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Gummed up Carbs and modern fuel

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exvalvesetdabbler:
Had a bit of a breakthrought today, I examined the emulsion tubes and noticed that one was corroded and larger than the other three right at the top where the fat part of the needle sits. In an impatient rush to try something I pulled an old set of carbs apart and salvaged a half decent one.

I can now hold 3000 rpm in top gear without it stumbling and snatching, even back on the throttle at 2000 in the lower gears is useable now.

The clutch basket sounds like a bag of spanners at tickover but that can easily be solved once I get a new set of tubes and needles in.

I'll give it a run around tomorrow and see what color the plugs are.

Regards
Dave

K2-K6:
Sounds like you may have something to work on then, it's worth having a real fine comb through.

Be interesting to see how you get on.

Yoshi823:

--- Quote from: K2-K6 on September 04, 2010, 07:48:10 PM ---Mostly all heat range 8 for NGK plugs on Hondas of this era that I've worked with as it covers most things you use it for.

Very few times but 7s for concentrated low ambient temp running and maybe short journeys as it allows you to get off choke sooner and still run cleanly.

And 9s for concentrated high speed / high temp running to prevent the plug tip from going overtemp and possibly causing pinking.

--- End quote ---

http://www.ngkpartfinder.co.uk/mc_search.php?type=SPARK%2520PLUGS&manufact=HONDA&model=CB400F1%252C%2520F2&engine=400
http://www.ngkpartfinder.co.uk/mc_extra.php?id=947

There's an excellent thread on the American site that explains very well all about ND & NGK plugs. The plugs recommended for my old CB750F2 were the D8ES before the DR8ESL became available, but after the engine was....modified, I installed D8EV gold palladium items. When the bike was wiped out I had a box of these left over that went into my Exup 1000, & allowed the engine to run over a much greater heat range than the standard DR8ESL. As the D8EV is no longer available, I now use the D8EVX, which isn't the Iridium version, but is the middle option of the three.

exvalvesetdabbler:
No more black plugs.

I went for spin today and I have just pulled the plugs and they all look ok.

I have attached a picture of the emulsion tube that was causing cylinder #3 to run rich. I have changed nothing else except swapping the plot jets between #3 and #4.

Thanks to PatM for the suggestion that fuel may have been getting past the main jet o ring, this wasn't the problem here but lead me in the direction of why too much fuel was getting past the needle at lower throttle settings when it should have been pulling it through the pilot jet, no doubt why the pilot air screw had little effect.

All of this goes to show that modern fuel is quite corrosive when it goes bad. I also read somewhere that fuel suppliers are soon to be adding even more bio ethanol to pump fuel, this is the last thing that we need.

Thanks
Dave

PatM:
Dave

I

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