Gs500 running issues **still not right...**

[_Iain_]

Changed inlet rubbers. No leaks there, still problems.

Have taken carbs apart, stripped and reset everything. Multiple times.

Choke off idle is perfect. Runs lovely, pulls away fine in first up to about 4-5k starts to run a bit weak. Any other gears above 1/4 throttle splutters, full throttle and it cuts out completely. Choke on runs like shit, wont idle however pulls significantly better and will hit 6500 revs on the throttle without cutting out.

Choke off, full throttle it revs to about 5k, then. Cuts out 100% and comes back on at 4k. Then "bounces" like a rev limiter!

Jets all look clean, no blockages. Slides move perfectly, and move up and down together when airbox off. Fuel tap works, no leaks, and its had a fresh inline filter put before the carbs which is catching a lot of shit. Engine cuts out if airbox snorkel covered. Idle doesnt change when WD40 sprayed round the various rubbers. Spark is good. Plugs are white.


Had carbs on and off this bike so many times i've lost count now.

Original problem was fuel starvation at about 7500rpm/ab ove 2/3 throttle.

After four days of starting up, switching off, run up the road, dismantle and repeat i've now got neighbours threatening to kick my head in. Dire need of advice from anyone who's got a clue what they're on about. Btw - its a four stroke
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Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[orac]

had a similar problem with mine, found it was a stikcing float, evem after the carbs were cleaned, found a stiny bit of grit in one of the float seat
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Current rides - 2016 Triumph Street Triple Rx, 1994 Suzuki Bandit 400 VM, TGB 204 Classic 125cc
"with nothing left to lose, there is everything to gain. It's not the size of the dog in the fight, it's the size of the fight in the dog"

[Casper]

[_Iain_]

Air filters good. I'll have the carbs back off and see what the floats are doing then.

Fuel flow appears to be fine up to the carbs - pulled it off the carb end with tap on prime & came out as expected if not marginally better than!
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[orac]

do have the float height listing, i may still have my GS500 manual to check if needs be
____________________
Current rides - 2016 Triumph Street Triple Rx, 1994 Suzuki Bandit 400 VM, TGB 204 Classic 125cc
"with nothing left to lose, there is everything to gain. It's not the size of the dog in the fight, it's the size of the fight in the dog"

[Casper]

[P.addy]

[Casper]

[ZaphodBeeble]

If the plugs are white then I'd say it's not getting enough fuel. Have you tried running it with the fuel tap on prime?

Did the bike slowly develop this fault or was it a sudden thing?

Do you have a stock air filter?

How long has the bike been misbehaving in this fashion?

I've seen problems like this where the carb main jets were too small causing the bike to reach a lower rev limit and behave like it's bouncing off a rev limiter. If you're taking the carbs off anyway have a look at the jet size and compare it to the stock size.
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.

[_Iain_]

Have you tried running it with the fuel tap on prime? Yes, tap is functioning correctly.

Did the bike slowly develop this fault or was it a sudden thing? Fault developed after i forgot to turn the tank tap on and ran it 100% dry trying to start it.

Do you have a stock air filter? Yes

How long has the bike been misbehaving in this fashion? Scince incident with the tank tap. Worse scince i cleaned the carbs.

Jets are all original. Ran fine on those jets before i drew all the shit through the carb. Im nearly certain it's due to me setting the float height incorrectly, or missing a bit of grit. Or possibly dropping grit in it when reconnecting fuel lines. Definately carburettor/intake related.
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[P.addy]

Could just strip carbs, maybe grab a jet thats 2 sizes up also.

Just to rule things out...that or you could possibly adjust some mixture somewhere to richen it up.

Should add though it does pop every now and then from the exhaust...quite a violent pop whilst ticking over

White plugs are never good and I would be whipping the carbs back off and just dropping the float bowl off, unscrewing both jets and leaving them to soak in carb cleaner before blowing them out with compressed air.

[gandy666]

when you stripped the carbs, did you set the air mix screw right?

assuming you haven't lost any tiny rubber bits or washers from the air mix screws when you stripped the carbs - I ask because I did when I did mine

carbs been ultasonically cleaned? when you say the jets look clean, there could be shit behind in the idle circuit.

any fuel leakin out the carb overflow pipe? i.e. flooding

if running out of fuel maybe the valve needle is set too high as it cuts off fuel once the float engages cos the bowl is filled up. or could be sticking. tried a carb rebuild kit?

try this site for your bike specific advice: https://gstwins.com

[_Iain_]

Popped carbs off today to find the airbox full of petrol. And the right cylinder. And petrol pissing out of the rotor cover...

And my tank empty.

Drained approximately 7-8 litres of oil/petrol from the crankcase.

Stuck float, floats incorrctly set & to top it all of a 60 main & 115 pilot. This is why i shouldnt work on shit when being distracted.

Oil change, jets swapped & will report back. Lesson learned, dont leave the bike on prime.
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[gandy666]

the joy of mechanics

sounds like a step in the right direction

[_Iain_]

And now its pissing fresh oil out from behind the rotor...guess the seal diddnt react well with all that petrol. However i do have another cover somewhere with a good seal on it.

However - it does start, it does idle, choke reacts as expected. Think we might be onto a winner...
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[orac]

glad you got to the bottom of it. shame about the seal tho
____________________
Current rides - 2016 Triumph Street Triple Rx, 1994 Suzuki Bandit 400 VM, TGB 204 Classic 125cc
"with nothing left to lose, there is everything to gain. It's not the size of the dog in the fight, it's the size of the fight in the dog"

[_Iain_]

Floats no longer stick. Engine no longer uses 4k like a rev limiter.

However.

Revs to 4-4500 and weakens. Hits 5k and splutters. Winding throttle on more makes it splutter more violently, then clears and goes but not propperly. Choke doesnt affect how it runs, although makes idle very uneven.

New intake rubbers were a bit shitty. Infact i did instantly regret buying them as the paint was cracked albeit not as bad as on my set. I'll post pictures. I've checked and cleaned the jets. 115 main, 60 pilot.
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[P.addy]

Can you get it to 3rd gear and about 4500, then drop into 2nd and pin it?

I still reckon your mixture is a little lean given the varying shades of white

[_Iain_]

Paddy - mixture is VERY lean.

But i have no idea how. I cant see how excess air is getting in the system, the jets havent been changed, it should all work.

The only mixture adjustment is via swapping jets or a slight adjustment at idle. Both idle mix screws are set 2 1/2 turns out as per factory setup.

I'm going to check float heights again if i can find some fecking clear tube. If i can see where its at whilst they're on the bike then i can be satisfied that it's actually working propperly & turn anger at the inlet rubbers.
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[P.addy]

Definitely not leaking around the rubbers, that's for sure.

You know where your mixture screws are? Try adjusting them for a slightly richer mix, not sure if your carb had needle adjustment at all either..

Remember/write down its current spec and have a gentle fiddle with the mixture. Half a turn and see if it gets better or worse.

[ZaphodBeeble]

Adjusting the mixture screws won't solve the problem above quarter throttle and at high RPM. If anything it would be jet needle height. I doubt very much that any adjustment will fix this though.

Strip the carbs again and use compressed air to clean all the jets and channels out. Make sure you remove all the jets before blasting it through. You can buy cans of compressed air in Argos I think. That or B&Q/Screwfix etc. Although having a proper compressor and air squirter is always better.

How are you setting your float heights? Are you measuring them or just tweaking/guessing? I don't mean to insult, I have to ask.
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.

[_Iain_]

But if everything fuel related is set where it was when it was working fine, and it's still spluttering and cutting out at the exact same point it was before, then all that will do is add a load of other potential causes for fail.

The mix screw only deals with fuelling on idle, its running fine on idle. Its at the point where the engines under load that it starts to die out, if anything pointing to a blocked main. Which isnt blocked, and sits lower than the pilot in the float bowl so as such wouldnt be getting fucked up by the float level being too low.
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[ZaphodBeeble]

[P.addy]

Should have a 40 and a 122 in there as standard.

You have a free flowing exhaust... and a partially wet air filter

[Casper]

Does your carbs have needle jets under that main? Mine does and it has around 20 jet holes up the sides of each one. They will look like this

https://nichecycle.com/mmNCS/Images/176_needle_jet.JPG

You need the main jet out as its under that and open the other end, take out the diaphragms and tap this out with a bit of wood like a pencil. Lots of people miss this when cleaning carbs.