Topic: CB650 feels like skipping sprocket teeth in 5th gear?

[Motohead1]

hey all I did a search and found a few 5th gear threads but mostly about shifting issues.   I have a newish to me 1980 cb650c that was sitting since 2011.  I went through the carbs and got it running great. 

Ive put about 1000 miles on it and just did a new clutch about 500 miles ago because After a long hwy run 6k+ rpm or a full pull upshift at WOT the clutch was hard to disengage or wouldn't let me pull the clutch lever as it would be hard as a rock.  letting it engine brake down to lower rpms for a bit would get my clutch lever back and all was normal.   Clutch looked original with not much wear at all when I changed it.  Did not fix the high rpm no clutch issue though

  A few days ago I was commuting about 30 miles and the last 6 miles was highway speeds about 80mph on slight uphill  not accelerating but steady.  The bike started to hiccup as i it where jumping teeth on a sprocket.  The short hiccup was not a dead spot it was more like a free rev not dead ignition.   If I downshifted to 4th it would maintain the load and be ok but it would not like accelerating.    the 1,2,and 3 gears were fine and I got home to find my chain very sloppy that was adjusted less than 300 miles before.  Thinking I was actually skipping sprocket teeth on what looked like original sprockets and chain I replaced them a few days later.     

Well just took it for a spin after new chain and sprocket install and it does the same thing as soon as I shift to 5th.   Clutch is holding fine but i am thinking somthing is up in the transmission especially since I was getting that hard clutch lever after high rpm.    Any idea what it might be?  What should I look for?

 Also will add the bike has about 12k miles on it.

Thanks.

[fizzlebottom]

That's an odd one. The troubleshooting section of the FSM mentions "Poor performance at high speed" and describes checking the following items:

1. Ignition timing and valve clearance
2. Clogs in fuel lines, fuel tank breather hole, and fuel valve
3. Clogs in carb jets / passages
4. Valve timing
5. Valve spring tension

The other unmentioned thing I can think of is this TSB which describes poor performance when the throttle is cracked at already high RPMs. If that isn't your issue, ignore it.

If you're going through the RPM range and the only time the issue is seen is in 5th gear, then you very well might be onto something in that the issue is inside the transmission. If that is the case, then plainly speaking, that sucks a lot. It'll mean opening the whole thing and possibly replacing some big parts.

But I hope someone else will pipe up and suggest something much easier.

[M 750K6]

What's puzzling is the clutch lever seizing. Usually that would point at something around the clutch, rather than gearbox. However, why is this only happening in 5th?

What can cause the clutch lever to seize that coincides with being in 5th gear?

[Motohead1]

its very strange for sure Im gonna go ride it and see if I can make it do it in 4th.    I was reading that 1-4 gears are dog and 5th is not correct?  I havent has one of these opened up to see the gear engagement.    Do you know if I can see most of the gears especially 5th with the oil pan off?  or maby a bore scope?

[PeWe]

It has been a thread about a CB750 that where tricky or not possible to shift to 5th gear.

After many thoughts and doings the issue was caused by a flipped  washer under the nut holding the clutch package together. That washer has a dome shape that must face outwards under the nut.

If CB650 clutch looks like that. The nut and washer has to be  removed when replacing the clutch.

[fizzlebottom]

It has been a thread about a CB750 that where tricky or not possible to shift to 5th gear.

After many thoughts and doings the issue was caused by a flipped  washer under the nut holding the clutch package together. That washer has a dome shape that must face outwards under the nut.

If CB650 clutch looks like that. The nut and washer has to be  removed when replacing the clutch.

The dome shaped washer is called a Jutter Spring, or Honda calls it a Disc Pressure Spring. The FSM says it needs to be installed with the cupped side facing inside. I really don't think that installing this piece backwards is going to mess up 5th gear, though it is possible. I do think that otherwise incorrect installation of other clutch items could impact things though. It really might be a good idea to break the clutch back open and double check that everything is installed correctly and in the correct order. It does sound to me like maybe the plates & discs were not seated properly before the spring retainer was torqued down.

[Motohead1]

I am gonna pull the clutch cover off tomorrow but here is a vid where I am leaning it left and right and at the beginning and end you can here a dinging noise that I dont think is the timing chain tentioner as I adjusted it and when its sloppy it sounds different.

[HondaMan]

This is a bit of a deviation, but...your symptoms also suggest low float bowl levels in the carbs. This was common in the 79-80 CB650 and Honda revised the air-bleed hose arrangement to the carbs 3 times in 2 years to fix it. Look closely at the carbs to see if yours even still HAS the bowl-vent hose system intact: the last one I worked on had a broken tee fitting, causing the bike to 'hit a wall' at 75 MPH and it wouldn't go faster. What was happening was: the float bowls would not fill all the way up above that speed from turbulence in the open bowl-vent hoses. I coupled them back together and ran the end of the hose down behind the engine to a small clip that was put there by Honda to hold the hose steadily in place and the bike ran up to 90 MPH with no issues afterward.

[Motohead1]

Ok things I know.  Holding the shift lever up in fith dosent help at all.  SO Im pretty sure Im dealing with  a bent fork or chipped shift barrel or c-clip popped out of the groove or a combo of those.

@Hondaman I read a few hundred miles ago about the service bulliton on the bowl vents  as I was getting that lean misfire around 5 to 6k rpm and light throttle  before any other issues when I first put the carbs back together and synced them.  So I ordered a new old stock airbox cover with the vent port built into it.  I installed it with the new sprockets and chain.   PN: 177225-460-670.  Totally fixed that lean condition as the thing pulls amazingly.  Wont lift the front wheel ever so slightly anymore with the new gearing but plenty for what I want to do with this bike.   

I didn't pull the clutch cover yet as the weather was just to nice and its seems to be happily spinning in 4th.   But I am going to park it today as something is shifting in the trans.  Im getting a slight dog gear dragging against gear noise when in neutral now.

The one thing that is still a mystery is the hard as a rock clutch after sustained rpm above 6k or when I do a hard 123 pull to redline.      Its done this since I first got the bike and assumed it was just a clutch issue.     I did a search but I haven't found anything similar discribing a hard clutch after high rpms.   Its strange and I have to be mindful to gear down coast coming off the highway for about a half mile before I can actuate the clutch again.

[fizzlebottom]

It is the clutch lever that feels hard as a rock to pull and not the shifter, right?

I can't imagine that being anything but something from the lever down to the clutch pack itself. But aside from hot oil, the clutch pack really shouldn't give a damn about how fast the motor or transmission is spinning. I'm actually wondering if you have the wrong springs in there. When the bike is totally cold, do some clutch pulls through the different gears and see if 5th still behaves like you said. I want to see if we can eliminate a hot/cold difference here.

If the problem persists, then throw out what I'm saying about the springs. I still think it is a clutch pack, cable, or lever issue.

If the problem disappears when the bike is stone cold, then I do suspect that you might have the wrong springs and they are expanding with heat just enough to bind up against their own coils with absolutely no room to compress. Wishful thinking maybe? Can't hurt to see what happens.

[Motohead1]

Stone cold shift right up into 5th it will skip. Temp is no matter there.  so that issue I think is nailed to a trans issue but the clutch handle hard as a rock issue is after long sustained above 6k and or a 1-2-3 redline pull.  It recovers very quickly on a 1-2-3 redline pull but sustained hwy rpms above 6k it takes about a half mile to recover.  Several times early on I would stall it on the off ramp as i couldent pull the clutch at all.  Im running honda 10-40.  But just read the other day that I might need to run 20-50?   I put a barnett clutch pack and springs in there and they are slightly stiffer if not the same as the old clutch should have been original.  I dont think the cover had ever been off.       At any rate I parked it and will get the motor pulled and flipped upside down on the bench to see what is bent or broken in there.

[HondaMan]

Is there maybe a pattern showing up here? 
Something along the lines of: the PO was having troubles with the clutch lever and decided to shift it anyway, which then bent the shift fork that moves the 4th and 5th gears? Just a thought...

In the early 750 (K0/K1 era) the bent "L" shift fork does something similar: it will barely engage 2nd gear because its tines got bent from [whatever hit the shifter when the engine wasn't running one day].. This makes the 2nd gear 'skip' in and out and eventually damages the dogs on the C5 gear that is being shoved by the shift fork because they barely engage the C2 gear.

In these early 750s it was most commonly found in bikes that either had an 'incident' that hit the shifter lever while the bike was parked (like, knocking the bike over with the car in the garage, shifter arm landing on a gallon paint can or such item next to the bike).

Honda's own oils today do NOT have zinc in them. This can make many parts in the SOHC4 bikes stick, wear prematurely, or not work. That's why I never recommend their oils anymore. All of the SOHC4 bikes REQUIRE zinc be in the oil, or all sorts of troubles erupt from parts sticking together that should be sliding on each other. Later new engine designs from them, beginning in the mid-1980s, were changed to omit the need for ZDDP except in their offroad products (like boat engines and dirt bikes).

[Motohead1]

Good to know. And knowing the PO it was definitely tipped over in the garage before and the wiring nightmare that I had to fix along with all the other little things theres alot that is possible. 

   So Honda GN4 is no good?   Ok so from what I have been reading I need rotella t4 20w50?   I have some t4 15w40 that I was going to use but whatever your experience recommends I appreciate the education.    I just hope it aint chewed up to bad.  Luckily the trans parts dont look too expensive.     

  I dont have any other bike to play with right now so this might get torn into sooner that I was planning.  Its always when the weather is perfect.   

[fizzlebottom]

T4 15w40 is what I've been putting in my '82 CB650 for ~13 years and it has done well. Cheap, available, and meets the needs.

Yeah I think you're up for a project opening up the cases. Rough time.

[Motohead1]

Well got the motor out today.   lots of glitter.  Ill open it up tomorrow.   My question is can I just open up the bottom half to get at the transmission without messing with the head?   And since I have it out are there any "might as well do now" stuff that is a must while the engine is out?   I did find my oi leak though.  Not sure what I am looking at but maby long bolt or over torque?  I will weld it or use some JB on it.   Im trying to load pics but there too big. 

[Motohead1]

More pics as I finally got the resized correctly.   What do you think is poking through the case?  Looks like bolt threads maby but thats where the bearing sits I thought.

[bryanj]

Yes you can take just lower case off after removing outer cases, clutch, gearchange mech and possibly primary shaft which i am not sure about as i have never stripped a 650.

No idea what you are talking about sticking up

[newday777]

No idea what you are talking about sticking up

Maybe this??

[bryanj]

THAT IS SERIOUS i would find a used engine.
Somebody has had the cases apart and not located the peg in the roller bearing properly which forces the peg/solid dowel into the crancase breaking a piece out.

I think you have found your smoking gun, an inept PO!!!

Pics are unclear on my dumfone so didnt see it in the original post

[Motohead1]

Well dangit.   I should have known after having to fix all the wiring issues.   This engine runs so good.   I will still tear it apart to see if theres anything salvageable.   The fun part will be finding another motor local.   

[newday777]

   The fun part will be finding another motor local.   

Where is local?

[bryanj]

I have seen the pins knocked back down and epoxy used on the top, problem is if its alowed the bearing to float endwise how much damage has been done to the gears, repairing a gearbox gets very expensive very quickly!

[Motohead1]

   The fun part will be finding another motor local.   

Where is local?

 Charlotte NC area.

[Motohead1]

I have seen the pins knocked back down and epoxy used on the top, problem is if its alowed the bearing to float endwise how much damage has been done to the gears, repairing a gearbox gets very expensive very quickly!

Assuming I need lower case halfs which at a quick search looks like $100.   And ebay transmission cluster is about another $150.   It will get expensive quick.   Anyway I can guess all i want but I wont speculate anymore till I open it up and post some pics for yall to educate me on how bad it is.

[MauiK3]

I vote for new motor, your glitter likely had done a lot of damage.