New Mikuni - won't start...

FastFred · Jan 9, 2011

Just fitted a VM34mm single Mikuni to my 850 that started first kick on the old knackered Amals but it won't start.

It's freezing cold over here in the UK so I warmed the sump/engine (as it's wet sumped) to help it a bit. It's nearly firing but won't quite go. Do these normally need the choke on (which is in the down position?). It seems to kick over a lot easier with the lever up (choke off). Why is this as there is no butterlfy choke in a Mikuni?

Going to try some fresh fuel today .

What's the best starting procedure for cold weather?

Thanks.

kommando · Jan 9, 2011

Can't help on the carb but you do need to drain the sump as warm or not that oil will be dragging the crank.

pelican · Jan 9, 2011

I forget it's been so long since I started mine. It's either push halfway start the the rest of the way after it warms up(idling- bout 30 seconds), or push all the way down to start then half way up after it's warm

plj850 · Jan 9, 2011

FastFred said:
Just fitted a VM34mm single Mikuni to my 850 that started first kick on the old knackered Amals but it won't start.

It's freezing cold over here in the UK so I warmed the sump/engine (as it's wet sumped) to help it a bit. It's nearly firing but won't quite go. Do these normally need the choke on (which is in the down position?). It seems to kick over a lot easier with the lever up (choke off). Why is this as there is no butterlfy choke in a Mikuni?

Going to try some fresh fuel today .

What's the best starting procedure for cold weather?

Thanks.

Its not a choke its a starter enrichment circuit push lever down do not touch throttle as this prevents the starter enrichment circuit from functioning.

After it starts push the idleup to 1200 with idle screw turn off starter circuit or you will foul plugs do not leave starter circuit on for more than 30 seconds.

Good luck Paul (VM38)

RoadScholar · Jan 9, 2011

Mikuni VMs have a spring on the float needle that limits travel; if your carb has been in someone's inventory for a while the needle could well be stuck. Use plj850s advice on the starting drill, if it won't light off, do check the bowl drain for fuel, if none then take a medium sized screw driver and give the float bowl a few smart whacks, if that doesn''t evoke a stream of fuel pull the carb and clean it.

RS

ML · Jan 9, 2011

Has it got a Pilot Jet of 35 or 40 installed?
850's start and run better with a 40, but there are other possible reasons why its hard to start i.e. battery condition, sump full of cold oil, scungy spark plugs etc'.

Mick

rocker1 · Jan 9, 2011

Hi just saying hello so I will be able to see posts.

rx7171 · Jan 9, 2011

Assuming you have the Mikuni with the lever for the enricher and not the cable to the handlebar
choke lever the lever at the carb should be all the way down, with hand throttle fully closed.

When I start my bike now and its just a bit over freezing here I need to leave choke on for a short while and then roll on a little throttle as I back off enricher.

If still not working check plugs. If wet then choke working. If dry then you have a fuel starvation problem.

Bob

Keith1069 · Jan 10, 2011

Not saying it is the problem but after 5 weeks idle I tried mine after Christmas and after 50 kicks it came to life. About 3-4 deg C, lots of tickling and no chokes. I think it was the old fuel as I'd drained the tank but not the carbs. Two days later first kick at 0C. The 40 weight oil didn't help either. Hope you sort it.