Ducati 350 scrambler 5th gear issue

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Ducati350ontario
Posts: 36
Joined: Tue Aug 15, 2017 12:15 am

Ducati 350 scrambler 5th gear issue

Postby Ducati350ontario » Sun Aug 20, 2017 1:08 am

Hi all. Im new to the forum here.
I bought a 1969 Ducati 350 scrambler about a year ago as my new project bike. Never owned a Ducati before...but I'm lovin this bike! I have a 63 Honda Benly and a 66 Honda Dream....so as far as old bikes go, this is different for me!

I never heard the motor run until recently. (Project is in its final stages) The transmission was working OK when I first started riding it to tune the carb, but it quickly started to have issues going into 5th.

What I've done so far:
-I Have pulled the selector box off it and went through it. The spring and detent ball etc all seem fine. It shifts well on the work bench and "feels" fine when I shift it on the bike.
-I've read all the advice on how to properly shift the bike.

At this point in time, unless I'm missing something.... I believe I'm going to have to bust it down and inspect the tranny.

One thing I should mention is that it was still going into 5th gear (not well, but engaging) until I changed out the front sprocket. After I did this I believe it seemed to get worse. I read some where that over-torquing could cause issues with a shim. I didn't use a torque wrench the first time, but am fairly confident I didn't apply any crazy amounts of force to it. I then used a torque wrench on it and was able to confirm that I had less than 50 foot lbs of torque on it. I left it torqued to 50 ft lbs. So unless I'm doing something wrong....I don't seem to think me changing out the sprocket should have really created any problems on this shaft?

I have ordered a Ducati workshop manual by Tom Bailey in preparations for a tear down.

Does it seem reasonable that I'm headed down the right path?, and also - any thoughts on what the issue may be? I was thinking some kinda shim issue or shift fork issue.

Appreciate any thoughts or comments on common issues.

thank you,
Jeff Fisk
Kincardine Ontario.
Canada
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Nick
Posts: 243
Joined: Sat Jun 01, 2013 4:57 pm
Location: Paradise

Re: Ducati 350 scrambler 5th gear issue

Postby Nick » Sun Aug 20, 2017 6:46 am

Nice bike! I've got a Dream too (love it).

Did you measure the width of the two sprockets? If the replacement sprocket was thinner/thicker perhaps it moved the shaft, exacerbating the problem.

Check parts book for shims.

As you probably know, worn dogs/bent shift forks, etc. are usually found in the lower gears.
Put a Mikuni on it!

ducwiz
Posts: 604
Joined: Tue May 22, 2012 12:52 pm
Location: near Frankfurt, Germany

Re: Ducati 350 scrambler 5th gear issue

Postby ducwiz » Sun Aug 20, 2017 8:55 am

Have you tried to improve the situation with the adjuster 0400.13.0160 (see https://www.ducatimeccanica.com/parti_di_ricambio/pages/partidiricambio0004.htm) ?
Imo, neither overtorquing nor wrong shimming can cause your prob.
The nut pulls the step/shoulder on the (hard) output shaft against the ball bearing, into a fixed position, as the bearing in turn faces against a shoulder in the casing. Overtorquing will only strip the thread from the soft nut.
Shims between ball bearing and sprocket cannot change the position of any gear or shaft behind the bearing, inside the engine.

Hans

Ducati350ontario
Posts: 36
Joined: Tue Aug 15, 2017 12:15 am

Re: Ducati 350 scrambler 5th gear issue

Postby Ducati350ontario » Sun Aug 20, 2017 12:40 pm

Nick wrote:Nice bike! I've got a Dream too (love it).

Did you measure the width of the two sprockets? If the replacement sprocket was thinner/thicker perhaps it moved the shaft, exacerbating the problem.

Check parts book for shims.

As you probably know, worn dogs/bent shift forks, etc. are usually found in the lower gears.

Thanks Nick.
No, I never did properly measure the socket. I will pull it back off, measure it and if there's any difference at all I'll stick the old one back on for a test. The new socket does have the proper threads..... So I assumed...

Thanks
Jeff

Ducati350ontario
Posts: 36
Joined: Tue Aug 15, 2017 12:15 am

Re: Ducati 350 scrambler 5th gear issue

Postby Ducati350ontario » Sun Aug 20, 2017 12:53 pm

ducwiz wrote:Have you tried to improve the situation with the adjuster 0400.13.0160 (see https://www.ducatimeccanica.com/parti_di_ricambio/pages/partidiricambio0004.htm) ?
Imo, neither overtorquing nor wrong shimming can cause your prob.
The nut pulls the step/shoulder on the (hard) output shaft against the ball bearing, into a fixed position, as the bearing in turn faces against a shoulder in the casing. Overtorquing will only strip the thread from the soft nut.
Shims between ball bearing and sprocket cannot change the position of any gear or shaft behind the bearing, inside the engine.

Hans

Hi Hans.
Yes, if your referencing the eccentric shift adjuster I experimented with it a fair bit....both on the bench and then on the bike. I scribed my start point, and tried going both ways...but always ended up back where it was set.
At one point I thought it made the 5th gear shift ok....but it was so far adjusted that I had to constantly "pull" the shifter back to get the shifter to reset. (Not really rideable IMO)

I was fairly confident that I'd exausted this avenue....

-jeff

Ducati350ontario
Posts: 36
Joined: Tue Aug 15, 2017 12:15 am

Re: Ducati 350 scrambler 5th gear issue

Postby Ducati350ontario » Fri Dec 28, 2018 8:22 pm

Hello all.
Its been over a year since I last posted about my 5th gear issue on my 69 350 (wide case) Ducati scrambler...., but I've finally got around to breaking it all down.
I made 3 utube videos that I was hoping someone would be to watch and hopefully give me their thoughts on. When its put into 5th gear the dogs just simply aren't mating deep enough. Looking at the parts book.... I found there is a 1mm shim missing between the bearing and 5th gear, and then an extra .5mm back on the same (driven) shaft beside 1st gear. Other than that I'm wondering if the shift fork and its gear aren't just too worn out?
below are 3 video's on u tube. I'd really appreciate any thoughts or suggestions.

thank you
Jeff

https://youtu.be/TweJxJMUq-Y
https://youtu.be/G2n8Yc7Pmtg
https://youtu.be/nH_GE2kAB_0

Eldert
Posts: 771
Joined: Sun Nov 01, 2009 3:23 pm
Location: Hazerswoude Rijndijk Netherlands

Re: Ducati 350 scrambler 5th gear issue

Postby Eldert » Fri Dec 28, 2018 8:47 pm

Hi Jeff

there should be a 2 mm shim between 5th gear and the bearing .
selectorfork should be 4.35 mm thick where it sits in the groove from the gear .

Eldert

Ducati350ontario
Posts: 36
Joined: Tue Aug 15, 2017 12:15 am

Re: Ducati 350 scrambler 5th gear issue

Postby Ducati350ontario » Fri Dec 28, 2018 11:56 pm

Eldert wrote:Hi Jeff

there should be a 2 mm shim between 5th gear and the bearing .
selectorfork should be 4.35 mm thick where it sits in the groove from the gear .

Eldert


Hi Eldert, thanks!

Looks like someone had put that 2mm shim on the other shaft up against the bearing beside the clutch basket. As soon as I moved that 2mm shim everything looks great with the 5th gear dogs. I measured my shift fork and I have around 4.4mm. I think everything looks good now.

But here's what i'm trying to figure out now..... what other spacer/washers belong on the two shafts?

Driven shaft - Right now I've got the 2mm spacer the other end should have .5mm washer?
Clutch basket shaft- Right now its got a .5mm washer on the chain case side, … the other end should get another .5mm washer?
Shift drum has .5mm washers on either end.

Does that sound close to right?

Some of the drawings I've seen are conflicting.

thanks again
Jeff

Ducati350ontario
Posts: 36
Joined: Tue Aug 15, 2017 12:15 am

Re: Ducati 350 scrambler 5th gear issue

Postby Ducati350ontario » Sat Dec 29, 2018 3:12 am

"But here's what i'm trying to figure out now..... what other spacer/washers belong on the two shafts?"

Sorry, ….. but after looking at parts books (instead of parts-web sites), it looks like I'm supposed to have the 2mm washer beside the bearing for chain sprocket and then another 2mm beside the bearing for the clutch basket. (so each shaft has a heavy duty washer at one end for thrust?)

If this correct..., am I right to assume these are meant as "thrust washers" for each shaft? If yes...., then would I be right to assume that the other two ends get shimmed AS REQUIRED to take out any excess play after the casing are mated against a gasket?

I found another 2mm spacer on ebay, … now i'm inclined to slap a .5 at either end and see how it fits.

Does this make any sense?
regards
jeff

Jordan
Posts: 1380
Joined: Fri Dec 24, 2010 11:29 am

Re: Ducati 350 scrambler 5th gear issue

Postby Jordan » Sat Dec 29, 2018 4:33 am

The input, output and cam drum shafts should have shims to provide very small end clearance, and the shim selection could vary depending on the crankcase centre gasket thickness.
All gears can be individually shimmed if required, which can help achieve full engagement of dogs and extend their useful life.
There is inter-dependency of clearances, so everything has to be checked when any shim adjustment is changed.
It's time consuming to do from scratch.


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