jet size ideas

[floridafzr600]

alright i have a 91 fzr 600 with pod filters and a delkevic ss70 exhaust. i have dj112 in the middle and oem 107.5 on the outside and i am still having hesitation in mid rpm i have the whole dj kit up to dj130 anyone have ideas on what sizes i should try next? and i have the r6 vr brand new iridium plugs and they are almost tan and happy.... btw the next sizes up are 118 126 130

[blensen]

Needles. Mid-rpm points to needles and to a lesser extent, float level. If you haven't done Reelrazor's timing mod, do it. If you haven't read YG's pods how-to in the wiki, do that too. That should give you enough to make some progress.

[floridafzr600]

ok well the hesitation is gone its runs evil now but if im running dj126 in the middle and dj118 on the outside what size start jets should i use cause stock isnt doing it

[DonTZ125]

Jet sizes sound wrong - water-cooled 4-cyls normally have the middle jets one step smaller.

[SouthendChris]

I thought the middle 2 pots have 1 size bigger main jets to compensate the fact they run slightly hotter than the outside 2 cylinders....

Chris

[DonTZ125]

Nope - a hotter intake means a less-dense charge and less fuel needed for the proper F/A ratio.

Air-cooled engines sometimes need the cooling assistance of the extra fuel in the center cylinders. Less heat is generated by the too-rich mixture, and the vapourisation of the extra fuel absorbs heat.

[ramster]

Needles. Mid-rpm points to needles and to a lesser extent, float level. If you haven't done Reelrazor's timing mod, do it. If you haven't read YG's pods how-to in the wiki, do that too. That should give you enough to make some progress.

I don't have pods but YG's input makes sense, reelrazors timing mod really improves things, throttle response e.t.c. and it's free

Jet sizes sound wrong - water-cooled 4-cyls normally have the middle jets one step smaller.

On The FZR600 all carbs have the same Jet size, you could buy a 600 to practice on or read the manual

The 1k's differ im unsure on the 750 tho. But is this the 600 forum?

If so all carb jets are the SAME SIZE.

[DonTZ125]

FZR600s use jets that are the SAME SIZE with stock exhaust, airbox, and filter. Shall I demand that he return those to stock before telling to return his jets to OEM as well? He has changed many things; the jet sizes will also need to change.

The FZR250, 750, and 1k use staggered jets; the 400 and 600 use straight sizes - with STOCK components. My comment was not that he MUST use larger jets on #1 vice #2 cyls, but rather the use of a larger jet on the inboard cylinders was not common practice and should be checked carefully. Considering the bike is not running well, it is something to check.

Has anyone thrown out the Factory Pro Carb Jetting link yet?

[ramster]

FZR600s use jets that are the SAME SIZE with stock exhaust, airbox, and filter. Shall I demand that he return those to stock before telling to return his jets to OEM as well? He has changed many things; the jet sizes will also need to change.

The FZR250, 750, and 1k use staggered jets; the 400 and 600 use straight sizes - with STOCK components. My comment was not that he MUST use larger jets on #1 vice #2 cyls, but rather the use of a larger jet on the inboard cylinders was not common practice and should be checked carefully. Considering the bike is not running well, it is something to check.

Has anyone thrown out the Factory Pro Carb Jetting link yet?

I own a 600, the exhaust aint stock nor is the air box or filter (it's a K&N) HOWEVER the Jet sizes ARE stock, she pulls like a train, NOOO flat spots whatsoever in any rev range. I can smooth the throttle, or go WOT and red line her.

What you should do is not "demand that he return those to stock" but maybe, get some experience I.E. do this on a 600 then give advice

[DonTZ125]

Within reason (excluding MotoGP etc), a modern water-cooled inline four is a water-cooled inline four, and certain tuning principles apply. Unless you are saying that only people who have tuned "a 91 fzr 600 with pod filters and a delkevic ss70 exhaust" using DynoJet components, stop trolling. It gets boring after a while, even for me.

[ramster]

Within reason (excluding MotoGP etc), a modern water-cooled inline four is a water-cooled inline four, and certain tuning principles apply. Unless you are saying that only people who have tuned "a 91 fzr 600 with pod filters and a delkevic ss70 exhaust" using DynoJet components, stop trolling. It gets boring after a while, even for me.

When did I say any of the above? scroll up

[floridafzr600]

well i have pods and the ss70 but ill try all one size and what not but i mean it dont run rich or anything now i just need to get more fuel to start now cause i had all 118s and it still hesitated. ill see if all 126 work or what not im lost now

[dru86]

Run all 4 cylinders with the same size jets, staggering makes bugger all difference. On the dyno we found that going one size smaller (from 120 to 118) made the a/f go from 11:1 to 11.2:1. For pods try 126 on all four and then adjust needles, pilots, etc.

Don is correct in that when they do run staggering the out side is normally bigger. For example the 3en series fzr400s, which use the same carbs as the fzr600, runs 92.5 on the outside and 90 on the inside.

[buzzawak]

floridafzr600, sorry dude but no one can really answer your question. It is a case of installing a size and going for a ride. Installing the next size up and riding again.
There are some good articles on the net about tuning CV carbies and having a understanding about how each of the circuit works and when they kick in helps
to know what to change. The best way is to start from original spec and only change one aspect at a time, test and take notes as you go.

The thing about any bike around 20 years old the emulsion tubes will most likely be shot, so idle -> around 1/4 throttle will be rich.

[floridafzr600]

i have it running amazing now i just need bigger jets that deliver fuel for the starting process