Top end cutting out

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Lewes96
Posts: 171
Joined: 20 Nov 2016 20:22
Location: Lewes

Top end cutting out

Post by Lewes96 »

My Strada faltering and power dying away when ridden hard, esp going up hills. Ok if back off and then give it another go but then same thing happens. Thought it may be fuel supply as there was a bit of crud in the float chambers so cleaned tank and fitted new taps. Carbs balanced and new gasket kit fitted and all looks/runs as it should when setting up. Air filters only got 500 miles on them. However, still the problem. Front plug sooty when pulled after one of these episodes but normal when not ridden hard. Any thoughts out there?
MickeyMoto
Posts: 2415
Joined: 22 Nov 2008 17:41
Location: Even further oop North

Re: Top end cutting out

Post by MickeyMoto »

What happens if you boot it down a couple of gears? Is it only in higher gears?

Might be worth checking out the ignotion components, too, including leads, caps and plugs.
harrymuffin
Posts: 292
Joined: 07 Apr 2014 16:06
Location: west midlands

Re: Top end cutting out

Post by harrymuffin »

Try it with both petrol cocks open. I had this problem with a hybrid if pressing on with a lot of throttle, otherwise ok when pootling. Fitted the cube type petrol cocks and ditched the electric one which simply do not allow the fuel sufficiently. You need a flow rate of at least 0.3pints/min for 40mpg and 0.5pints/min at 30mpg and that is with a Forgotten Era 372 with all the trimmings, so as you have a cooking Strada; if that imporoves things in addition to the above check the gause filters in the cocks and finally make sure you have the tank more than half full to give a higher head and therefore greater flow. Oh, one more thing make sure the tank is not air locking - check the breather holes in the cap.
Lewes96
Posts: 171
Joined: 20 Nov 2016 20:22
Location: Lewes

Re: Top end cutting out

Post by Lewes96 »

Hi, this is with two new taps fitted and both open. Dropping down gears makes no difference. I will check the ignition bits though.
3potjohn
Posts: 1243
Joined: 02 Jun 2007 13:58
Location: Devon

Re: Top end cutting out

Post by 3potjohn »

You can swap the ht side and see if the fault moves to the rear. It is also possible to undo the float bowl nut and collect the fuel ( though I did this with the tap on once) and check that the volumes are the same or there about. Best to have the bike on the main stand to try and limit fuel passing to the left hand carb. I use a ramekin to collect it.
Are the valve clearances sufficient?
John
George 350
Posts: 450
Joined: 16 Jun 2007 09:43
Location: Northampton

Re: Top end cutting out

Post by George 350 »

I had a similar sounding issue with my sport a few years ago. Turned out to be a lack of ignition advance on the rear cylinder. Certainly worth painting/scribing/sticking a mark for 'ANT2' on the flywheel so that you can check the advance on both cylinders if only to rule it out as a possible cause.
George
350 sport 1978, 350 Strada 1978
650 Norton 1967, 650 Kawasaki 1977 and 650 Enfield 2019
Lewes96
Posts: 171
Joined: 20 Nov 2016 20:22
Location: Lewes

Re: Top end cutting out

Post by Lewes96 »

Having checked carbs thoroughly tried a plug change to BP7EV from B7ES and problem seems solved. I guess the more slender electrode works better.
EVguru
Posts: 1528
Joined: 01 Aug 2006 11:13
Location: Luton
Contact:

Re: Top end cutting out

Post by EVguru »

Unless you made a typo, you had the wrong plugs fitted.

The P in the code is for projected nose.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
Lewes96
Posts: 171
Joined: 20 Nov 2016 20:22
Location: Lewes

Re: Top end cutting out

Post by Lewes96 »

Finally got to the bottom of it. The block where the main jet/float bowl retaining nut screws in had split vertically. Not much but was allowing excess fuel round the main jet, hence rich running to end. Replacement carb body ( Ducatipaddy - nice refurb) and all good.
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Top end cutting out

Post by mbmm350s »

Hi
Glad you found the problem - sounds pretty rare to me, may be the main jet was overtightened in the past?
Mark
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