M900, run with no Fuel Pump

[Nasher]

All

Can anyone see any reason why I couldn’t run my 97 M900 with the fuel pump bypassed temporarily to prove a point?

It’s not got the Vacuum tap fitted at all, just a straight through inline tap in the pipe from the fuel filter to the fuel pump.
And I realise I’ll need a relatively full fuel tank to get the level above the carbs and let gravity feed them.

It didn’t run very well yesterday, OK at slower speeds and accelerating up to speed on the motorway, but then stuttering etc after a very short while.

It felt like fuel starvation, and I went through all sorts of things afterwards without finding anything.
It will start and idle, and run well at lower speeds, but my gut feel is the fuel pump isn't keeping up with the float bowls being emptied.

It could of course be one carb having problems, but the fuel in both float bowls was nice and clean and I’ve not touched anything recently.

It did completely cut out completely at one point, not go down on to one cylinder, which points to a shared fuel or Ignition issue, but by the time I’d coasted to a halt and pushed the starter button it fired up immediately and ran OK again for a short while.

So it definitely appears to be something that is effecting both cylinders at the same time, not just one, so at this stage I’m assuming it’s not individual carbs, IC Ignitors, Coils etc.

I did have a full tank of fuel at the time, so I might be barking up the wrong tree, as the fuel would probably gravity feed through a weak pump anyway, or maybe it would form a big enough restriction to slow gravity feed down.

Running it gravity fed for a test ride will at least prove or eliminate a weak fuel pump.

Nasher.

[Darkness]

Can’t see why not, but don’t lift the tank when it’s still full.
It would be worth checking/changing the fuel filter whilst under there, and if you open the fuel filler after running you may find there is a partial vacuum in the tank due to blocked/kinked breather pipe?

[Nasher]

Thanks Darkness.

I did have a quick check of the fuel filter, ran some fuel through it backwards and it came out clean.

The effect was similar in some ways to what I've seen in the past on boats when I've forgotten to open the vent valve on a petrol tank and a vacuum had formed.
Considering the experience I have from above, for some reason I didn't think of the tank vent, so will have a look, thanks.

Nasher

[utopia]

You may find one of these auxiliary fuel bottles handy.

https://www.ebay.co.uk/itm/MOTORCYCL...EAAOSwOddYxs-n

Obviously you could only do a static test using one of these (and even then, not at sustained high revs) but it would ensure enough gravity feed pressure as well as eliminating everything else related to the std tank (pump, filter, tap, breather, etc).

[Flip]

Before I did an overhaul of my fuel system a couple of years ago, my 900 would suffer from vapour lock fuel starvation. It only ever happened on really hot days when the motor got really hot usually when filtering through heavy traffic. The engine would splutter and cough to a stop but restart on choke (obviously badly because it was already hot but it drew more fuel in) only to die over and over. The only solution was to park up and let it thoroughly cool down before it would run properly again.

After checking all the pipes and vents etc. I didn't find a definite cause but suspect it was down to the vacuum fuel tap (which you have done away with) and the vacuum fuel pump getting weak and not working as they should so, along with all the pipes I changed them both and have never experienced the problem since and we have had so seriously hot temperatures this year.

Are you planning to give the bike a run with the fuel pump bypassed?

I am not sure it will get any fuel to the carbs without it as the tank's outlet is so low but either way don't forget to blank off the vacuum pipes from the inlets that operate the pump.

Allens performance do a repair kit for the vacuum pump and the pipes are available from Motorapido.

https://www.catalyst-findit.co.uk/in...64&pid=MK-DF62

[Nasher]

Flip hi.

I am planning to run it for a test ride without the pump. Looking at it the float bowls are far enough down the tank that as long as I've got a 3/4 full tank I should be OK.

I'd not considered vapour lock, thanks for that, it's another avenue to consider.
It wasn't as warm Sunday afternoon as it has been on recent trips out where I've had no problems, but as you say it could still be related to the pump becoming a little tired.

Once again I'm stuffed for time in the garage until the weekend, so will have a play then.

Nasher.

[Mr Gazza]

Could it just be a leaky or collapsed vacuum pipe?
I believe that was the cause of the problem Eleanor had, soon after her bike won the Concours d' Grot.

[Nasher]

It could be Mr G, another one to add to the list.

As the bike has been modified over the years by previous owners, some of the pipe runs have been changed when the Vacuum tap was removed. So it's conceivable one has kinked or even split.

I have been through a lot of the mods and tidied them up, or even reversed them back to standard in some cases as I felt they were detrimental to the bike.

Have to say though, it's still the best bike I've ever brought.

Nasher.

[Flip]

Originally Posted by Nasher

It could be Mr G, another one to add to the list.

As the bike has been modified over the years by previous owners, some of the pipe runs have been changed when the Vacuum tap was removed. So it's conceivable one has kinked or even split.

I have been through a lot of the mods and tidied them up, or even reversed them back to standard in some cases as I felt they were detrimental to the bike.

Have to say though, it's still the best bike I've ever brought.

Nasher.

That's why, as I was in the middle of a strip down anyway, I replaced all the fuel and vacuum hoses (I think there was one that is no longer available from Ducati) along with a new tap and pump diaphragm- those kind of things are starting to show deterioration as the bikes get on a bit.

I have to say that in doing so along with replacing all the ground cables the bike turns over and fires up instantly now hot or cold.

I agree with you Nasher- Mine's still the best bike I have ever bought too

[Nasher]

Thanks Flip

I've been meaning to buy an Allens performance rebuild kit for a while, I even have a spare pump to rebuild.
I've had a look at the parts explosions for all the pipes last night, they do have some annoying pre-formed bends, so it would be much easier to buy them from Ducati than just a length of hose.

I think the old girl is worth it though.

Nasher

[Flip]

Originally Posted by Nasher

Thanks Flip

I've been meaning to buy an Allens performance rebuild kit for a while, I even have a spare pump to rebuild.
I've had a look at the parts explosions for all the pipes last night, they do have some annoying pre-formed bends, so it would be much easier to buy them from Ducati than just a length of hose.

I think the old girl is worth it though.

Nasher

Definitely worth it Nasher!!

To be honest I was a bit lazy when I asked Craig about the fuel lines and sent him a photo of the 750 ones and said 'I'd like these but for my 900 please'



As usual he did his parts magic and came back with this-

Righto, I’ve had a look at the parts on your diagram (but for a M900) and found the following prices:

Item # 2 No longer available

Item # 7 £6.72

Item # 13 £14.3

Item # 9 £12.22

Item # 6 £14.33

Filter hose £13.97 – this is the hose coming of the ‘straight’ union on the fuel filter

Vacuum petrol cock £33.30

All of the quoted prices are retail and include VAT. You will of course get 10% discount on anything you order.

I think I’ve covered everything, but let me know if I missed something.

Best regards,
Craig Richardson – Parts / Accessories

Not overly cheap I know but then again, as you say there are some preformed bends and at least this way I knew they would fit without me faffing around.

Bear in mind this was a couple of years ago now so they may have gone up a bit since then.

[Nasher]

Flip

Hi.

Thanks for that, I had a quick look in the garage late last night and was planning on getting the part numbers off the Stein Dinse website today.
I found that the outer layers of #6 are deteriorated quite badly if you bend it.

Because the old girl has lost vacuum tap at some stage I only really need vacuum pipe #9.
The other vacuum stub in the inlet has been blanked off with a screw, so whilst I’m about it I might whip that out and make sure it’s sealed completely.
Her Fuel pipe #6 has been shortened to attach to an on/off tap, and a longer piece of braided hose used in place of #2 and the tap assembly.

I’ll order up #9, #13 and #6 and hopefully find a piece of generic pipe to replace #2.
I’ll give Craig a call later.

I ordered a rebuild kit from Allens yesterday, who really need to do some work on their website.
I’ve not had a confirmation email at all so will call them if it doesn’t arrive in a few days.

Nasher.

[Nasher]

Have to give Allens their due, the genuine Mikuni Pump rebuild kit has arrived earlier today.

I've also managed to find a brand new #9 on EBAY for less than £5.

The old Girl is having some money spent on her this week as I'm refreshing the ignition as well, as per another thread on here.

Nasher.

[utopia]

That's my experience with Allens too .. stuff usually arrives the day after ordering.

[Nasher]

I was actually quite glad of the rain today, it meant I could spend some time in the garage instead of carrying on with the Garden projects Lady Nasher has me doing.

I found the non-Ducati piece of pipe that was in place between the Fuel Filter and tap was very soft and kinked very easily. That has been replaced with a length of fuel pipe I had in the garage, being injection hose it's far more robust and kink resistant, and the Fuel itself shouldn't attack it.
I also replaced the Tap to fuel pump hose with the same as the original shortened Ducati hose was split all over it's outer surface.

The Vacuum hose I've brought hasn't arrived yet, but having taken the old one off and inspected it I'm sure it's OK.

And so to the Fuel Pump.
It came apart really easily, and the Mikuni rebuild kit from Allens fitted really well.
I don't think it could have been pumping properly for a long time.
The main issue was the clear diaphragm between the pump body and the vacuum chamber the pipe connects to.
The diaphragm is supposed to be flat, but had deformed into a dome almost filling the chamber and can't have been moving properly, it was stuck to the body by the gasket and had to be peeled off, but the space that was left in the chamber on the vacuum side was full of fuel.

I put the pump back together and the bike started really well, but of course I'd now like a dry day to try her out.

Did manage to do some garden stuff in the garage though.
I want a raduised corner on the deck I'm putting in, so broke out the Epoxy and laminated up a 90deg section of curved joist to use in that corner.

Nasher