Author Topic: Carb jets  (Read 624 times)

0 Members and 1 Guest are viewing this topic.

Offline disc valve

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 33
Carb jets
« on: December 27, 2020, 11:14:22 AM »
Hi group
Where can you get different size mains and pilot  jets from ?
To speed things up are there any UK suppliers.cheers

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 915
Re: Carb jets
« Reply #1 on: December 27, 2020, 01:20:46 PM »
     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.
Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline disc valve

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 33
Re: Carb jets
« Reply #2 on: December 28, 2020, 04:00:11 AM »
Hi Brian
When you say you run the pilots through a die do you mean a 0.9 p nut

Offline disc valve

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 33
Re: Carb jets
« Reply #3 on: December 28, 2020, 06:33:07 AM »
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

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 915
Re: Carb jets
« Reply #4 on: December 28, 2020, 07:21:17 AM »
        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.


Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline disc valve

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 33
Re: Carb jets
« Reply #5 on: January 01, 2021, 06:18:36 AM »
Anybody tried the chinese copies.ive ordered some to access them

Offline disc valve

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 33
Re: Carb jets
« Reply #6 on: January 09, 2021, 07:16:02 AM »
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 ?

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 915
Re: Carb jets
« Reply #7 on: January 09, 2021, 07:49:16 AM »
      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.
Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline disc valve

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 33
Re: Carb jets
« Reply #8 on: January 10, 2021, 05:44:39 AM »
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.

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 915
Re: Carb jets
« Reply #9 on: January 10, 2021, 08:37:35 AM »
           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.     
Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline disc valve

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 33
Re: Carb jets
« Reply #10 on: January 15, 2021, 10:44:53 AM »
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

Offline OldSwartout

  • Global Moderator
  • Trade Count: (0)
  • *******
  • Posts: 1213
Re: Carb jets
« Reply #11 on: January 16, 2021, 08:50:57 AM »
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.
Karl Swartout
Mooresville, IN
BS175 Roadracer. BS200RS, BS175HS
BS350 GTR

Offline disc valve

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 33
Re: Carb jets
« Reply #12 on: January 19, 2021, 11:48:15 AM »
 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

 


Gallery


Views:6
Comments (0)
By: Chibi62

Views:9
Comments (0)
By: Chibi62

Views:11
Comments (0)
By: Chibi62

Views:6
Comments (0)
By: Chibi62

Classifieds

1970 Bridgestone Mach II SS Motorcycle 200 CC

Price: $3200.00
Date: 01/17/2021 01:37 pm
Time Left:
1970 Bridgestone Mach II SS Motorcycle 200 CC
Price: $3200.00
Date: 01/17/2021 01:36 pm
Time Left:
GTO
Date: 12/29/2020 01:08 pm
Time Left:
GTO
Date: 12/26/2020 02:46 pm
Time Left:

Recent Downloads added

1970 sales brochure
Rating: *****
Filesize: 6753.33KB
Date: July 16, 2020, 10:01:18 PM
2018 Article in Motorcycle Classics
Rating: (None)
Filesize: 3877.88KB
Date: June 29, 2020, 05:26:00 PM
350 GTR pdf version

Rating: *****
Filesize: 7366.26KB
Date: March 14, 2020, 09:41:23 AM
Parts Manual for BS175-200 Lights
Rating: (None)
Filesize: 971.88KB
Date: March 06, 2020, 04:30:46 PM

Powered by EzPortal