Topic: Cb 500 cuts out while driving

[Vonbulow]

Hi guys

My very first post to this forum - so be gentle.

Having rebuild the engine, new pistons, honed the cylinders, valvejob, electronic ignition, carb rebuild and new electrical system - I am a happy camper. The bike starts and idles just perfect. When riding it, it runs great seems to be a bit rich mixture though, looking into that a the moment. But here is the tricky part, the bike cuts out when shifting down and releasing throttle whilst engaging the clutch.

Any ideas? is it electrical or a carb or ignition issue?

All help much appreciated!!     

[flybox1]

Welcome...we need more info..
what is your jetting #'s,  intake and exhaust config(airbox, filter, pods, stock or modded exhaust(what)..etc.)?
What plugs?
what do their tips look like( need a picture of insulator deposits)?
3000mi maintenance items done?

[Vonbulow]

Hi Flybox

I'm running one oversize on jets. Having Kn pods mounted on the standard keihin carbs. At the moment i'm running the stock exhaust due to the upcoming MOT. When that is done an open flow exhaust system will be fitted.

Using D7EA NGK plug - will post a picture later on.

3000mi maintenance - I have done a complete rebuild of the engine, so hopefully that is covered  

[calj737]

Year of bike? Stock ignition or aftermarket? (I see you're in Europe, so the models differ slightly)

When you say it "cuts out" do you mean it stumbles and dies, or suddenly stops as though "electrical plug pulled"?

Does it happen from any gear, and does it happen reliably?

[Vonbulow]

Its a 1976

I am running an electronic ignition system. It seems like a plug is pulled when releasing the throttle and engaging clutch. Don't think the it is related to the gears Doesn't seems like it.

[calj737]

does your bike by chance have the side stand switch? Or can you verify the CLUTCH safety switch?

[strynboen]

if you not use the safty stop..just get the vires a short inside the mainlight its( green/green hvite) as i renember..but try to press on the svicth in the handel..iy can have moved aut..so it not funktion prober

[Vonbulow]

Hi guys - I proberly should have given more information earlier on. I completely rewired the bike. I have done this on a number of bikes with no issues. I do not have either clutch or stand switch on this bike. It is so frustrating! The runs great, looks great and handles like a dream. Can I post a video to this forum?

[calj737]

best to post a link to the video within your message.

If you've rewired it, and it cuts out as described, Id suspect the BLK/WHT wiring from the KILL switch to the coils may be the culprit. When this happens, is the power still on, but motor is dead?

[faux fiddy]

I think you have to go to you tube or photobucket to do a video.

I have never done the pods, but I have read here that pods lower vacuum so generally you need a bigger jet for the same amount of fuel delivery.  You may be going in the right direction with larger jets. It could be the motor starves for fuel when you let off the throrrle and RPM's drop intake vacuum drops, too. It is not always as  easy as just a next oversize.

You can search this forum for the pod threads, many  conclude that unless you want to go through months of testing and trying variations, and then changing it all when you change pipes, you are better off getting the stock air box installed.

[Vonbulow]

Calj737 - That was a brilliant idea, I will check that tomorrow! can't actually not remember whether the lights stay on. Faux Fiddy -  I'm not suspecting the pods for being the culprit. I have been building and tuning a number of bikes with pod setups and with great result. I know there is a lot of different opinions on that topic, which i will go deeper into in this thread. But thanks