Leaking left side now running on one cylinder

[victorr]

78 RD400 everything was running smoothly on the previous ride, then today, it started, but died. I tried again and gave it some throttle and proceeded to ride away. This is when I noticed it was running on just one cylinder. I parked it and noticed it was leaking gas/oil from the left cylinder where the exhaust bolts on to it and dripping down the expansion chambers.

Any idea where I should start?

Thanks in advance!

[Dvsrd]

78 RD400 everything was running smoothly on the previous ride, then today, it started, but died. I tried again and gave it some throttle and proceeded to ride away. This is when I noticed it was running on just one cylinder. I parked it and noticed it was leaking gas/oil from the left cylinder where the exhaust bolts on to it and dripping down the expansion chambers.

Any idea where I should start?

Thanks in advance!

With a non-running engine, or in this case, a partly non running engine, always start with electrics
1: Battery voltage. If the horn is clear and loud when the high beam is on, you should mostly be OK. Better yet, measure battery voltage. Should be at least 12.5V with engine not running.
2 : Check spark plugs. If oily or sooty, replace. If wet with fuel, dry them
3: Spark. Make sure you ground both plugs, check if you have a spark on both.
4: If you have a spark, check ignition timing.
5: Compression. Basic check, ignition off, full throttle, hold your thumb against spark plug hole, Kick it several times. If you are unable to maintain a seal with your thumb, it should be able to run.  Same procedure on other side. Better yet, take proper compression readings with a gauge.
6: Fuel and air. Blocked air filter? Blocked vent in gas cap? Fuel in tank? Blocked in-line fuel filters? Stuck floats or float valves (in carbs) Blocked jets? Vacuum leak at intake or crankcase seals or joints?
7: Read books about motorcycle engines, systems and electrics in general. Get a manual for your bike. Read it. Use Youtube for instructional videos , but apply a little bit of scepticism and common sense.
Suddenly your bike runs, and you have learned something new :)

[victorr]

Thanks! I already did 1-4. It's the oil leaking from the exhaust flange that is totally new and hasn't happened before. I'm wondering what could be the cause of this. I pulled the plug of the cylinder in question and it is black with oil deposits.

Ended up checking the reeds on the suspect cylinder and they were just like new. I ended up replacing both plugs and she is running much better than before. I'll keep my eyes on the plug..hopefully all remains good.

[GHtokyo]

I wouldn't worry too much about the dripping oil.  Its an indication the engine was misfiring, and unburned gas and oil for pushed out of the exhaust port.  For some reason plugs can get fouled very easily on 2 strokes, probably due to the oil in the mixture.  Were you revving the engine on the choke, or have a dirty air filter?  Or any other reason it would be to rich?  Otherwise, as you did, replace plugs and move on

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[victorr]

Thanks!
Wasn't revving on choke. Funny thing is it only needs the choke upon start up, even on days where it is 50*. I forgot to turn the choke off one time and rode with it on and it wouldn't rev up the rpm range on each gear. Turned the choke off and it ran nicely.

Rode it again a bunch today and yes, it is running a bit rich. It has pods on it (from P.O.). I'll re-clean them and see if there is a change.

Much appreciated!

[victorr]

Yesterday I took the filter pod off the left cylinder and noticed that the throttle valve slide wasn't seated as far down as it should have been. Actuated the throttle a couple of times and saw that it was binding a bit. Unscrewed the top part of the mixing chamber and saw that the throttle cable was a bit bent. For now, I straightened it out, cleaned everything in there and the throttle slide is now going up and down smoothly. Couple of test rides and the bike is running with no issues.

[Striker1423]

Pods? Like the flat back metal kind? Get rid of those.

[m in sc]

sounds like typical flooding situation. check needle and seat and float height. it can be just high enough to flood motor but low enough not to drip out the overflow. I bet it had a bit of trash behind the seat thats now flushed thru.  Sound sliek you got it though, but keep an eye on it.

[victorr]

Got rid of the pods in exchange for the Y hose K&N system. I also replaced the needle valve, float assembly and gaskets and while in there, cleaned all ports and replaced some dried out hoses, and then set float height to 23mm (both were at around 21mm). Glad to report she is running better than ever.

Thanks to all that helped and to Economy Cycle for the fast shipping!