Running rich and would like some advice

[Honda Al]

Hi all,

My CB500 K1 is running rich and I need some advice with where I can go next. All four plugs are sooty, all four have the same appearance. The exhausts are sooty at the ends. The bike will start without the need for choke, and although it runs it always sounds and feels lumpy, especially the lower rev range. Fuel consumption has increased. The bike is standard.

This is what I have done so far -

Clear tube test to determine fuel/float levels. They settle ~2mm below the top of the float bowl. Also used a gauge to set the floats 22mm.
The carbs have 40pilots and 100 mains. All clean and in place.
Air mixture screws are 1 +1/8 turned out.
If you apply the choke whilst running it gets worse, and I removed the air filter and it rode marginally better.

What next steps can I take or do to determine why she is running rich?

Thanks, Alan.




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[Johnwebley]

check your ignition timing,it may be retarded,

 are you using points? or electronic" pointless"  ignition>

 also,try turning the air screws out 1/4 turn at a time,see what happens,

 my CB500 has the same jets etc,with electronic system,but runs with a 33thou plug gap,and airscrew over 2 turns out,since
balancing the carbs with gauges ,I have gone from 10miles per litre,to 12miles per litre,

 an extra 20 miles further before going on reserve ,

[Honda Al]

Using electronic ignition. I'll take a look at the plug gap and try turning the screws out some more.

Cheers, alan.


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[deltarider]

I'd say the airfilter, but if you say it runs just marginally better without...

and 100 mains. All clean and in place.

The little O-rings around the main jets, are they still good and do they seal well?

[Honda Al]

I'd say the airfilter, but if you say it runs just marginally better without...

and 100 mains. All clean and in place.

The little O-rings around the main jets, are they still good and do they seal well?

It's sharper on the throttle response, but still don't need the choke to start it.

I've replaced the little o rings and they sit well in the hole.




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[deltarider]

Is yours a UK CB500K1 or USA? What is the stamped carb number, 627B, 649A? Do you know if someone has changed the needle position?

[Honda Al]

USA K1. The carbs have 627B on them. Not sure about the needle setting.


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[deltarider]

USA K1. The carbs have 627B on them. Not sure about the needle setting.

I'd check the needle clip position, it should be in the middle IIRC

For some reason the yanks had the aircrews 2 turns out and the needle in 4th groove. This according to an American Honda Motor spec booklet published in 1977. If your needles happen to be in 4th groove (in Europe they were in 3rd, middle position), it's well possible you run too rich. I'd start with the easiest: opening the airscrews more. Please report back.

[Honda Al]

I've adjusted the air screws and they are now 1 +3/4 out. Bike picks up better from a standing start (before it was always a little boggy) but I still don't really need the choke to start it.

I'll see how I get on with this tank of fuel.


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[Bryanj]

500's only ever need a bit of choke just to start, maybe all of it for 10 seconds in the dark of winter

[Honda Al]

500's only ever need a bit of choke just to start, maybe all of it for 10 seconds in the dark of winter

That's good to know. Thanks.


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[deltarider]

500's only ever need a bit of choke just to start, maybe all of it for 10 seconds in the dark of winter

Yes, I myself only apply the choke when I start and in the seconds immediately after that I slowly open the chokes again. Within 10 seconds at the most chokes are completely open again. That's the way it was ment. Honda didn't want us to fiddle with that chokelever whilst riding. Maybe you should try airscrews two turns out and see what that does.

[Honda Al]

Maybe you should try airscrews two turns out and see what that does.

I started at two but the engine sounded a bit rough when accelerating. 1 + 3/4 seems to be better.

I'll keep you updated. :-)


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[deltarider]

That makes sense, all 500s and 550s with the oldstyle carbs need a relative fat idle for good pickup and driveability whilst accelerating.

[paulbaker1954]

Hi Al
I think you may have replied to my post on a similar issue. My 500 four was running very rich at low throttle and was a pig to get off the line

Eventually I bit the bullet and bought a set of carb service kits (jets, floats, needles etc) from Rusty riders in the US. But the main thing i did was borrow the ultrasonic cleaner from work and fully stripped and cleaned all the carbs. I found in the process that 3 Of the pilot air circuit circuits had been blocked and the cleaning cleared them fantastically


I have just got it all back together and it I'd running like a different bike.

I recommend you strip the carbs get them ultrasonically cleaned (you can buy a cleaner on fleabay for around £40. - you need a 3L tank) and change all the jets etc. It's quite a lot of work but well worth it in the end in my experience