the starter jet in the carb.

I'll do one more check on the vacuum side of things, then the carbs will have to come back out.

[beRto]

It does sound a little like a vacuum leak.The carbs could be out of balance.Have you checked the intake boots?Fouled plugs can do some crazy things.Are they producing a bright blue spark?Have you disassembled the petcocks and checked them?The one in the tank has a screen that could be blocked.The frame mounted one could have a bad vacuum diaphram.That could cause an internal vacuum leak and suck excess fuel into the engine.Use this to check your plugs. http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html When you took the tops off the carbs(black plastic lids) did you put the little tiny O-rings back in?That can cause the diaphrams to act crazy.

... back to the drawing board then 

[CndnMax]

let me ask you one question, was it slowly turning over and not catching or was the started cutting out? because today i tried to start the bike after work and it wold turn over for a sec then the started would just stop and do nothing even with the buttton pressed- seems kinda odd.

[qwertydude]

I've found that during the cold months that setting your idle to about 1500 definitely helps it keep running smoothly. I don't mind the slightly higher idle if during warmup my bike pops less and is smoother.

[bval]

Reply to CndnMax . . . starter seems to have no problem. It turns the engine no problem, but if the engine catches with the choke fully on I have to rev it to keep it idling, otherwise it will slowly drop idle speed until it stalls. After about 60 seconds, it will hold an idle, but I have to keep revving it to keep it from stalling.

Reply to qwertydude . . . whether I set the idle to 1500 or not, it will do the same as above when it first starts, it won't hold an idle and just fizzles out unless I keep revving the engine.

Seems to me that either it's not getting enough fuel through the enricheners or too much fuel. If it's the former, it could be due to a vacuum leak, but I haven't been able to find one. Had the carbs off again this weekend and readjusted the float levels back to what they were when the bike was new, plus checked all the starter circuit passages and they are all clear. The vent pipe for the carb bowls is not plugged. Plugs looked a bit sooty, so that indicates a rich condition. I readjusted the mixture screws and it's running nice when warm, but still has the same idle problem with the choke on. Again, this seems to me to point to the carb enrichener circuit.

[bval]

Final Solution:

Well, I guess it's confessional time and time to give the prize to  . . . . Ben2go!

The confessional part is that I didn't really understand what "little o-rings" Ben2go was referring to. There are several in a carb, on the needle holder and the pilot screws, plus the ones between the carb body and diaphram cover, which Ben2go was referring to. However, these o-rings magically disappeared before I even knew they were there, so I thought the ones I saw on the needle holder were the ones he was referring to. They must have stuck to the cover and fell off before I saw them, so I didn't even know they were there.

Kudos to all those who kept thinking vacuum leak, because that's really what was happening with those O-rings missing. When the carbs were cold, the metal would have contracted leaving a gap at that spot. When the carbs were warmer, the metal would expand and the gap would become smaller and affect the problem less.

I finally discovered it when considering raising the needles a bit, even though I was still convinced it was a vacuum leak but couldn't find the leak. I noticed the recess where the o-rings go and started to wonder what they were for. When I pulled up the online fiche, it was staring me in the face - number 40 - an o-ring that lined up exactly with that spot. Not having any o-rings small enough on hand, I improvised by cutting two small rings off the end of an alligator clip insulator that fit exactly. When I installed them, Presto Mondo! The bike fired right up, stayed about 1500 rpm for about 3 seconds, then shot up to 4000 rpm as it always did. When I backed off the choke lever, the revs dropped to about 2000 rpm and held steady.

Thanks guys . . . as always you've been a great help and I should have asked for clarification on the o-rings you were referring to Ben2go.

Cheers -  - Bval

[beRto]

Congrats! 

Isn't it satisfying to finally have it solved? I find doing my own work to be much more rewarding that bringing it to a dealer (although I often forget this while I am actually doing the work).

[bval]

Thanks. I guess I'm a "fixer" by nature, so problem solving is kind of in my blood and I tend to be far more persistant than some of those around me (read, wife) would like me to be.  I like doing my own work and I don't trust the dealerships, but the learning curve is steeper than I thought for what at first seemed like a simple machine. Bikes definitely have their own set of challenges, but I'm getting there. I have to say though, the GS500 is a great first bike to learn motorcycle mechanical on as well as learing to ride on. I feel it's really important to know your bike inside and out if you're going to use it for touring. So despite the fact I passed over a couple of simple "newbie" things that sent me off on wild goose chases, I have no regrets because in the process I've really come to know this bike fairly well; particularly with the help of this most excellent site and all the members who are so generous with their knowledge and experience. Nice to be part of the GSTwins family. 

[barnunn]

This thread is a little old now but I thought i'd throw this in. I read in another page that a guy figured out how to advance the timing using the stock parts. he said it takes away a  lot of the cold blooded problems and the bike runs a lot better. I had a toyota 4 runner like this. I'd have to set the timing to specs to pass emissions inspection and then advance it 5 degrees when I got home. that minor change in timing made a noticeable difference. I think the timing is set to keep the bike running lean for emmisions reasons but that does not mean it is set to where the bike runs at it's best.