carbs

[paulmceleney]

can anyone help took my z900a4 for a ride today i have changed the main jets i have fitted k&n fillters ,iam using 28mm carbs and it has a harris 4into1 fitted apart from this the engine is standard .now the problem is when between 3 4 rpm its start to miss and after 4 rpm it runs fine and below 3 its okay it ticks over fine 1200 rpm thanks paul

[paulmceleney]

took the carbs apart tonight i using 130 main jets i was going to adjust the needle setting but ran out of adjustment iam looking to go bigger maybe 140 what do you think anyone thanks paul

[Pigford]

Once you got good full throttle its working back from there.....

You said you'd run out of adjustment????? I assume the needle was set on lowest clip (highest needle position)

Put needle back to middle & get main jetting right (WOT) & then fine tune with needle settings.

[paulmceleney]

thanks for your reply mark it was on the lowest clip ,ive got 1 150 jet that iam going to use this as a gauge, and drill the 130 bigger if i can get a suitable drill bit. once iam in the mood i just like to get on with it, i will give this a try to day and let you know if it works out paul

[maralyn]

Hi Paul,

I have got a mikuni carb tuning manual in pdf format if you want me to e-mail you a copy of it?

As a guide, I would think you should be around 135/140
http://www.motocarb.co.uk/index.php?_a= ... oductId=61

It might be cheaper to buy a couple of sets in the long run, with the time and effort required trying to drill yours out. Motocarb will supply genuine mikuni jets, next day delivery.

Paul

[paulmceleney]

update drill jets out to 150 set needle second notch from the top ticking over nice took it for a run pulls like train kept sliding in the seat straight upto 130 no problem if you hold back on the throtle around 5 to6 rpm slight hesitation back to the garage now to adjust the needle setting by one notch hopefully this will cure the problem. also maralyn thanks for your reply i will pm you with my email address

[paulmceleney]

just been out the bike pulls smoothly in each gear no hesitation ticks over at 1000 rpm still very very slight hesitation if you hold the throttle at 5 6 rpm improvment from last time, try adjusted the air screws but that didn,t work so put it back to where it was, will raise the needle another notch and see if it improves tomorrow

[Pigford]

Paul, when you say

very very slight hesitation if you hold the throttle at 5 6 rpm

What throttle opening is that - slight, half, wide open?????

If its only on slight openning, probably pilot jets a size too small

Needle higher will only enrich 1/4 - 3/4 throttle, not part open

[paulmceleney]

thanks for your reply mark its when the throttle half open i could leave it but i will have another try tomorrow

[paulmceleney]

the bike is now fixed brought myself a gunson colortune pin point the problem to a split in the rubber manifold that i could not see