Cylinder not firing

G

gdimaggio23

New Member
So i bought my first bike a few months ago, a 1972 cb350, but i haven't been able to put much time into it until recently. When i bought it the right cylinder wasn't firing but the left was. I checked the coils, replaced the plugs and the battery, and adjusted a miss placed wire. The right cylinder began to putt a bit and get warmer than before, but it still wasn't firing properly and getting hot like it should. After that, the bike wouldn't turn on at all. So I cleaned out the carbs and the bike fired back up. I noticed there was a big oil leak coming from a loose cylinder gasket on the left of the chain, near the gear shifter. I fixed that leak, but seconds after the bike started to drip oil from both the oil tank, and from the right cylinder head (picture below). What could this leak from the cylinder head mean? and does anyone know what i should do next to try and get the right cylinder to fire and to fix these leaks?

First Photo: Cylinder Head
Second Photo: First Leak
 

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Are you sure the one in the second photo is leaking? I can just see all the grime from the chain. If it is, its an easy oil seal that's not hard to get. Are you sure the battery is fully charged? Mine used to kill the right cylinder when it was getting low on voltage. Common on hondas. Also may happen if the battery you are using is too small. I would try to identify if its spark or fuel that's causing it not to run. Remove spark plug, connect to wire, and ground to head to see if that right plug is visually sparking. Then smell if fuel is present in the cylinder that's misbehaving. Id try these things since they are free before worrying about that head gasket. Then once the bike has warmed/run on both cylinders a bit consider a compression test to verify.
 
I'm not much of a Honda guy but what wahvtec said plus have you checked the points ?
 
As wahvtec and Dreadrock noted, compression/spark/fuel should definitely be verified (probably in that order too). One thing that wasn't mentioned was that even if you cleaned the carbs once, the dead cylinder's corresponding carb may not have the float adjusted right, may have a sticky float valve, or may have gotten another piece of rust/crud in the jet, all of which could prevent the cylinder from firing regularly.
 
I appreciate the responses.

The second picture was the original oil leak that i fixed.
Both cylinders have spark. I charged the battery before i ran the bike so it should have been fine but i need to buy myself a volt meter and a compression test this week. The fact that oil was leaking out of the right cylinder head made me a bit nervous. Im not really sure what my next move should be.
 
Also, I did check the points with a buddy when i first got the bike and cleaned them up and they were good. Float heights were also checked when i cleaned the carbs this past weekend.
 
FYI you can typically borrow a compression tester from your local generic auto parts store. Just make sure it comes with a 14mm fitting to match the 350s plug size. They may make you give a deposit but you get it back when the tool is returned.
 
Oil leak might be the tachometer seal just above it. They commonly leak and the oil is tricky to be seen traveling down. Cheap part. I had a right cylinder that would be intermittent too. Think mine was a stuck valve, but you need to check timing and may want to swap left and right carb to confirm. Coils can be finicky of old but are rarely bad. If it's always cold and never firing I would be money on the carb.


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I just went through this same thing, right cylinder not firing consistently on my 350.
Checking and double checking battery voltage, compression, and carbs. I was getting spark on both plugs when they were held against the motor too.
I did notice that my points were sparking a lot. I did some research and found that this was a possible cause of failing/failed condensers. I was checking the condensers functionality and notice that the coil bracket, that the condensers are mounted to, was not grounded. Fixed that and verified points were clean and working properly, timed them again, as well.
Fired the bike up and it was running great, just a few tweaks on the carbs and it was idling at a steady 1200 RPMs.

This link on the Honda Twins Forum has an easy step by step to setting points timing, if you're interested:
http://www.hondatwins.net/forums/50-electrical-discussion/23580-how-time-honda-twin.html
 
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