Gas on right side spark plug - CB360

Matnetik

Active Member
1974 CB360 - finding gas on the right side spark plug. Left side looks clean.

Bike starts first try every time, idles, I can drive, it has power throughout all the gears, no bogging or anything, literally runs perfect. After warming up, I am getting a light amount of white smoke from the exhaust, once I start going it’s gone, doesn’t smoke while driving at all (at least I can’t see any).

I’ve probably only put 150 miles on it since I rebuilt the top end (new rockers/bolts, camshaft, chain tensioner, adjusted valves, new head and shockwave electronic ignition and oil filter clean, oil change).

Recently discovered my new carb boots weren’t completely seated to the carb, they popped off a few times on startup and I would just push them back on. After removing the clamps last weekend, turns out if you push hard enough they snap in place (had no idea) and now they are seated correctly. Haven’t messed with the carbs since I got it two years ago other than adjusted the idle and mixture screws.

My question is, where do I start? I’d searched a few threads and have gotten mixed answers, any help is appreciated. I checked the plug on Sunday and it was covered in gas and black, used a dremel and cleaned it, threw it back in and went for a 20-30 minute ride, averaged around 40-50mph the entire time with stop and go’s in between. The picture below is after that single ride, doesn’t look too bad but it’s still wet and I can smell the gas. Also no gas in the oil, only on the plug. Thanks in advance for any replies!!
 

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Matnetik

Active Member
Installed new plugs, rode around for about 15 minutes and still smoking. Also smoke coming from the breather tube near the exhaust clamp (which I clearly need to shim and tighten down). Wondering if it’s actually oil and not gas, idk smells like gas for sure.

 

Matnetik

Active Member
New plug after the 15 minute ride -
 

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irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Your idle is really high. White smoke is oil. Oil will foul plugs too. Your tappets are pretty loud. I'd let it completely cool and go over all of your measurements first, then go from there.
 

Matnetik

Active Member
Your idle is really high. White smoke is oil. Oil will foul plugs too. Your tappets are pretty loud. I'd let it completely cool and go over all of your measurements first, then go from there.
Good note here, think I am going to tear it apart for the winter and check everything over, new gaskets and rings - couldn't hurt I suppose - will check all measurements by the book while I'm in there and report back! Thanks
 

Matnetik

Active Member
I lowered the idle And tried swapping plugs and wires. It’s definitely burning a lot of oil, I topped it off about 50-60 miles ago and it’s back to the “add” mark now. Just ordered a set of .5mm oversized pistons and new gaskets for the entire top end. Going to tear it down, have a machine shop bore and hone the cylinder and reassemble myself. Will report back soon I hope! If anyone has some recommendations for machine shops in the valley of Los Angeles, feel free to let me know!
 

pidjones

Over 1,000 Posts
Let me suggest that you take the old pistons and jugs to whichever shop you find and let them tell you what size piston to order.
 

Matnetik

Active Member
Let me suggest that you take the old pistons and jugs to whichever shop you find and let them tell you what size piston to order.
Yeah? I mean I already ordered the .5 over (it was the smallest next step) - my cylinder could be in spec for all I know but figured if I am going to tear it down, might as well bore it up 1 size - I can always return them if they aren't enough or too much - thanks for the advice here
 

pidjones

Over 1,000 Posts
I had an XR100R bored this summer. Asked the machinest if I should go ahead and order a .25mm over piston (I had already measured and knew it needed a bore). He said to wait until he had bored it to make sure it cleaned up (mostly taper and out-of-round). He called and said go ahead and order the .25 over, than honed the cylinder to fit correctly when I took it in. May not be that easy (or cheap - $30) in LA though.
 

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