Honda CB360 Engine/Carb issue??!!

stormple

stormple

New Member
Hey all- First Post - Just bought my first bike, 76' Honda CB360T. Been having some strange behavior. So the bike seemingly runs great, starts right up, lots of power, idles well. That's for the first 20 minutes or so.

After about 20 minutes of riding things take a turn.
-It seems to lose a lot of power under load.
-It begins to run sporadically (the power comes and goes while riding).
-It starts to idle at about 3000-3500 rpm (initially idles at around 1500 when 'cold').
-The right cylinder is putting off much more heat than the left

Everything is stock, carbs included. Anyone thought's on whats going on? Where should I start? I've been reading through a lot of the forums but no one seem to be having this specific problem, or set of problems. Any direction is much appreciated.
 
I think there could be one of two things happening. Number one, a possible vacuum leak, which would cause a lean condition and one cylinder to run hotter than the other. Or, a possible blown head gasket, or cylinder head issue. Next step would be to do a compression test, do one hot and one cold. Good luck and let us know what you find.
 
welcome, My only bike is a 76 cb360. Please post a pic of yours.

Check timing. Before you burn a hole in a piston.
and yes do a plug chop.
Sounds like the right is very lean. Making things really hot. = white clean plug
Left may be rich. fouling w gas enough to cause plug to quit firing = black plug = loss of power.
sounds like its time to remove carbs and give em a good cleaning. check diaphragms for pinhole leaks...especially on the left. synchronize them. float heights and so on.
check insulators (manifolds) for cracks...even small cracks make for big leaks. replace gaskets.
 
if you let her idle for a bit before shutting her down they will be black. you need to clean em or use a fresh pair and do a proper chop at speed. if its lean enough the one or both should do a pretty good job of cleaning itself.

and make sure plug gap is right.

check timing w a proper strobe light and advancer is working. heres a piston with timing slightly advanced.
http://i91.photobucket.com/albums/k315/1crazypj/Honda%20CB360/Brendon2.jpg
 
trek97 said:
heres a piston with timing slightly advanced.
http://i91.photobucket.com/albums/k315/1crazypj/Honda%20CB360/Brendon2.jpg
Click to expand...

A little JB weld will fix that right up....LOL
 
Quick update.

I sprayed starter fluid on all the carb boots to check for leaks and on the left side (the side running cooler) where the air filter feeds the carb spraying the fluid caused the bikes idle to slow and almost die then recover. This was confusing because from my understanding the idle is supposed to increase if there is a leak not decrease. But again I'm super new to all this. Thoughts?

Gonna check the timing tomorrow.
 
No, haven't rebuilt or done any carb adjustments. I just bought the bike a month ago. First bike. Have some learning to do. And I charged the battery about a week ago.
Could a low battery effect just one cylinder?
 
I'd check the battery after a full charge, it should read 13.8 or so, any lower and it's dead. A dead battery or bad connection to or bad charging system would cause those symptoms. I'd also consider cleaning the carbs, especially the pilot jet, if one gets blocked it will kill the cylinder at anything but open throttle
 
Update. So I pulled the carbs last night and cleaned them. Soaked all the jets in carb cleaner, made sure there were not leaks in the diaphragms etc. Put everything back on. No change. So I did some experimenting and it seems like the left cylinder isn't even firing at idle and only sporadically above say 3000 rpm. I put new plugs in, no change. I still need to check the timing. (which is what I should have down first). The battery is good. The carbs are freshly cleaned.
I'm lost here.
 
stormple said:
Update. So I pulled the carbs last night and cleaned them. Soaked all the jets in carb cleaner, made sure there were not leaks in the diaphragms etc. Put everything back on. No change. So I did some experimenting and it seems like the left cylinder isn't even firing at idle and only sporadically above say 3000 rpm. I put new plugs in, no change. I still need to check the timing. (which is what I should have down first). The battery is good. The carbs are freshly cleaned.
I'm lost here.
Click to expand...

Check for spark on the right side after youv checked your timing first.
 
stormple said:
Update. So I pulled the carbs last night and cleaned them. Soaked all the jets in carb cleaner, made sure there were not leaks in the diaphragms etc. Put everything back on. No change. So I did some experimenting and it seems like the left cylinder isn't even firing at idle and only sporadically above say 3000 rpm. I put new plugs in, no change. I still need to check the timing. (which is what I should have down first). The battery is good. The carbs are freshly cleaned.
I'm lost here.
Click to expand...

To do a proper cleaning, the pressed in emulsifiers need to be removed. The problem isn't just jets, but internal passages. There are a number of transfer passages that need to be cleaned that a simple soak may not help.

I also hope you did not soak the carb in cleaner. There are throttle shaft seals that are difficult to replace and can be ruined by carb cleaners.

The best cleaning for these is to let them sit in an ultrasonic cleaning tank for a while. This really loosens any deposits in hard to reach passages, and then can be blown out with compressed air.
 
Update - Checked compression, both sides to speck. Adjusted the points gap and checked the timing. Points needed some adjusting but the timing was spot on. After adjusting the points the left side will backfire at idle but the exhaust is still really cool compared to the right. It seems like Im right back to the carb. I cleaned the jets but I think I will do a proper cleaning tomorrow as mydlyfkryzis suggested. Don't have access to sonic bath. Is there a soaking solution that will work that is safe on any internal seals? People suggested Berrymans carb dip or just boiling water but again, I'm worried about internal seals.

This is getting ridiculous.
 
check the connection between the coil wire and the plug boot, sometimes they get worn out and are barely connected, if needed, cut half inch off the wire and rescrew the boot in
 
Another easy way to check for spark is to plug a spare spark plug into the side you're testing and lay it on the engine. You should see a nice hot spark when cranking/running.

I feel your pain - I'm fighting with my '76 360 too. They are a blast to ride when you get them right though!
 
stormple said:
This is getting ridiculous.
Click to expand...

BWWAAHAHAHA

The understatement of the century!!! you with a grand total of 6 posts. Your 360 will run great once you hit the 2000 post mark.

AND THATS GREAT NEWS FOR WORST CB650 EVER. CAUSE HE IS HALFWAY THERE.

See how Myself, Mydlyfkryzis have around 2000 posts.
Virtually every one of those IS HOW TO GET OUR CB360 TO RUN CORRECTLY. LOL

Sonreir is over 5000 posts and PJ is close to 10,000. Im not sure that either one of their modified 360s are running at the moment.

patience_grasshopper_zpsf4a8bed1.jpg
 
stormple said:
Update - Checked compression, both sides to speck. Adjusted the points gap and checked the timing. Points needed some adjusting but the timing was spot on. After adjusting the points the left side will backfire at idle but the exhaust is still really cool compared to the right. It seems like Im right back to the carb. I cleaned the jets but I think I will do a proper cleaning tomorrow as mydlyfkryzis suggested. Don't have access to sonic bath. Is there a soaking solution that will work that is safe on any internal seals? People suggested Berrymans carb dip or just boiling water but again, I'm worried about internal seals.

This is getting ridiculous.
Click to expand...

If timing is "spot on"
then I really doubt "the left side is backfiring" its probably not firing at all. (thats why its cool) Then it does try to fire up...occasionally. (seems like a backfire, but its not) Remove your points cover and try to start her up. The points may be grounding out on the cover.
or the left side fuel mix may be too rich/lean and plug is fouling or not getting enough fuel to fire.

Like w650ever said, " pull the plug out, ground it on the engine, and crank her over...make sure you got spark on the plug. If not try a new plug. If so...its probably a fuel issue.

When your riding and experience a "loss of power" its because the left side quits firing and your only running on the right side cylinder. Go through all your ignition electrical connections make sure they are clean and snap together snugly.
 
Funny thing, Sophies runs better with every post I make...I thought it was the work, but now I see a direct correlation to posting and running....

I think I have it figured out.

Posting Pressure.
1. Get 100 to get the DCC 10% discount (buy parts with discount to get bike running better)
2. Need to make progress on repairs and a troubleshooting so I have SOMETHING legitimate to post.
3. Have issues, need help, more posting
4. Get running, but need to improve so you have more to post about....

See, by the time you have 2000 posts, you have done all the work needed to have a running bike.....just so you have something to post about.....

Trek is on to something there... 8) 8)
 
Ok, well thanks to everyone for all your help. It is much appreciated. After checking the points, compression, valves, carb (twice), electrical, it was the carb. I didn't checking the first time I pulled the carb but the two were WAY out of sync. So much so that idling at 2000 the left side butterfly wasn't even open while the right was open enough to get the bike the idle at 2000. Once I really looked at them they were obviously and visibly off. I adjusted them (just eyeballed it) and put the carb back on and she ran like never before. Still need to do a proper sync with a vacuum gauge but at least I tracked down the culprit. So obvious, such an idiot. I would have checked that earlier but this is my first bike and I have no idea what Im doing. But at least I know the the bike a bit better know. Thanks again to everyone for the tips and direction.
 
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