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Discussion Starter #1
so im breaking in my new top end on the rd350. im on about my 3rd tank of gas and 3rd week of heat cycles. however...i believe that i have got an exhaust leak because the right pipe makes a louder slapping sound than the left one. a little louder than normal. the puffs of smoke are not always consistant either. the left side sounds ok with a steady push through the rpm range. i think im going to pull off the heads and make sure everything is ok...cylinder walls clean and pistons good. and also replace those exhaust gaskets. hopefully that will keep my temp down and fix that slapping water noise out of the right side. another question...i check the plugs everytime i park her back into the garage and this last time, the left side was all clean with very minimal coffee on the little prong of the plug. the right side however, was clean with almost no sign of firing at all. both plugs are new and look like they weren't even used when i pulled them out. what the hell does that mean?

thanks guys..

cheers

hely

74 Yamaha RD350 cafe
 

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quote:
so im breaking in my new top end on the rd350. im on about my 3rd tank of gas and 3rd week of heat cycles. however...i believe that i have got an exhaust leak because the right pipe makes a louder slapping sound than the left one. a little louder than normal. the puffs of smoke are not always consistant either. the left side sounds ok with a steady push through the rpm range. i think im going to pull off the heads and make sure everything is ok...cylinder walls clean and pistons good. and also replace those exhaust gaskets. hopefully that will keep my temp down and fix that slapping water noise out of the right side. another question...i check the plugs everytime i park her back into the garage and this last time, the left side was all clean with very minimal coffee on the little prong of the plug. the right side however, was clean with almost no sign of firing at all. both plugs are new and look like they weren't even used when i pulled them out. what the hell does that mean?

thanks guys..

cheers

hely

74 Yamaha RD350 cafe
If you are hearing a slapping noise, check the pipe and make sure it is tight. If it is loose at all when running you should see some blue smoke coming out of whereever the exhaust leak is. One thing I would check however is the piston pin. You may be getting what is known as
"piston slap", where the piston is not going straight up and down in the bore. Usually a bad piston pin and rings are the culprit. also check that your spark plugs are on tight and that compression is not escaping through the top of the head.

Any auto parts store can sell you an inline spark tester, which will tell you if the plug is firing or not. If it is then look at the fuel, but I suspect that you may have to run the engine longer to see a difference on the plugs. Another way to tell, but is not recommended, is to feel the pipe that you think is not firing. if it is not hot to the touch then that cylinder is not having combustion. Remember whenever touching anything hot to use the back of your hand and not the palm so that 1) you can still use your hand if you burn it, and 2) so your hand doesn't muscle lock around the pipe and cause a lot more permanent damage.

good luck
 

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Discussion Starter #3
i just replaced the exhaust gaskets today and that made a big difference. i found a little exhaust leak near the weld on the bracket. im going to have that fixed next. if i check for that possible "piston slap" do i have to replace the rings? that is of course if they are ok and i don't have this piston slap? what are other symptoms of piston slap? i figured that is what needed to happen with the plugs. they were relatively new with only about 30 miles on them. thanks again.

omar

74 Yamaha RD350 cafe
 

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Discussion Starter #4
i checked the heads today. i took them off and found that one of the washers on the head bolts was bent. i replaced them and while the heads were off i checked the cylinders for scores and scratches. CLEAN! both were very smooth with not one scratch and both pistons looked brand new with very little color on each one. the one with the leak had a little less coloration though. i've ordered some new float valve assemblies and im sure the bike will run 10xs better with the new ones in.
thanks all

hely

74 Yamaha RD350 cafe
 
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