M900, run with no Fuel Pump

[Nasher]

Managed to get out for a short blast yesterday afternoon, and am happy to report the old girl is back to her usual self, if not a little better.

A polystyrene tray of Frozen Potato strips dropped in hot oil for 2 mins, and a mug of supposedly coffee flavoured hot water served from a hut on the beach at Hayling Island is a must do activity on a bank holiday, getting there on the M900 is the most enjoyable bit.

Nasher.

[Nasher]

I thought I’d sorted this issue, the old girl has been fine for weeks, but it happened again, and I believe I’ve discovered the unlikely cause.

I took her out for a ride yesterday, having volunteered to drop some paperwork down to one of Mrs Nashers colleagues who lives on Hayling Island as an excuse for another mug of coffee-like flavoured hot drink and a tray of re-fried, previously cooked and frozen potato strips.

Everything was fine until I crossed the bridge onto Hayling Island when the bike died as if starved of fuel.
This in itself was odd, because it’s @10 miles from home, and I’d got there with no problems.
What’s really strange is that it was exactly the same spot as the problem happened before, but I’d taken a different route to get there.
Once I’d coasted to the other side of the bridge the bike started instantly on the button.
I carried on, but it happened again on an open stretch of road down the West side of the Island.

Anyone guessed yet?

I dropped the paperwork off, visited the White painted concrete block hut of culinary dreams, and watched the boats go by whilst contemplating the problem.

It was whilst doing this that I realised it was a bit windy, and my tray of re-fried, previously cooked and frozen potato strips was getting cooler by the second.
Then I remembered it being windy when I first had the problem a few weeks ago, and there being a strong cross wind on both the bridge and the open stretch of road then and today.
To test my theory I headed home, and went a little slower along the open stretch of road, but obviously in the opposite direction.
Sure enough, the bike died, as if starved of fuel, but restarted again instantly.
And then going back over the bridge it died again, but restarted and ran fine for half a mile up the road.

So, I’ll explain, and I’ll have to put up with the smirk I’ll get from Flip because he told me ages ago this would come back to haunt me.

When I brought my M900 4 years ago one of the ‘mods’ that had been done to it by a previous owner was the breather boxes on the sides had been removed.
Possibly because like me they didn’t like the look of them.
The main carb breathers are cut off just after the valves, and the common float bowl breather was left to hang vertically just above the horizontal cylinder head behind the oil cooler.
I had tidied this up @3yrs ago by extending the float bowl breather down the side of the engine, but had starvation issues at speed which were sorted on the hard shoulder of the A3M by cutting the new breather pipe back again. I’d forgotten I’d done this until yesterday, it’s my age you know.

Anyway, I took out my Handkerchief, bundled it round the end of the float bowl breather pipe and stuffed it up above the small frame rail.

I then managed to ride backwards and forwards over the bridge, and through the cross wind, with no problems at all.
As a final test I removed the handkerchief and the bike died almost immediately the cross wind caught me.

Luckily, one of the things I’ve brought and squirrelled away over the last few years is a pair of breather boxes, so the Port side one went on the bike last night and I’ll test it as soon as I can.

I still don’t like the look of them, so might have to design and make a hidden version under the tank.

Nasher.

[Mossleymonster]

Or stay away from windy bridges. I don't know you well enough to smirk...

[Nasher]

Of course if only I'd enter the modern age and go all fuel injected it wouldn't be an issue.

[Mossleymonster]

Yeah, then you could idle away the hours polishing your Lambda sensors.

[Nasher]

There has to be a joke in there somewhere about a Welshman polishing his Lamb-da sensor.

But I'm not Welsh!!

Nasher

[Mossleymonster]

Lamb Dai sensors in Wales, Boyo.

[jerry]

I have seen this problem on my 750ss when one of the carb oneway vent tubes became loose and started flapping in the airflow , bike ran like crap

[CarloL]

I am having similar issues , Took the pump apart , doesnt look too bad

Obvious issue , I could find a split in both carb body breather hoses, I do not think it would affect it

1. Q: Should the check valve on the breather hose only work on way? I can pass air through the valve and suck air in from the same port
   
2. Is it possible to eliminate the check valve and just run a vacuum pipe?
   
3. Best Place for the repair kit for the Fuel diaphragm ?
   https://www.catalyst-findit.co.uk/in...64&pid=MK-DF62
   
   

PICs

Fuel Pump









Carb Breather pipe

[utopia]

As far as I'm aware .....
They're not check valves.
They are merely little chambers full of a wodge of mesh, possibly nylon, and should flow both ways.
My assumption is that they are either there to stop earwigs and spiders crawling in, or maybe to stabilise the flow.
However, in one of your pics the hose to one of these units is kinked .. to the point where it will allow little or no flow at all.
I reckon that's likely the cause of any trouble you've been having.

The perished/split pipes will probably be having little if any affect .. though I'd change them anyway, but only cos they're clearly past their best.

The pump diaphragm looks a little tired.
You'll need to replace it anyway at rebuild time.
Allen's Performance sell repair kits, I believe.

[CarloL]

Sorry , I kinked the pipe for the pic

I had a look on Allen's Performance, could not find them

RK-0003?

http://www.allensperformance.co.uk/c...-mikuni-carbs/


Think it is this?
Repair Kit: Fuel Pump MK-DF62

[CarloL]

fuel pump is all rebuilt as per instructions , no leaks ; she has fuel going to her

pipe at the rear is the vacuum pipe
90 degree side pipe is the fuel in
top straight pipe is the return pipe

But she still wont start , I Presume it is air locked, needs the bike to run to remove the air

I tried some petrol in the carbs , she starts then cuts out ; I am just killing the battery keep trying to start it

Am I missing a step?

Vacuum pump on the rear of the diaphragm to pull through the petrol?

[CarloL]

I took off the return line on the fuel pump this morning , petrol pouring out ; decided to crank her over , with some petrol in the carbs

She started and continued to run but cuts out after 15 secs , probably just down to being cold

I drained all the float bowls, re-installed the carb breather

All vacuum lines look good , took her for a drive and she dies out of the drive ; as soon as the revs drop she dies

Some perseverance I got her going in 1st , was fine till I had to slow down

Now she just wont start!

I am going to give her a damn good thrashing!

[CarloL]

She is always driven , this happened about a week ago

• Drained float bowls , just petrol
• Removed airbox
• checked fuel filter , all clear
• Checked peacock valve all good, we have fuel when open , none when closed
• Peacock valve to Fuel pump all good, we have fuel
• Fuel pump to Carb , all good , nice flow of fuel with everything off
• Checked vacuum pipe from fuel pump to exhaust , no cracks , cleaned with brake cleaner
• Checked nipple on Exhaust for the vacuum pipe, no blockages , leaks , removed and cleaned with brake cleaner
• Check breather hose (below the carb fuel line) to breather , no cracks ,leaks , cleaned with brake cleaner
• Breather hoses on side of the carbs need replacing but wont stop her from starting
• Removed Spark plugs and cranked her over a few times to remove any crap , excess fuel
• Checked spark plugs removed and cleaned , we have spark (They are only a few months old)

I tried to start her without the airbox , she just cranks ; twice she started for literally 2-3 seconds

I am a bit perplexed , air, spark and fuel should mean happy bike

[Darkness]

That’s a sneaky bin shot in there!