unbalanced cilinders?

[vuzzi]

Hi,

 

I took my exhausts off today and noticed that the right header was sort of white inside, while the lift one was black. I checked the spark plugs, and they gave the same black resp. white colour.

Coud this indicate the cause of engine vibrations? (I cracked a header earlier this year; the engine vibrates a bit too much @ 3500 and 5000 rpm, while 4500 is OK)

 

The balance seems ok, when testing and setting with a carbtune.

 

What is the good colour? My guess is the lighter coloured right one. But how can the left one turn black? Oil consumption? Bad injector?

[Guest ratchethack]

Many hereabouts (myself included) have found the exact same thing, (color diff. on both plugs and inside headers) with TBs balanced and in optimal state of tune. Of course, it depends on how many miles are on your plugs, but there will be a characteristic black "shadow" on the plug tower on the exhaust side of the plug -- one moreso than the other. This, and other temp and operating variances are due to the staggered firing sequence, particularly at idle. No prob, IMHO.

 

HOWEVER, if you've run the motor both hard and long with a cracked header, there may be some risk of a burned or warped exhaust valve as a result. A leak-down test may be in order, if for no other reason than peace of mind.

 

Remember 30 years back, when hemi-head pushrod motors were ALREADY obsolete??

 

Here's a link to a 1977 NGK color spark plug reading chart that still applies to V11's today.

 

HOW TO READ A SPARK PLUG

 

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

[GuzziMoto]

Hi,

 

I took my exhausts off today and noticed that the right header was sort of white inside, while the lift one was black. I checked the spark plugs, and they gave the same black resp. white colour.

Coud this indicate the cause of engine vibrations? (I cracked a header earlier this year; the engine vibrates a bit too much @ 3500 and 5000 rpm, while 4500 is OK)

 

The balance seems ok, when testing and setting with a carbtune.

 

What is the good colour? My guess is the lighter coloured right one. But how can the left one turn black? Oil consumption? Bad injector?

You could try switching the injectors and seeing if the issue moves with them. Reading colors is not as useful as it used to be due to completely different fuels we use nowadays. But it is odd that you have such differences between the two sides. It could be from one side being too rich, but it also could be burning oil on one side or a burnt valve (oil burning is more likely in my experience, but it could be rich). As I recall Guzzi's are odd in that they do not use valve guide seals. Instead they depend on the valve guide and stem to seal and keep oil out of the ports. Not a good idea when you make your valve guides from hard cheese and your valves from soft cheese. As mentioned, a leak down test would be useful. And swapping the injectors would be the first step towards isolating a sticking injector. If none of this pans out then I would take a look at your valves. It is not hard to pull your heads on a push rod motor like your Guzzi. Best of luck.

[vuzzi]

Thanks guys,

 

the colours seem to be somewhere around 'good', on the scale from cold/rich to hot/lean.

I think i 'll swich the injectors for a try (relatively easy to do) and see how they 'll look after some trips