Fuel pump is all rebuilt as per instructions , no leaks ; she has fuel going to her (its a diaphragm fuel pump, runs off exhaust vacuum) 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?
check that vacuum pipe to pump isn't split and check to see if fuel is exiting from the Mikuni diaphragm pump - they often take on **** and water. If the transparent diaphragm has got a 'set' in it should you strip it down then don't forget to flip it over the opposite way round upon re-assembly.
usually not noticeable under 20k-ish* miles anyway, but the very part that performs the pumping action by continuous 'panting' gets deformed in one direction after time* so turning it over helps to return it to original intended stroke/action.
She has about 5800 miles When I stripped it , I used a new mikuni gasket/diaphragm rebuild kit , everything is new I will check the return line and the vacuum line tomorrow! Vacuum line all looked good, will triple check
you are right though, you can get an airlock when you have stripped the pump - it eventually clears but sometimes involves rather a lot (too much) starter churning so you could try (carefully) priming if this is the case. There are sometimes two other things in the pipeline (npi) depending on year, and both can be problematic - an on/off petrol cock and the fuel control valve (sits next to tank hinge). There is another starting method but would have to P.M. you.
Thanks Peacock I checked, once opened she pours out fuel What's the best way to prime the fuel pump, apply a vaccum on her? Will check all vacuum lines tomorrow It's the 1997 m900 if that helps
Can be messy, but I use a very small spout, you could even carefully prime the carburettor bowls this way, this would definitely give you enough to start the engine and this action alone will often sort the diaphragm pump out providing everything else is working normally.
just realised that I hadn’t read your thread from beginning (doh!) - I blame the time of night and my age :—-)
If you are trying this method take the spark plugs out first and the motor will spin freely and quickly without killing the battery charge
Great idea if you have removed the output from the diaphragm pump or if you have clear fuel hose but otherwise you could then flood the engine.
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!
Did you find or look for any water in the diaphragm pump or the carb bowls? Has it stood for a bit/got damp? Best to go around all the usual suspects like above plus water in the tank plus clogged fuel filter plus clogged up carbs centring on idle mixture screws above all else.
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
Thanks for the update Carlo, that’s going to help everyone who replies now, if you reckon it’s alright on the spark/ignition front, then I would probably go carburettor idle mixture jets or even carb strip next.
Heres the fuel pump when I dismantled , she needed a rebuild ; I just presumed it was the issue in the first place
it was definitely part of the problem- you can see the water! - you have to assume from that that there maybe water/corrosion in tank and carbs, (I know you drained bowls)
