1978 darmah - trans gets stuck in neutral

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doug s.
Cucciolo - the Lil Pup
Posts: 7
Joined: Fri Sep 02, 2016 5:17 pm

1978 darmah - trans gets stuck in neutral

Post by doug s. »

hi all!

i'm having a bit of a problem w/my 1978 darmah. 1st a bit of background - almost 5 years ago, i had the sprag bearing, flywheel assembly starter and starter gear replaced. it's been ridden maybe 2.5k miles since then; the bike has ~27k on it total. it was in the shop for something else, and the mechanic said i should do it, as the sprag bearing was on its last legs, as well as the other stuff. i was able to source a nice used starter and had it rebuilt before install.

so, this problem of the trans getting stuck in neutral has happened twice now; the bike sits for ~5-6 months over the winter, and gets started about once a month, but not ridden. 1st time it happened was last spring, was the 1st time out for the season; after about 3 miles down the road, it suddenly got stuck in neutral. putting it on its center stand, letting it run, and playing w/the shifter a bit, it finally (and inexplicably?) engaged, and i was able to ride it. i rode it around for a while, and rode it a few times over then next several months, until last fall, when it got parked. well, two days ago, i took it out for the season, and same thing, only this time, it happened in 0.2 miles - at the end of my drive. same thing; i was finally able to get it to engage, and took it on a nice 15 mile back-road cruise w/no further problem. does it just need more use, or is there something else happening? it's got full synthetic in it; probably needs to be changed out w/new. the oil didn't get changed last year; am i mistaken thinking i can get away w/every two years because it's synthetic?

thanks!

doug s.

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81mhr900ss
Parallel Twin
Posts: 103
Joined: Tue May 31, 2016 3:49 pm

Re: 1978 darmah - trans gets stuck in neutral

Post by 81mhr900ss »

Hi Doug: Could be a couple of things; I'd start with the easiest, the clutch. I don't know why, but there seem to be a lot of owners that have clutch pull issues. If the clutch doesn't disengage fully, it can be, for obvious reasons, tricky to get the bike to go into gear. Usually the complaint is the other way around; can't get the thing into neutral.

Clutch issues can be complicated or simple:

Start simple and ensure that the clutch cable is pulling "easily", yes a misnomer for a conventional bevel twin clutch but you know what I mean; there should be about 2-3mm of play in the cable, the cable should pass freely under the tank without any kinks or tight curves and the little clutch lever on the right casing should move freely.

If the pull feels harder than you remember, it may be that you need to clean and re-lube the clutch pushrod and the hole in the gear shaft through which it passes. Your clutch pushrod may have worn components. Easy job, just remove the right side rear sprocket cove and the little, left side cover "Ducati" inspection/adjustment cover plate. Carefully undo the locknut on the left side "special screw" and remove the screw. Get a wire coat hanger, straighten a section about 12" long and push the clutch rod out from the left to the right there should be eight pieces, nine including the special screw. The first four parts are 8mm diameter including a ball bearing, followed by four 6mm diameter parts; long, short, long, short. Clean everything including the clutch lever in the cover and the hole through the gear shaft. I do this using a twisted piece of fine cloth, coaxed through the hole using the coat hanger or a thread tied to the cloth that is first pulled through the hole with the coat hanger; you will find a way. Grease all the push rod components and put them back in the same order they fell out but put the special screw in loosely first on the left side. Re tighten the special screw locknut, put the left cover back on, reattach the clutch cable and see how it feels. Not a bad idea while the little Ducati cover is off, to measure exactly how much movement there is of the clutch pressure plate. I recall around 3mm being OK; I've never done this as I've never had clutch issues.

If the clutch still feels wrong, your clutch pack may be worn but this usually results in clutch slippage during riding not gear shifts. It's also possible that the metal tangs of the steel clutch plates have cut little grooves in the slots of the clutch housing. Now it's a PITA job as the left casing has to be removed; inspecting the clutch itself is really easy, just 6 little bolts, springs and spring caps and the pressure plate and all the steel and sintered pads can be pulled for inspection. Note that the outermost steel plate's tabs point in towards the engine slightly.

That was the easy stuff. If the clutch is fine then there is an issue with the gearbox, most likely the shift mechanism. The most common issues are broken springs but this usually results in yes/no operation not sometimes OK. There are two springs, the bigger one is the return spring and it's more prone to failing than the smaller, fork spring. The tell tale is broken spring pieces falling out when the left cover is removed; sometimes they just sit inside the engine casing lip under the clutch. There's also a little eccentric screw used to balance the up and down movement of the gear selector; sometimes just tweaking this a little can resolve gear change issues. Bad news is that this is all hidden behind the clutch housing.

On topic; when the clutch hasn't been used for a while it can get sticky. On kick start only bikes like mine, if I haven't used the bike for a couple of weeks, I "break" the clutch first by pulling on the clutch lever and kicking the bike over two times. If your bike has a kick start too, maybe it's a good idea to do the same; makes life easier for the sprag.

Also on/off topic; you probably know this but sprags often fail due to weak batteries; they like strong, big, 12.7 volts to start the bike. Weak starts due to low volts leads to failed sprags. If you don't already do this, put your battery on a trickle charger regularly. My phone calendar reminds me to do this every second Sunday.

doug s.
Cucciolo - the Lil Pup
Posts: 7
Joined: Fri Sep 02, 2016 5:17 pm

Re: 1978 darmah - trans gets stuck in neutral

Post by doug s. »

81mhr900ss:

thanks for the detailed reply. i'm thinking (hoping) that it just need more use, and things are sticky. i did notice that, when it was seemingly stuck in neutral, the clutch lever/arm action seemed normal. and i could hear things inside, the engine/trans cases, like the transmission gears changing when i shifted the gearshift. just that the bike remained in neutral; quite strange, it seems to me.

anyway, i think i will ride it a bit more than i normally do, give it a fresh oil change, and perhaps do some mechanical investigation per your suggestions. i'm not too flat-fingered with tools, and i do have a service manual, so it couldn't hurt to clean things up a bit.

thanks again,

doug s.

doug s.
Cucciolo - the Lil Pup
Posts: 7
Joined: Fri Sep 02, 2016 5:17 pm

Re: 1978 darmah - trans gets stuck in neutral

Post by doug s. »

well... it seems the issue is that the drive sprocket worked its way off the shaft. !?! when i pulled the sprocket cover, the lock nut and the (mangled) lock washer fell out, and the sprocket wasn't engaging the shaft - that's why no-go!

i'm now awaiting new lock nut and lock washer; i will likely be re-using the the sprocket, as it seems ok, now that i removed a bit of the star washer that had "welded" itself inside the sprocket, preventing it from going back on the shaft. i think this is a better option than buying a new sprocket to use w/my old chain. if i could find a new steel 38 or 39 tooth rear sprocket, i'd be tempted to go w/a complete new sprocket/chain setup, but i have only found aluminum rear sprockets, and i don't really want that.

i believe that the transmission itself is ok; i'll know for sure when i get it back together.

here's a pic of the sprocket:
Image

doug s.

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81mhr900ss
Parallel Twin
Posts: 103
Joined: Tue May 31, 2016 3:49 pm

Re: 1978 darmah - trans gets stuck in neutral

Post by 81mhr900ss »

Bizarre! This is a new one for me; I'm glad you found the problem. I suspect that the lock washer had been reused one too many times. Good luck!

doug s.
Cucciolo - the Lil Pup
Posts: 7
Joined: Fri Sep 02, 2016 5:17 pm

Re: 1978 darmah - trans gets stuck in neutral

Post by doug s. »

yes, bizarre indeed. i think i dodged a bullet; i was very lucky that the threads on the shaft that holds the sprocket are still ok. the lock nut threads were damaged from the very end of the shaft, but the shaft threads themselves are ok. by reversing the lock nut, i was able to thread it onto the shaft until the damaged thread from the side that normally faces the sprocket prevented its going any further.

doug s.

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