NOT FIXED: GS500E/S - Low power when throttling on (Lean?)

[veeeffarr]

Hi,

Checked the carbs earlier to see if I could get the restrictors out of the bike (I can't theres none in there that I can see)

Put the bike back together (I hacksawed off the rounded off airbox screw, and I couldn't find the other airbox screw in time, the screws that mounted the airbox to the carbs, but its a tight fit anyway with nowhere to go)

Took it out for a test run, and when the fuel tap is either "ON" or "RES" the bike cuts out like it has no fuel.

If I switch it to "PRI" however, the bike runs, but backfires when letting off of the throttle at high RPM.

Suggestions?

T

[sickpup]

Sounds like theirs a problem with the vacuum hose, kinked or something.

Er5's do have possibly the most stupid fuel tap design I've seen in the last 20 years.

You looked into the rubbers on the engine for restrictors yes? how about under the carb tops?

[veeeffarr]

You mean where carb meets cyl head? Nowt in there.

Taken the carb tops off to, looks ok.

Quick question: I've left it outside on PRIME, will this matter if I leave it overnight or should I really go turn it off?

[hmmmnz]

if its running on prime only, then its most probly your petcock.
prime is just gravity fed strait into the carbs (still via the pet cock)
but reserve and on positions require the carbs to suck it through.
recheck your hoses first.
your restrictor will most probly be the slide type then if its not the washers,an extra hole is drilled in them, quite often they change the main jets as well, so thats worth looking at as well
good luck
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[hmmmnz]

go and turn it off, quick. youll end up flooding the carbs and right into the engine, what are you waiting for get out there!
____________________
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[veeeffarr]

I've done it.

When we were putting it back together we had a few problems

1) The airbox was being a complete twat to get on. So we mounted the airbox rubbers to the carb, positioned the airbox and took the air filter out and pulled the rubbers through from the inside.
2) There is a hose running from the bottom of the airbox to the right hand side of the bike, the end is seal and it looks like there's a filter full of yellow shit at the airbox end (Some kind of breather?) Anyway, we figured that it was just a breather, and as it was 2am in the morning decided to leave it off until next week.
3) It wasn't me working on the bike, and I know we had some problems figuring out where some of the pipes went afterwards.
The two pipes connecting to the fuel petcock, could it possible be that they are on the wrong way round? Would this have an effect? Also, the pipe that runs from the BOTTOM centre of the fuel tank, does that connect to anything or is this just a breather too?

As I said, when it is on RES or ON the bike doesn't run, which one if the vacuum tube? As you said if this isn't routed properly then I imagine it's starving the engine.

Why would it backfire on prime? Is it just overflowing the carbs? We didn't actually take them fully apart, so we didn't drain the fuel from them, could this be the issue?

By the way? Which slides are you talking about? The ones that lift with the throttle on the engine/carb side, or the solid ones that come up with the diaphragm on the carb/airbox side?

Neither have any holes in, apart from there's a tiny semicircular opening at the bottom of each carb/airbox slide.

[veeeffarr]

I don't understand how the vacuum tube works, can someone post a diagram please?

[hmmmnz]

https://houseofmotorcycles.bikebandit.com/partsbandit/assets/schematics/Suzuki/SU0084_013.gif
number 7 is the slide

yep the one coming from the bottom of the airbox is an overflow, same as the one on the bottom of the tank
here is a pic of the hose routing
https://cgi.stanford.edu/~sanjayd/gs500/uploads/Main/hoserouting.jpg
back firing is because you are getting to much fuel, (its not regulated by the carbs in prime, so thats fairly normal)
it would matter if the pipe from the tank were the wrong way around it would just make the on become reserve and the reserve become on.
the air box is always a prick to get back on

if its not a washer restrictor (between the carb and the engine, or a slide restriction #7 then that only leaves a jet restriction)
good luck.
dont forget about that prime if you ride about remember to turn it back to the on or reserve position
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[veeeffarr]

Ok so basically I should inspect my vacuum hose (I'm getting up in 4 hours to do this ) and check that I've got the on/res hoses on the right way?

[veeeffarr]

Also where does the vacuum hose from the left carb connect to?

[hmmmnz]

make sure you havnt jammed any hoses basically, i think its gunna have to be a tank off mission to get it right
good luck.
im off to bed,
but on the plus side i get to sleep in
night mate and good luck
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[hmmmnz]

the petcock as well the little pipe
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[hmmmnz]

https://img201.imageshack.us/img201/5664/petcockgl5.jpg
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[hmmmnz]

thats it im defently going to bed now
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[irving]

[irving]

[veeeffarr]

Very helpful!

I got up at 7am as I need the bike badly for tomorrow and success! Vacuum hose disconnected on the fuel tap side.

Cheers guys, always satisfying to have the problem fixed with 20 minutes left to go back to sleep!

Irving: My carbs, on the carb/engine side the slides have small grooves cut into the bottom, could this be it?

[irving]

[veeeffarr]

It's not cutting out anymore, but it is running like a bad of cocks... There's no pull in it, like it's running out of fuel, but its not..

[hmmmnz]

sounds like its running lean, you have a air leak
its probly the air box not on properly
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[finpos]

If you pulled the carbs off, make sure you didn't buckle one of the carb rubbers when you shoved 'em back on, creating a hooooomungus air leak between the carb and the engine. Very easily done and sometimes tricky to spot.

finpos.

[Pete.]

I agree it's easy to fold the rubbers over when fitting the carbs, usually at the bottom. You might notice a slight difference if it happens the airbox side but if you do it on the engine side you could be running very lean.

[veeeffarr]

[Ichy]

[Ichy]

Check all the carb rubbers are fitted fully home and clamped corectly.

All cylinders firing?

Any better when running on prime?

Do the carbs have drain screws at the bottom? If so then slowly undo each one in turn until a bit of petrol comes out.

Check the thottle cable is workng properly.

All vacuum pipes or stubs are connected or plugged.

Did you take the top off the carbs? Any chance you might not have seated the needle or slide correctly? Springs ok?
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