SP2 with Smoking Habit - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 13 (permalink) Old 08-14-2009, 03:13 PM Thread Starter
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SP2 with Smoking Habit

Hello all, new member first post.

I've done a search within the forums for a similar problem but it revealed no results. I have an '03 SP2 with the PAIR and flapper mods done, full Yosh system, and 4800 KMs (Canadian, sorry metric sysytem). I've put very few miles on the bike this season with the full system (fist season with the exhaust) without a Power Commander, it was running lean but the temps stayed low, but it started burning oil. It smokes under idle only, once it has reached operating temperature. It will smoke slowly under idle, but when you blip the throttle quite a bit of smoke will blow out, if you continue to twist the throttle the smoke dissipates. I've had the bike serviced and the techs are stumped. The problem has been narrowed to the rear cylinder (as theres no residue on the front cylinder),rear exhaust valve guide and seal replaced and machined, rear cylinder piston rings replaced, cylinder honed, and abreviated break in done...and it STILL SMOKES!
I'm mechanically inclined and have ruled out a number of possibilities, as have the technicians who have worked on the bike, but I'm at a complete loss.
If anyone has had a similar experience, I'd very much like to hear from them.
Thanks in advance.
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post #2 of 13 (permalink) Old 08-14-2009, 05:57 PM
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your bike isn't old enough to smoke!
on a serious note, i wish i could help you
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post #3 of 13 (permalink) Old 08-15-2009, 08:04 AM
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I'm not sure on how the system works on an RC, but I would check into excessive crankcase pressure. Perhaps, there is a crimped hose in the breather? I haven't explored my bike that much, (it functions perfect) but I am a former GM automotive trainer.

Three things will cause excessive oil consumption/smoke: 1) worn, out of round, cylinder/piston, broken ring, 2) worn valve guides or seals, 3) excessive crankcase pressure due to blocked breather

Or out in left field, Cracked rear head?

John
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post #4 of 13 (permalink) Old 09-24-2009, 08:05 AM
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half way reading your post I thought a burned exhaust valve has worn its guide, but then you said it was replaced. A compression leak test would have lead you to replace piston/rings, was it really in need of replacing? Honed the cylinder? It is plated and unless there was a manufacturing fault the original should not even be broken in yet.
If you don;t have a powercommander and you are still running lean possibly it is the front cylinder by now.
Have you checked the intake for oil? Take the filters off and look down the intake with throttle wide open. If you see any oil evidence trace it back as CBXJohn said.
On the fireblades rc51 forum I remember talk of a similar problem and it was on one cylinder. Can't remember whether it was oil or not but there was crud on one intake and not the other.
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post #5 of 13 (permalink) Old 09-24-2009, 08:57 AM
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Just out of curiosity... what COLOR is the smoke?

-Tony B
00 RC51
06 Evo IX
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post #6 of 13 (permalink) Old 09-24-2009, 10:29 PM
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Usually smoking due to a valve guide seal will occurs on deceleration when the high intake vacuum pulls oil past the seal.
Smoking during idle or increased smoking during open throttle is usually caused by worn rings. However you said those were replaced on the rear cylinder.
A compression check would show wear on the rings.
Have you checked and drained the line for the crankcase breather storage tank?
It may be possible it's full and the engine is sucking oil into the intake.
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post #7 of 13 (permalink) Old 09-28-2009, 11:58 AM
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Post is over a month old! Hopefully he figured it out. Wish he'd post his findings though. That's what a forum is about!
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post #8 of 13 (permalink) Old 12-01-2009, 03:22 PM
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Hi,
I had a similar problem with my bike after I adjusted my valve clearence. There is a dowl on the rocker cover that the air for the PAIR system passes through when connected. This dowel has a rubber O-ring seal around it to stop the oil from the head running down into the exhaust port. Mine was missing and was causing the bike to smoke its tits off when ticking over, popped in a new one and no more smoke. I believe it only does it at tick over due to the exhaust pressure rising when revving the engine forcing the oil back into the head.
Hope this helps
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post #9 of 13 (permalink) Old 12-01-2009, 04:12 PM
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That's a very plausible explanation.
On another forum, a customer's engine was being rebuilt/performance-prepped and the builder not only removed the PAIR system, but tapped and inserted a grub screw to block off the un-needed passageway.
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post #10 of 13 (permalink) Old 12-02-2009, 05:14 AM
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Quote:
Originally Posted by doctorpotford View Post
Hi,
I had a similar problem with my bike after I adjusted my valve clearence. There is a dowl on the rocker cover that the air for the PAIR system passes through when connected. This dowel has a rubber O-ring seal around it to stop the oil from the head running down into the exhaust port. Mine was missing and was causing the bike to smoke its tits off when ticking over, popped in a new one and no more smoke. I believe it only does it at tick over due to the exhaust pressure rising when revving the engine forcing the oil back into the head.
Hope this helps
Thanks for the heads-up! Something to watch for when doing a valve adjustment.

John
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