Topic: Help with CB500f carb tuning

[Scott S]

 Are you sure it's not something simple like the rubber from the throttle grip rubbing on the RH control? I've seen grease on the handlebars get gummy and make the throttle not snap back as intended.
 Are your cables stock Honda or aftermarket? It looks like you have Clubmans or clip-ons....how is the cable routed?

[dave500]

yeah,,scotts a good geezer,hes alwright,know what i mean?check for any sort of like out of the ordinary,you know like the mods have been muckin about like,tamporin like with your frottle and so forth?"

[MotorFist]

So I disconnected the throttle cables and ran the bike just using the linkage on the carbs. Still same problems.

I am going to pull the carbs again and recheck the pilots. I bought two aftermarket rebuild kits. One kit for my 500 and one kit for my girls 400. My 500 kit came with those little pilots and I never installed them. The 400 kit came with the longer #40 pilots and even have the logo on them. I am suspect of them after all this. They could be counterfeits after all.

I should mention that when I push down on the slide linkages to drop the idle, the only travel I get is a tiny bit from rested idle position down to the when the slides bottom out on the carb body. I don't think they are sticking. But obviously I don't know what the problem is! I REALLY appreciate everyone's help.

[MotorFist]

Well I pulled it apart and cleaned everything again. Also pulled the air screws and cleaned them again as well. Put it back together and it is running much better.
If i leave my Idle adjusted really low, like 500 rpm-ish it wont really idle well on its own but the hanging idle stays at 2000 rpm. It is turn my idle screw to where the regular idle is 1000 rpm, then the hanging idle goes up to 3000 rpm or so.
My slides are moving freely and my air screws are at 1 full turn out.

I went and rode it hard for 10 miles or so and it runs well despite a new intermittent flat spot at 1/2 to 3/4 throttle. I wonder if this is from moving my needle clip up to the center position? Or is it because it was cold enough to literally be snowing on my test ride?

I'm burnt out on it for the time being. It still isn't right but it runs well enough to ride. I will revisit this after a few days or maybe sooner if anyone has and advice.

I think I might follow Dave's advice and go buy a timing light and make sure that's right as well. I'm embarrassed to say that I'm almost to the point of taking it to a good local mechanic I know that has been working on SOHC's since they were new.  I really want to be able to fix this kind of stuff out with my own hands but I'm feeling a little defeated.

One thing is for certain, I learned how to thoroughly clean carbs!

[Scott S]

 You're Effing with the carbs and haven't set the timing? That's ass backwards. Carbs are LAST....after valve adjustment, cam chain adjustment, timing...hell, change the oil and filter and spark plugs....THEN start fiddling with the carbs.

[MotorFist]

Yes it is I admit. The only reason I even messed with the carbs to start with was to replace the needle valves and bowl gaskets as they both leaked last summer.

The bike ran ok when I put it away other than the same hanging idle problem I have now. I just had to shut off the gas every time I stopped the motor and the carbs were leaking/messy.

[chewbacca5000]

I also changed the pilot jets as I could just not seem to get them clean no matter how much a soaked and sprayed and blew compressed air through them.
 

When I rode it last summer it ran pretty good but I have always had a hanging high idle problem. 

 And therein lies your problem. I went through the SAME thing on my CB500. It's the poorly designed aftermarket pilot jets.



 They're too short and don't stay submerged in the fuel in the float bowls. The holes are not the correct size nor are they spaced properly. You're idle is hanging because it's lean. It's lean because the pilot jets are crap.
 Find some genuine Keihin jets and try....I bet it will solve your problems.

Thanks for posting this I was getting ready to drive this bike off a cliff.  Should be a crime to sell such lousy parts.  After market idle jet full 4 to 6 mm shorter than stock and has small little emulsion tubes. I was begging to thing that these carbs were somehow "special".  I kept thinking the idle circuit is so simple on these and is nearly identical to the cb750 so why I am I having such a hard time.

I read every post on this forum and one from Hondaman that basically said not enough gas.  Did everything double checked float height, checked for vacuum leaks, replaced / adjusted both throttle cables hopped on left foot and spun in circles nothing.... Until I read this post.  Got the kit for the needle valves and seat and used the pilot jets and did not think anything of it at the time.

Bike runs great but would die when I let go of the throttle.  If if was not for the dimples in the float tang doubt there would be enough fuel to do anything at all.

We'll anyway thanks a bunch!!

You know these things have a way of chipping away at you if you let them.

[TwoTired]

How do you know that each slide moves freely in it's bore along it's entire travel length?

Has the slide lifter linkage been dismantled since new?  Could there be parts missing, like the pivot ball "shoes"?

Has the throttle return spring been replaced with a weaker spring?
Is the spring using the original perch mounts?

Not smart to fiddle with carb tuning before the 3K tune up check list is confirmed.  Easily leads to frustration, imo.

[MotorFist]

Hey all.  I never did post resolution to this thread and I apologize.  I ended up taking the bike to a local wrench/friend that has been working on these bikes for decades.  I had to go to Asia and needed the bike running when I got home for the relay.  He did end up adjusting the timing and also told me that my coils need replaced.  The plug wires have been trimmed so many times over the years that they can't be trimmed any more.  The looseness at the spark plug cap/plug wire is giving me a weak spark and had pitted my contacts on the points.

Biggest mistake was not doing as you guys mentioned and performing the 3000 mile tune up.  LESSON LEARNED!  Bike runs great now but I do need to look into replacing the coils.  I have seen so many threads about issues with guys running the wrong aftermarket coils that I am thinking of trying to find a good used set of OEM coils.  Any thoughts on this?
Thanks to all that chimed in and helped me

[TwoTired]

Why don't you just put new leads on you existing coils?

http://www.ngksparkplugs.com/products/performance/splicers.asp

[MotorFist]

Well I guess that is an obvious solution I had no idea splicers existed. ThanksTT!

[TwoTired]

It is not easy getting steel strand core wires.  But, copper strand core seems to be available.