SOHC.co.uk Forums > CB500/550
Cb500 fouling plugs once warmed up.
K2-K6:
Looking back at your original post, I don't understand "main jet set at 100" what is that referring to?
Also, what position are the main needles set to, i.e. the circlip postion on the needle grooves. Usually five grooves with factory setting ordinarily the centre one.
paul_D:
--- Quote from: K2-K6 on March 30, 2014, 10:50:53 PM ---Looking back at your original post, I don't understand "main jet set at 100" what is that referring to?
Also, what position are the main needles set to, i.e. the circlip postion on the needle grooves. Usually five grooves with factory setting ordinarily the centre one.
--- End quote ---
Sorry, main jets were 100's. I've swapped the 100's out for 78's. The carbs are 649a which called for 78 main jets. 627b's had the 100s.
The circlip is in the 3rd. Middle clip.
--- Quote from: K2-K6 on March 30, 2014, 10:50:53 PM ---Looking back at your original post, I don't understand "main jet set at 100" what is that referring to?
Also, what position are the main needles set to, i.e. the circlip postion on the needle grooves. Usually five grooves with factory setting ordinarily the centre one.
--- End quote ---
New plugs have a strong spark. The fouled plus have a very small blue/purple spark or none.
When I install new clean plugs, each cylinder does fire up and get hot.
K2-K6:
It seems wierd that we can't collectively get anywhere with this.
So at the risk of "stating the bleedin obvious-teaching grandmother to suck eggs" and any other number of sentiments, let's state what we have got.
Incomplete burn of fuel only happens (assuming it fires when it should) if you have the ratio of fuel and air at any given point in rpm/load at a miss-match. Black/rich plugs are too little air or too much fuel. As the fuel appears to be sensible, then it must be not enough air. so what causes a restriction?
It didn't have anything stuck in the inlet/carburetors before assembly did it?
As oddjob says, have you seen the chokes working fully when installed on the bike?
Picking up on what Lester has posted, can you verify if the ignition advance is doing it's job?
paul_D:
Yep its incomplete burn. I don't know what's causing it. The ignition is set correctly. Advance is working.
I've exhausted everything I could think of. What you could think of. What other forum searches could bring up.
I took it too an old bike mechanic in hopes he can find something I've missed. Hoping its cheap and simple.
I'll post back with the findings.
ka-ja:
Hi,
Any chance you are loosing compression as the engine warms up? Ken
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