JRC Carb advice

[jfligg]

Hi Guys
Does anyone have any experience with JRC Carbs. I would like to put one on a 1961 BSA Super Rocket 650cc. Any help would be great thanks. Jeff

[muskrat]

G'day Jeff,
              I've got a pair on the cafe. trouble is their both left handers, hard to get to the choke on the right one.
Once set up their great but a real bugger to set up, there is so many needles and jets to juggle.
 Have a look here.
piled-arms.com/jrccarb.html
Cheers

[mike667]

Jeff
what muskrat said -  i have them on my 61 triumph - and after getting them dialed in like them a lot. But if you don't like tinkering with carbs, it may be a bit frustrating - i like playing w/ carbs so it was fun in a sick way- the guys at JRC carb are great for advice (as is muskrat) on getting them dialed in

[rocker21]

I am now the importer into the UK of JRC carbs and for info there is a cable conversion for the choke which makes it easy for twin carb setup, also the throttle stop can be moved from one side to the other , for a twin carb setup there is also an extended pilot air screw adjuster which has a knurled thumb screw which you can turn by hand, no need for a screwdriver.  if anyone wants some help or info contact me.
www.brillbikeparts.co.uk
I have fitted this carb to my own A7ss and we have done several A group twins including a plunger A10 all with good results.

[muskrat]

 G'day rocker21,
                      I'd be interested in the choke cable set up for twin carbs, and also the extended air screws. How much $ ?.
Cheers

[rocker21]

twin carb choke conversion kit which terminates in a standard looking lever on the handlebar is £31.20 including vat but does not include postage.
extended air screw is £5.10 including vat but not postage.

[jfligg]

Hi Rocker
  Did you have any tuning issues when putting these carbs on a A10?  May I ask what jets you are using and what idle screw setting worked for you.  I am having a bugger of a time with my 61 A10 SR bike.  I would appeciate any help and advice you can give.  Thanks Jeff

[rocker21]

no troubles at all, took it out of the box and just fitted it and it started first kick, pilot air screw it about 1 turn out, needle is in the middle notch, left the standard main jet in,  you do need to keep the tufnol heat spacer in, my mate who runs a classic bike restoration and repair shop has bought quite a few and has fitted them to all sorts from velo, assorted bsa machines and a vincent special and so far all he has done is taken them out of the box fitted them and away they go, maybe the odd tweak on main jet size  but that is it. one problem i have found that did not show itself before the conversion was a mag problem but once that was sorted everything went ok and the bike has now done a few thousand miles without trouble.
so far all the ones that i have sold are working fine, only one customer had a problem and that was his fault as he had fitted the throttle cable wrongly,
difficult to diagnose problems without seeing the bike, how old is your carb? i have only been selling them this year and everything is brand new and they just seem to work.

[jfligg]

Hi Rocker
           Thanks for the reply.  You were right,  My major fault was a points plate in the mag that was slipping in the tapper.  Problem solved.  The bike seems to run ok, but I cant get the idle to drop to below 1300 rpm ish.  I dont really trust the old chrono.  I have the air screw fully seated and thats the lowest I can get the idle.  Is it time to drop a  pilot jet size?  I went 2 sizes smaller on the main jet and the plug colour is still black.  i am alittle scared to drop again to a 115 jet it seems small.  The plugs are still black.  I have a siamesed exhaust is that part of the problem?  Jeff

[rocker21]

should tick over a lot slower than that, something else must be wrong, check timing on both cylinders there should not be a lot of difference between them,
does the slide close fully? if you remove the carb and  hold it up to the light you should be able to set the throttle stop so that you can just see daylight, how are you using the choke? it should be fully depressed when running, you lift it for cold start and it also gives a fast idle as it is a fuel enrichment device, it sounds like you have trouble there as if that is not closing it will give the symptoms you describe.
my a7ss ticks over @ approx 800 rpm and a couple of gold flash's all tick over at less than a 1000 rpm

[jfligg]

Hello
  Can someone please help me tune this carb.  I am on the verge of selling the @#$%$# bike.  Should I put the amal back on it.  Thanks in advance.  Jeff

[rocker21]

where do you live?

[jfligg]

Lucan ON Canada

[rocker21]

to far away for me to deal with as i am in the  UK, have you tried dealing direct with Bill at JRC as he is in California .
email address jrcengineering@aol.com
if you had been in the uk i would have said come and see me and we will get it sorted.

[jfligg]

Hi Rocker
  Thanks for the reply.  I am going to install the original main jet and air filter.  Then I am going to do a plug chop.  I am not real confident in doing a plug chop,but here it goes.  Jeff