Author Topic: CB650c 1 cyl. rich? (Read 1912 times)

Sandy650 · « **on:** September 23, 2017, 02:30:16 PM »

1980 CB 650c
Running reasonably well now after cleaning out the carbs and re-installing the airbox. I know it is rich overall. It starts first crank from cold with no choke. Waiting for a new air filter, the one in the bike is clogged enough to affect air flow. Ignoring the overall rich condition one cylinder is "more rich" than the others. These are not CV carbs.

I would appreciate some advice on how to try and improve the one extra rich cylinder. Willing to tackle almost anything but not sure best way to start.

When I got this bike the PO had been unable to get it to run after "rebuilding" the carbs. The main thing I did was install the airbox after cleaning things out. I have been riding it for a few days and it generally runs well.

thanks,
Sandy

scunny · « **Reply #1 on:** September 23, 2017, 02:38:49 PM »

check the fuel levels in the carb bowls.
http://forums.sohc4.net/index.php/topic,135470.0.html

Sandy650 · « **Reply #2 on:** September 23, 2017, 08:58:02 PM »

Thanks for the reply.
I will verify float level first.
Sandy

Sandy650 · « **Reply #3 on:** October 06, 2017, 07:02:37 AM »

Physically checked all float levels and after putting everything back together I used clear tube method to check fuel levels. All are about 3 mm below top of float bowl. Both cylinders 3 and 4 are still too rich. Verified by test ride and also sooty pipes.
I'm a bit confused as to why the other 2 cylinders are ok. I thought maybe 1 and 2 were being leaned out by air leaks but found nothing when I checked. Any suggestions appreciated.

thanks,
Sandy

evinrude7 · « **Reply #4 on:** October 07, 2017, 06:05:40 AM »

are the carburetors bench synced and vacuum synced? valve tappets adjusted correctly?

Sandy650 · « **Reply #5 on:** October 07, 2017, 04:15:46 PM »

Bench synced and valves set. I ordered vacuum gauges to build a sync tool. Sorry if I caused confusion but I have another thread going because I thought I had 2 separate issues but I think now it is all one issue.

http://forums.sohc4.net/index.php/topic,168734.0.html

many thanks,
Sandy

DaveBarbier · « **Reply #6 on:** October 08, 2017, 05:52:23 AM »

What are the jets in there? Possible that the PO drilled out jets to try and get it running right. Happened to me. Verify jet hole diameter by sight and/or putting in wires of known thickness.

A 100 main jet hole size is 1mm. A 45 slow jet hole size is .45mm. A 130 main jet hole size is 1.30mm and so on. You can measure up some wire and use them as feeler gauges.

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Sandy650 · « **Reply #7 on:** October 09, 2017, 07:48:12 AM »

Main jets are 90 and don't appear to have been altered. I have identified carb 2 as leaking out the overflow. Going to fix that first and then come back to any rich problems.

thanks,
Sandy

Sandy650 · « **Reply #8 on:** October 15, 2017, 05:15:41 PM »

Progress report. (These are PD40 carbs)
Got the leak stopped on carb #2. The float appears to have been hanging up but still not sure why. The bad news is that #1 cylinder has dropped out. No heat on #1 header pipe. Verified spark, compression and fuel in the float bowl. Cleaned the needle and seat and the main jet for the third time. This cylinder was firing before. Made an attempt to remove the pressed in jet without success. Decided to leave it for now because I don't want this thing to look like a gorilla worked on it. I read a couple of threads which said it should come out easily. Not this one.

Based on the cylinder being dead do you think I need to get this jet out as my next move?

Any suggestions would be appreciated.

thanks,
Sandy

TwoTired · « **Reply #9 on:** October 15, 2017, 06:25:00 PM »

The pilot jet is an interference fit part, or press fit. It will come out if you pull hard enough.
I use a parallel jaw pliers to perform a straight out pull. Mine has soft jaws. I've not damaged a jet yet with it!

Cheers,

DaveBarbier · « **Reply #10 on:** October 16, 2017, 04:19:57 AM »

If you put leather or something between the jaws you won't damage it. Just pull straight up, don't rock it. You can twist a bit back and forth. Maybe hit it with some propane first to loosen any varnish.

Did you also unscrew the main jet holders which the mains are threaded into? Also called emulsion tubes?

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evinrude7 · « **Reply #11 on:** October 16, 2017, 06:13:26 AM »

Quote from: Sandy650 on October 15, 2017, 05:15:41 PM

Progress report. (These are PD40 carbs)
Got the leak stopped on carb #2. The float appears to have been hanging up but still not sure why. The bad news is that #1 cylinder has dropped out. No heat on #1 header pipe. Verified spark, compression and fuel in the float bowl. Cleaned the needle and seat and the main jet for the third time. This cylinder was firing before. Made an attempt to remove the pressed in jet without success. Decided to leave it for now because I don't want this thing to look like a gorilla worked on it. I read a couple of threads which said it should come out easily. Not this one.

Based on the cylinder being dead do you think I need to get this jet out as my next move?

Any suggestions would be appreciated.

thanks,
Sandy

just to be sure are you pushing it out the right direction?

Sandy650 · « **Reply #12 on:** October 16, 2017, 03:03:59 PM »

The carb is still on the bike so I was pulling straight down to try and remove the pressed in jet. Seems like this may not work well and I may need to remove the carbs again. I appreciate the help already given.
As much as these SOHC's are my favorite bikes, please remind me not to buy another bike with 4 carbs. I'm pretty good with single carb situations but this has pushed me close to insanity.

best regards,
Sandy

TwoTired · « **Reply #13 on:** October 16, 2017, 03:53:21 PM »

Quote from: Sandy650 on October 16, 2017, 03:03:59 PM

As much as these SOHC's are my favorite bikes, please remind me not to buy another bike with 4 carbs.

No. We learn and grow wiser in the face of adversity.

Patience + persistence + perseverance >>> satisfaction.

Cheers,

Sandy650 · « **Reply #14 on:** October 16, 2017, 05:41:03 PM »

I know you're right. I'm way too stubborn to give up. This thing has just given me a few "I feel sorry for myself" moments.

best regards,
Sandy

Sandy650 · « **Reply #15 on:** October 17, 2017, 06:57:00 PM »

Has anyone removed the #1 carb without removing the entire assembly? I admit to being tired of taking all this apart but I also have concerns about how many more times the rubber parts will stand being forced on and off.

thanks,
Sandy

scunny · « **Reply #16 on:** October 17, 2017, 07:03:59 PM »

Don't think that's possible.

Sandy650 · « **Reply #17 on:** October 18, 2017, 04:40:55 PM »

I sort of thought it wouldn't work.

I've decided to try compressed air one more time before I remove the carbs again. I would't bother trying the air but it is only 1 carb and it is on the outside.

Wish me luck.
Sandy

tlbranth · « **Reply #18 on:** October 18, 2017, 06:01:01 PM »

Quote from: DaveBarbier on October 08, 2017, 05:52:23 AM

What are the jets in there? Possible that the PO drilled out jets to try and get it running right. Happened to me. Verify jet hole diameter by sight and/or putting in wires of known thickness.

A 100 main jet hole size is 1mm. A 45 slow jet hole size is .45mm. A 130 main jet hole size is 1.30mm and so on. You can measure up some wire and use them as feeler gauges.

Sent from my iPhone using Tapatalk

Main jet doesn't have any effect 'til you crank it wide open. The problem is elsewhere.

Sandy650 · « **Reply #19 on:** October 18, 2017, 06:30:16 PM »

My plan is to try and blow out the pressed in jet (low speed jet?) not the main.

best regards,
Sandy

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Author Topic: CB650c 1 cyl. rich? (Read 1912 times)