News:

Registration Issues: email manjul.bose at gmail for support - seems there is a issue that we're still trying to fix

Main Menu

Engine lost power and cut out on motorway - Battery? Fuel?

Started by snuffy, August 10, 2019, 01:47:27 AM

Previous topic - Next topic

snuffy

Hi, looking for a bit of advice on the potential cause of this issue...

I ride to work and back two or three times/week, it's a 20 min 9 mile ride with over half of it on motorway/freeway at 70mph. I have not trickle charged the battery for about 3 months or so.

Yesterday whilst riding down the motorway I noticed the engine quickly start to lose power, the throttle response didn't do much. I pulled into the slow lane, changed down gears and still the throttle didn't do much so pulled onto the hard shoulder and then it cut out. I had half a tank of fuel, but wondered if it was fuel related, tried turning it over in reserve, nothing. Tried it in prime and after several attempts it started. I was then able to ride the additional 3 miles to work.

I tried starting it at lunch the same day and it started and ran ok for a minute or two, so turned it off and went back to lunch.

After work, it started fine, rode about half a mile down the road and it lost power and cut out again. I called for a recovery truck (3.5hrs later it arrived!), and in the meantime after about an hour I tried it again, it started, thought it was going to be ok, but after 30 secs of idling it started running badly and then stalled. By this time the battery was dead and wouldn't turn over.

It had been showering quite a bit throughout the day, but it's been sat in the rain before without a problem. I put dielectric grease on the plug lead connections 6 months ago after it wouldn't start after giving it a wash and it's been ok since. Not sure if related maybe.

I trickle charged it overnight last night and this morning it started fine, and left it idling for 5 minutes or so and it sounded normal. Not taken it out for a ride yet.

Do these symptoms suggest a battery issue? The fact that it's running ok this morning suggest it could be, yet there was enough juice in it yesterday to turn it over and make a number of starts, even after it had died on the motorway. I don't know enough about batteries and their function during actual riding to know. I took the live wire off the battery this morning whilst it was running to see what would happen and it idled along fine, but when I twisted the throttle nothing much happened apart from a backfire! so I guess the battery does have some function related to throttle/fuel somehow?

Anyway, most confused at this point. I'll check the battery voltage over the course of this week and see if it drops much.

Any ideas/advice?

Cheers.

Oscar_Muffin

First it's the inside lane, not the "slow" lane. Second did you try changing the fuel tap over to the prime position. I had similar symptoms where my bike would lose power and eventually stop. The Gs500 has two fuel taps, the one you can see is opened by vacuum in both the on and reserve positions however, it has a separate inlet for the prime position that doesn't require vacuum. If that works I would remove the tank and test the vacuum on the left carb. My exhaust timing was off which caused vacuum readings of about 75mm which isn't enough to operate the tap properly. Also check that the rubber caps on the test ports are in place, there's one on the top of each carb and one on the right of the right hand carb.

snuffy

Haha, yes I stand corrected, officially it is the inside lane :police:. On the M32 into Bristol however, it most defininitely is the slow lane. 2nd slowest motorway in England apparently.  ;)

Yes, I turned the petcock to Prime. I knew there was a vacuum that opens the other two settings so when it started back up again on the motorway I thought that was the problem. Turned it back to main tank setting when I got to work so the tank didn't drain onto the floor... I read that's what happens.

When attempting to ride home after work I put it back to Prime when it cut out, but that time it had no effect, still wouldn't start.

Since running it this morning for 5 minutes on main tank setting i guess the vacuum must be ok. Either way I'll lift the tank and have a look at where the vacuum attaches to the left carb. Haven't got a tool to measure vacuum (yet) so will research that. I think I've seen one used in a carb balancing video. I'll locate these three rubber caps on the test ports also.

The plugs also look a bit old and tired so I've just bought a new pair.

Thanks, will report back findings.

mr72

IMHO you have more than one issue. Battery shouldn't be dying like this unless you really crank and crank and crank for minutes on end. So that might indicate the battery is close to the end, but the nice thing is you can have that checked easily enough. However, low/dead battery is not going to cause the bike to cut out or die as you describe.

The charging and cutting out could be related but it would have to be something like a bad ground or bad positive battery connection that is common to the ignition and the charging system. However, if you had a weak connection then the bike would still run fine, it just wouldn't charge the battery. If you had an intermittent connection, then it wouldn't just weaken and then eventually die but it'd totally die immediately and then suddenly come back on. So I don't think that's likely your problem.

Vacuum leak or failing petcock could do this. If you have a fuel filter, it could also do this, so remove it. Clogged pilot jet could also do this. You can check the vacuum but as usual I just recommend taking a half a Saturday to clean the carbs and replace all of the o-rings as well as the pilot jets, reset the float height, idle mixture, idle speed, etc. just to make sure you don't have any carb problems going forward.

FWIW poor compression due to bad rings or bad valve seats could also do this. I'm sure that's not what you want to hear, but it's worth it to do a compression test just to rule it out.

sledge


Oscar_Muffin

You should get a balancing tool, I have a cheap set from eBay for £25. Apart from balancing it can reveal a variety of issues without having to tear the head down. Also, person above me, I thought the vent was underneath the tank? Or is that just an overflow?

sledge

Geeeezzzz........

"Vent in the FUEL CAP"

Is your fuel cap underneath the tank?

Oscar_Muffin

#7
Yes, I know the fuel cap is on the top of the tank. However, I was under the impression that the pipe underneath the tank was to vent the fumes instead of letting them out of the fuel cap. I think what you're calling a vent is what I know as a breather. Allows air into the tank to replace the displaced fuel and prevent a vacuum forming in the tank.


sledge

To the person above me!

The pipe you are talking about is not a vent for fumes, it's a drain for water/fuel that would otherwise become trapped around the filler neck.

There is a vent arrangement incorporated into the cap itself, if it becomes blocked it leads to the symptoms described above, high speed fuel starvation due to a partial vacuum forming in the tank. It's a  common problem with the GS5 along with a failing vacuum operated fuel tap which gives rise to similar issues. Both have been mentioned and discussed many many times in this forum over the years......try searching.

If you believe stripping the carbs/ head and suspecting compression/rings/vavles is the way forward carry on. My advice is to look at the simple things first.

mr72

totally could be tank vent. I never think to check that.

snuffy

Brilliant, thanks for the suggestions everyone. I'll check all these, and report back my findings.

snuffy

Further info tonight...

Opened the fuel filler cap and put my mouth over the little hole in the bottom of the cap. Could suck air through it, so it's not blocked. Was really hoping that was the issue!

Fully charged battery, voltages at different RPM:

Idle, 1200 RPM = 12.30 v
2000 RPM = 13.60 v
4000 RPM = 12.80 v
5000 RPM = 12.62 v

Normal? I'm not good at electrics  :cry:

Went for a ride this evening:

Petcock on the ON position. It cut out with the clutch in approaching a T-junction. Put on PRI position, started and rode to a safer spot. Put back on the ON position. Rode for a few mins and it stalled with the clutch in coming up to a junction again. Duck-walked to the side of the road. Still in ON, started at half choke, 2500 revs. Revs came down, more choke, came down more, full choke, went up to 4500 revs then came back down and stalled over 10 secs or so. Put on PRI, and started, back to no choke and rode for 5 minutes with coming to a stop and starting off again at junctions, roundabouts etc. No problem. Put to RES and rode for 5 mins, also no problem. I think it's the ON position that's the problem.

Does that make logical sense? Or should the ON and RES settings exhibit the same symptoms given that they're both vacuum operated? Maybe a blockage in the ON position fuel line? I have no fuel filter that I can see.

Also, new plugs seem to make it feel a bit more sprightly, so think it was time for new ones.

mr72

ON and RES/PRI each draw from a different place in the tank. Two hoses coming into the frame petcock from the tank, one is for ON (normal) and the other RES/PRI .. so this tells me your ON fuel hose may be leaking so air gets sucked in, collapsing, or is there a fuel filter there? If so, remove it. Anyway, could still be bad petcock or vacuum leak, worth checking.

Your voltages are low, FYI. But that's not super abnormal for the GS reg/rect stock. It eventually has a tendency to melt down the connector and lots of corrosion gets there and the reg/rect is just a piece of junk on these bikes anyway. Should really be over 13.4V from anywhere 2K rpm and up.

There are details on how to check the reg/rect/voltages and what numbers to expect here in the forums/wiki. Ditto that for the petcock testing.

snuffy

I'll check the ON hose then. No fuel filter that I can see, I did lift the tank slightly to have a look around. Will probably just replace the hose with a fresh length to be sure. I'll check the forum for correct size.

Vacuum leak... think I saw a video on that once... spray some kind of propellent on the outside of the carbs/air intake boot to see if the revs increase as the propellent is sucked into the engine from what I recall.

For just £16, for a new Reg/Rec, I think I'll get one if that's the case. https://www.ebay.co.uk/itm/Regulator-Rectifier-Voltage-Fits-Suzuki-GS500-2004-2011-GS500K-2001-2009-UK/133109176198?epid=2078034769&hash=item1efdecd786:g:tHIAAOSwa1NcyPqK

Cheers, more tinkering to do then. I'm forced to learn a lot with this bike, so that's a good thing!

mr72

Use water to check for vacuum leaks. Easy to damage the fragile rubber diaphragm in the carb with solvents. But imho just replace o rings and hoses and be done with it.

A new regular rectifier just like the original may not really be an improvement. Do the voltage checks and inspect all of the connectors for signs of overheating or corrosion. The part is probably not bad, but the wiring may be.

pandy

Snuffy, your symptoms are identical to those I had with my main commuter GS500. I became an expert at changing my petcock over at freeway/highway speeds. Mine was a fuel starvation issue, and you'll find a lot of info on this site about fuel starvation.I have to admit that i love the FI on my SV. Good luck with finding your problem!  :thumb:

pandy
'06 SV650s (1 past Gixxer; 3 past GS500s)
I get blamed for EVERYTHING around here!
:woohoo:

Amberdog22

My problem when i got a Gs was that in the rain it would cut out like that. It was the connection wires to the coils were all crapped up! Clipped the wires and replaced connectors and never did it again. Coils are in a perfect place to constantly get wet when raining!!


Sent from my iPhone using Tapatalk

snuffy

Thanks all... have made a list of some further things to test that you have suggested if the fuel hoses I replaced yesterday don't do the job. I suspect I will be troubleshooting further. I replaced the three hoses as they were pretty stiff to get off and had to cut into them to release them unfortunately. I updated the wiki with comments below the image here: http://wiki.gstwins.com/index.php?n=Maintenance.ReplaceFuelLines

I also filed off the petcock tab to give the extra reserve tank prime postition as suggested in another post I saw.


SMF spam blocked by CleanTalk