Author Topic: CB400f clutch kick start HELP (update-SOLVED!!!) (Read 7888 times)

swan · « **on:** January 23, 2009, 10:05:40 PM »

I am finishing a 1977 CB400F motor and have run into a problem with the clutch and kickstart assemblies I simply cannot figure out.

The rebuilt motor turns over EXCEPT when I try to crank the kick start. I can easily rotate the crankshaft with a socket wrench at the contact plate, rotor and mainshaft. Pistons and cam chain are correctly set up, oiled and timed. Transmission and associated components shift through all 6 gears and neutral perfectly. Kickstart assembly, gears and teeth are all crisp, clean and lubricated. Clutch springs and plates all measure within manual's specifications. I have triple checked everything.

When the clutch assembly is removed or losened, the kick start assembly rotates the countershaft correctly. When tension is applied to clutch springs and the kickstart freezes. WTF?

The clutch assembly locks up and will not turn the mainshaft. All gears and teeth are in very good condition, line up correctly, turn freely and the bearings are clean and oiled. All shafts were checked with dial indicator and are not bent.

I have the luxury of having a second CB400f motor I just bought on the bench so I can swap parts between the two. Both kickstart and clutch assemblies work on the parts motor but not on the restored motor. What I am missing? I am getting frustrated and cannot figure this out.

Anyone else had a similar problem? Ideas? Thanks!

swan · « **Reply #1 on:** January 23, 2009, 10:11:15 PM »

Additional photo

Bodi · « **Reply #2 on:** January 23, 2009, 10:43:38 PM »

There's nothing I know of that would lock up. The clutch just couples (and uncouples) the outer hub (and the crank through its gear) from the transmission shaft.
Perhaps you have a rebuilt engine that's just stiff and you aren't pushing hard enough on the kick lever? It's quite difficult to "kick over" an assembled engine off the frame. The whole engine just flips over.

bryanj · « **Reply #3 on:** January 24, 2009, 01:00:17 AM »

Is the clutch outer binding on the mainshaft gear when tightened?

swan · « **Reply #4 on:** January 24, 2009, 04:47:33 AM »

Bryanj-Good idea but no, the outer clutch is not binding on the mainshaft gear and teeth line up and mesh correctly.

Bodi- I can crank it over with a wrench everywhere except the kickstart. I have put my full body weight on the kickstart and it does nothing. I can crank over the parts motor easily with the same kickstart assembly on the bench (with the cylinder head on, not as pictured). You are right the clutch simple couples and uncouples the outer hub. This what is driving me crazy.

I'll put the motor in the frame, replace the outer cover, try to kick it over and post my results.

Thank you both!

mattcb350f · « **Reply #5 on:** January 24, 2009, 08:04:53 AM »

Couple of thoughts...

On the small fours, the engine won't kick over with the clutch disengaged (clutch lever pulled in). When you say it won't turn over when tension is applied to the clutch springs, I think you mean when you thread in the bolts that hold the clutch springs.

This says to me that the assembly as far as the countershaft (output shaft) and the shaft that the clutch bolts too are free, and that the problem is further up the assembly, closer to the engine.

Try taking off the clutch bolts and retainer plate and turning that shaft with the nut behind those parts. This would be the same thing the kicker is trying to do.

Matt.

swan · « **Reply #6 on:** January 24, 2009, 08:57:35 AM »

Matt,

Yes, it will not turn when 4 bolts on the clutch spider are turned in, applying pressure and friction to clutch plates so that they should (but do not) turn the clutch drum/basket allowing its gear to turn the mainshaft and rotate the crankshaft.

With tension off the clutch spider bolts and/or the clutch plates removed the clutch center spins on the countershaft but not the geared clutch drum. The castellated nut behind the clutch plates on the countershaft spins freely and turning it by wrench will not rotate the clutch drum/basket because there is no tension or friction to drive the geared clutch drum.

Arrggg!!!!

Thanks for your thoughts but it still does not work....

Bodi · « **Reply #7 on:** January 24, 2009, 09:24:31 AM »

You see my lack of an idea how this could jam. As I recall the clutch outer mounts on and spins freely on the transmission shaft, not touching the case or any other engine parts. The clutch inner splines to the transmission shaft, held on with the oddball nut. The plates just connect the inner and outer, the pressure plates and springs pull the plates together. Pushing the clutch inner inwards against spring pressure declutches the thing.
Anyway... nothing the clutch itself does ahould do anything except couple or uncouple the clutch inner and outer baskets, and they need to be coupled to have the kickstarter work. SO why is the thing jamming?
The only thing I can imagine is that somehow the clutch assembly is jamming against the engine cases. The problem is that the 400F clutch has the spring pressure completely inside the clutch - they pull in so they can't be forcing the clutch parts out against the engine case...

I would take a long hard look at the assembly drawings and that any spacers or whatever are in place, and that the outer basket isn't hitting the case behind it or anything else. Since the open clutch (because of the spring setup) applies zero force to the engine or cases when engaged I don't see how its presence or absence could affect the transmission shaft. With the cover on and declutching pressure applied, there is an axial force on the clutch against the transmission shaft, somewhere there must be a thrust face or washer to take this.

Good luck!

mattcb350f · « **Reply #8 on:** January 24, 2009, 07:00:31 PM »

My brain misfired on the previous post, .....Bodi explained it better anyway.

What I meant to say is that with the clutch disassembled, can you turn the clutch basket which is geared to the engine.

I sounds like you can't, meaning the problem is likely not the transmission since you say that part turns freely.

The problem sounds like it is either in the clutch assembly itself, or further towards the crankshaft in the flow of power in the area of the main chain.

Just a thought, is it possible that the bolts you are using to tighten in the clutch springs are a bit too long and threading though the back of the basket?

Matt.

750goes · « **Reply #9 on:** January 24, 2009, 07:09:26 PM »

I'll second the thoughts of either the clutch basket binding on the motor cases somewhere, or there is a spacer missing from your assembly - take the clutch out, and if I forgot that this already works....then use the kick start.... to turn the motor over - then it must be in the clutch basket and assembly......

swan · « **Reply #10 on:** January 25, 2009, 06:45:49 AM »

Motor is in the frame and I still cannot turn it over withe kickstart assembly. If I remove the clutch spider, plates and clutch center, thread a long screwdriver across the clutch drum/basket and apply pressure, I can crank over the engine.

The thrust washer is in good shape and behind the basket assembly and the dished washer is in correct position with the "outside" stamp facing outward. The clutch basket is not hitting the case and the clutch bolts are not too long as suggested. The bolts fit into the clutch drum and cannot protrude out the back.

Thanks for the suggestions but nothing has worked yet. I torn down the parts motor and am cleaning the cases, remove gaskets etc. If I cannot figure this out I will rebuild this motor and use i t. Back at it tonight....

mattcb350f · « **Reply #11 on:** January 25, 2009, 07:39:12 AM »

This is a real head scratcher for sure

If you can turn the basket with the screwdriver and turn the motor over that the problem is not the engine or the shaft driven by the main chain, it must be either the clutch assembly or the transmission then.

Did you try installing the clutch assembly off of your spare motor and trying it?

Also, make good and sure that it's in neutral, that might cause it to be tight.

Matt.

swan · « **Reply #12 on:** January 25, 2009, 07:59:51 AM »

Matt,

You are right this is driving me crazy.

Transmission works smoothly through all 6 gears and it is in neutral. The engine and crankshaft all turn and work correctly as confirmed by socket wrench turning at the contact plate, stator and mainshaft. Clutch plates removed, remeasured and replaced correctly as per manual specs.

I tried both full clutch and kickstart assemblies with the same results. One basket's rivets are a bit loose so I am using the tighter basket.

Gotta walk away from this for a while and not think about it....

750goes · « **Reply #13 on:** January 25, 2009, 02:34:40 PM »

Is there a chance that the kick start is not assembled correctly ??

Do you need to split the cases for this to happen ??

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

750goes · « **Reply #14 on:** January 25, 2009, 02:36:17 PM »

sorry, that link didn't work properly

just select your year and model and then kick starter section - shows up a nice parts explosion

swan · « **Reply #15 on:** January 25, 2009, 07:39:13 PM »

Kickstart is assembled correctly and both kickstarts work in my parts motor, but not in rebuilt motor as described above.

750goes · « **Reply #16 on:** January 26, 2009, 01:09:47 AM »

then the rebuilt motor must have something out of alignment...maybe a spacer not included or in the wrong spot.....sorry I have no further clues....

clueless in Sydney..........

Tim2005 · « **Reply #17 on:** January 26, 2009, 11:56:42 AM »

This doesn't make a great deal of sense to me either, however one thing that may be interesting to try would be to remove the 4 central bolts, the lifter plate and the springs, then undo and remove the main central castellated nut & both washers. Then, leaving that lot off, replace the springs, the lifter plate and the 4 bolts and tighten them up.

It'll be interesting to see what effect this has- you should then be able to just pull out whole springs and plate sub assembly as there should be no force on it. It may be a little grippy on the splines and basket edges, but should wriggle off fine.

Keep us posted

swan · « **Reply #18 on:** January 26, 2009, 05:57:54 PM »

Tim,

I tried your suggestion to no avail. It was not grippy, pulls straight out and the teeth and splines of the gearshaft and clutch are crisp and tight, no wear or free play.

Thanks, my "parts" motor is looking more like a "replacement" at the moment...

mattcb350f · « **Reply #19 on:** January 26, 2009, 06:10:29 PM »

I hate to think you're gonna have to use your spare engine, but maybe there is something the matter that can't be rectified without spiting it....again.

But there may be something we've missed. Before you write it off, maybe PM the member "ttr400" with your problem. He knows these little fours pretty well.

Matt.

Tim2005 · « **Reply #20 on:** January 27, 2009, 10:59:35 AM »

Quote from: swan on January 26, 2009, 05:57:54 PM

Tim,

I tried your suggestion to no avail. It was not grippy, pulls straight out and the teeth and splines of the gearshaft and clutch are crisp and tight, no wear or free play.

Thanks, my "parts" motor is looking more like a "replacement" at the moment...

At that point, what was the locking-up situation? To be consistent with earlier findings it should have been locked solid when the clutch was slid in, then free when it was slid out. In which case the parts motor looks hot favourite.

swan · « **Reply #21 on:** January 27, 2009, 09:50:05 PM »

YES!!!!!!! I figured it out!!!!!!!

You are not going to believe how simple the problem was. I am embarrassed to say the problem was not having the bolts installed on top of the crankcase. The bottom bolts were in and torqued to spec., but I had not put in the top crankcase bolts.

Tonight I split the cases, double checked everything, cleaned, fresh Three Bond, etc. When put the cases back to together it hit me, the bottom bolts were misaligning the cases slightly so the clutch would not spin with the kickstart assembly. Top bolts were added and now everything works like precision clock work.

I am owning up to my stupid oversight so no one else suffers this in the future.

The rest is downhill; cylinder head, timing, finish wiring, install rebuilt carbs, exhaust and fire her up!

Thanks everyone for your input and I hope I did waste too much of your time. Sometimes it is the simplest problem and you just need to walk away from it for a while, not think about it and the come back to it with a fresh mind.

mark · « **Reply #22 on:** January 28, 2009, 06:02:01 PM »

there should be dowels(tubular or solid, I don't know) aligning the case halves. ref, 16 and/or 17 on crankcase fiche.

swan · « **Reply #23 on:** January 29, 2009, 04:18:49 AM »

The cases were aligned properly with dowels. When force was applied by the kickstart lever, the cases without top crank case bolts clamshelled slightly opening about 1 mm at the rear, misaligning the clutch and mainshaft alingment.

Everything works perfectly now and it has plenty of compression.

Eddie Kirby · « **Reply #24 on:** May 18, 2021, 05:14:59 AM »

Gday Swan. I have exactly the same problem!!!!!!!!!! Reading your article am I correct in assuming I have to strip down my engine "again" to check and realign the crank cases. Regards Eddie

swan · « **Reply #25 on:** June 02, 2021, 06:54:26 AM »

Eddie, Before you do that, simply tighten all the crankcase bolts to specified torque.

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Author Topic: CB400f clutch kick start HELP (update-SOLVED!!!) (Read 7888 times)