Ok I'm coming to the end of my options! ... and tether! I've got the jubilee running, it ticks over nicely and accelerates well if I open the throttle slowly, however it completely dies if I open the throttle quickly and this is at any revs. This is made better if I put the choke on which I thought meant it was running lean. The bike has a concentric fitted with jets the same as the monoblock. I've tried raising the needle and increasing the size of the main jet to 140 to no avail, the problem continues, I've also fitted navi monoblock with jubilee jets but that did exactly the same thing leading me to think it must be something else.... maybe the old rule of 90% of carburation problems are electrical is holding true!
ive checked the timing with a strobe (Boyer) changed plugs and made sure the coil earths properly. I've checked for air leaks as well.
Its not helped by the fact that I don't have much space to test ride .... does anyone have any bright ideas or is this cutting out when you wack open the throttle normal?!
Dan
Well I've bitten the bull…
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I managed to track down a…
I managed to track down a correct new monoblock from Feked, but was disappointed that the slide slicks in the jet block, Amal still have to get their quality control sorted. Anyway i fitted an old block and all was well, Iâll look for the sticking point later. Having fitted it and started her up It wasnât an instant success but much much better, the bike happily cruises at 50 now. I still intend to switch to 2 6v coils and change the plugs, hopefully that will improve the still slight hesitation when I open her up. Once Iâve done that I can concentrate on the navigator and M50 engines I bought this year!
one thing I should add is the spare heads i fitted with reground valves are much noisier than the originals, I may re do the valves on those in due course.
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Hi Dan, Sorry to join in l…
Hi Dan,
Sorry to join in late in the conversation - but I suspect it may be the concentric carb itself. The Jubilee is very fussy about carburation (from experience) and only runs well on the correct monobloc. I'm typing this late at night, bleary eyes, etc - but I believe there is not an exact concentric to replace the monobloc used.
The monobloc spec is 375/43, with a 25/32" bore (choke) size = 19.844mm.
The nearest concentric you can get is 600 series on 20mm bore - similar, BUT crucialy NOT the same.
It may cost a few bob - but a new CORRECT monobloc is available again - see http://amalcarb.co.uk/monobloc-series/375-series/base-line-specifications/standard-25-32-monobloc-carburettor.html
Alternatively - why did you remove the old one? Is it worth trying it again?
Best wishes
Andy S
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Wow - as I 'posted' my n…
Wow - as I 'posted' my note - a few more conversations appeared - & you have already gone ahead with this.
Sorry for re-inventing the wheel.
Andy S
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Not a problem Andy we must…
Not a problem Andy we must have been typing together!! there appears to be a shortage of 25/32 monoblocks but I found one!
Iâd be interested to know how other peopleâs jubilees perform? I remember mine being quite revvy but this one vibrates quite a lot at higher revs, but is quite pleasant at 45- 50mph although it doesnât get there very quickly!
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Well I've bitten the bullet and bought a 25/32nds 375 monoblock. It Should arrive next week, they are a bit like rocking horse pooh at the moment. I'll keep the concentric and see if it works on my M50 box of bits project! I think it's too big even for the navi.
Fingers crossed