Hello everyone,

Last fall, I had some smoke coming from my CBR 600 f4's exhaust. Wasn't sure what was going on, so I tested the compression and found it was low.

I re-built the head. Full new gasket kit, polished the ports a bit while I had the chance. Here's link to a gallery, if you're interested in seeing a 600F4 torn down. I was going to post a DIY, but read below...

https://plus.google.com/photos/10962...99793855538961

After that, things ran well. I did about 700-800km (450mi) with no issues. Actually, I had a bit of an oil leak, but I found that I left the cap bolt off the chain tensioner during re-assembly. No problem, put one in there.

The next time I wanted to go for a ride, the bikes started, then starved to death. Any attempt at re-start was just dry-heaving.

I tested and found that the fuel pump was dead, so I replaced it and the filter.

Since then, the bike has run like you see it in the video here:

2000 CBR F4 smoke coming from tail pipe - YouTube

So what would you think the problem is? Running rich? Oil? I'm at my wits end with this unreliable Honda!

 

I have a few questions.
What color is the smoke? Looks blue on this end, please confirm.
What did you do to fix the low compression? Unless it had bad valves, valve seats, or blown gasket the head won't lose compression. Usually its in the lower end.
Is it misfiring? Sounds like it, but hard to tell.
Have you pulled the plugs to see which cylinder is burning the oil, coolant, or fuel?
Are you low on oil or coolant?

 

looks blue to me - so that would be oil. i can slightly hear a knock or a mis or something - but all i really hear is the exhaust, so it makes it a little harder to tell.

have you checked compression since then? you didn't touch the bottom end, correct?

 

Smoke looks blue sometimes, white other times, It's really difficult for me to be certain at this point.

I found the valves to be leaking. I changed all the valve guide seals and lapped the the vavle seats. You can find a video of the leaking valves on my Youtube channel.

Didn't notice any bad gaskets during the re-build, and the cylinder walls looked good. The gallary has a few specific shots of the cylinder walls. And the bike ran well for a while.

I dont' think there is a misfire, but I'm not sure how to check for sure. All the exhaust pipe are hot after runnning, so they are all at least hitting most of the time. There's also no hesitation on accel, as yo ucould hear, it goes when you rev it. But of course I never went above 5000rpm, bliping the throttle.

I have not pulled the plugs yet. I replaced them during the re-build, of course. I'll have to check the plugs during winter.

Fluid levels look good. I've been checking them as I run it. But I've only ran it for about 30 minutes like this, and mostly at idle.

Haven't re-checked compression, never touched the bottom end.

Thanks guys.

 

I'm thinking it's oil blowing by the rings. If you pull the plugs out, one or more of them will show signs of burning oil. Don't wait until winter, do it now. You can't run it like it is.

 

i'm with you. i think it's blowing by the rings, and thus the plugs will look black with tons of oil on them, and the compression will still be low.


edit - i just looked at the gallery on google. those cyl walls do look pretty good, but it's odd to me that you have one piston that has HUGE amounts of carbon build up. cyl #1 looks significantly worse than 2&3 and a not as bad - but still lots more carbon than cyl 4. my guess is on that cyl, the plug will look bad. as well, if you have a mis - a header is still going to be around 200 degrees or so, but it should be up around 350-400 if it's really running.

 

Was the cylinder head ever checked for flatness or cracks? The piston tops on 2 and 3 being much cleaner than 1 & 4 may also indicate coolant entering the combustion chamber through possibly a warped or cracked head. This will basically steam clean the carbon from the cylinders that the water is leaking into as the engine is running..

I would do a compression & leak down test asap and post back with the results.

Did you ever find the source of the 0 compression on #3 cylinder? What were the compression numbers on the other cylinders?