Topic: Cb650 slows To sharply in downshift.

[checkflag]

Ok. Check this out, and offer your knowledge and experience.
When, say, I leave my house and I am in First gear and travel
to the street and release the throttle the bike wants to stop
sharply. Next, I'm I'm coming to a red light and an downshifting
the tires will actually chirp as I hit 3rd, 2nd, and go into 1st.

It feels like there's a rope holding the bike from behind. I do not
think this is normal.   

[Gordon]

Sounds like you're downshifting a little too early.  At what rpm do you typically downshift?

[lone*X]

Sounds like you're downshifting a little too early.  At what rpm do you typically downshift?

Agree with Gordon, downshifting at too high an rpm.  We all can chirp the rear tire on downshifts without thinking anything about it.

[checkflag]

i can be just leaving my house in first going not so fast and simply release the handle and it feels
like it just wants to stop.. its like there is no feathering.. its either engaged or not engaged. Even when
I try to feather it by releasing slowly, she just wants to stop.

[KB02]

First things that come to my mind are wheel bearings and brakes. Hop the bike up onto the center stand and roll the rear wheel in neutral. It shood spin nice and freely. If it doesn't, try backing off the brake adjustment to see if that frees it up a bit. If still spinning stiffly, it could be bad wheel bearings. Try this with the front wheel, too.

Also, check your clutch adjustment. Does the bike want to pull ahead when the clutch level is fully in?

[MJL]

^ +1.

Also, when you say "release the handle", is that clutch or throttle? Or something else?

[checkflag]

First things that come to my mind are wheel bearings and brakes. Hop the bike up onto the center stand and roll the rear wheel in neutral. It shood spin nice and freely. If it doesn't, try backing off the brake adjustment to see if that frees it up a bit. If still spinning stiffly, it could be bad wheel bearings. Try this with the front wheel, too.

Also, check your clutch adjustment. Does the bike want to pull ahead when the clutch level is fully in?

The rear wheel spins smoothly. The front spins pretty good too, but I think that the pads are a bit to tight and rubs slightly.
I dont know the cure for that. I hear a wsh wsh wsh when it spins.

^ +1.

Also, when you say "release the handle", is that clutch or throttle? Or something else?

i mean the clutch. Or.. when the clutch is dis-engaged (handle released) and i down throttle it feels like the brakes are
stopping the bike.. but its the gear. (mostly in first and second)

[Hush]

How tight is your chain?
It sounds like either binding brakes or a very tight chain, there should be roughly a half inch slack at in the middle of the bottom length of chain.
Get someone else to hold the bike upright (if you do this on the centre stand it can give a false reading) and using your finger try lifting the very bottom length of chain, 1/2" is about right.

[mlinder]

What RPM are you downshifting from and at what speed?

To be blunt, sounds like user error. I'm not there watching, though, so I may be totally wrong.

[bucky katt]

+1 on the user error, the only thing that should be slowing you down when downshifting is the engines compression.

[Brian G]

I agree with mlinder and bucky - it sounds like a problem with technique. The SOHC 4s have very little flywheel effect, so if you wait too long between downshifting and re-engaging the clutch, the engine revs will have dropped to the point where engine compression will cause the rear wheel to lock momentarily when the clutch is re-engaged. Try 'blipping' the throttle while downshifting to bring the revs up and re-engage the clutch while the engine speed is still up from the 'blip'. Its hard to explain but makes sense when you finally get it right.

Perhaps this video (at the 34 second mark) here will illustrate what I'm trying to describe - its not a Honda but the technique is the same: match the engine speed to the transmission speed.

Hth,
Brian

[Gordon]

What RPM are you downshifting from and at what speed?

To be blunt, sounds like user error. I'm not there watching, though, so I may be totally wrong.

I asked that in my first post and didn't get a response either.

[razor02097]

I agree with mlinder and bucky - it sounds like a problem with technique. The SOHC 4s have very little flywheel effect, so if you wait too long between downshifting and re-engaging the clutch, the engine revs will have dropped to the point where engine compression will cause the rear wheel to lock momentarily when the clutch is re-engaged. Try 'blipping' the throttle while downshifting to bring the revs up and re-engage the clutch while the engine speed is still up from the 'blip'. Its hard to explain but makes sense when you finally get it right.

Perhaps this video (at the 34 second mark) here will illustrate what I'm trying to describe - its not a Honda but the technique is the same: match the engine speed to the transmission speed.

Hth,
Brian

I do that also... I have always done that... in fact in the MC safety course I took they teach that technique

[checkflag]

         sorry.. i hadn't payed attention to the tach.. but its around 3,500 RPM.
I am including this short video I just made 10 minutes prior to this post. Notice the
front wheel diving while I release the clutch. I am NOT using any brakes whatsoever.

[razor02097]

        sorry.. i hadn't payed attention to the tach.. but its around 3,500 RPM.
I am including this short video I just made 10 minutes prior to this post. Notice the
front wheel diving while I release the clutch. I am NOT using any brakes whatsoever.

I don't see anything out of the ordinary... my cb will also decelerate rapidly when I let off the throttle.

[Gordon]

         sorry.. i hadn't payed attention to the tach.. but its around 3,500 RPM.

Try downshifting at a lower rpm.  I could be wrong, but i don't think the issue is with your bike. 

[Frankenkit]

Checkflag... this might be a dumb question, but do you drive a manual car?  I find the feel is quite similar. 

[Hush]

I've re-watched your video a few times,

in first going not so fast and simply release the handle and it feels
like it just wants to stop.. its like there is no feathering.. its either engaged or not engaged. Even when
I try to feather it by releasing slowly, she just wants to stop.

I think your clutch is adjusted too sharply, give yourself some more slack at the lever....by that I mean let some go from the bottom of the cable down under the engine and adjust the slack from the lever end so you have a smoother release.
It appears you have a stop/go situation, like a light switch either off or on with no inbetween.
Your first post didn't make much sense until I re-read it and watched the video a few times more, it's not that you "can't" ride it's that the clutch is causing you grief, sorry for the assumption.

[KB02]

Yeah, I watched the video a couple of times, too. I see what you mean. I can't really see your clutch hand working due to the angle of the video,  just the throttle, but if that is with the clutch lever pulled in and not just a release of the throttle, there's something up. I see what you mean.

I'm still thinking brakes, but it could also be a chain that is too tight like Hush said. With the clutch lever pulled in, it should definitely roll more freely than that. If you're just letting off the throttle, than it simply looks like you've got good compression.

[mlinder]

Sorry, but looks normal. You weren't at 3500, more like 5000, and you just closed the throttle without any clutch action.
Where you at? Be nice to get someone who's ridden these bikes a bit to see if it works the same way with them.

[Spanner 1]

Sticking front brake...bike should not nose-dive like that when you shut the throttle at any rpm but should ' free-wheel' with a slight dip in the front forks....IMO.
Try opening the brake bleed screw and release a little fluid, then try a run just like in the vid. without touching the front brake lever..... any different ?

[checkflag]

Sticking front brake...bike should not nose-dive like that when you shut the throttle at any rpm but should ' free-wheel' with a slight dip in the front forks....IMO.
Try opening the brake bleed screw and release a little fluid, then try a run just like in the vid. without touching the front brake lever..... any different ?

This is what i'm trying to get across. its dipping WAY to much for just letting go of throttle. I feel it should feather out somewhat.

[Pinhead]

We've got to get terminology straightened out before anyone can troubleshoot what you're talking about.

"Clutch engaged" means "no hand on the clutch lever" and the clutch plates are engaged together, connecting the engine to the transmission.
"Clutch disengaged" means "clutch lever pulled in" and the clutch plates are NOT engaged together, thus separating the engine from the transmission.

SO

If you're in 1st gear with the clutch engaged, the bike looks entirely normal though the front forks may need either more/thicker oil or heavier springs. If you're in 1st gear with the clutch disengaged, there's definitely something amok. However, from watching the video of the start, stop, and "blip" on the throttle I would assume that you're testing with the clutch engaged and therefore the only thing that should need work is the front fork dampening.

[mlinder]

We've got to get terminology straightened out before anyone can troubleshoot what you're talking about.

"Clutch engaged" means "no hand on the clutch lever" and the clutch plates are engaged together, connecting the engine to the transmission.
"Clutch disengaged" means "clutch lever pulled in" and the clutch plates are NOT engaged together, thus separating the engine from the transmission.

SO

If you're in 1st gear with the clutch engaged, the bike looks entirely normal though the front forks may need either more/thicker oil or heavier springs. If you're in 1st gear with the clutch disengaged, there's definitely something amok. However, from watching the video of the start, stop, and "blip" on the throttle I would assume that you're testing with the clutch engaged and therefore the only thing that should need work is the front fork dampening.

Was going to mention this. You've got 4 inches or more of travel in the front forks at relatively mild acceleration and deceleration. You have oil in your forks?

[checkflag]

We've got to get terminology straightened out before anyone can troubleshoot what you're talking about.

"Clutch engaged" means "no hand on the clutch lever" and the clutch plates are engaged together, connecting the engine to the transmission.
"Clutch disengaged" means "clutch lever pulled in" and the clutch plates are NOT engaged together, thus separating the engine from the transmission.

SO

If you're in 1st gear with the clutch engaged, the bike looks entirely normal though the front forks may need either more/thicker oil or heavier springs. If you're in 1st gear with the clutch disengaged, there's definitely something amok. However, from watching the video of the start, stop, and "blip" on the throttle I would assume that you're testing with the clutch engaged and therefore the only thing that should need work is the front fork dampening.

Was going to mention this. You've got 4 inches or more of travel in the front forks at relatively mild acceleration and deceleration. You have oil in your forks?

yes.. there is oil.. and 8lbs of air pressure. I apologize for my dyslexic description of engaged or disengeaged.  Yes, the clutch is engaged and I am just letting go of the throttle.

KIT.. yes, i drive maunual.. wouldn.t have it any other way. I only made this thread because I felt the slowing and diving were a little extreme.