Old smokey................ - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 23 (permalink) Old 08-21-2011, 02:24 PM Thread Starter
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Old smokey................

Just picked up an SP-1, while I am really enjoying it. I am not liking the oil consumption. On start up no smoke, but after warming up and riding for 20-30 minutes it smokes like chimney when it returns to idle after a few seconds. Like if I stop at a traffic light at first no smoke but after a few seconds it will start to smoke. If allowed to idle for a few minutes the smoke seems to diminish.

Any ideas on the particular problem?

Sean
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post #2 of 23 (permalink) Old 08-21-2011, 04:34 PM
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Do a compression leak-down test for each cylinder.
That will tell you if the rings are shot.

If the compression-leak down test is good, then it sounds like the valve stem seals may be worn and oil is leaking past into the exhaust or intake.
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post #3 of 23 (permalink) Old 08-21-2011, 05:54 PM
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Do a compression leak-down test for each cylinder.
That will tell you if the rings are shot.

If the compression-leak down test is good, then it sounds like the valve stem seals may be worn and oil is leaking past into the exhaust or intake.
the only way to tell really is to do a test, but check the air box for oil.
how many miles on the bike?
my old 2000 was doing the same thing after i got the valves adjusted @ 18k, dealer said the exhaust side was tight and then to come to find out they over filled the oil and had burped into the air box and was getting a lot of smoke from that, but after cleaning and replacing the filters i still had a puff when i blipped the throttle or stopped at a light.
never did any test and rode it for another season before i got rid of it. good luck

"...Loctite -- or kiss your nuts goodbye..."
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post #4 of 23 (permalink) Old 09-26-2011, 01:25 PM Thread Starter
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Just got back home from work opened up the airbox and it is very clean and dry. While I was messing with it anyway I went ahead and removed that pesky intake valve too...............

Next will be a compression test.....................

Sean

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post #5 of 23 (permalink) Old 09-27-2011, 10:35 AM
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Just got back home from work opened up the airbax and it is very clean and dry. While I was messing with it anyway I went ahead and removed that pesky intake valve too...............

Next will be a compression test.....................
Are you talking about the flapper?

You understand that's not just a compression test, it's a compression leak-down test. To determine how long your holding that compression. If it leaks the pressure to quickly, that means oil is washing by and could explain your smoking.

I've had leaky valve seals before, and the smoking was just like what you said. But that was in a car. Worst at start-up, cause a little oil was sitting there waiting to be burned.

John, 2000 RC51 #000100

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post #6 of 23 (permalink) Old 09-27-2011, 03:18 PM Thread Starter
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Are you talking about the flapper?

You understand that's not just a compression test, it's a compression leak-down test. To determine how long your holding that compression. If it leaks the pressure to quickly, that means oil is washing by and could explain your smoking.

I've had leaky valve seals before, and the smoking was just like what you said. But that was in a car. Worst at start-up, cause a little oil was sitting there waiting to be burned.
Yep I know the difference, thanks.

That is what worries me most is that it is after the bike has warmed up and been running for a while.

Sean
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post #7 of 23 (permalink) Old 05-22-2012, 11:23 AM Thread Starter
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Finally got some wrench time on the bike. Pulled the valve cover off of #2 cylinder to make sure the oil drains from valve train. They were clear and everything looks good. No scratches or anything suspicious on the cylinder walls. Feel pretty confident that the valves seals are to blame.

Will pull the engine this winter and change out the valve seals, as an interm "bandaid" fix attempt I'll throw some marvel mystery oil in the crankcase, won't hurt and might help the ailing seals some.

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post #8 of 23 (permalink) Old 11-26-2012, 01:54 PM
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When you have it in parts look it up so it is ok... and not out of rounds.
My front was that. piston ok rings ok but worn out "sleeves" and she liked oil sooo much.
I am no pro on engines but at least that was my case.
Realy hoping for you that it will be something less expensive.
Rebuilding it your self will of corse be costefective.
I did but it tooook forever.
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post #9 of 23 (permalink) Old 11-26-2012, 04:41 PM
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Finally got some wrench time on the bike. Pulled the valve cover off of #2 cylinder to make sure the oil drains from valve train. They were clear and everything looks good. No scratches or anything suspicious on the cylinder walls. Feel pretty confident that the valves seals are to blame.

Will pull the engine this winter and change out the valve seals, as an interm "bandaid" fix attempt I'll throw some marvel mystery oil in the crankcase, won't hurt and might help the ailing seals some.
Please never put any of this into any engine you care about especially a RC. It was designed in the 1920's, It may have been useful back then not so much now, Same goes for STP its all a sales gimmick.

04 Nicky
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520 conv. 15/40 RK quick accel kit
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post #10 of 23 (permalink) Old 11-26-2012, 07:32 PM
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Is it throwing oil out? Take a piece of white paper, let the engine warm up to temp.

Take the paper and hold it up to the exhaust and rev the motor, are there oil marks on the paper? If so I would say 90% that it's rings and or out of round cylinders.

Either way money...



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