TOPIC:

Ok... so it worked this time. The picture ended up reversed as to the order of the cylinders it came out of. So left is actually right. The left one was the wet looking one.

I have a laser temp gauge but I am suspicious as to how well mine works. I guess even if it isn't accurate it should give me an idea of which cylinders are hotter.

Last night I also dumped some carb cleaner into the tank and today after I put the plugs back in I took it for a short run and it was firing on all six again under load.

On cold starts it starts immediately and runs but as soon as the choke comes off it backfires through the carbs a bit until it warms up. Once it gets warms up and the idle is normal it doesn't backfire anymore.

The pipe isn't stainless. Just steel and chrome. It is the DG brand.

Lucien-Harpress wrote: The blueing could be a couple things. If the exhaust is stainless it will do that anyway. If not, those two cylinders are running overly lean and burning too hot.

It may be worth getting an IR temperature gauge. You can kind of judge mixtures by header temps (hotter is lean, cooler is rich) and get a sense of where your mixtures are at, and what cylinders are firing.

As for the carb boots, I wouldn't worry too much about them if they are "upstream" of the carbs. All that's happening is a bit of unfiltered air is getting mixed in with the filtered. The carbs will sort out what they need. It's the air leaks "downstream" that you really have to worry about.

Normally, I would tend to agree BUT if you look at the front of the carbs you'll see 4? ports just under the venturi. 2 of those are the point of entrance for the air for the air bleed idle circuit. Allowing air leakage around the air filter means that the air bleeds can suck in unfiltered air and the brass air jets in those 2 small passages can get plugged with debris and then no air to the idle circuit. Obviously the dirtier the air filter gets the more likely the air will be drawn in around the leaking points of the air box rubbers (path of least resistance) and the more unfiltered air entering the carbs.

Ledkz1300 wrote: Thanks Lucien.

I pulled the plugs today. Number 1 cylinder was wet and black. The rest are dry with whitish ash. Hopefully this picture posts as sometime it won't work for me.

Cylinders 2 and 3 are more white than I like to see and that would suggest that they are running lean. The primary cause assuming the main jets are stock is that because 2 and 3 are fed by the same carb, the float level is too low. A lot of people don't realize that when the float level is off, it affects every circuit in the carb. It's more important to ensure the float level is adjusted before making any other adjustments on the carbs.

Engines running carburetors normally are jetted so that the spark plugs burn a light tan colour since carbs do not have the capacity to adjust for changes in altitude, barometric pressure, ambient temperature or engine temperature so the carb is usually jetted/adjusted to accommodate as many variables as possible. In order to do that, we tend to run the carbs a little more to the rich side than the lean side and when you do that, the appearance of the soot on the spark plugs tends to be a shade of brown. A whitish brown would be a great color if you did a high speed run on a particular day when you were going racing but if it's just the case of " let's plug the plugs and see how things are running", a whitish brown would tell me that things are set up just a little on the lean side and I might want to richen things up just a tad to ensure that I don't burn hole in a piston. My personal preference for all round color checks on the spark plugs is a darker brown like a dark amber beer.

On the other hand, a fuel injected engine does have the ability to monitor ambient temperature, barometric pressure (which also accommodates for altitude) and engine temperature so it's expected that the spark plugs should be burning a whitish colour to an ever so slight tan colour. If you pulled the plugs and found a tan colour, you should suspect some trouble is brewing. It could be a feedback signal from one of the sensors telling the computer some false information and the computer is running the injectors more rich or it could be that the fuel injectors are passing more fuel than they should or dribbling and not spraying causing a bad burn in the cylinder.

I am a motorhead. Always have been since about 10 years of age. I'm fascinated with internal combustion engines from the design right through to the ultimate build out. Back in the 70's, pulling 50 HP per litre was a "good engine" Today's standard for an every day automobile is around 100HP per litre. Put all of the best parts in an engine and 200 HP is achievable. Throw on a turbo and NOS, the skies the limit. I have a buddy running a Mustang with a 302 cubic inch punched out to 372 cubic inch and NOS running the quarter mile @ 7.8 seconds. Calculated horse power based on weight of the vehicle and time through the trap, works out to just over 1800 HP. 372 cubic inch is just over 6 litres so he's pulling close to 300 HP per liter naturally aspirated and NOS.

Further to KB's comment:

www.kz1300.com/index.php/forum/carburato...ystery-blockage#8782

Sometimes you have to: "Think Outside of the (air) Box" !

Thanks Kawboy.

Whatever caused the plug on cylinder 1 to be wet and black has changed because after a little drive it is now whitish like the others.

I used the laser the laser heat gun. All of the cylinders except for number 4 and 6 are within 5-10 degrees of each other as measured at the pipes 1 cm below the collars. About 60 C. Number 4 (which is actually number 3 in the picture as it is reversed) is about 80C, while number 6 is about 40 C.... which is really weird because it is the bluest pipe by far.

I did this twice to get an average and it seems to be holding that way. It is not super accurate because 1 cm in difference in the measuring spot changes the temp by a few degrees.

So based on the white coloration, all of the cylinders are a bit leaner than they should be.

Despite the fact it looks like all cylinders are firing I still feel like there is a miss under load. The exhaust tone is just not completely right. Maybe I am imagining things? Acceleration seems a little rough at lower Rpm... under 4000. It smooths out above 5000.

I also hear an odd rattle pulling away at very low rpm. I remember the same sound from my old one many years ago. This bike also made the same rattle with its old engine in it.

Kawboy wrote:
The primary cause assuming the main jets are stock is that because 2 and 3 are fed by the same carb, the float level is too low.

you sure about that John ?? did you mean 1 and 2 ?