Hi All:

After doing a track day, I found out that I lost the #3 cylinder of my 98 Blade. It gets spark, it just won't run. All the other cylinders heat the exhaust quickly...the #3 doesn't. Where should I begin to remedy this?

Also, whilst testing the spark for the #3 cylinder, I noticed that the spark plug had a copper/rusty color to it. I pulled the others and it was the same story. What does this mean?

If it makes a difference, I ran 104 octane unleaded race fuel at the event. The water temps were well within the limits...almost too cool. So what do you think? I have another track day coming the second week in Nov and I need to get this sorted shortly.

--Thanks, Chris

Is there pressure in the cyclinder? Could a valve of bent etc? :S

There is some pressure because when I tested for spark, the car actually started and blew air out. Should I run a compression test?

Yeah thats what id do, And maybe a cylinder leakage test, Then listen for air coming out of exhaust/carbs etc and if there is air coming out, then theres a bent valve or summat

If you have a spark the next thing to check is fuel before assuming a bent valve or worse.

If it carb check mixture and that there are no blocked jets. If injection check/clean the injector.

That doesn't sound good. Hopefully it is something much less macabre I'll test it tomorrow.

Any other ideas?

--Chris

quote:

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Originally posted by andyharding
If you have a spark the next thing to check is fuel before assuming a bent valve or worse.

If it carb check mixture and that there are no blocked jets. If injection check/clean the injector.

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I had this with my blade so tried some new plugs, it moved from No.3 to No.1 cylinder. I then bought some NGK plugs as was in it when I bought it and the problem dissapeared.

If the plugs have been flooded at all then they are generally useless.

Steve

Hmmmm, you used 104 fuel in a stock motor? The higher the octane rating, the cooler and slower the burn. If you don't incease the compression ratio to make benefit of this, you'll only get a partial burn which will mean a lack of power and it will technically run rich!

This won't do any long term damage, but I would suspect that you've simply fouled a plug! Buy a new set and just run standard pump fuel - you'll see no benefit from 104.

You could always skim your head massively and keep using the 104!

I'd ditto a compression test- then if that's abnormal a leakdown test.

You could just try swapping round the plugs, you might find the misfire swaps cylinders- ie it's the plug.... Bike plugs are rather fragile...

The copper rusty colour you describe is just copper grease on the threads which stops the plugs from seizing in the head. Its a very popular and necessary trick with Ford OHV engines over here to prevent plugs from snapping in half when trying to remove them.

[Edited on 31/10/07 by RichieW]

Except you should only use copper slip on spark plugs when the engine specifically states the requirement for it or it has a reputation for seizing the plugs (like the Ford Ka).
Otherwise if you torque up the spark plugs (which we all do, right?) it will be torqued to a much higher reading than indicated on the torque wrench... which can result in problems with the insulating material breaking...

how can the insulator break? the thread and hex nut are on the metal part.

I didn't use copper grease, but will replace all the spark plugs anyhow. Hopefully, that's all it is. If it doesn't fire after that, I'll chase the bigger issues.

The concerning part is that the current plug does spart--though not as much as other's I've seen. I really hope that's all it is.

Next time I hit the track, I'll make sure I just use 93 octane pump gas. I used the racing fuel because that was all that was available at the track.

--Chris

It can still spark, but it may not fire as the spark has to be substantial to ignite the charge when under pressure. As I said, you won't do any harm at all running 104 octane fuel, you'll just foul plugs if you don't have a high enough compression ratio to burn the charge! The higher the octane rating, the slower the flame path....

And a dab of oil on the plug threads is a very good move....

Thanks Coose. Hopefully that's all it is.

On a slightly different note (since I'll have my carbs off to make sure the needle is sliding OK), what should the mixture screws be set at? I smell like I'm running rich, and not just on the race fuel either. My #4 cylinder's exhaust is nice and shiny whilst the others have colored...

--Thanks, Chris

Also check the plug cap, I've had one break down... Take the plug out and you get a (weak) spark, put the plug back in and the cap shorts to the head = No real spark.

If you check in the back of any petrol haynes manuals there is a spark plug condition chart, I'd be more than happy with a copper coloured electrode, if you had bent a valve I would have thought the plug would have been oily as oil would have been getting past the valve guide.
Tony

I'd go with Coose's diagnosis, I think its simply the high octane fuel that's fouled the plugs. The plug should be a light tan/coffee colour if its running about right, if its dark brown or black then its too rich.