15 replies to this topic

[ChrisG]

Finally got round to trying to work out why the Mrs Diversion doesn't like to start when it's been left for a while.  It has a vacuum fuel pump which looking on the internet is quite possibly the same as the one on the 850

https://www.ebay.co....9?ul_noapp=true

 

If I remove the tank and crank the engine with my finger over the pipe that would normally attach to the tank, I feel a couple of small pulses but then not much.  Presumably I should feel continuous suction?  Forcing some fuel in with a syringe causes the bike to start first time.  So am I right in thinking the pump's knackered?

 

Annoyingly I have an electric pump like this one in the garage that I bought years ago to fit my Mk1, and it doesn't seem to work

 

So do we think it's the pump, and am I better off getting an electric one rather than a replacement vacuum one?

eg https://www.ebay.co....b7d63d33440f2ea

[curlylegend]

I got a super cheap vacuum pump off Ebay recently and it was a scoop to fit !  No messing about with electrics....and it cured the starting problem.  My 3VD starts on the button even after standing for a fortnight.

[dapleb]

Can you open up the old pamp cwis? Worth trying the arsey Tate trick to see if it's the pamp. Then ewe can decide if you want a super reliable mechanical pamp or add in extra complications of electrickery!!!

[ChrisG]

Yeah I opened it up but can't see any obvious issues with it.

 

Sounds like your symptoms were the same Curley, I was having to give it a dose of easy start in the intakes if it hadn't been started for a few weeks, although now I know I can pop the fuel pipe of the tank a shove a syringe full of fuel in there

 

All the super cheap vac pumps seem to come from china by bicycle and will arrive by next year, electric one sounds less hassle as it can be here next week.  There's already switched supply on a relay there for the intercom so easy to wire in.

[dapleb]

Is the diafragramatical dead flat or bulbous and flappy?

[ChrisG]

Looks flat, seems to be a clear and fairly stiff plastic sheet rather than the rubbery thing I was expecting

[ChrisG]

Am I missing something or have I bought a duff one?  Got a new (with warranty!) electric pump, it's definitely getting 12v but does nothing.  I've tried priming it with fuel in case it has something that stops it running when dry and that makes no difference.

[wicklamulla]

Crispo,  have ya tried tapping the pump body with a piece of wood or a screwdriver to see if it kicks inta life?  Tried reversing the wiring and see if that does it?

[ChrisG]

Well I thought I had, bit in the interests of exploring all avenues I went and tried again.  After gently introducing it to the persuadertron a couple of times, the next time I turned it on it went clunk, so I persuaded a few more times and then it magically started working 

 

Noisy little bugger though, louder than the engine at tickover!  When I put my thumb over the exit it cut out, but after running the bike for a bit it seems to just keep going when I turn off.  No sign of fuel leaking and starting the engine after 30 seconds or so of just the pump clacking away it didn't seem to have flooded, so I'm hoping it's just air in the system and will sort itself out.

 

Both bikes now ready for MoTs!

[MipeTDM]

If you mount the pump using some rubber dampers, it can become much quiter.

[Bjørge]

If you mount the pump using some rubber dampers, it can become much quiter.

I bought a 2.nd hand Fazer 600 (methinks?) pump, which is actually wrapped in a rubber "jacket". Not installed yet, though :-)

[MipeTDM]

I bought a 2.nd hand Fazer 600 (methinks?) pump, which is actually wrapped in a rubber "jacket". Not installed yet, though :-)

Indeed, thats also what Yamaha realized it needed. I bought one like this:
https://rover.ebay.c...tm/171963169609
So needed to invent some mount, 2nd try with some rubber damping, myself

[ChrisG]

Rode it 15 mins or so to the MoT bod and it quietened right down, can't hear it at all now, so I reckon it was just air in there somewhere.

 

However it runs fine with the fuel tap set to prime, but not when the vacuum operated tap is on Main or Reserve.  Could knackered inlet rubbers or something stop it creating enough vacuum?  I cranked it with my finger over over one of the vacuum points and it was definitely sucking, but I'm wondering if it's not sucking enough and that's why the vacuum pump didn't work properly?

 

That looks identical to the one I bought Mipe, I've currently cable tied it to the old mount as it's a completely different shape, I'm thinking I can get some rubber or silicon sheet to wrap around it to allow it to wobble about it more if it wants.

[dablik]

Slip some silly cone over the pump ? or not

[Bjørge]

Indeed, thats also what Yamaha realized it needed. I bought one like this:
https://rover.ebay.c...tm/171963169609
So needed to invent some mount, 2nd try with some rubber damping, myself

Yeah, they're extremely noisy  . The first time I switched om power I was 100% sure something was wrong. I actually disassembled it before I understood that this was exactly the noise it's supposed to produce...

[MipeTDM]

Yeah, they're extremely noisy  . The first time I switched om power I was 100% sure something was wrong. I actually disassembled it before I understood that this was exactly the noise it's supposed to produce...

Indeed, I even reported it as defective:
https://mpesgens.hom...2_175304741.mp4
Only over 50 km/h the sound finally vanished in the wind noise...