Needle height

Yeaah very lean.. Im planning to enrich needles but I don’t want to over rich 6000-7000rpm !!

Maxbou92 wrote:

Yeaah very lean.. Im planning to enrich needles but I don’t want to over rich 6000-7000rpm !!

You will need to experiment, a bigger main and lowering the needle may sort the low end and midrange but will be rich at  the top end ?

Im not trying to steal your thread but maybe you have the same issue i have.

Im intentionally bringing this up because so far nobody has explained why it’s bad to have different jets in each carb. I respect that zed and wookie and allot of other guys know more about these bikes than I,  im not trying to pick a fight. i made the choice to use exactly the right jets in each of the 3 circuit to get afr to 12-14afr under driving conditions, and that means each carb is slightly different than the other carbs. Im not arguing this is correct, I agree its not. But my definition of incorrect might not be the same as the guys who have told me this is wrong. Nobody has told me why it’s incorrect, just that it’s incorrect. I dont really have a choice because I know that running lean will destroy the motor and it wont run rich. So when I hear that it’s incorrect im assuming they are telling me there is something wrong with the motor. I cant argue with that. Tuning fuel injection teaches you that some engines are more efficient at pumping than others so i assume i have worn cylinders that are ineficient. I live with not doing it right because I assume the age and mileage of this bike has created pumping efficiency differences from cylinder to cylinder. For example lots of blow by or lack of compression. So until I get around to checking the valves and pistons I have jets that keep temps down and afr correct across the entire rpm range. I would really like to know if there is another reason why this is incorrect (even guesses). I have different jets so that I dont damage the motor further. it does run bad for about 10 minutes at idle.

1978 kz1000a
4 into 1 with pods. when i remove the pods I get the same result
fuel levels are all identical. 3mm
air corrector jets, all new jets in all carbs and circuits
new choke seals
carbs are spotlessly clean, rebuilt and sealed. all passages are clean and clear.
checked all leaks by pressurizing and leak down test
brand new pingle high flow and new fuel/vacuum lines
Bike runs great but is very cold blooded but like I said Afr is 12-14 on all circuits when it warms up
My jets arent fighting lean conditions they are fighting rich conditions for example one main jet is 95 but most are 102 and 105 so i dont suspect an air leak

I would honestly like to find a reason other than fix the cylinder efficiencies. thats why I question my compromise. I just dont see an alternative. the bike has 40k and more than 40 years on it.
 

Thats a good Gap between main jet.. maybe you have low compression on some cylinders? Bad Valve clearance?
 

Bry195 I don't think anybody has said it's "bad" or "wrong" to go the route you have, simply there is a question around the "effort Vs results". As previously mentioned even tuning individual cylinders will give varied results due to changing factors during the process (latent heat build up effecting intake air temp etc) in a perfect world you would measure all 4 at the same time (4 probes, 4 meters etc) Even with most FI systems you can't tune AFR on individual cylinders. IMHO they key difference is that with FI you can "map" AFR at any given point in the rev range or load condition where as with carbs changing jets, needle heights etc will impact across a much wider rev range until throttle fully open. The only way you can dial in different points in the rev range as you would "mapping" FI would be with a custom needle profile (all you need is money, time and unlimited dyno access)

Maxbou-Im thinking the same thing.

Wookie-You are right. There were a couple people following the very time consuming process and said that the jets need to match. Some positive and some negative but with no explantation. That is alright. I’ll keep listening and tweaking and this usually results in a solution.

Im not trying to get fuel injection results from a carb. maybe it’s easier to think of my method as a color tune under load, temperature, and across rpm range. its a series of trail by fire compromises that results in a wider than expected operating range but not fuel injection level flexibility.  

You should look at your compression first!! I tuned mine with colortune. Screws aren’t tuned equal with that. Some are at 1 3/4 turn out and others at 2 1/8 turn out!! We see everything in the combustion chamber!! Be sure your float level are on spec (clear tube method)