setting up a Mikuni carb on a lightning

[geraldhattrick75]

I'm nearing completion of my 1965 Lightning fitted with a mikuni carb and had a few attempts at starting it.

However, after lots of kicking over, choke down on the Mikuni, both fuel taps on,  I don't seem to be drawing any fuel into the engine.... (plugs are bone dry )

Does anyone out there have experience of setting up a Mikuni carb on a (1965 ish) Lightning please?

Or better yet- know what jets, slide, needle position etc I should use?

Regards and thanks,
Dave.

[DAVE BRADY]

Hi Dave,

I have had a 30mm Mikuni on an A65T since about 2009 but I do not know what jets are in it.  When I ordered it from Allan's I asked for suitable jetting.  It ran well.  Recently I replaced it with a 28mm Mkll Premier jetted as standard and it runs well.  I fitted the Mikuni on to a long stroke 750 A65T without changing anything and it runs well.  So no really useful information there then.

I found this on line but it is for twin 32mm Mikunis. ​
Pilot jet = 25, 1.7 turns out
Main jet = 180
Air jet = 2.0
Needle jet = 159 P4
Needle = F5, center groove
Slides = 2.5

SRM do a kit so may well advise on correct settings.  Likewise Allan's.

The starting issue phenomenon is something that I have experienced and found that once started the problem disappeared. It is as if there is an airlock stopping the fuel from being sucked up through the very small passageways in the carb.  The down side of the Mikuni is that there is no tickler.  Try putting a bit of fuel directly in to the carb.

Dave.

[geraldhattrick75]

Thank you Dave, that's really useful. I'll put it into practice as soon as I get back from a small 'break'.....

Love the reassurance that the 'starting issue phenomena' is just something to overcome and not a regular recurrence.

I'll let you know when I get it going.....
Incidentally, I've been told to expect my long needed silencer within the next 24 hrs.... (So if you go out anytime today, wear some sort of head protection, those flying pigs don't mess around...)

Regards and many thanks,
Dave.

[Guitarzanbikes]

Hi, no fuel getting through is an experience I had on the A10 combo couple of weeks ago in the 30 degree heat (thanks for the push lads btw). The Mikuni was set up on the lighting in the mid 90's with the help of the late Phil Allen. I went for a 30mm and all the data, spare jets etc I had went with the bike when I had to sell her in the mid 2000's. Once we got it set up she ran absolutely beautifully and I just want to reassure you that unless someone has messed with the settings since I had her then I'd expect the same now. I did put all the settings in a notebook that went with the bike but am guessing you didn't get that when you acquired her. Good luck with the no fuel getting through problem and if I can help in any way do let me know. Mark

[Dean Southall]

Remember when starting using the Mikuni cold start to put you right thumb in your mouth.

[chaz]

My A50 has a Mikuni, there is a seperate plunger line teed off the main fuel feed and injects fuel into the inlet manifold.  only used for starting.

[DAVE BRADY]

Hi,

An interesting solution to a problem that should not exist.  As the Mikuni cannot be tickled it is worth delaying trying to start to allow the carb. to fill with fuel.  If the bike has been standing for awhile or it is hot the fuel level may not be up to the level needed in the float chamber.  So turn the fuel on, put your gloves on, depress the choke lever on the carb., turn the engine slowly once with the ignition off,  turn ignition on and kick the engine in to life with no or very little throttle.  The bike will start and quite quickly the choke lever can be raised and once even slightly warm an even tick over can be achieved.
Well that is how it goes for me.

Dave.

[geraldhattrick75]

That's a lot of really helpful comments that I'll set in on when I get back from our break.

So please don't think I'm being rude if you hear nowt from me for a little while.

I'll tell you how it all goes once I set in on the wee beastie.

As ever, your help is really appreciated....

Regards,
Dave

[DAVE BRADY]

Hi,

Don't forget that as you are only having one carb. you will need the specs. for a Thunderbolt.

Dave.