Missing down changes

jotajoe said:
My Jota has precisely the same characteristic. Just a tad of a touch upward on the gear lever prior to a down shift and all is hunky dory.
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Joe, Gerald,

This symptom is also very common.  The selector pawl that bears on the pins in the outer selector drum is at fault.  The teeth of the pawl are just a tiny bit too "sharp".  Remove about 0.5mm from the tips of the pawl teeth only and the pawl will slot onto the selector drum pins as it should!  No heed for all that fiddling in between shifts.

piet
 
Hi Piet,

is that the same for a bike that only ever has problems to accept to shift from 3rd up to 4th (heavy resistance, until RPM drops a bit and than it "clicks" in)?

 
Get you home and more tip....back in the 70's I had my first experience with a broken shifter return spring. The dealer in Perth had none and it would be a week or more to get one from the east. So using several large rubber bands made by cutting up an inner tube then wrapping 2 of them around the shift lever so there was equal up and down tension it worked perfectly. Since then I have always carried a spare spring and have needed it , Cheers Dave.
 
Laverdalothar said:
Hi Piet,
is that the same for a bike that only ever has problems to accept to shift from 3rd up to 4th (heavy resistance, until RPM drops a bit and than it "clicks" in)?
Click to expand...

Nope, don't think so!

Sounds like the slector drum binding a bit, need to juggle the sprocket cover around a bit.  We'll take a peek Wednesday.

piet
 
Or it could be the problem I had...broken cam chain tensioner going for a swim in the gearbox! stopped first gear selection, unless the lever was held down, it jumped out.this happened on the way to the port for a trip to Spain I went ahead anyway and by some miracle it was ok all the way back from Santander to Cherbourg. back in Blighty the problem resurfaced. fiddled with the adjuster to no avail. assumed major gearbox problem. Bought one in readiness for the stripdown. Not needed ! Engine came out anyway for head /barrel fittoing, and while at Keith's he did summat to the selector pawl anyway which has made it better than it ever was..less false neutrals. he also re-bushed my rearsets(I had assumed they all wobbled about  like that!) which makes things all the more precise..
Nick7
 
laverdakeith said:
Dead easy to adjust Joe, takes ten minutes. You will curse that innacurate downchange barreling into a bend one day.....


    Keith.
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Couldn't agree more Keith. My SFC had a tendency to miss gears on downchanges and its a very unpleasant feeling to freewheel helplessly into a fast bend, and quite dangerous of course. Sometimes whilst fishing for a gear it would go through the intended gear and down into the next one, which would then lock the wheel as the clutch was fed in. After it almost put me on my arse I ended up stripping the box and sorting the job properly. There's no need to put up with a crap gear change on a Laverda, when correctly adjusted they are a nice 'box to use.
 
If it has happened all of a sudden and not gradually check chain tension but more important check the cam chain has not worn through the cam chain tension blade and half of it is living in the bottom of the crankcase,this posting should get some stick,but just check anyway.
 
Moving the eccentric adjusting screw a tad clockwise did the trick for me :)
Up and down shifting is now as it was before, but I'm still a bit puzzled why I had to adjust it.
Over the years I've had the sprocket cover off many times, never needed to adjust anything when
I reinstalled the cover. Maybe something else has worn and I can't see it (yet)

Anyway, had a great hour and a half tour in the hill country :D

Gerald
 
Vince,

Mines been doing that for years. I just got used to it because every Ducati I've ever owned has done the same thing. After reading this thread though I might get a new spring and have another look.
Amazing what we put up with for donkeys years with out another thought.

Cheers
Chris
 
The broken spring was replaced but the down change is still sticky,I want to check a few things.Is there supost to be a large washer on both sides of the spring and what way does the bent leg go.I have rear sets and am going to fit the origanal right gear lever and try to feel where the least resisance to the shalf is and then snug up the bolts on the outer clutch cover,any better way to do this.I am getting all gears but still need a tiny up movement before it will select 2 and 1st going down.BTW I seem to remember seeing left and right handed bent leg selecter springs years ago is this correct and does it make a differance?
 
Vince,

One washer only to the outside of the spring.  Prevents the spring wearing away the inside of the cover and keeps the spring from tilting too far.

The legs of the spring should engage the peg at its' base, so the bent leg is on the outwards side.

Try shifting through the gears without the small cover fitted.  If the pawl hangs up and won't engage the next gear without a bit of assistance, remove a smidgeon from the very point of the pawl so that it can engage the next pin of the selector shaft.

Never noticed any different springs, shouldn't make a difference anyway...

piet
 
Vince,
sometimes the cause can be as simple as the height adjustment of the gear change lever. If you are having troubles with downchanges only, and the pattern is one down and four up, adjust the lever (not the pedal!) up a little so that you naturally tend to push it down further when changing down through the gears. This is an easy adjustment particularly if you have rearsets, and is readily changed back if it doesn't help.

bazzee
 
I take your point re hight of the rearset gear pedal,I had to shorten the rod between the levers by 5mm to get a good pedal hight with 90 deg angles on the levers.I couldn't shorten it without cutting it as the threads were bottomed.I am thinkings its slight binding on the shaft
 
Well I mucked about again,did Piets light file on the tip of the pawl but still misses 1st gear,goes in with a slight up move . Goes in from neutral but hits a solid resistance going from 2nd to 1st,not keen but I am going to try a tiny adjustment to the cam.Needs more packing to tilt over,lost too much oil today
 
Ah ha! That explains the scratches on the inside of my gear change cover when I removed it to put the original clutch actuation lever back on. One washer was on the inside of the spring, one was outside of the case behind the lever!

I know what I'll be doing this evening....

Cheers for the info as always Piet!

Bloody hell the clutch is heavy now. And that's after I spashed on the Venhill featherlight clutch cable too! I best man up a bit, do my hand exercises and stop moaning....

Chris


sfcpiet said:
Vince,

One washer only to the outside of the spring.  Prevents the spring wearing away the inside of the cover and keeps the spring from tilting too far.

The legs of the spring should engage the peg at its' base, so the bent leg is on the outwards side.

Try shifting through the gears without the small cover fitted.  If the pawl hangs up and won't engage the next gear without a bit of assistance, remove a smidgeon from the very point of the pawl so that it can engage the next pin of the selector shaft.

Never noticed any different springs, shouldn't make a difference anyway...

piet
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