14 replies to this topic

[ChrisG]

The wife's Diversion 600, which has has a vacuum fuel tap, seems to run fine when set to Prime, but if I set the tap to Main it seems to run ok (rode it a couple of times around the block) with some revs on but conks out at idle.  I've fitted a new seal kit to the tap, which seems to have cured the small leak but not the conking out.     All I can think of is it's somehow not getting a good enough vacuum at low rpm to keep the tap open, but I've just checked the neighbor's Divvy and the vacuum line is connected up the same, seems to be tight both ends and no obvious splits.

 

Any other ideas?

 

[celticbiker]

Probably the diaphragm on the vacuum side of the tap, it's not uncommon for them to split thus not pulling the tap open enough.

Higher revs give a greater vacuum and more lift which is why it runs ok at higher revs.

Only other thing is that it could be a build up of crap blocking the main fuel outlet but then I would expect it to be bad all the time not just at idle.

Edited by celticbiker, 25 March 2016 - 05:12 pm.

[ChrisG]

I'm guessing Prime is using the same bit of pipe from the tank to the tap as Main is, in which case probably not a blockage.  Replaced the diaphragm as part of the seal kit, and it's not solved it so hopegully not the diaphragm inless there's damage to the tap body that damaged the new diaphragm.

 

Just realised I've got some big syringes so could test if the pipe and tap are holding vacuum.

[celticbiker]

Prime and reserve (if you have such) use different parts of the pipe internal of the tank.

[leehenty]

My old divvy had fuel problems and I solved it by fitting an electric fuel pump from a carburated R6, IIRC Saved me no end of problems when switching over to reserve.

 

It had one of those vacuum fuel pumps like the 850 and conked out at idle just the same, worth checking the pump.

Edited by leehenty, 26 March 2016 - 11:04 am.

[divvxj]

thought i had done something wrong, hope it all works out for you , the only fuel related problem i had was when i put  a litre of diesel in the tank , popped and farted now and again , the bike not me

[celticbiker]

True, I ran my old 600 on half a tank of diesel once and apart from a bit of smoke and lack of power it ran ok.

[ChrisG]

Neighbor said he recently fitted a new fuel pump whish has stopped his divvy randomly conking out.  Think I might have an R6 pump knocking about the garage that I bought for the Mk1 but never fitted.  Not sure it's the pump though as it would it work fine on prime if that was the case?

[leehenty]

well the leccy fuel pump will have more suck so that might be it, prime as far as I know bypasses the vacuum valve and runs direct so you can fill the carbs with no vacuum.

[ChrisG]

Well I've finally got round to taking a look at this and why the damn thing won't start.

 

It's not been run in months so wasn't keen on starting.

If I disconnect the fuel line going in to the carbs I get fuel coming out when I crank the engine, so presumably that means the fuel pump is working ok.

I replaced the vacuum line to the fuel tap in case there was a leak there causing the fuel tap issue

Also replaced the fuel line from the tank to the filter as I had to shorten it some time ago as it had perished, this meant there was a bit of a kink in the pipe that could have been causing trouble

Had to dribble some fuel in to the carbs to get it to start up, but eventually got it going and it ran fine on prime

 

Switch to main fuel and after some minutes the idle dropped from 1000 to around 500 for a while and then conked out.  Restarted ok and ran fine with some revs on but still slow idle and stalled after a while at idle.  Back to prime and it ran fine again idling at 1000.

 

 

I can't believe it's the fuel pump if it runs fine on prime, but can't see what the issue can be with the tap as it had a new seal kit not that long ago.  

 

 

 

Given Lee's point above, I found this lurking at the back of the garage

 

 

Hmmm, image not working, how about this? https://www.dropbox.....39.09.jpg?dl=0

 

Think it's either and R1 or R6.  Big bugger compared to the vacuum jobby on the divvy.  Presumably the bigger pipe is the inlet and the smaller one the outlet?  If I were to fit this, will I need to mess about with the carbs to get it to work ok, or should they deal a different fuel pressure ok?

Edited by ChrisG, 01 August 2017 - 07:51 pm.

[Studley Ramrod]

The fuel pressure shouldn't be much greater than the vac pump so the carbs might be fine.

 

Just wondering if the filter might be restricting the flow when using the main supply ?

[ChrisG]

Fuel goes through the filter before it reaches the pump, so it's the same whether it's on prime or main.  I didn't check the filter but I'm pretty sure I flushed it out when I looked at it last year.

[Swarf]

Vacuum diaphragm in the tap? Prime would bypass said vacuum I'd think.

[ChrisG]

Yeah but I put a new seal kit including the diaphragm on last year and it made no difference, unless the housing's damaged and it knackered the new diaphragm straight away I suppose.

[ChrisG]

Left it a couple of weeks and the bastard won't start again!  Think I'm going to have to try that other fuel pump to see if it makes a difference.