Hey guys couple of things happening with the bike that I would like to resolve

1 -I always have to use the choke when starting even with outside temps being 30 degree's Celsius, if I don't the revs are too low and it stalls, after riding for a few mins the revs are higher and it keeps running without choke but the idles is just under 1k, after about 10-15 mins the idle is about 1400 and then idles find

2-The engine loses power when under heavy acceleration so if I'm accelerating onto the motor way you feel it bog down and lose all power, if you only do light acceleration though it will accelerate fine.


I'm assuming that these 2 issues are caused by the same things, it's a 2004 model, neither of these things use to happen, carbs etc are all stock so have not been changed. Bike has 108k km's on the clock.

Cheers

I'd check tank fuel filter and spark plugs. That's what what fixed mine with the same symptoms.

Choke is needed for every start that's not warm-hot. Touch the outer cases. If its not warm, use choke.
I actually tune the carbs to the point where its slightly lean at idle. If you set it rich at idle, hot and warm starts will be much harder. So 30c makes very little difference, you should be over 70-75c at the crank case to let you start without choke. Hope we dont ever see 75c ambient - like ever.
Cool.
Buddha.

Needing the choke to start is normal with stock jetting.

Issue 2 could be many things. Pinched fuel line, dirty carb, clogged air filter, bad gas, maybe even loose headers. Has the bike been sitting at all or is it ridden regularly l?

108,000 I'm is 67,000 miles which is a a good bit of miles. Has the bike ever had a top end rebuild? You might have low compression

also check valve clearance

Spark plugs are good, once the bike warms up runs fine, air filter got replaced at last service has been doing these before and after that.
Bike is ridden almost everyday it's my to work and back commuter so ridden about 30km per day.
Never had a top end rebuild, I check the valve clearances each service only ever had to replace 1 or 2 shims otherwise always in spec

It's probably been like this the last 20k km's just never gotten to resolving it as it hasn't stopped me from riding

wow the oil cooler in the 2004 F models must be doing the job to maintain valve clearances

Quote from: HPP8140 on September 21, 2022, 03:42:56 PM
wow the oil cooler in the 2004 F models must be doing the job to maintain valve clearances

More like his riding style, environment and possibly the oil he uses. The little devil in me also thinks the cam wear = valve seat wear and those 2 compensate for each other almost perfectly but then again who knows, no one mics the cam, and in any case, unless there is a serious manufacturing defect they should all cover for each other. Cams are soft (Parkerized) but bathed in oil, valves and seats are hardened but sit in a burning chamber dry, so effectively they should about wear equally.
Like I said - who knows. Maybe it is the magic of the beer in his country that its only 1-2 shims changed at 68K Miles.

PS: Sorry, cam on the closed side can not wear. OMG cant believe I didn't know this after effing 20+ yrs of messing with this crap. The only wear to the loose side is in the shim, bucket, top of valve stem etc. Yes cam can wear, but it will all be in the lobe not the back (closed) side. That part contacts nothing but oil, in fact that is the valve clearance you measure. Sometimes you have to post it and read your own BS to know I guess. Is that like getting high off your own supply ?

Cool.
Buddha.

1. using the choke to start is normal. That's how it's supposed to work
2. if you've been riding it a long time, certainly it hasn't always had trouble accelerating, right? Because if something has changed, you need to chase down what caused that change. Like, did you spray carb cleaner into the carbs? If so that can screw up the diaphragms and make it do this. Or did you try to do some other service on the carbs? Like try to adjust the pilot mixture so it would start easier when cold without choke? Because that can cause it too. Otherwise there's a good chance it's as simple as a vacuum leak, and there are lots of places for that to happen.

Quote from: mr72 on September 22, 2022, 12:28:48 PM
Otherwise there's a good chance it's as simple as a vacuum leak, and there are lots of places for that to happen.

Good point. Could be something as simple as the manifold intake boot o-rings.

Have any of the rubber parts related to fuel/air ever been replaced? They may be due for some love. Even a 2004 GS is now 18 years old and yours is relatively high mileage. It could be time to replace those rubber parts (intake boot o-rings, any o-rings in the carb, vacuum lines and might as well do new fuel lines). Also check the carb diaphragms for pin-holes or deformities and check the needles slides in the carb for wear.

At 67,000 miles you are at the point where a lot of things are going to start wearing out over the next few years. Even things like bearings or shocks that you had never thought about before. You need to decide if you want to commit to keeping it running like new or to let it slowly deteriorate. It can be hard to decide how much time and money to put in to a high mileage bike. I'm at ~56,000 miles on my 2006 so I know that first hand. Mine was totaled by insurance at one point so it feels weird even spending $200 on chain and sprockets on a bike that insurance says is worth $400. So I decided, this is my bike and I'm going to keep it running good until something catastrophic happens. Actively making that decisions makes it much easier to rationalize doing something like refreshing that fuel/air system.

The carbs and rubber boots etc have never been serviced or replaced. I alway use this oil https://www.supercheapauto.com.au/p/penrite-penrite-full-synthetic-engine-oil---10w-40-6-litre/348769.html
Generally don't ride it hard especially when it's warming up. As far as I'm aware nothing has been adjusted on the carbs but a mechanic has serviced the bike a couple of times when I have been short of time so I guess they may have changed something.
I never used to have to use choke in summer here in QLD, also yeah it never used to do the bogging down thing so I guess something changed.
I have purchased a carb rebuild kit but I've never worked on carbs before, like you said I don't want to spend a lot of money on the bike but would like to keep it going for as long as possible.

did you follow the link in my signature? here's the thing: it has 100% of all of the information you need. If you read it, it will save us both a ton of trouble. If you don't, well, I'm not interested in this thread any longer.

If it started without choke before, something has always been wrong. It should not start easily without choke. My GS500 will not start AT ALL without choke, and that's true for nearly all of them unless they are set up WAY too rich. And way too rich will cause exactly that bogging you talk about because it fouls the spark plug at high revs.

Now something else is wrong. With that many miles, it's definitely time for intake boot o-rings and all o-rings in the carbs. Everything in my blog post.

Quote from: mr72 on September 26, 2022, 05:25:13 PM
did you follow the link in my signature? here's the thing: it has 100% of all of the information you need. If you read it, it will save us both a ton of trouble. If you don't, well, I'm not interested in this thread any longer.

If it started without choke before, something has always been wrong. It should not start easily without choke. My GS500 will not start AT ALL without choke, and that's true for nearly all of them unless they are set up WAY too rich. And way too rich will cause exactly that bogging you talk about because it fouls the spark plug at high revs.

Now something else is wrong. With that many miles, it's definitely time for intake boot o-rings and all o-rings in the carbs. Everything in my blog post.

I didn't see the link sorry, going there now

Quote from: mr72 on September 26, 2022, 05:25:13 PM
If it started without choke before, something has always been wrong.

I don't think we can say this as being true in all scenarios. With stock US jetting, I agree. But when I went +1 on the idle jet using one of the Buddha's jet kits I would often not need choke in the summer, or only need it for like 15 seconds. I think some countries came stock with that larger idle jet. Also, after getting my bike tuned with a Dyno Jet kit by a shop with an actual dynometer, my bike also doesn't always need choke in the summer. It starts easier with choke but sometimes it will lope along with a rough idle without it.

My GS1000 with stock jetting needs full choke 100% of the time, no matter the ambient temp, which is how a GS500 with stock jetting should behave.

I set my bike to be a hair lean at idle, and to have a higher idle ~1700 than most. Its a mix screw setting. Because hot ambient temp, low humidity and a hot engine coupled with a richer than stoich idle will lead to a mess of a hot re-start situation. Like start it and it will want to stall before you get your helmet and gloves on. Put the choke on and it will act worse. You have a way to richen at startup (choke) no way to lean it a shade at startup.

However you're in a much colder ambient area. You may do fine except on very very very exceptional conditions.

Cool.
Buddha.

Quote from: Bluesmudge on September 27, 2022, 08:42:57 AM
when I went +1 on the idle jet using one of the Buddha's jet kits I would often not need choke in the summer, or only need it for like 15 seconds.

I'm coming to you from good old Texas, USA, where we have what others would call 10 months of summer. I'm talking about running the bike in summer, since that's basically all I have.

Thing is, I set up the mixture in this climate, and therefore it will not be too rich when it's hot. FYI there are more than one reason for needing choke, and it's not exactly the same reason as why you would wind up with a leaner mixture in cooler ambient temps than when the air is hot. Hot air has fewer oxygen molecules per unit volume than cold air, but fuel is not nearly as temperature dependent. So as it gets colder, fuel level per volume air stays relatively constant, but oxygen per volume air goes up, making it lean.

TL,DR: if you set it up in cold weather, it'll be too rich when it's hot, which may make it start fine without choke but also will make it run really rich when the engine is hot. You should set it up in the temps you tend to ride in.

Man, I wish my !Vespa were as easy to tune mixture as my GS. I despise working on GS carbs, but at least it's possible to get them to run right. Trying to get a carb on a 125cc engine to run with closed loop lambda and AFR and idle speed control is a fool's errand par excellence.

Humidity has a bigger effect as well. You much like me in NC/SC have wild swings in humidity. Left coasters are blessed with dry round the year, only have to worry about ambient temps. Throw in mountains a few hrs north and west and I'm likely in the hardest place to jet for - maybe colorado - they got wild swings in all 3 dont they ? Plus they get that crappy 85 octane gas too dont they ? Fun.
Cool.
Buddha.

I'm looking for parts now for when I service the bike next, I have a carb rebuild kit so that should have the o-rings, does anyone on her have some intake boots or know where I can get them? Looking on eBay they are over $100AUD is this normal price?

You probably don't need intake boots, check them for cracks or warped mating surface where it connects to the head. You definitely need new intake boot O-rings. They are like <$10 each in the US even from a Suzuki dealer, which is very expensive, but also necessary.

I can get boots for about $18-20 each but then again - I'm clear on the other side of the world and get an employee discount at this dealer, though I never did work there. I used to do carbs for them on a freelance basis - turns out the service guy had to enter me as an employee to tell customers our mechanic is on it. That was also like 2006.

PS: It will cost $35 USD each at Ron Ayers, and about $30 each locally. So I'm sorry, I was remembering my previous purchase of this item.

Cool.
Buddha.