Drain carbs if sat for a week?

[utopia]

Yep, that all sounds reasonable to me.
And leads me to think that, next time the float bowls are drained, it might be worth blowing back down the vent tubes to check that they're clear.
I'm thinking that this wouldn't be possible when the bowls are full as there would be no vent path, but I would think that there should be no such problem if the bowls are empty and the drain valves left cracked open while blowing.

Mind you, if the vents are blocked then presumably the bike would be running poorly and rather lean under "normal" conditions (due to inadequate filling of the bowls), and this appears not to be the case.

I'm inclined to plump for the "there is no problem" option.
Then again, cleaning out the float bowls and overhauling the fuel pump wouldn't be a bad ploy, particularly in an older bike.
Maybe the sluggish starting is exaggerated by a "lazy" fuel pump which takes a little longer to refill the bowls.
But either way, I would have thought that most carbed monsters must be due for a fuel pump overhaul by now, particularly given the ethanol situation.
That said, my 18yr old, 26k miles 750 is still seemingly fine on its original, unserviced vac fuel pump.

If needed, Allens Performance apparently supply rebuild kits for the pump.

[Nasher]

I did mine with a kit from Allens kit a few months ago.
Mikuni MK-DF62 kit is the one to go for.

Easy and cheap job for peace of mind.

Bilbo Worth a read of the end of this thread:
http://www.ukmonster.co.uk/monster/s...ad.php?t=56823

Nasher

Thanks , I’ll take a look at that thread.

[Flip]

Personally I would have the carbs apart and see what's going on in there- there's obviously something amiss if draining and then them refilling is disturbing something enough for it to start afterwards. I know it's a bit of a pain in the ass but hey it's Winter, the weathers' rubbish and think of it as 'bonding time'.

For what it's worth here's some of my recent findings from over eighteen years ownership of a 1997 900:

Firstly and possibly the most important thing is that the battery is not only good but has a healthy charge- turning the motor over on the starter while it is trying to huff and puff into life runs a very real risk of damaging the sprag clutch.

Next is to make sure all the *ground (earth) connections are as good as they can be*-

The wiring here was marginal to begin with but over the years is likely to have built up a degree of corrosion causing some resistance. You can check this easily using a multi meter set to the Ohm (Ω) range and measuring the resistance along each individual ground cable- the higher the number equals more resistance stopping the cable from doing it's job which is bad.
Coupled to that Ducati also chose to use a lot of brass terminals for this wiring which isn't quite such a good conductor as copper would have been adding slightly to the issue.

Now we can get onto the fuel pipes and pumps, firstly there are two vacuum pipes that need to be in good order. They run from each of the inlet manifolds with one going to the vacuum fuel tap located under the fuel tank- this isn't rebuildable and costs about £30 (if I remember correctly) from Moto Rapido. The other goes to the Mikuni vacuum fuel pump fixed to the frame which is rebuildable with a kit from Allens Performance for about £20.
Any other weaknesses in the fuel lines will show themselves more readily by leaking fuel.

The problem I encountered only showed itself on very hot days and typically when filtering through slow traffic so with either (or both) the vacuum tap or the vacuum pump not working as well as it should it caused the fuel system to vapour lock as the float bowls were not filled fast enough- compounded by the engine running so hot helping to evaporate the already in short supply fuel.

I'm only down the road too, so likewise shout if I can help further- if only it was better weather, there'd be a Monster run out there eh Nasher?

Fuel pipes:


Vacuum fuel tap:


Vacuum fuel pump insides:


Rebuilt:


I also replaced the other fuels pipes etc.


**A poor ground (earth) connection can also be the reason why on older bikes some headlights are not as bright as others (not to be confused with the poor beam pattern of the standard Bosch unit). Just for fun try this little test:
You'll need a length of wire long enough to go from the negative terminal of the battery to the headlight. Fix a M6 ring terminal on one end and a small crocodile clip on the other. Take the light unit from the bowl and make sure you are able to get the crocodile clip onto the ground (should be the black one) of the three terminals (don't clip it on yet though) .... turn the light on and note it's brightness, now attach the crocodile clip to the ground terminal and (possibly) be amazed how it becomes brighter!!
If it does then that is the result of corrosion and thus resistance of the light circuit going to ground.
**Disclaimer- I am not, will not and can not be held responsible for any blown bulbs, fuses or any other part, person or thing during this experiment

[Mr Gazza]

Smashing reply Flip. If we had house points on here then that would deserve one..

Billbo, have you ever caught the contents of the float bowls when you drain them?
If not it might be a useful exercise, if it is possible.

What usually comes out of troublesome carbs is little globules of water and/or particles of reddish brown grit.
If you have contamination of this kind on such a repeated basis, it is probably coming out of the tank. Therefore a good rinse out of the tank and flush through of the pipes could do some good.
Unfortunately if you discover that the tank is very rusty inside it might not be just a simple matter of a rinse! But it will certainly help in the short term.

However, water and dirt entering the carbs usually manifests as poor running and cutting out after it has started and the dirty fuel has flowed.
It would be very coincidental if the bowls collected just enough dirt or water to prevent starting whilst running well each time before you switched off.

Looking at the problem from another angle. I wonder if maybe the fuel tap is not shutting off the petrol when stopped and causing the carbs to flood.. This scenario would require leaky float valves too, but it would explain why you can start after draining.
If this turns out to be the case then there is a danger of fuel running down into the bores and then entering the crankcases when standing.
Does you oil level rise? Does it smell of petrol in the oil filler hole?

[Darren69]

All the comments and deductions seem logical to me and would suggest that the vacuum pump is the cause. The only carb Ducs I've had before have been SS's which have an electric pump in the tank and I never had any issues with any of those. But to re-iterate battery, battery, battery! It has to be in top nick to start one especially if its been laid up for a while and dried out so regular start ups will help too.

[Darren69]

Originally Posted by Mr Gazza

The answer is 42.

Is that 118, 118?

[Mr Gazza]

Originally Posted by Darren69

Is that 118, 118?

No, give it some deep thought.

[Darkness]

Originally Posted by Mr Gazza

No, give it some deep thought.

And a nice strong cup of tea.

[Nasher]

Don't forget your Towel!

[Mr Gazza]

[Darren69]

Well it looks like Monty Python doing 118 to me. Life of Brian stageshow maybe as I don't think its from the movie?

[Mr Gazza]

That is the look on the faces of Loonquawl and Phouchg, when they receive the answer "42" from the computer Deep Thought.

Deep Thought was a computer the size of a city constructed by a race of hyper-intelligent pan-dimensional beings, as they demanded to know the answer to life the universe and everything. Deep thought ran for several million years and finally gave the answer 42 to the pair, who had been born to receive the answer... This was obviously queried and it turned out that Deep Thought didn't really understand, as it wasn't a proper question and so..... Well it's a very long story, you need to read some Douglas Adams.

Getting back to the OP. I didn't really understand as I don't think it was a proper question, but lets hope it takes less than 7.5 million years to solve it.

Hope that clears thing up?

[Flip]

Or if you’re too lazy to read (like me most of the time) the wonders of the internet can take you back in time to 1981 where only the magic of television existed and with it this:

https://youtu.be/2dwid0171bw

Before it was ont telly it was serialised weekly (I think) on the radio.

There was also a feature length film in 2005 but I’ve never seen it so can’t comment.

[Nasher]

Has anyone else noticed the original Marvin from the TV series in the queue at the Vogon Post office in the recent(In relative terms) Film with Martin Freeeman?

I remember listening to the original Radio series with my Father,and it being really exciting when it was made into a TV series.
I'm so sure about the recent film, although it's a good attempt to capture the feel of the original series.

Nasher