Non-uniform blueing

1976 kz900 4 into 2 MAC. Pipe #'s 1, 2 & 3 are all blueing just about exactly the same but #4 is blueing to a much lesser degree.

Bike is running very well, I think. Starts on first push of the starter button on full choke with no throttle. Pulls very well and has no perceptible flat spots.

Any thought as to why #4 appears to be running somewhat cooler?

Thanks.

I had a similar issue with my KZ750. The #2 header wasn't blue and the other 3 were. It didn't bother me since the bike seemed good for power.
When I checked the valves, the intakes were all the same. The exhaust were the same except for #2. The 3 others were close to the upper limit (0.006", the range being 0.003" to 0.007") and the #2 exhaust valve was at the tight side, 0.003". I re-shimmed #2 so all the exhausts were 0.006" and then did a carb sync. the #2 cylinder was pulling more vacuum than the other 3 after the shim change.
So, I don't know if #2 was running cooler since I had more fuel going to that cylinder or what. I am curious what others have to say. Perhaps my #2 cylinder is just problematic for me. After changing the valve shim and syncing the carbs, the header still isn't as blue as the others but I have only put on 200 miles or so since the change.

BARNEYHYPHEN wrote:

1976 kz900 4 into 2 MAC. Pipe #'s 1, 2 & 3 are all blueing just about exactly the same but #4 is blueing to a much lesser degree.

Bike is running very well, I think. Starts on first push of the starter button on full choke with no throttle. Pulls very well and has no perceptible flat spots.

Any thought as to why #4 appears to be running somewhat cooler?

Thanks.

Perhaps pilot mixture screw is set richer on #4 carb. Could screw out to lean. Number of turns out from lightly seated should be close to same on all carbs. Believe initial setting is 1 and 3/8 out.

Also, float bowl fuel level may be higher in #4 carb allowing it to run richer. Would suggest the quick easy clear plastic tube float level test.

Post edited by: Patton, at: 2007/06/06 10:18

Post edited by: Patton, at: 2007/06/06 11:44

After reading Patton's post I realize I should ask questions instead of trying to answer them.:blush:
The fuel level being higher makes sense to me as now I remember that the fuel level on carb #2 was higher than the other 3. I guess #2 cylinder is trouble for me.
Simplest things first.

Thanks everyone for the input so far. My initial feeling was the pilot air screw but I haven't messed with the carbs since I did a total strip down, Berrymans soak, rebuild and mercury stick sync.

I took an extended period of time to get them spot on, the last time I did the valve shims so suspect they are likely not the issue. Also tried very hard to get all the floats right on and thought I had succeeded.

I'll start tonight with the pilot air screw, run it a couple of hundred miles and report back.

Thanks again.

Mine's just the opposite... one cylinder is a little bluer than the other three.
Another rider here at work told me I should sync the carbs. He's an experienced wrench on old Hondas, and I think he probably knows his stuff.

Just a reminder (if applicable) that the on-the-bench-upside-down float level adjustment is only a ball-park setting. Whereas the clear plastic tube test shows the real world service fuel level. Suggest the clear tube test with carbs held level before reinstalling carbs onto bike. During float tab adjustment process, it's okay and faster to use just one float bowl screw when checking level between adjustments. Small adjustments often make large differences, so go with tiny increments.

And float levels should first be correct for best sync results.

Post edited by: Patton, at: 2007/06/06 12:20

Barney, what stadium are you in in your picture?

The mighty Colleseum sorry, Adelphia sorry, Colleseum sorry, LP Field. Our office is half mile down the road from the Titans stadium. A lady here at work has season ticket (PSL's) she allows me to use sometimes.

Thanks again everyone for the additional input.