GS400B camchain tensioner adjustment

[GS400B]

Ok tried resetting the set-screw; The flat area was visible down the recess, so assuming the set-screw can lock/unlock the pushrod ok.

Start engine, knurled wheel is motionless. Give it 10 seconds and it starts oscillating very slightly.

Some more information:

I watched the wheel very closely, and did notice that the wheel movement is actually only very slight, maybe 5 deg max.

This movement is accompanied by a change in engine noise - there is a distinct rattle that starts, and if you leave the bike ticking over, the rattle and wheel oscillation will stop of its own accord, but then restart again some seconds later.

Looks like tensioner assembly will be coming off the bike after all.

I'm making notes of all this in the hope that others who experience the same problem may be able to find a remedy from what's going on and what's being tried here.

[tom203]

Take it off….after locking the set screw! It’s hard to explain its correct function, but holding and caressing it will make it obvious how it’s supposed to work. The plunger is only to push out towards the chain . The knob with its spring pushes on a ball riding on ramp that prevents the plunger shaft from retreating. Fiddle with it ,you’ll understand quickly

[GS400B]

Thanks Tom - that's the plan for the morning. Hopefully a stripdown/clean/reset will do the trick.

The worrying bit is bolting it back on, starting her up, only for it to all go pear-shaped in a big way - that will NOT be the result I'm looking for!

[rphillips]

Just a thought again. For someone who knows these things, Can the spring, holding the knurled wheel be a turn too loose and not holding enough pressure to keep the plunger shaft from slightly backing out. and making that wheel jump back and forth? I know the position of that spring is important.

[GS400B]

That's a very good point, and was something I was thinking of when I did the dry run with the spare engine tensioner.

On that one, the spring was detached from its two securing holes, so I followed the notes in bwringer's missive Step 6 -

"Count the number of turns of spring tension. Mine had one turn of spring tension, and the holes were in line with one another."

When I refitted the spring, I twisted it down until I had good tension on the spring, along with the spring-securing holes lining up. One turn of spring tension seemed to be exactly what was required to achieve this. Anything more or less ended up with the holes going out of line, so I stuck with that.

I'll check tomorrow to see if the on-bike tensioner can be adjusted in a similar fashion once I've removed it - could well be that the spring tension is actually not set strong enough.

[GS400B]

Back to the bike this morning - TDC set, tensioner assembly off the bike. I did the job with carbs in-situ, and it was a tight squeeze, even with my little 'chimp hands' as my wife calls them!

Bwringer's advisory says in part4 "Inspect the angled surface (ramped area) of the pushrod for dents or pits formed by the ball bearing on the end of the adjuster. These dents will cause the tensioner to hang up." The pushrod had a very distinct depression on the angled face where it had been in contact with the ball. 30 minutes with a sheet of sandpaper smoothed it out ok.

IMG_1470.jpg

The key phrase/advice (in BikeCliff's article) during the rebuild process, and which made it all go together properly, was this:

"Mr. Billy Ricks adds:

With the tensioner removed from the cylinder block loosen the lock nut on the left side of the tensioner and back the slotted bolt out 1/4 turn. Turn the knob on the right side of the tensioner, which in the Suzuki service manual is called a lock shaft handle, counterclock-wise. As you are turning the knob counterclock-wise push the pushrod all the way back. Keep turning the knob until it refuses to turn any further. With the pushrod still pushed in as far as it will go tighten the slotted bolt so that the pushrod will not plunge out."

Stripped/cleaned/reset the unit as per the given advice. The spring behind the knurled knob was reset with one full turn of spring pressure. The spring retaining holes didn't line up 100% but very close to. Unit was put back on the bike, plunger released/locked, and the engine was turned over from the 19mm nut on the crank. All seemed ok, so fire it up.

Result - no movement from the knurled wheel and I'm not sure if I'm imagining it, but the engine actually sounds like its running better. There's a definite 'smoothness' which wasn't there before, and a distinct sound to the motor, which I remember very well from my GS750 days - its like an engine whine, but not in a bad way - its just how I recall that they sounded.

Been out for a 5 mile test run - no problems, bangs, rattles, and it was like riding an almost-new machine. Suffice it to say, I'm very pleased with the result.

Thanks to GSR for the so-very-useful advice notes, and to those who have commented/helped on this thread . Maybe keeping it here for reference will help others to sort out their own similar issues in future.

[rphillips]

Good feelin' ain't it??? Congrats.

[Nessism]

Good job getting it sorted. Getting your hands dirty "earns" you a fixed bike.

[Gorminrider]

Good! Now We Know What causes this..yes, from bwringer's rebuild I was thinking you could just file the divot out on the plunger shaft... It came to mind wondering how soft the steel was and if it was (or should be!) "case hardened". It really shouldn't wear in like that...