Author Topic: fzs 600 carburettors (Read 10280 times)

rsvphil · « **on:** 13 November 2015, 02:08:11 pm »

Hey everyone got a problem with my brothers bike. He asked me to do some work, fork seals, chain sprockets etc but then decided to tell me it wasn't running properly. It would only run on the choke and wouldn't tick over, as soon as you touched the throttle it would cut out. I drained the carbs and removed them and gave them a quick clean made sure the jets were all clear. Refitted them and couldn't get it running. After leaving it overnight it fired straight up and revved really high for 2 seconds then wouldn't fire again. If you leave it for a period of time it will start or attempt to start for a couple of seconds then nothing. It does turn over and spark fine it's just not getting fuel. The float chambers are full of fuel. Any help much appreciated .

darrsi · « **Reply #1 on:** 14 November 2015, 11:58:20 am »

Is it definitely not getting petrol, or could it be an air leak with too much air?
Working with choked air could point to that.

Try starting it then whip a plug out and see if it's wet with petrol, or dry, which will determine whether petrol is getting through or not.
If it's wet then maybe check the carb rubbers for cracks, and make sure they're refitted and seated properly.

rsvphil · « **Reply #2 on:** 14 November 2015, 12:36:50 pm »

It ran on the choke before the carbs came out now the choke doesn't have any effect. If you leave it for a period of time it will fire straight away and rev to about 6000rpm for two seconds then dies then won't fire again unless you leave it for half hour. Whilst it does run twist the throttle has no effect. Checked over everything again and again and can't see anything out of place or damaged.

unfazed · « **Reply #3 on:** 14 November 2015, 01:07:50 pm »

Check the air and fuel filters

Rule out the obvious first

rsvphil · « **Reply #4 on:** 14 November 2015, 01:44:16 pm »

Fuel filter replaced and air filter checked.

darrsi · « **Reply #5 on:** 14 November 2015, 02:28:19 pm »

Is the tank breather hole clear, that could cause fuel starvation?

rsvphil · « **Reply #6 on:** 14 November 2015, 03:22:58 pm »

Yep all clear. But surely that wouldn't explain why it will run for 2 seconds when it's been left for half hour then not run at all? It's baffling me. I think the carbs are gonna have to come back out

His Dudeness · « **Reply #7 on:** 14 November 2015, 08:56:55 pm »

Quote from: rsvphil on 14 November 2015, 03:22:58 pm

Yep all clear. But surely that wouldn't explain why it will run for 2 seconds when it's been left for half hour then not run at all? It's baffling me. I think the carbs are gonna have to come back out

If that's the case then there's a restriction somewhere and the carbs aren't filling quick enough. Try hooking up another fuel supply straight to the carbs and see if it runs

celticdog · « **Reply #8 on:** 14 November 2015, 09:42:04 pm »

Quote from: darrsi on 14 November 2015, 11:58:20 am

Is it definitely not getting petrol, or could it be an air leak with too much air?
Working with choked air could point to that.

Try starting it then whip a plug out and see if it's wet with petrol, or dry, which will determine whether petrol is getting through or not.
If it's wet then maybe check the carb rubbers for cracks, and make sure they're refitted and seated properly.

It's also worth looking at the position and condition of the fuel switch under the tank and the fuel pump. It the floats have fuel I'd say it's a carb problem. Have you checked to see if your getting fuel in the cylinders?

rsvphil · « **Reply #9 on:** 14 November 2015, 11:22:22 pm »

So far I've checked that there's fuel going through the filter into the pump. The pump is working as it should. And the float chambers are full I just really don't understand it.

rsvphil · « **Reply #10 on:** 17 November 2015, 08:47:56 pm »

Right had the carbs out again and took the top covers off and removed the diaphragms and needles then removed the float chamber bowls and made sure the jets were all clear. Checked over everything I could see and rebuilt them and fitted them back on the bike. Managed to get it running and without the choke so was mightily relieved. However later on went back out started for a second then died and won't fire. So back to square one.

unfazed · « **Reply #11 on:** 17 November 2015, 10:08:31 pm »

What did you set the pilot screws to?

rsvphil · « **Reply #12 on:** 27 November 2015, 10:15:49 am »

Everything is set as it should be according to manual. As it was before I fettled with it.

unfazed · « **Reply #13 on:** 27 November 2015, 06:34:14 pm »

Is it a foxeye or boxeye?

hmmmnz · « **Reply #14 on:** 01 December 2015, 01:13:29 am »

you didnt get the main jets mixed up with the blanked off jets did you??
they are the same size and shape as the mains.
although it should still run on the choke (enrichment circuit)

BBROWN1664 · « **Reply #15 on:** 02 December 2015, 08:12:00 am »

try leaving the fuel cap open. This will confirm if you have a breather problem.

Fazerider · « **Reply #16 on:** 02 December 2015, 09:57:26 am »

If the carbs are full, fuel starvation sounds unlikely. Have you followed up on Darrsi's suggestion and taken a look at the plugs?
Flooding can be due to dirt, damaged needle valve tips or seats, failure of the o-ring seal around the brass valve body, mis-adjustment of the float arm or leaky floats.

unfazed · « **Reply #17 on:** 02 December 2015, 05:38:59 pm »

Out of curiosity did you put the fuel pipe from the tank to the fuel filter under or over the frame rail?
It is supposed to go under the rail as going over the rail could cause it to be squashed by the tank limiting the fuel flow.

rsvphil · « **Reply #18 on:** 06 January 2016, 10:16:13 pm »

Hi all sorry for the delay had some unexpected health issues since my last post. Fingers crossed I can get this bloody bike going now. Just been out this evening and turned the bike over. The fuel pump primed straight away But made no attempt to fire. Checked all spark plugs and getting good spark. At a complete loss.

unfazed · « **Reply #19 on:** 06 January 2016, 11:00:30 pm »

Did you try it with the choke on or off?

rsvphil · « **Reply #20 on:** 06 January 2016, 11:57:15 pm »

Tried with choke without choke. Nothing won't fire at all.

joebloggs · « **Reply #21 on:** 08 January 2016, 07:05:30 am »

Switch off your fuel tap and remove one of the wires from the back of the fuel pump. This will prevent any more fuel being fed to the float bowls (If its a flooding issue) Then try starting it, if flooding is the issue then hopefully it should run on until it runs out of fuel.

rsvphil · « **Reply #22 on:** 08 January 2016, 09:49:00 pm »

Tried turning the fuel tap off and still nothing.

kebab19 · « **Reply #23 on:** 10 January 2016, 07:14:39 pm »

I suspect one (or more) of your carb's slides is stuck open. I had a very similar sounding experience on my RD350LC about 20 years ago.

rsvphil · « **Reply #24 on:** 24 January 2016, 07:58:30 am »

Is there a cure for the carb slides sticking open? How did you fix your issue?