Missing air filter cover

[Vaudray]

Hi guys!
i recently bought a 1981 cb650 for 500$
and i would like to bring it back to its original condition!
i juste got the carbs cleaned ( local honda shop for 445$ )
the bike runs like new, idles fine
but when i want to go higher than 85 km/h at around 4800 rpm it wont let me
it loses power

My mechanics tells me that it might be because i am missing the air filter cover.
what do you think!

thanks in advance

[cb650]

Try new plugs

[socal1200r]

That's not it. I bought my '79 CB650 with less than 7K miles, and had to have an indy shop go thru it, especially the carbs. They got it all dialed in, and I actually removed the air filter cover to help it idle a little better. If you compare the small air filter cover opening, and in my case it was pointing towards the back, with all the open space without the cover, it can pull in a LOT more air under load. If your shop got the carbs right, it should pull hard all the way to redline. I made a small bracket out of some aluminum flat stock I had, and used the two cover bolts to secure the air filter in place.

And having the air filter cover off didn't effect it's ability to pull to higher rpms at all, lol!

https://www.youtube.com/watch?v=2xYd3cZyUcE

[Vaudray]

i apreciate the input
if its not the cover could it be an electric problem?
if so what do i need to check?
otherwise the bike runs fine i did have a little problem when i was charging my new battery

just behind the battery at the end of the tail light wire there was a
silver solenoid type thing that was touching the frame and shorting the bike

again i really apreciate the input, since i am already in 450$ at the shop

[socal1200r]

So are you saying it pulls past 4800 rpms on the way up to 85km/h, but once you get there and it's around 4800 rpms it falls off? If it has issues pulling past 4800 rpms in all gears, then it sounds like a carb/fuel delivery issue to me. From when I got my carbs done, they can be somewhat fussy with the jetting. I think the shop had to change the jets twice before they got it right.

[Folsoml]

just behind the battery at the end of the tail light wire there was a
silver solenoid type thing that was touching the frame and shorting the bike

Perhaps a picture of this would help. I can't imagine what this is.

I would definitely go through the wiring harness and clean every electrical contact on the bike. How is the charging system on the bike? If the bike is not getting in the neighborhood of 13.5 to 14 volts at 3000 rpms, you will experience problems just like you are describing.

I don't know what kind of "dialing in" the shop did on your carbs, but nothing should work better than the original jets with the original airbox.

[Vaudray]

Its raining now i will try to get pictures tomorow

I spoke to the guy at my local moto shop and he told me, his mecanics put "something"
To act as the air filter cover, turns out that "something" was two strips of duck tape!
With only about an inch of air access.
Could this be the cause of my trouble?
Previous told me the bike was running fine whitout the cover
Not supose to rain tomorow cant wait to try it

[Vaudray]

Problem solved!
When up to 130 km/h no problems

Thanks guy!

[Folsoml]

What did you do to fix it?

[Vaudray]

I just removed the tape now the bike runs great!

I just have the feeling the battery is not charging right
Maybe i should start another tread?

[Folsoml]

just behind the battery at the end of the tail light wire there was a
silver solenoid type thing that was touching the frame and shorting the bike

Perhaps a picture of this would help. I can't imagine what this is.

I would definitely go through the wiring harness and clean every electrical contact on the bike. How is the charging system on the bike? If the bike is not getting in the neighborhood of 13.5 to 14 volts at 3000 rpms, you will experience problems just like you are describing.

No real need for another thread. Have you tested the charging system with a multimeter? I'd still start by cleaning every contact and making sure they are all good and tight--not just the plastic plugs, but the actual metal connectors inside the plug.

[Vaudray]

Can i just put the multimeter on the battery and rev the engine to 3500 rpm?

[Folsoml]

You can, but if you have a dirty or loose connection somewhere you may get inconsistent readings.