Topic: 1971 CB500 K1 High RPM when coming to stop issue

[barwickn]

Hello everyone! This is my first post here. I am super happy that I found this great resource online. I am brand new to motorcycles , and working on motorcycles so having a group of people online willing to lend advice is priceless. Now on to the problem. I recently bought  a 71 CB500 out of a guys barn / garage. It runs and gets me around town (looks a little rough though, im working on that). I recently rebuilt the carbs and increased the size of the main jet to accommodate for pod air filters. Main jest size went from stock 100 to 125 ( i have a set of 130s to if i want to try that). However the past few days when I pull up to a stop and pull in the clutch and engage brakes the bike revs up to around 4000 - 5000 rpm, it hangs there for several seconds ( sometimes as much as 15 seconds), and the drops to normal idel (1000 or so rpm).

Im thinking the throttle could not be disengaging, or possibly a carb float type issue?

Any help or words of wisdom would be greatly appreciated.

Thanks!

[flybox1]

Welcome.  tell us more about the type of pods and exhaust systme you are running.

How do you know the 125's are the right main jets for your carbs at WOT(wide open throttle)?  what do your plugs look like.
(IIWM, 125's would be too big of a jump just for poods.  110's, 115's at most.)

Do you know that in increase in air flow(pods) effects all throttle positions, including idle?
Did you make any adjustments of the needle clip position, pilot jet, or mixture screw to accommodate for the increased airflow at these other throttle positions?

Unless you find a air leak or poor seal at the carb boots, or your slides are not snapping completely closed when you let off the throttle, or your vacuum sync is waaay off, you're experiencing(high revs) because of an air fuel mixture issue.

you need to first verify if the 125's are in fact the correct jets for your bike
please take a look at your spark plugs, and tell us (picture) what they look like.

[dusterdude]

Just for giggles,put the bike in neutral when its reving and tell us what happens

[barwickn]

I put the 125s on there because honestly I didnt really know what size to go up to. I had read conflicting things about what size to use so I went with something that was middle of the road for what I had heard. Maybe I will throw the 100s back in and see what happens. I did have an idea that it would increase in all throttle positions. I had to adjust the idle screw to bring it back down to a good idle when I first put them on. other than that i did not make any adjustments to the needle clip position, pilot jet, or mixture screw. I have the mixture screws at 1.5 turns out.

Here are my plugs they look as if it is burning rich I believe

http://imgur.com/gallery/9j8XKvA/new

So to adjust the air fuel mixture I need to synch the carbs? is that correct.

When I shift into neutral it it still hangs at a high rev for a bit then goes back down to normal.

Thanks for the help guys

[turboed13b]

I don't know where you guys are getting information from but 125 is way too big for a cb500 put a 105 in there.

[Vinhead1957]

Check your advance springs. They become weak and don't return when going back to lower rpms

[flybox1]

when you post pics of your plugs, we need to see the tips.