Carb jets

[disc valve]

Hi group
Where can you get different size mains and pilot  jets from ?
To speed things up are there any UK suppliers.cheers

[BRT-GTR]

     I use Motocarb in Liverpool.
     Current main jets screw straight in but the thread pitch has been changed on the modern pilot jets. The 5mm thread is now ISO with a 0.8mm pitch. Original BS carbs use 0.9mm pitch, so I carefully run the pilots through a 0.9mm die before fitting. Only removes a minimal amount of metal and they work just fine.

[disc valve]

Hi Brian
When you say you run the pilots through a die do you mean a 0.9 p nut

[disc valve]

Pilot     m5 × 0.75 p
Mains   m5.3 × 0.9 p

You could run the pilot through an m5 × o.8 p standard coarse die which im sure is what you meant.do the mains come from Motocarb in m5.3 × 0.9p which is a bastard size and screw straight in as you say

[BRT-GTR]

        Sorry, I didn't have my brain in gear when I wrote the above reply. Must be lockdown or I'm getting old !

   You are correct with the thread pitches stated above, I'll start again !

     The main jets supplied by motocarb did screw straight in, so must still use the m5.3 X 0.9p thread, although I didn't measure the threads because there wasn't a problem.

   The pilot jets supplied would not thread in readily, they were tight ( I have read of people finding this on older Mikuni carbs and just forcing them in !).
   I measured the suppied pilot jet thread as the modern ISO m5 x 0.8p. So I bought a good quality, HSS, thread cutting die m5 x 0.75p. There is only a couple of thou difference in the threads, so you can easily wind the new jet through by hand using a well fitting screwdriver on the jet. Just make sure the jet is square to  the die.
  They then screw in to the carb easily and seat at the bottom.

[disc valve]

Anybody tried the chinese copies.ive ordered some to access them

[disc valve]

Hi Brian
Just to clear any confusion.BS pilot jets are m5×0.75.standard metric coarse thread is m5× 0.8 and die nuts are readily available.where did you get a die nut of m5×0.75 ?

[BRT-GTR]

      I use a company 'Tracy Tools Ltd' for all my taps/die etc, good to deal with and are sensibly priced. See link
   
       https://www.tracytools.com/taps-and-dies/metric-taps-dies/5-x-75-metric

     As there is only a few thou of metal to remove and I would rarely use it, I opted for the Carbon Steel die at £5. First one they sent was 25mm OD but had distorted threads from poor manufacture. No problem, they happily sent a free replacement which was 20mm OD, that was fine.
    So ask for the 20mm OD, CS die or opt for the HSS die at £15 which would be better quality.

[disc valve]

Well take me to the foot of our stairs.never knew you could get so many non standard metric taps and dies.you can even get JIS m5×0.9p and m4×0.75p
Cheers Brian.
Steve Cooper at motorcycle mechanics did a series of articles on improving the running of an rd350 with Spa motorcycles Rob Pemberton here in the UK.theyve done a lot of work to get 2 strokes running properly on modern fuel.they do a carb kit of replacement emulsion tube and jets that improves the bike no end.this maybe someone ill need to contact in the near future.theyve gone a lot further with elec programmable ign curve further mikunl carb mods and plug seat temp sensors to a temp gauge plus more.

[BRT-GTR]

           Foot of our stairs is also quite busy, they probably stock any tap/die you could ever need. I now have a full range  for all the JIS pitch screws on a Bridgestone, from 3mm through to 12mm.
       If you contact Steve Cooper, I'm sure all members here would be very interested to hear of any improvement they might make to the carbs and ignition. As supplied the carbs were overjetted and benefit from 130 mains and 27.5 or 25 pilot jets on the 350
       Going further, a number of people have experimented with redesign of the combustion chamber to suit modern fuels.
  Rubber mounting the carbs would also be advantageous, have thought of repacing the phenolic carb insulator with  rubber but not sure how effective it would be.     

[disc valve]

Made contact with Steve Cooper regarding a fuel tank lining issue so hopefully will discuss the gtr fuelling at a future stage.i also know another vjmc member whose restored a kawasaki 350 A7 avenger very similar to the GTR and hes had the heads reshaped and also had ali liners made and plated instead of cast iron.he toured Spain on it last summer

[OldSwartout]

There wouldn't be any reason to sleeve the GTR cylinders with aluminum since they are already solid aluminum, unlike the Kawasaki, which did have iron liners. If the GTR cylinders are scored or the plating peeling, then go for a Nikasil replate.

[disc valve]

 Yes i concur old swart.my cheap pilot jets arrived from china.16.5mm long instead of 14mm.c/bore into bleed holes is 1.3 mm dia instead of 1.75mm dia and bleed holes not deburred internally.when i sent them a picture of their  jet next to a mikuni jet they offered a 50 % refund.you live and learn.not saying there all bad though and i could try them with some modifications