Author Topic: 78' CB750k8 Clutch issues.. (Read 2099 times)

zeus87 · « **on:** April 22, 2008, 10:18:29 PM »

Picked the bike up with it needing a clutch (it slipped when acclerating after about 4000rpms) i bought a set of friction disks and beefy ebc springs. Upon disassembly i found what was inside to be a decent shape (nothing that i would expect to cause the slipping) anyway i installed the new disks (7 in the order shown in the honda shop manual, soaked them prior) and the new springs. I adjusted the clutch a bunch of times starting with the motorside adjustment bolt at 1/4 turn out then tryed it in further out further still nothing...same symptoms. I decided to take it apart to see what i could find...and nothing that looks like an issue to me was found. I have a few pictures, one thing i did notice was lack of oil inside the basket area, when i removed the original it was pretty wet inside, even a little dripped out when the cover was removed. This time around it seems pretty dry. I checked the hollow shaft, and a wire sailed through it untill it hit metal on the other side. I noticed a couple of the washers were pretty blue in color...maybe this is normal(heat)? I have done 2 oil changes hoping to flush any old crap out, but still nothing. the disks look to be half dry half wet, but the last disk (the directional disk) seems to be what is slipping, due to wear on that and none of the others. Maybe try assembling it without a disk? also those springs are unbelievably hard to compress, and i was worried about stripping out the bolts, maybe this was an issue? not tight enough? THANKS!

Tower · « **Reply #1 on:** April 22, 2008, 10:34:16 PM »

Make sure the oil holes in the clutch centre are clear - no burrs, no gunk.

Also, this would be an exellent time to drill a few more holes in the clutch centre. Only need a couple more to ensure the clutch is oiled properly. Place them in the grooves (and not the lands) space them so that one is nearer the pressure plate edge, one nearer the other end of the clutch inner and two more in the cetre area. Debur and micro bevel all the holes (including the old ones). Don't do more than 4 extra holes, max.

zeus87 · « **Reply #2 on:** April 22, 2008, 10:52:29 PM »

alright, consider it done. What do you think is giving me this issue?

zeus87 · « **Reply #3 on:** April 22, 2008, 11:14:57 PM »

recent find: Could this be the culprit? I will replace it anyway, but could this be causing the problem?

750goes · « **Reply #4 on:** April 23, 2008, 12:18:34 AM »

definitely would not help - the clutch inner would be flexing when you pull the clutch in - maybe too much......

Tower · « **Reply #5 on:** April 23, 2008, 06:43:05 AM »

Need you even ask

Definitely, that's the problem. Your springs will have widened and caused the plates to go off centre forcing them up into the basket and causing the plates to bind.

That's a rare problem, sometimes caued by tightening one side more quickly than the others. The lifter plate is typically the one that takes the hit. Its probably a manufacturing defect.

Edit: Great pictures!

zeus87 · « **Reply #6 on:** April 23, 2008, 09:15:39 AM »

to the salvage yard. I know he has about 15 of these around, but they are going to be a bear to get to. Thanks!

P.S. you think there is enough oil in there?

Tower · « **Reply #7 on:** April 23, 2008, 10:43:37 AM »

If your disks have been sitting in oil for a couple of days that would be ideal. As for how much oil is or should be inside the clutch? Well, everything should be dripping with oil and when its opened, the oil will tend to run out - that's why you tilt the bike over a little when servicing the clutch.

Symptom of lack of oil is glazing and burning in disks that are furthest from the oil holes in the clutch centre. The stock oiling system is marginal. But, the addition of the extra oil holes goes a long way to making it excellent. It will also smooth out the action of your clutch as well as last much much longer. Just by way of a comparison: I give a typical clutch 15K-20K miles (I said, typical) With the extra holes it should last 40K miles and longer. (Now we'll get posts claiming all kinds of variations on this longevity claim

)

mustangcar · « **Reply #8 on:** April 23, 2008, 10:47:59 AM »

Quote from: Tower on April 22, 2008, 10:34:16 PM

Make sure the oil holes in the clutch centre are clear - no burrs, no gunk.

Also, this would be an exellent time to drill a few more holes in the clutch centre. Only need a couple more to ensure the clutch is oiled properly. Place them in the grooves (and not the lands) space them so that one is nearer the pressure plate edge, one nearer the other end of the clutch inner and two more in the cetre area. Debur and micro bevel all the holes (including the old ones). Don't do more than 4 extra holes, max.

thanks for that neat idea on drilling couple of extra oil holes,would you happen to have pics or diagram where to drill them , i guess i have to take it apart to see the original factory oil holes?

Tower · « **Reply #9 on:** April 23, 2008, 11:05:00 AM »

Just a note for salvage yard diving...those pressure plates come in two (maybe three?) part numbers (1969 - 1971 pn 22350-300-010, 1972 - 1975 pn 22350-300-030, and possibly a third for 1976+) I think they are interchangeable, but wouldn't stake my clutch on it. Perhaps take calipers for measuring bolt pattern (cross width and length).

Mustangcar, once the inner is apart, you'll notice the holes already there (some of the early inners had only 1 hole) Now imagine putting three of four more holes in so that they are evenly spaced around the clutch inner (perhaps opposite side to the ones that are there already) Space them so the holes oil as many of the clutch disks as possible - as each hole can typically oil only the three disks in its immediate area.) Next time I take it apart, I'll try to remember to take pictures.

mystic_1 · « **Reply #10 on:** April 23, 2008, 11:05:53 AM »

I used the search function and searched for "clutch drill holes". This thread was result #1, result #2 is the one you want:

Clutch Hub modification posts

cheers
mystic_1

mustangcar · « **Reply #11 on:** April 23, 2008, 11:22:55 AM »

thanks guys!! learned about the extra oil holes and to look out for stress cracks A+

greenjeans · « **Reply #12 on:** April 23, 2008, 11:56:02 AM »

I love this site....just had my clutch out over the last 2 weekends and it will come out again this weekend to
add some holes....mine doesn't have any! At least I'm getting quicker at taking the clutch out etc...

Tower · « **Reply #13 on:** April 23, 2008, 02:13:41 PM »

Ha. Should have guessed TwoTired or Hondaman would have posted about the extra oil holes.

Everyone paid a lot of attention to this in 1971. Something I picked up on about that time also, when a Honda dealer mechanic friend noticed the burned disks were always coming in the same pattern and realized why Honda had upgraded the clutch centre for a third time in two years - with the only real difference being the extra holes - duh). Instead of replacing the old centres, he just drilled holes.

Note: Got to get a hold of those old service bulletins. They must still be kicking around (But, I don't think this problem was in a bulletin actually).

mystic_1 · « **Reply #14 on:** April 23, 2008, 02:15:50 PM »

Bulletins are HERE.

mystic_1

zeus87 · « **Reply #15 on:** April 23, 2008, 10:05:39 PM »

hmm...im a little worried about the oil situation. Like i said, it was pretty darn dry in there, nothing dripping, and very little on the bottom (as far as pooling) is there anyway i can make sure it is getting oil in therE? start the engine without the clutch together maybe? Id hate to put it together than find a oil issue. Thanks, so should i order the part? it seems i can find it from a honda page for about $28, is this possible? Part #7

http://www.westernhillshondayamaha.com/fiche_section_detail.asp

Tower · « **Reply #16 on:** April 23, 2008, 10:48:18 PM »

These things rarely break, so there's not much demand (unlike the lifter plates)So, $28 sounds good to me

The part number seems right (22350-300-30). But what do I know about selling Honda parts?

I wouldn't advise starting/running it with the clutch out. You might get oil places you don't want it to be.

zeus87 · « **Reply #17 on:** April 23, 2008, 11:48:18 PM »

can it hurt things though? judging from the amount of oil it had in there when i first took it apart (replacing the clutch) there is very little now...what to do...

oldbiker · « **Reply #18 on:** April 24, 2008, 12:26:05 AM »

Mystic-1, I followed your link to the service bulletins and was able to access the bulletins for the cb750 but when I tried to look at the ones for the cb400f I was told I was mot allowed to access them. Any idea why?

mystic_1 · « **Reply #19 on:** April 24, 2008, 05:43:33 AM »

Odd, I'm getting the same thing:

"Permission denied you can not view this section"

Not sure why, perhaps one of the mode can chime in on this. Same error happens for the 500/550 bulletins.

http://sohc4.com/tiki-list_file_gallery.php?galleryId=4

http://sohc4.com/tiki-list_file_gallery.php?galleryId=6

mystic_1

zeus87 · « **Reply #20 on:** April 26, 2008, 10:02:49 PM »

hmm, i just compared the springs....these EBC springs that i got from dennis kirk are aleast a half inch longer than the stock, also i noticed that they are all bent from being overly long for the space provided. Is this normal? i checked the part numbers and they match with the catalog and part needed. They definetly are way long and rediculis to squeeze, i had to tighthen them down with extra long bolts just to get them started. Let me know what you guys think. If they are bad, Kirk is gonna pay for a barnette set.

Tower · « **Reply #21 on:** April 29, 2008, 11:25:30 AM »

Springs being a little longer is not a problem...a lot longer is a problem because when compressed they may still not fit into the space provided. A little extra strength is not a problem...a lot more spring strength is a problem. On the stock 1972 clutch, the recommended spring height is 1.4" or 35.6mm and strength is 220 lbs. By comparison, later Hondas (1976+) used the longer 1.5" / 240 lb springs. But know that they were a fit for the newer, 1/4" longer, clutches.

In any event, don't exceed strength by more than 10% (242lbs) as this causes undue stress on the stock parts and is not really necessary for good clutch operation. Also, racing type springs tend to be uncomfortable to the rider.

News:

Author Topic: 78' CB750k8 Clutch issues.. (Read 2099 times)