White explosion (Mega lean) @ high rev for 1 cyl.

Dear kawa fanatics ,

I'm now rebuilding my 1983 kz550 f1 spectre.

I have a problem that has been there for a year (since purchased). I've rebuild the head (valve check , head resurfacing , leak tested , head gasket and valve seat changed and change piston rings) also rebuilt and cleaned the carbs (checked fuel level in float bowls).

700$ later still the same problem. Let me explain!

When idling everything is fine (some carbs are a little bit rich but no big deal) but when i past the 3500-4000 range you see (through colortune spark plug) my #2 cyl go blue, blue-whitish then white backfire boom totally dark (just spark) past 4500 rpm.

I've been investigating this problem and its driving me nuts until i play with carbs while the engine is running.

I decided to put my finger here (see picture)



Wow now the idle is very rich (orange) but the explosion is blue-orangish at 6000 rpm ( not checked higher)

I think to reduce the airflow (put something inside) from this small intake will correct the problem. do you know what is wrong with this carb?

Oh btw, how to adjust the mixture at idle speed (see picture, took with lights off to see the flames)?



I've tryed the air screw but even seated or fully taken out still blue flames at the exhaust (rich condition).


Thank you for reading this big topic!

Wish you a nice motorcycle season!

Regards,
Laurent


EDIT: PLEASE CLICK ON THE IMAGE! I don't know why but the thumbnail is not the right picture

Pods :laugh:

I've tryed with my new pods or my old airbox same problem.

Also swapped my vacuum assembly from one carb to another still this carb is the problem. This swap confirmed that the membrane is still intact no vacuum leaks!

EDIT: don't forget this only happen to cyl #2.

#1 #3 and #4 are ok at high speed with pods, airbox and straight with no air filter!

I don't think putting an air restriction only for fixing the carb #2 lean condition is the right way to do it

Laurent

What? Pardon?

Sorry for the confusion!

Fixed some non sense stuff. Too much happy I've found a clue, a year after investigating

oh geez, here I thought I was opening a porno thread...

in my humble opinion, you might want to go through those carbs again.......if the diaphrams are good(?)..clean the crap out of them and put in NEW jets.....check the carb to motor rubber manifolds also....

9am53 wrote:

oh geez, here I thought I was opening a porno thread...

you missed your chance with "supercrank"...:laugh: :laugh:

You need to thoroughly rebuild the carburetors.

You likely have an air leak somewhere...
like a decent size tear in the #2 carb slide diaphram, and its sucking in a huge amount of extra air with throttle.

The hole that your putting your finger over is the vacuum port that controls the rise of the slide. There is a hole in the bottom of the slide that vents directly into the carb throat, so don't cover that hole! It needs that air to function properly.

Make sure all the air jets and fuel jets are there, and clear.

Make sure fuel level in carb is good and stays good while running.

The idle mixture adjust screws are top front center of the carbs. In the small square tower. Yours may be under small plugs that will require drilling (Very carefully), so as not to damage the screw just underneath.

Turn mixture screw out to add more fuel at idle, in to lean.

That however will not solve your lean when revving problem. That is oviously just a huge amount of air getting in there...

Good luck!

If you have a C clip at the top of your high speed needle lower it one groove,
If no C clip look for small washers at top of needle, pick up a couple at a hardware store.
Last note make sure the spring retainer is installed the right way.


good luck
Jim

time for the OMR carb mod!

like a decent size tear in the #2 carb slide diaphram, and its sucking in a huge amount of extra air with throttle.

I've checked for tears or tiny holes nothing! Even swapped the assembly (diaphragm) from #1 carb which i know it work well at high speed ... still the same problem. I've blow compressed air into the tiny passage which go to the float and alot of fuel got out of the main jet (at least i know is not a blocked passage).

in my humble opinion, you might want to go through those carbs again.......if the diaphrams are good(?)..clean the crap out of them and put in NEW jets.....check the carb to motor rubber manifolds also....

Rubber are like new, no scratch holes or dried rubber sign.The head have leaked a little bit of oil on them for years (by miracle it kind of preserved them) which the previous owner was to lazy to change the valve cover head gasket

The carb has been fully dissembled often...well i can't count on my hands how many times I've clean them in less than a month. I've also installed 4 new fresh carb rebuild kit from K&L (18-2461). The only part i didn't touch is the Choke shaft. Is this part related to vacuum problem ? Btw, how does this thing work (regulate air or fuel)?

The idle mixture adjust screws are top front center of the carbs. In the small square tower. Yours may be under small plugs that will require drilling (Very carefully), so as not to damage the screw just underneath.

Turn mixture screw out to add more fuel at idle, in to lean.

As you see in the second picture, all screws were fully seated still to rich at idle from #2 (big blue flame) and a little bit from #4.

Then again the question of the choke shaft comes into mind maybe it's that darn thing if its related to mixture!