carburettor overhaul and seized screws

[ricardo]

Hi. I'm overhauling the carbs on my 400-4 . I've got as far as removing the carb pistons to replace the needles. I can't unscrew the 2 small screws at the bottom of each cylinder. I've soaked overnight in wd 40 to no avail. Any other suggestions please. I don't want to buy new ones as they are so expensive. If push comes to shove I can continue to use the existing jets but I'd rather know that they were all new.

HELP
Ricardo

[Bryanj]

It is better to use original jets and needles if undamaged rather than aftermarket parts

[andut]

Those little screws can be a pain - you need a good, well fitting screwdriver, and I found giving the screwdriver a bit of a tap helped them free off.

I would echo Brians advice to keep the original jets and needles unless they are definitely not usable.  The jets will not wear - they just need to be clean. 

Andy

[paul G]

+1on what Andy says a really good fitting screwdriver is a must.

[Nurse Julie]

I think I used a little PH bit as him indoors doesn't own any JIS screwdrivers, I can't remember having any issues getting them out.

[ricardo]

OK thanks. Glad I'm not the only one. Problem is I don't know if they're blocked. I don't have a well fitting screw driver. What is a Jizz set. sounds a bit rude. Is white vinegar a bad idea??

[hairygit]

JIS screwdrivers are Japan Industrial Standard, and they are different heads to the common Philips and Pozidrive crosshead screwdrivers. If you fins chewed crossheads on a Japanese bike, it's usually becase some previous numpty has tried using Philips or Pozidrive screwdrivers in them. I personally would not put vinegar, in fact ANY acid or alkaline near carb parts!

[paulbaker1954]

I had difficulties with mine and sorted with a JIS driver !!


They are expensive but one of the best investments I ever made

VESSEL are a good brand, I bought this set and have never looked back

https://www.ebay.co.uk/itm/JIS-Screwdriver-Set-Vessel-Megadora-P1-P2-and-P3-12705-6-8/171753460588?epid=1342330113&hash=item27fd4dd36c:g:5ckAAOSwmCVY~LCG

I am assuming here you are referring to the 2 small screws that hold the needles in place at least this is on the 500, are they the same carbs on the 500. If so and you do need to replace they are an M3x10 screw - should be easy to find anywhere cheap

If you really cant get them out, personally I wouldn't sweat they only hold the needles and these should not wear. As long as you can knock out the emulsion tube and ensure all is clear. (Again this is 500 speak)

MOST important in my experience is Ultrasonic clean everything you will re-use, especially the carb bodies they have ver very small channels in them for the idle air circuit

[ricardo]

Thanks to all of you. I'm now sorted. Haynes doesn't say is what a bitch the pivot arms are to reinsert??? 1 of those tiny spacers between the screw and the ball head of the arm was missing.  Disaster or not ?? it's only draws the fuel cylinders back and forth.  Please tell me soon before I put the unit back in the bike!!

Thanks
Ricardo

[Trigger]

JIS screwdrivers are Japan Industrial Standard, and they are different heads to the common Philips and Pozidrive crosshead screwdrivers. If you fins chewed crossheads on a Japanese bike, it's usually becase some previous numpty has tried using Philips or Pozidrive screwdrivers in them. I personally would not put vinegar, in fact ANY acid or alkaline near carb parts!

Never used a JIS screwdriver in my 27 years of removing these screw and i must of removed a million by now 

[JamesH]

Get on Amazon and get yourself a pair of these..absolutely awesome...

Vessel Megadora 980 Impacta P2x100 P3x150 JIS Cross Point Screwdriver Set of two items Original silicone cap https://www.amazon.co.uk/dp/B077CMH7QW/ref=cm_sw_r_cp_api_.7wKBbQB2ZVJB