emulsion tube replacement gk76

[silbeer]

You should be able to get the correct mixture using the o-9 needle jets by playing with the needle clip position and shims.

[stripes1976]

You should be able to get the correct mixture using the o-9 needle jets by playing with the needle clip position and shims.

i hate to correct you on this but adjusting with clip height and shims will adjust the fuel range above 1/8 th throttle to WOT. To correct this properly across the rev range you will be changing main jet for full range adjustment. The needle taper adjusts the set amount of fuel at a given opening point so if you adjust one you will be then looking at changing pilot jet size to. Gets confusing and easier just to use a 0-9 and a std main and a can which most people have already without changing main jet. Drop a K&N in with the large port and use a 117.5 main. (never try tuning a 76a without knowing the carbs are right to start with or you'll end up chasing your tail and creating more issues)

[Variablevalves suck]

Stripes is spot on with the rejetting.
The next paragraph is from a forum the Bandit forum, coppied from some Yam guys and is a basic help to jetting and give s a few ideas. If you up the needle jet you will have to alter other parts of the carb (ignore th 102.5 as this is for a B4)-

Also, using this guide I found as well (I don't remember where, FJ forums I think) helped a great deal and is fairly accurate even with our bikes. Starting jetting point would be 102.5 Mikuni:

1 jet size for custom 4 into 2 exhaust

2 jet sizes for 4 into 1 exhaust

1 jet size for K&N filter (single inside airbox)

1 jet size for drilling out the bottom of the airbox

2 jet sizes for both single K&N and drilled airbox

2 jet sizes for individual filters

2 jet sizes for no muffler (open header)

1 pilot jet size for every 3 main jet size increase

Add up all the jet size increases and subtract one. (Remember they go in steps of 2.5 for each jet size)

[cruicent]

Been emailing a guy from factory pro who said they didnt have any gsxr400 tubes to play with so will be sending some piccies and measurements as soon as I find my camera charger! Might also send my tubes down to them as I wont be able to muck about with the bike at the end of the monthas Im away for a couple of months Maybe by the time I get back they could have replicated them.

[stripes1976]

send me the contact details for the person you have contacted. They have already a set of std and sp ones from me and i haven't heard back since i sent them over a year ago. I have another set i can send so just want this sorted. Cheers mate

[cruicent]

pm'd (I think, its in my outbox so maybe not sent, not sure...).

[silbeer]

i hate to correct you on this but adjusting with clip height and shims will adjust the fuel range above 1/8 th throttle to WOT. To correct this properly across the rev range you will be changing main jet for full range adjustment. The needle taper adjusts the set amount of fuel at a given opening point so if you adjust one you will be then looking at changing pilot jet size to. Gets confusing and easier just to use a 0-9 and a std main and a can which most people have already without changing main jet. Drop a K&N in with the large port and use a 117.5 main. (never try tuning a 76a without knowing the carbs are right to start with or you'll end up chasing your tail and creating more issues)

No worries, I'm not a carb expert! I see what you mean looking at mikuni's fuel flow charts. The jet needle is influential to a greater throttle range than the needle jet which complicates this more than I thought, makes perfect sense now thanks!

[stripes1976]

going from memory the std 76a uses 0-5 emulsion tubes open tube design not 0-8 or 0-9 on a 33mm carb.
now the sp model uses a 35mm carb a 0-9 and a half shouded design which allows the airflow to draw more fuel for a given tube size. Dont quote me on this as i havent found my parts manuals in a year or so. I'll drag a set of carbs out at the weekend and have a look to confirm. I'm still waiting on a reply from factory pro. Will keep you updated on progress when i have some.

[panda]

Dont know if this will be much help to people but i bought replacment tubes from fowlers at bristol
standard 0.5 part number 09494-00704 had to be orderd from japan at took about 3 weeks to come in
and cost me about £95.00