Hello, First Poster and a Question

[user11235813]

And finally, do you think increasing idle to offset the low charge

If you think you need to do that you have other problems. Fix them.

[karlhoffman_76]

And finally, do you think increasing idle to offset the low charge

If you think you need to do that you have other problems. Fix them.

Sorry, what other problems are you referring to?

[Watcher]

And finally, do you think increasing idle to offset the low charge

If you think you need to do that you have other problems. Fix them.

Sorry, what other problems are you referring to?

Probably a dying stator.

[sledge]

Needles and emulsion tubes:
When you pull the carb apart carefully examine the needles and the tubes they sit in. You are looking for flat spots in the metalwork and areas that look polished. Ideally you need  to use some sort of magnifier.

Spindle seals:
Found on the shafts the butterfly valve pivot on where they pass through the carb body.

Stator:
Only one way to get to it, drain the oil and pull the cover. Some insist gaskets can be successfully reused on the basis it worked for them, some say they are not intended to be reused and are one shot items that become unreliable if reused and should therefore be replaced every time. Being that I believe in doing the job right first time and having the piece of mind it brings I am sure you can guess my take on the subject. However it's your call and if you want to take the gamble 

Idle speed:
If you are happy to do this and call it a fix that's up to you. The only issue I can see is a potential to overheat if it's left stationary for long periods. Personally I think you need to do a bit more digging and identify and get to the root cause, if indeed there is one before making assumptions and throwing money at replacement parts that may not be at fault.

[karlhoffman_76]

And finally, do you think increasing idle to offset the low charge

If you think you need to do that you have other problems. Fix them.

Sorry, what other problems are you referring to?

Probably a dying stator.

Needles and emulsion tubes:
When you pull the carb apart carefully examine the needles and the tubes they sit in. You are looking for flat spots in the metalwork and areas that look polished. Ideally you need  to use some sort of magnifier.

Spindle seals:
Found on the shafts the butterfly valve pivot on where they pass through the carb body.

Stator:
Only one way to get to it, drain the oil and pull the cover. Some insist gaskets can be successfully reused just because it worked for them, some say they are not intended to be reused and are one shot items that become unreliable if reused and should therefore be replaced every time. Being that I believe in doing the job right first time and having the piece of mind it brings I am sure you can guess my take on the subject. However it's your call and if you want to take the gamble 

Idle speed:
If you are happy to do this and call it a fix that's up to you. The only issue I can see is a potential to overheat if it's left stationary for long periods. Personally I think you need to do a bit more digging and identify and get to the root cause, if indeed there is one before making assumptions and throwing money at replacement parts that may not be at fault.

Thanks for the input chaps.

I think I will do a stator inspection on my next oil change; if it's junk I'll replace it on the oil change after that.  If that still doesn't improve charging capacity I'll look at upgrading to a MOSFET reg/rec.  For now I'm happy to have idle set at 1500 RPM.

Will probably get a spare gasket for the LHS cover and replace if necessary, otherwise I'm happy to reuse gaskets if they appear to be in good condition.

Next time I take the float bowls apart to replace the valve seat o-rings I'll inspect the emulsion tubes for wear as you suggest sledge.

One other thing though; does replacing the spindle seals require separation of each carb?

[sledge]

Yes, and the butterfly needs to be removed from the shaft.

This guide explains the procedure, it's not the carb used on the gs5 but the method is the same. It also explains how to replace the choke plunger seal, which is another part that rarely if ever gets mentioned when discussing carb rebuilds in this forum.

https://litetek.co/Guide_MikuniBDST_Rebuild.html#ThrottleShaftSeals

[sledge]

Interesting.....there has been some supersedes but it seems some parts sites say the orings are interchangable between the gs5 and the dr350 and some dont.

[mr72]

If you set the idle speed too high by adjusting the throttle stop then you will invariably end up with so-called "hanging idle" and a chorus of posters on this forum may suggest it means the mixture is lean at idle, when it isn't. Then you'll be on the carousel of carb mistuning when the original cause is idle speed set too high which you did on purpose.

How often do you start the bike and just let it idle a long time anyway? So who really cares if it charges at idle? I'd be more concerned if it overheats the r/r at 5k cruising.

[Kookas]

The charging system on the GS isn't really adequate to charge the battery at idle, I thought. I don't see a proper charging voltage until at least 2000 rpm.

[mr72]

The charging system on the GS isn't really adequate to charge the battery at idle, I thought. I don't see a proper charging voltage until at least 2000 rpm.

That fits with my observation as well. However, once I got rid of the intermediate wiring between the reg/rect. and the stator, I was able to get close to 14V at idle. Then it melted down the wiring to the reg/rect.

So it's not just that the charging system is inadequate, it's that the reg/rect and wiring can't handle the charging current if the voltage is high enough. It's just totally underdesigned.

OTOH my MOSFET reg/rect makes 14.6V solid as a rock at every rpm I tested from about 900 to over 5K. Basically if the GS is able to run without stalling, it'll charge the battery. And it has 10AWG low-side wiring so it won't melt down with charge current, and given it's a MOSFET rather than diode-shunt it won't dump a ton of heat into the wiring anyway. It's still a pretty archaic and crummy design but at least it's not also woefully inadequate for the task.

[user11235813]

Well worth getting a new gasket for the stator cover, it usually gets pretty baked on. Careful putting the cover on as it will want to pull itself out of your hands and jump on which can jam the gasket into a bad position. You also might want to use a bit of hi temperature silicone sealant on the rubber grommet where the wires come out the top.

[karlhoffman_76]

If you set the idle speed too high by adjusting the throttle stop then you will invariably end up with so-called "hanging idle" and a chorus of posters on this forum may suggest it means the mixture is lean at idle, when it isn't. Then you'll be on the carousel of carb mistuning when the original cause is idle speed set too high which you did on purpose.

How often do you start the bike and just let it idle a long time anyway? So who really cares if it charges at idle? I'd be more concerned if it overheats the r/r at 5k cruising.

The idle doesn't hang; it drops straight down to 1500 or below and will only really reach 1500 after some hard riding.  Usually it will sit at around 1400 after a thorough warm up.  I've had the idle set like that for pretty much the last four months and I haven't had any issues, even in the blistering Aussie heat.  I think the GS500 is pretty efficient when it comes to cooling; it takes forever to warm up properly in my experience.

The charging system on the GS isn't really adequate to charge the battery at idle, I thought. I don't see a proper charging voltage until at least 2000 rpm.

I get ~13.5 VDC @1500 RPM; whilst not 14 VDC, this has been enough to keep my battery charged.

[karlhoffman_76]

How often do you start the bike and just let it idle a long time anyway? So who really cares if it charges at idle? I'd be more concerned if it overheats the r/r at 5k cruising.

I do a lot of city riding, living a few kms from the center of Sydney so yeah, I do spend a lot of time sitting at traffic lights.  It's annoying because it usually means I have to lightly throttle my bike to maintain charge when she's not warmed up.

[Kookas]

How often do you start the bike and just let it idle a long time anyway? So who really cares if it charges at idle? I'd be more concerned if it overheats the r/r at 5k cruising.

I do a lot of city riding, living a few kms from the center of Sydney so yeah, I do spend a lot of time sitting at traffic lights.  It's annoying because it usually means I have to lightly throttle my bike to maintain charge when she's not warmed up.

Repeated short journeys without long journeys every now and then would probably drain your battery, yeah. Also oil condensation. When I lived just 3 miles (5km) from work, my fix for both things was to add an extra 20 miles onto one of the commutes. Not such an issue in summer as I tended to go on weekend rides anyway, but over the winter it became more hassle (that said, I don't think you have much of a cold winter there, do you?).

[karlhoffman_76]

How often do you start the bike and just let it idle a long time anyway? So who really cares if it charges at idle? I'd be more concerned if it overheats the r/r at 5k cruising.

I do a lot of city riding, living a few kms from the center of Sydney so yeah, I do spend a lot of time sitting at traffic lights.  It's annoying because it usually means I have to lightly throttle my bike to maintain charge when she's not warmed up.

Repeated short journeys without long journeys every now and then would probably drain your battery, yeah. Also oil condensation. When I lived just 3 miles (5km) from work, my fix for both things was to add an extra 20 miles onto one of the commutes. Not such an issue in summer as I tended to go on weekend rides anyway, but over the winter it became more hassle (that said, I don't think you have much of a cold winter there, do you?).

Compared to the US and EU?  Nah, our winters are extremely tame; it doesn't get below zero very often.  Still, cold enough if that's what you're used to lol.

My commute to work is about 10kms, but I still do a fair bit of riding in the city as well; all good, I'm used to it by now I suppose.

[Kookas]

Still, cold enough if that's what you're used to lol.

Yeah, seen enough people from the likes of Florida talking about not riding the moment it dips below 20C!

[karlhoffman_76]

So tonight I decided to do a battery load test and also check the reg/rec output charge at the battery terminals with the headlight detached.

The load test with headlight on and waiting a minute for the battery to discharge from 12.8 to 12.5 VDC yielded 9.2 VDC, which is below the 9.6 VDC recommended.

The load test with headlight off and waiting a minute for the battery to discharge from 13 to 12.8 VDC yielded 10+ VDC. I'm gonna take this later reading to be more representative of the state of my battery as normally the headlight would be switched off on startup.

So the battery seems to be okay.

Checking charging output at the battery terminals; with headlight on, I'm getting a steady 12.8 VDC at 1300 RPM and 13 VDC at 1500 RPM.

With the headlight off I'm getting a whopping 14.5 VDC at 1300 RPM dropping to 14 VDC at 1500 RPM.

So it does seem that the headlight being always on has a significant effect on the charging circuit.

[mr72]

Sounds to me like the regulator rectifier is on its way out.

[sledge]

So tonight I decided to do a battery load test

The only way to load test a battery is with a load tester! Like this......

https://www.tooled-up.com/sealey-bt91-7-battery-drop-tester/prod/26755/

Until you are 100% certain the battery is serviceable and can accept or deliver a charge it's pointless looking at other components. Take it to an auto shop and they will have the kit to do it, often for free.

This is what the factory manual says. Not Clymer, not Haynes. The yellow one that Suzuki issue to the shops. Part no 99500 34060 018

Start the engine and keep it running at 5000rpm with lighting switch turned ON and dimmer switch on High.
Using a voltmeter measure the voltage between the battery terminals.
If the meter reads under 13.5v or over 15.5v, check the AC generator no-load performance and reg/rect.

It then says......
NOTE:
When making this test BE SURE the battery is fully charged.

Can you say with 100% certainty your battery is fully charged?..... How?

Only when you can determine a battery can accept and hold a full charge can you say it is likely to be fully charged and the way to do this is with a load tester.

When dealing with charging system faults you have to start with the battery. They are always the weak link and a faulty one can often give rise to symptoms that point to something else. Get it load tested, if it comes back as ok, look elsewhere for the problem. If it doesn't get a new one and run the tests again to ensure there are still no other faults.

Generally if the voltage across the battery is lower than specified its the generator at fault, above and it's the reg/rect but a duff battery can fudge the true figures. This is why it's absolutely vital to ensure it is servicable.

Adopt a methodical approach and follow the recognised procedures.........or you can keep guessing 

[sledge]

How are the lights behaving? Are they flickering, particularly at idle or going brighter as engine speed increases?

Is the battery getting warm, bubbling frothing overflowing, acid becoming white or the smell becoming noticable?

These conditions are symptomatic of a failing reg/rect.