Topic: Cylinders 1 & 2 Not firing, ideas?

[63SSRagtop]

Hola all, started working on the '77 CB750 now that is finally starting to warm up some..   Bought this bike and parked it.. When I first checked it out you could tell from the exhaust it's running really rich and I do believe it was spritzing gas out the tail pipe..  loaded it up and brought it home anyways lol..

I figured it was a coil/plug problem so I went ahead and put in a pamco timing kit with coils, got it installed yesterday and I'm still dead on 1 and 2..  Ok, so put in new D8EA plugs.. same same.  Pulled out the plugs one at a time and checked for spark which it seems to be getting, new plugs had fuel on them for these two cylinders..

Suppose a compression check is next then look at the low idle side on the carbs? 

[innovativems]

If you give it throttle do they fire? 


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[flybox1]

Not gas out the tailpipe...its condensation from not bing run for so long.
Too bad you went with an electronic ignition as this is a carb issue.
Remove and clean your carbs and clear tube test your bowls for adequate fuel levels.

[63SSRagtop]

If you give it throttle do they fire?

Not sure what you mean here, I just pulled them and grounded against frame and they are sparking

Too bad you went with an electronic ignition as this is a carb issue.
Remove and clean your carbs and clear tube test your bowls for adequate fuel levels.

I don't mind the electronic ignition at all, do like eliminating it as the issue.. Understand the fuel supply side is paired 1&2 and 3&4.. which is why I started thinking low idle jets.. Might explain why the guy said it ran like a scalded ape on the highway but only on the highway.. 

Those carbs are going to have to probably be done.. This bike for everything I can see is completely original.. even the coils looked to be the originals but she is in great shape..

[flybox1]

Clean the carbs and perform the 3000mi scheduled maintenance.
This will take care of 90+% of the issues these bikes have.

[innovativems]

I'm referring to with the bike running, at idle neither 1,2 is firing correct?  If you give it some throttle, do they begin to fire?  That would mean a plugged pathway in the carbs


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[63SSRagtop]

Ah I got you.. no I didn't notice them firing then either.. pipes stayed cold no matter what the throttle position was... They way the previous owner described it running fine on the highway does tend to lean that way though..  going to go ahead order carb kits.. who's the best source these days??

[Brian G]

There was another thread on two adjacent cylinders not firing recently -

http://forums.sohc4.net/index.php/topic,163992.0.html

Lots of good ideas there.

Regards,

[63SSRagtop]

Yeah, that's money!  thanks for the link!  Didn't get a chance to mess with it this weekend, hopefully this week.. I've got clean plugs (new) with fuel on them.. I'm getting spark but to me it looked week.. only kicker is for the bike to run its gotta be on full choke.. 

[evinrude7]

i'd pull the carbs, clean them and bench sync.  put them back on and see what you get. 

[Spanner 1]

'For the bike to run it needs to be on full choke '... there is your problem. Nothing to do with plugs/ ignition, need to remove the carbs and clean them by the full and proper procedure  . Plenty of help at the FAQ section... good luck.

[Deltarider]

Forgive me for asking but you do know when chokeflaps are opened and closed, don't you? You wouldn't be the first...

[PeWe]

Start spray into carbs 1, 2 will not help? This to find if this is a fuel issue.


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[DaveBarbier]

Don't replace the brass with the ones in the kit you get. Clean and reuse the stock brass.