Engine smothers down after warming up (Carbs?)

If it's broken or just needs tweaked

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Pesco
Posts: 18
Joined: Sun Jun 03, 2012 10:16 pm

Engine smothers down after warming up (Carbs?)

Postby Pesco » Sat Aug 24, 2013 5:45 pm

Hello there,
hopefully someone can help me figuring out what's going on with my 82 CB650.
It's been a while that my bike loses power after it warms up.
Bike starts great, runs great for a while, then while riding it the bike smothers down, sometimes for a few seconds, sometimes for minutes, then it snaps out of it, like it gets unclogged, and runs ok again. When the engine is smothered down like that, it won't keep the idle, it won't go more than 5000 rpm.

I looked at the carburetors and they are clean, i also clean the air filter. No results.

Any suggestions on what it could be and where should i look for the problem?

Thanks

Andrea

kstylian
Posts: 92
Joined: Fri Jun 15, 2012 1:56 pm

Re: Engine smothers down after warming up (Carbs?)

Postby kstylian » Sat Aug 24, 2013 7:25 pm

What do your plugs look like? Also possibly sounds like an intermittent ignition issue. how's your timing? spark advanced cleaned and working smoothly?

Pesco
Posts: 18
Joined: Sun Jun 03, 2012 10:16 pm

Re: Engine smothers down after warming up (Carbs?)

Postby Pesco » Sun Aug 25, 2013 2:00 pm

I'm going to look at the timing and spark advance, clean the plugs and take it from there (by the way, i can't find a socket that gets to the inner 2 ones... how do you take them out??)

entropy
Posts: 21
Joined: Mon Jul 08, 2013 6:46 pm
Location: Blacksburg, VA

Re: Engine smothers down after warming up (Carbs?)

Postby entropy » Sun Aug 25, 2013 5:51 pm

Re the plugs:

If you don't have the Honda spark plug tool (from the tool bag), you may have to modify a socket to fit. There are a hundred threads on the internet on how to get these plugs out, where you can maybe find a socket, etc.

I, having no luck finding this no-longer-made Honda socket for less than a prince's ransom, went and bought the cheapest, crappiest (read: thinnest-walled) 3/8" drive 18 mm socket that I could find at my local store. I then spent a half hour with the bench grinder and a bucket of water, shortening and tapering the tail of the socket. Coupled with a universal joint, a short extension, and a scrap strip of rubber rolled and stuffed deep into the socket (to "grab" the tail end of the plug), I can remove all four plugs with ease.

Image

As always, your mileage may vary.

Pesco
Posts: 18
Joined: Sun Jun 03, 2012 10:16 pm

Re: Engine smothers down after warming up (Carbs?)

Postby Pesco » Sun Aug 25, 2013 6:28 pm

Yes, i was able to take those spark plugs out. i found a thin walled 18mm socket that worked, very laboriously, but finally worked..

Plugs are fine, so i still don't know what is the nature of the smothering engine.
I noticed that there is smoke coming out from one of the 2 exhausts. The color of the smoke is grey, and it comes out only from the right exhaust.

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Volker_P
Posts: 5508
Joined: Mon Mar 06, 2006 1:53 am
Location: southern Germany

Re: Engine smothers down after warming up (Carbs?)

Postby Volker_P » Tue Aug 27, 2013 2:21 am

Pesco wrote:Bike starts great, runs great for a while, then while riding it the bike smothers down, sometimes for a few seconds, sometimes for minutes, then it snaps out of it, like it gets unclogged, and runs ok again.

Sounds like it runs only on two or three then. Probably a tricky, temporary ignition issue.
Might be just plugs, one may measure pickup coils resistance (should be 530 Ohm) and have a lock at the pulser gap, too. Check out the advancer, too.

If it does this again, one may try to pull the spark plug cables to see which will stop it completely then (urgently wear good (!) gloves ).
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

Pesco
Posts: 18
Joined: Sun Jun 03, 2012 10:16 pm

Re: Engine smothers down after warming up (Carbs?)

Postby Pesco » Tue Aug 27, 2013 11:56 am

Yes Volker, you are a genius... or maybe it's just me that i'm a poor beginner..

The engine starts going on 2 after it gets warm, disconnecting plug cables #2 and #3 doesn't change performance of the engine.

Changing the plugs, let's see...

jagans
Posts: 30
Joined: Thu Aug 08, 2013 10:51 pm

Re: Engine smothers down after warming up (Carbs?)

Postby jagans » Tue Aug 27, 2013 7:51 pm

Great Diagnosis Mr. Volker.

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Volker_P
Posts: 5508
Joined: Mon Mar 06, 2006 1:53 am
Location: southern Germany

Re: Engine smothers down after warming up (Carbs?)

Postby Volker_P » Wed Aug 28, 2013 2:40 am

So something is wrong with your 2+3 circuit.
You may just swap components with 1+4 to see which one makes the problem move to 1+4.
Swapping the spark plugs is a first try.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum


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