suzuki gs500 rebuild....tart up

[one arm bandit]

HO HO HO.....Managed to get it started ok...but I think its being starved of fuel. It starts with the choke,and once its warmed up,it ticks over nice and even.But as soon as I try to open the throttle,the revs rise a little...then it starts to splutter and goes to stall as if its not getting enough fuel into the carbs. On the gs500 website,they reckon it could be the vacumm operated diaphram on the fuel tap sticking.Will be looking into this at the weekend.

hook it up to a gerry can to test that out first, no point messing with the fuel tap if thats not the problem

[hornet6]

Right. See if you can get your head round this one. Went out to the bike again and tried it, as it is set up.Started as usual,first time....so I let it just tick over for a few minutes to warm up.Tried to open the throttle again and its still the same...revs rise slightly then it goes all fluffy and going to stall.
So,I set up a small bottle with some petrol in and a proper hose tail in the cap of the bottle.....take off the reserve hose and attach this to the bottle of petrol,and start it up again.Petrol is now going straight into the carbs.....SUCCESS.It works,not perfect but at least I can open it up and the revs are rising and falling back to tick over.Its still a bit fluffy and pops occasionally but I think it just needs the carbs balancing and tuning.
So,here comes the confusing part.I re-attached the reserve hose back onto the tap as in the proper set up on the bike. Started it again and it still seems fine.Its as if it needed purging to get it working right.Had it running for quite some time so it was nice n warm.It seems to be a step in the right direction but still not sure why it seems to have cured itself.

[hunter]

Hi hornet,Does the petrol tap have a vacuum pipe fitted,
If so check that the pipe isn't split or collapsing.

[Manky Monkey]

I was going to suggest the same. Or the rubber inlet manifolds have perished. Used to happen a lot on my old Jap bikes. Gaffer tape provides a temporary repair -a bit of tape around the vacuum pipe & carb rubbers might eliminate one possibility.

[one arm bandit]

isnt the fuel pump built into the tank on these, it may have become blocked slightly and running the bike with a bottle the pump would still pump and free its self of and debries?

[hornet6]

Theres no fuel pump on it.Theres a tap thats permanatly on which feeds a second tap on the frame. Bit of a bizzare after thought by suzuki I think.Will try it again later and see if its still ok.  

[hunter]

Is there a pipe that runs from the tap to the inlet stub,
If so is it good.

[hornet6]

All the fuel lines seem ok.The diaphram inside the frame mounted tap is ok as well.The only one I havent checked properly yet is the the vacuum pipe to the diaphram. I started it again tonight and it was back to its normal self of almost cutting out when I try to open the throttle. Once it gets really warmed up after about 5 mins of running off the choke,it does become a bit more responsive.
I dont think theres that much wrong with it.I think I will leave it as it is for now and carry on just doing the bits n pieces to get the whole thing finished....then maybe strip and clean the carbs again and try and find out if it just needs a little fine tuning.   

[stumpy]

pull vac pipe off remote fuel tap put a suitable one on to suck yourself run it up and suck pipe to open diaphragm bud pipe to hold vacume .... suck it and see i just rebuilt one of these for son in law from the ground up engine rebuild etc ... bastard front engie mounts and exhausts flange bolts rusted to hell but got there hope you solve it soon

[BikerGran]

I had a problem a bit like this with a car once - turned out that although the fuel pipe looked ok, it was slightly perished and would let in extra air in certain circumstances - particularly when the ambient temperature was not very high.  

Having just re-read earlier posts - as the tank ran dry it's prolly muck from the tank partly blocking the fuel tap(s) and/or carbs.  It'll do this intermittently just to drive you mad!

[hornet6]

Still no joy with it. Disconected the tank and the taps to the carbs. Rigged up a bottle of fuel to go straight into the carbs. Started it up again and its still the same....ticks over ok, but as soon as the throttles tweaked, it pops and fluffs and goes to stall. Tomorrow...remove air box,carbs and strip down time.      

[hornet6]

Its all crap. Took the carbs apart again,and found that there was a tiny "o" ring missing at the top end where the vacuum pipe fits. To be honest I probably lost it myself when I had taken them apart the first time to clean it out. Any way I bought 2 new "o" rings for both carbs and fitted it all back together,checking things to make sure it was all ok.
Hooked up a can of fuel to go straight into the carbs so as to avoid any problems with the taps.....and its still the same. Ticks over fine,but wont rev up...starts to splutter and stall.Ime thinking that it might not be the carbs at all,and may be the cdi or summat. At a total loss on this one.  

[hornet6]

Hi again.Had a good end to the day. While I was watching some of my stuff finishing on ebay,I started looking on the web for gs500 carb diagrams. It was only when I saw an exploded view of the top end of the carbs and needle setup that I realised I had assembled my set wrong. Fortunately, it was easy enough to fix without taking the carbs to pieces.
So now it starts and revs up as it should....just needs fine tuning as it pops a little bit and misses occasionally...but ime a happy little bunny now .Need to get back on track now with a bit of fabrication to hold the licence plate,get the seat fixed and covered,new indicators,a lick of paint,job done.Then mot , tax and insure it Ime back in the saddle.

[hunter]

Nothing better than a good ending to a story.
Well done Hornet.

[Manky Monkey]

That's great news! So everyone lived happily ever after then.