The International CBX Owners Association

Well after about 9 months and a very long list of issues, the latest problem to surface has me feeling pretty fed up.

When I shift into 4th gear it feels like the clutch is slipping. It isn't. It pulls beautifully in 1st, 2nd, 3rd and 5th, but in 4th it will suddenly start revving as though the clutch is slipping. I suppose it never exhibited these symptoms because I was being gentle in 4th, since that's illegal speeds around here. 1st through third it runs great. I've looked through the photos of the gearbox when I dis-assembled. My lack of experience obviously resulted in me missing damage.....

The research I've done and comments on the CBX Facebook page points to transmission problems including selector forks and drum. So my question is, what is the least I need to do to get at the gearbox? I will need to drain the oil, remove the exhausts, remove the carbs, drop the engine, and then flip it over to open up the crankcase? Anyone done this before?

Until someone with actual knowledge steps in....... It would seem the only two possible scenarios is either the clutch is slipping, or your gears aren't completely meshing. You seem pretty sure it isn't the clutch, so that leaves mis-aligned gears. If so, there will be metal shavings in the sump. Take off the oil pan and look. I'm betting there's no metal, and in fact, the clutch is the culprit. Why? because if the gears were not meshing, there would be an awful noise, which you didn't mention.

Let us know what you find.

Not certain what you mean by "suddenly start revving". A slow gradual increase? A very quick free spinning rev? I ask because I would think that a slipping clutch would be even more pronounced in the lower gears. The clutch doesn't know which gear the transmission is. If it is a sudden 'free' spinning rev when you shift into 4th gear, that is a 'false neutral'. Could be caused by several things, including, I think, a bent shifter fork. Personal experience: I occasionally get the false neutral shifting into 4th gear. (82 prolink) Best I can figure on my part is lazy shifting. Be snappy when you shift. Dog type transmissions don't like gentle shifting. Don't try to break the shift lever; BUT, be firm and quick.
If you do have to get into the transmission, the only way in is split the cases. Not fun. First thing would be to do as Rick mentioned -- check the sump screen for metal particles/pieces.

Physics: A slipping clutch shows first in higher gears, not lower gears. The torque relation between engine rpm and rear wheel rpm makes the clucth slip in high gears.

Thus supporting my thought that the OP's claim that it slips in 4th, but not 5th, seems highly unlikely.

Pull the oil pan.........

Do drop the sump and check for debris, but it's really not that tough to remove the engine, flip it over and split the cases. The transmission is the first thing you come to, so nothing deeper needs removed. I'm still curious as to exactly what your bike does in 4th gear. If it jumped in-and-out, you would feel a violent jerking. Or if it just plain hit neutral, it would rev very high immediately. I'm with the others, the clutch would slip far more in the lower gears than 4th.

Dave

daves79x wrote: ↑

Thu Aug 27, 2020 11:03 pm

I'm with the others, the clutch would slip far more in the lower gears than 4th.

No it wouldn't - see EMS post two or three back.

I had a Kettle that used to do the same thing and to cure it I didn't thrash it about using wide open throttle

Treat these old girls with respect and ride them accordingly - if you want to tear about, get a modern bike.

I'm going back to my drag racing days - a slipping clutch shows up quite quickly and in every lower gear. My 'trashed' drag clutch worked perfectly well for normal or even spirited street riding, in all gears, for 20,000 more miles, until I finally replaced it.

Dave

I agree with Dave if it was the clutch it wouldn’t be just the 4th gear. It would be all gears and usually in the higher rpm range first. On a second note I know he checked all clutch plates before he reinstalled. He just got this thing running.

Anyway - the first thing I'd do to take the clutch out of the equation is to remove it, make sure the bushing and shim are placed correctly, remove and verify orientation of all fiber plates, reassemble and adjust at the clutch hub per specs. Then adjust free play via the lower and upper cable adjusters. You can do all this without dropping the engine oil if you work on the sidestand. Test ride and see if there's any difference.

If not, then it would seem that you will need to go into the transmission.

Dave

I really don't get how we always get into discussions about absolutely simple and basic things. ANYBODY who ever had a manual transmission clutch go out, will have to confirm that it happens first in high gears. The torque load on the engine from the rear wheel through the transmission is higher at high vehicle speeds, thus the clutch will slip there first. I really don't give hoot if 30 years ago during drag racing days, this was the other way around.

Mike - I just confirmed that was not the case for me and described it exactly the way it happened. The original clutch that I drag raced with would slip in every gear until hooking up. I could run 11.50s before it started slipping, 12 flat with it slipping. I did not race it much after that and as I said, rode 20,000 or more street miles with NO slippage whatsoever, with that clutch. It never slipped in any gear, no matter what you did on the street. But drop the hammer at 7500 rpm and speed shift, and it would slip.

But all this, as usual, is just a distraction from the poster's problem. He built the bike to as-new specs from the ground up. I assume this included all-new clutch plates. As I said, barring something installed incorrectly with the clutch, and adjusted correctly, with the 4th gear problem remaining, there's no choice but to go in and see what's going on.

Dave

Thanks for all your inputs. It most definitely is NOT clutch slip. It ONLY does it in 4th and it would, I suppose, feel like a false neutral because all of a sudden the revs will go from, say 3000 to 5000 with no increase in speed.

Anyway, the engine is out. I drained the oil first. I made the mistake of not taking the top 4 crankcase bolts out before I flipped it, so will flip it again today and take them out, then flip it again. I'd post pictures here but it is somewhat cumbersome to do. I started a thread on the Honda CBX 1000 Owners Club FB page and there are photos there if you are interested.

As far as I can gather, I need to take the crankcase end covers off, the clutch needs to come out and the oil pump drive chain and sprocket need to come off, then I can split the crank?

That’s pretty much it. Just follow the shop manual for this and you’ll be good.

Dave

Could you specify exactly which Facebook page you posted on? There are several and I couldn’t find it anywhere. The page associated with the club is the CBX Six Cylinder Owners.

Dave