4 replies to this topic

[BaronVonchesto]

After having the engine cycle hot cold a few times, it's time to retorque the head and adjust the tappets. So I took the plug off and was rather surprised to find a noticeably uneven fuel mixture between the 4 cylinders.

These are what the plugs look like after driving the whole day in town and on A roads, then sitting overnight.

 

 plugs.jpg   31.62K   0 downloads

 

Plug no 1 looks just right. No 2 looks slightly rich. No3 and No 4 are clearly sooty and running too rich. Especially no 3.

 

The head was just serviced with all the valves inspected and relapped, and I made sure to set the tappets per minispares spec for my cam (14 thou intake, 16 thou exhaust).

 

I'm thinking of leaning the mixture by 3 or 4 flats, but that would make cylinder 1 run extra lean. I've always had uneven mixture on my cylinders, but this seems a bit much. Any reason to be concerned?

[Lplus]

After having the engine cycle hot cold a few times, it's time to retorque the head and adjust the tappets. So I took the plug off and was rather surprised to find a noticeably uneven fuel mixture between the 4 cylinders.

These are what the plugs look like after driving the whole day in town and on A roads, then sitting overnight.

 

plugs.jpg

 

Plug no 1 looks just right. No 2 looks slightly rich. No3 and No 4 are clearly sooty and running too rich. Especially no 3.

 

The head was just serviced with all the valves inspected and relapped, and I made sure to set the tappets per minispares spec for my cam (14 thou intake, 16 thou exhaust).

 

I'm thinking of leaning the mixture by 3 or 4 flats, but that would make cylinder 1 run extra lean. I've always had uneven mixture on my cylinders, but this seems a bit much. Any reason to be concerned?

If they've always been uneven, were 3 and 4 always the rich ones?  Since you just had the head off I'd swap them over and run it for a few more days unless it starts blowing a lot of smoke or misfiring, then check them again.

[BaronVonchesto]

 

After having the engine cycle hot cold a few times, it's time to retorque the head and adjust the tappets. So I took the plug off and was rather surprised to find a noticeably uneven fuel mixture between the 4 cylinders.

These are what the plugs look like after driving the whole day in town and on A roads, then sitting overnight.

 

plugs.jpg

 

Plug no 1 looks just right. No 2 looks slightly rich. No3 and No 4 are clearly sooty and running too rich. Especially no 3.

 

The head was just serviced with all the valves inspected and relapped, and I made sure to set the tappets per minispares spec for my cam (14 thou intake, 16 thou exhaust).

 

I'm thinking of leaning the mixture by 3 or 4 flats, but that would make cylinder 1 run extra lean. I've always had uneven mixture on my cylinders, but this seems a bit much. Any reason to be concerned?

If they've always been uneven, were 3 and 4 always the rich ones?  Since you just had the head off I'd swap them over and run it for a few more days unless it starts blowing a lot of smoke or misfiring, then check them again.

 

 

I don't recall sadly, but I think so. These are new plugs by the way. I'll clean them up then swap em over and see what its like.

No smoke and no misfiring.

[StefanMini]

Do you have twin carbs or a single one? With twins the mixture at one side can be wrong.
If a single carb, check the compression from the cylinders.

[BaronVonchesto]

Do you have twin carbs or a single one? With twins the mixture at one side can be wrong.
If a single carb, check the compression from the cylinders.

 

I have a single HS4 carb. Newly rebuilt engine.

Will check the compression hot and cold.