UK Monster Owners Club Forum Ľ .: Technical :. Ľ Fuels & Oils » Draining Carbs

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Old 04-01-2020, 04:42 PM   #1
gwyndaff
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Unhappy Draining Carbs

Iíve got a 1998 M600 that I canít get to start. I havenít been able to start it since September. The fuel in the tank/carbs is over 12 months old so Iíve been trying to drain the carbs. The right hand side is easy but I canít see how to get access to the left hand side. I can see the drain screw but I canít see how to loosen it. Anyone done this task?
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Old 05-01-2020, 11:50 AM   #2
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I think you will need to take the carbs off and strip them down to clean out all the resinous stuff left in them from evaporated petrol. The jets will have to come out and all the drillings in the carburettors blown through with an airline. Better still would be an immersion in an ultrasonic cleaner.
I suspect if you do not do this you will be chasing a poor starting /poor running bike for the rest of the year. Just draining the carbs will leave the gum in the carbs and putting new petrol might dissolve some of it but there will be jet blocking globules that will drift in and out of play unless they are completely removed.
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Old 05-01-2020, 09:06 PM   #3
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Thanks for the response 350TSS. I’ll have to get the old Haynes book out. I’m a mechanical luddite but I’ve got basic tools and I don’t mind giving it a go. Any pitfalls I should be mindful of? Wish me luck ��
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Old 06-01-2020, 02:00 PM   #4
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I would get them off and give everything a large dose of plusgas particularly the slow running jets located (maybe ) under some rubber bungs (bungs usually go AWOL) just in front of the float drain plugs.
The cross head screws on the carburettors are soft and Japanese standard cross head (forget the correct reference letters - JP1?) whatever a PZ1 or PZ2 or a Phillips cross head will almost certainly chew it up before it undoes and then you have a problem.
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Old 06-01-2020, 02:58 PM   #5
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Quote:
Originally Posted by 350TSS View Post
The cross head screws on the carburettors are soft and Japanese standard cross head (forget the correct reference letters - JP1?)
JIS? (Japanese industrial standard).

JIS screwheads are usually marked with a dimple/punch mark or an 'x'.

It's definitely worth having a couple of JIS screwdrivers in your toolbox. If you're used to struggling with Phillips/Pozi drivers on JIS screws, the first time you use the JIS driver is a revelation!
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Old 06-01-2020, 07:48 PM   #6
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Cheers Luddite - good username by the way
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Old 06-01-2020, 08:49 PM   #7
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Vessel Megadora make some very good Japanese Industrial Standard screwdrivers.

https://www.ebay.co.uk/itm/Vessel-Me...oAAOSw2Xdd4o~l

They are similar to philips drivers, but with a smaller radius at the centre of the cross.

https://www.instructables.com/id/Whe...ot-a-Phillips/
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Old 06-01-2020, 09:10 PM   #8
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Everyone is right, modern fuel goes off very quickly (more so in small quantities) and the carbs dry out reasonably quickly when left for any length of time and the fuel leaves a horrible yucky glaze behind which blocks jets and airways.

These should help you get the float bowls off but I would give the screws a good squirt of release spray and allow to penetrate before attempting to remove them as they are indeed made a cheese like material- possibly Dolce Latte?

https://www.ebay.co.uk/itm/US-PRO-To...wAAOSwqWZdMEfy

If they hint at getting rounded off I would stop and try and get a pair of pliers on them if you can to start them off.

Also if you're not familiar with CV carbs take care when handling the diaphragm when you remove the slide as they can be easily damaged.

And finally, have a nice clean work area with some little pots (rattle can lids are ideal I find) for putting the bits in as You dismantle, clean then reassemble one carb at a time.

Enjoy
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Old 07-01-2020, 02:12 PM   #9
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I'm going to throw in a curved ball here.
I've been following this thread and wondered why all of a sudden the advice is to remove and strip the carbs?
Yes the op did ask how to drain the carbs because he wanted to get rid of the old petrol.. Fair enough, fresh petrol throughout will be a big help... But.
The usual advice with a 600 that won't start after a lay-up, is to prime the carbs with petrol, as the vacuum pump and tap take their time to fill the carbs and it needs a LOT of cranking. Folk usually report that the battery goes flat before it will start, due to all the cranking. This leads to unnecessary fiddling with electrics sometimes, although it can reveal a sad battery too.

Just saying.. It might be worth getting rid of as much old fuel as possible and then trying again with the carbs full of nice clean stuff.. either expect a lot of cranking to get it through or devise some means of filling the carbs before the cranking starts.

I think stripping the carbs at this stage is just going to open a whole new box of frogs that could lead to more problems.. Your call..

If it does start with full float bowls the next step would be the Italian tune up..
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Old 07-01-2020, 03:26 PM   #10
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I've got to say ... Mr Gazza's advice sounds good to me.
I'd be inclined to give the battery a damn good charge and then be persistent with the starter button. ...very persistent.
If it still doesn't start before the battery goes flat, I'd be inclined to recharge and repeat before stripping the carbs.
I would probably also check that fuel was reaching the carbs before stripping them. There is every possibility that the diaphragms in either the fuel tap (if a vacuum tap is fitted) or the fuel pump itself have deteriorated though standing dry for a while.
Removing the carbs is quite a lengthy process, never mind stripping them.

Removing the plugs to see if they're wet (indicating that fuel is reaching them) would also be worth doing.
While they're out it might be worth cranking the engine a few times as it would spin up faster with the plugs removed, thereby pumping fuel to the carbs faster too.

Club member Dookbob used to prime his floatbowls using a syringe if his 600 had been standing for a while.
Eventually I think he even fitted a manual priming pump.
Personally I've never had a problem as long as I've been persistent with the starter button after a period of non-use.
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Old 07-01-2020, 06:08 PM   #11
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I tend to agree with Mr Gazza and Utopia. I've been riding carby bikes for many years and have never had to strip carbs to start a bike that was laid up. Fresh petrol and a well charged battery, making sure the battery connections are tight as there's a fair current flowing which will heat up and melt any poorly connected joints if you have to keep it spinning for a bit.

What i have done many years on first start up is set a hot air paint stripper a few feet from the bike pointing at the engine for an hour or so before starting. They always start first jab of the button, just as if they've been ridden within the past hour or so. A hair drier might do he job too, it's just about raising the temp of the motor a bit.
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Old 07-01-2020, 09:11 PM   #12
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Okay, lets wind this back a bit then.

How full is the fuel tank?

They are almost impossible to drain in situ as a siphon wont really work and if it's over half full I wouldn't want to be using the hinge to support it so the only real option is to remove it and drain it properly.

If there isn't much fuel in there then the chances are the Ethanol has drawn in water and there is some swilling around at the bottom waiting to rust it out or intermittently block the outlet.

Moving on, as Utopia rightly suggests the diaphragms of the vacuum pump (and vacuum tap if it is not a manual one on a 600?) will likely be not at their best given the bikes' age- I replaced them on my 900 a couple of years back as both were shot.

If you can't drain the carbs in situ then you have no real idea if they are empty (likely they are) or if they still have fuel in which then poses the issue of that is a fair amount of stale fuel to shift or fill with fresh while turning the bike over on the starter.

A word of warning on this too, as already hinted at, the starter electrics are fairly marginal to say the least on the early bikes with the ground connections being a particularly under sized gauge for the job expected of them (it's amazing the difference fitting beefier cables will make to the speed the motor turns over) add to the this that if you run the battery down constantly with the starter it will mostly likely damage the Sprag clutch bringing another world of pain to you.

Only you know what fuel you used most when it was running but if like so many that have been fooled into thinking Shell's V Power is the best thing ever, those carbs will likely be horrible inside where it has evaporated and left its' residue and the chances are until they are cleaned out properly you'll never really know.

I appreciate that many carb'd bikes will start reasonably easily after a lay up but most are either gravity fed or electrically pumped whereas the Monster is peculiar with it's (in many cases) double vacuum system which, if not at it's best can manifest itself in all kinds of ways.

During my eighteen years of ownership (at time of refresh) my '97 900 (very) occasionally suffered from vapour lock, occurring on very hot days when filtering in traffic with an extremely hot motor which would eventually die through fuel starvation.

My fix was to completely refresh the fuel system and while doing so the effects of Ethanol coupled with age were obvious:



All the 900/750/600 models are getting on in years now and as such they all need that little bit of extra lovin' or owning one will just become disheartening.
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Old 12-01-2020, 04:53 PM   #13
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Thanks for all your help. I finally managed to get the old clunkerbunk started today and after a few minutes coughing and farting it seems to be running well.
I went for the old try everything at once technique.
I drained about 1/2Litre of the old fuel through the carb I could get to. Then I added 5 litres of super unleaded and 1/2 bottle of octane booster. Then I trimmed the HT leads back about 5mm and replaced the plug caps. Finally I hooked the battery up to car and turned it over with some “easy start” squirting in the air intake. A voilŗ I now have a 23 year old monster ticking over. Thanks again for all your help and advice.
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Old 13-02-2020, 12:42 PM   #14
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Quote:
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Club member Dookbob used to prime his floatbowls using a syringe if his 600 had been standing for a while.
Interesting to read that! I did exactly the same on my Suzuki VX800, which also had a vacuum stopcock and vacuum pump. I tee'd in a spur in the pipework below the pump and used to fill the carbs with 50ml of fuel from a big glass syringe. It saved a lot of punishment for the battery and starter-sprag, though one VX-er suggested that the engine oil wouldn't have gone around so well prior to firing.

That bike (the VX) was charming but had to make way for the S4R: chalk and cheese, I reckon!

Nick
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Old 13-02-2020, 03:57 PM   #15
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Interesting to read that! I did exactly the same on my Suzuki VX800, which also had a vacuum stopcock and vacuum pump. I tee'd in a spur in the pipework below the pump and used to fill the carbs with 50ml of fuel from a big glass syringe. It saved a lot of punishment for the battery and starter-sprag, though one VX-er suggested that the engine oil wouldn't have gone around so well prior to firing.

That bike (the VX) was charming but had to make way for the S4R: chalk and cheese, I reckon!

Nick
For my recent refill, i took out the plugs and spun it for a while till petrol smell appeared in the cylinders. Took a fair wee bit of time to prime it. The battery would never have lasted with the compression on it.
I thought about your idea of the tee spur-ed into the line past the pump but ended up not doing it.
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