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cbr1000 plug colour opinions
Edwardo - 20/9/20 at 08:03 PM

Finally got to take the car out for a good thrash today - and the kids finally got a ride which they absolutely loved!

Car is running much better since stripping the carbs down/cleaning the jets and putting new plugs in.

When I was cleaning the carbs, I found the mains had been changed from the standard 120's to 136 - which seems a pretty big increase?!

So after the blast today, took the plugs out for a look. I was expecting them to be sooty all over. They are a bit sooty on the base - but the electrode is white??? The pictures don't really show it perfectly - the electrode is quite a bit whiter than it looks :-

Seems a bit odd to me to be black and sooty on the base indicating rich and white deposits on the electrode indicating lean (as far as I know)?

Is this normal?


rf900rush - 21/9/20 at 06:15 AM

No Idea on the plug.

But when I first built my car, I used a Suzuki RF900 and had to change my jets from 112 to 140 just to get it drive able.
I found that just changing the bikes air box to a sausage filter on mine was the need for such a large change.

Some how the air box made better power than the sausage filter, but there was no nice way to fit it.

The only way I had any decent progress on the tuning way when a use a wide band O2 sensor but that was later when
I had a fuel injected Kawasaki engine.

TimC - 21/9/20 at 11:28 AM

Iím far from an expert but Iíd interpret that as too lean. I definitely needed a dynojet kit to get my CBR1000F engine running well (canít be more specific - it was c.15 years ago!)

blue2cv - 21/9/20 at 06:19 PM

Looks weak

Edwardo - 21/9/20 at 06:56 PM

Thanks for the replies all - Blimey, the airboxes must be really-really restrictive when they are on the original bikes then I guess?

To need that much of an adjustment in fuel supply at full throttle from the main jet must mean the carbs are flowing a lot more air with trumpet filters?

The idle jet is bog standard bike size. I haven't checked - but I guess the fuel mixture has probably been tweaked up too.