B31 carburetor clean

[rhyatt]

Do also check the condition of the needle and its needle jet , over time, the needle rattles around in the jet and wears.
As mentioned before , start with a baseline and remove unknowns

[V500]

I've seen a few needle jets which have worn visibly oval. The bikes (all singles) ran OK-ish but were pigs to start, so a new needle and associated jet is always fitted if the existing carb is being reused.

[rustyboots]

.Update.
Hi all.
Today i have fitted a new 260 main jet, a new 3.5 slide and a new 30 pilot jet, needle set at position 2.

Previously for starting   it would need about 3/4 advance, today it just coughed, spluttered and kicked back quite hard at the same setting.

It did however start with the lever barely pulled back from the top (Fully retarded)? position.

If the work done today is affecting the retard/advance, can someone who knows explain what if anything is going on and do i need to do something else.

Unable to road test at the moment, and cant run for long in the workshop as my remote fuel tank is scuppered .
TIA

[rhyatt]

If the timing is mechanically the same as before , (ie , you've not changed anything) then the different carburation brought into play with these new bits has had an effect for sure.
The burn rate and mixture are different , once available , a road test will prove things

[limeyrob]

I would say that's a good sign. With a manual A/R the mag "strong" point is set at fully advanced so as you retard you get weaker spark. More noticeable if the mag is already weak. Before the carb clean mixture was wrong, now it looks like its right and you are getting combustion with more retard.  Once you find the sweet spot for the new carb settings it should be easier to start.

[DAVE BRADY]

Hi,

I would have thought that fully retarded is the starting position so a bit of that sounds OK espcially as it started.
The kicking back at 3/4 advance can be expected.
How much throttle did you use?
Open too much can create a weak mixture which combined with the advanced position will also potentially cause kickback.
It will be interesting to see how it is when you can run it for a bit longer.

Dave.

[rustyboots]

Cheers guys,
Those comments are extremely encouraging. Thought I was in for a nightmare.

[limeyrob]

Its many years since I sold my B31, but I seem to remember it started at around 1/2 way on the lever travel, about in line with the bars.  This was for a slack wire advance.