GS400B camchain tensioner adjustment

[GS400B]

A quick question, if I may ...
GS400B - The camchain tensioner adjustment mechanism - with the engine ticking over at idle, should there be any visible movement of the knurled ring+spring assembly on the RH side of the adjuster (when viewed from sitting on the bike), or should it be perfectly still?
Thank you.

[tom203]

No….sounds like knob is vibrating , probably not putting tension on plunger shaft. Read this link, there’s another link inside it too

http://members.dslextreme.com/users/storagecliff/images/engine_odds-n-ends.html#A05

[GS400B]

Thanks Tom - here's a youtube link I found - it shows exactly what the tensioner is doing.

https://www.youtube.com/watch?v=jVxpe8Ftchc

Is removing and resetting the tensioner assembly the only way to correct this, or can it be adjusted with the tensioner still on the bike, as is the case right now, and as shown in the clip?

just asking for confirmation - don't want to remove the tensioner assy from the bike if its not actually required to do so - thanks.

[Gorminrider]

It's best if you understand how the tensioner works...The shaft of the tensioner pushes forward against a moveable plastic blade to take up slack on the camchain-BUT it's supposed to be a one-way device and should not be bouncing back. The bigKnurled knob is involved in THIS important feature.

Again, it's best if you understand how it works to do this.... There's usually a diagram and some instruction in the shop manual. Use a shopmanual for a similar 450 or just about any early 80s suzuki....also the link on that video has help http://www.bwringer.com/gs/camchaintens.html

You will probably have to remove it. DO Engage the lock screw before removing. On mine, the starter cover at least has to be removed to get room for tools. If so for yours, Avoid dropping the bolts deep into the uncovered hole with a rag spread over...

It doesn't always need a full dissassembly or complete rebuild, but the orings and gasket that keep oil from dripping commonly do need replacement.

[GS400B]

Thanks Gorminder - no problems with doing the task - just checking to see if it could be done with the tensioner assembly in-situ.
I do have the factory manual, plus the Haynes and Clymer manuals, and the only part of the process which is not made entirely clear in any of them is whether the engine has to be set to TDC before the tensioner assembly is removed.

[Gorminrider]

I don't bother but you can if you want. or just turn the engine round to "a tight place" . Then Lock the pushrod and take the assembly off. When you reinstall it, have the pushrod locked all the way "in". Then release the locking screw (about a 1/4 to 1/2 turn)...then tighten the lock nut to keep that lock-screw away from the shaft but still very near the flat-spot on the pushrod*....anyways, you can turn the engine over with a wrench while turning the Big Knurled knob a little as you turn the engine over ... this allows the pushrod to actually go back in...and once you have released the big Knurled Knob your tensioner will be in a place that should account for the slack and tightness....I even do this on a running engine. I think it very unlikely a camchain is going to leap off doing this carefully. you can even make the tensioner a Manual one by turning the lock screw in and locking the pushrod where it seems best...

The fact your Big Knurled Knob is moving suggests a problem in that particular aspect...I wonder if the pushrod has rotated ...too much slack in the lock-screw? something that hasn't happened to me anyways.

(*the flat-spot on the pushrod that you'll notice when you have the thing on the bench....)

[rphillips]

Like you Gormin, I've not noticed or read about this before. Been scratching my head trying to imagine what's happening.

[GS400B]

OK - using my spare engine for the purpose, which had a damaged knurled wheel spring (the spring had come out of its two mounting holes, allowing the wheel to rotate), I have done the following:

Using the instructions as per the links, and with cross-ref to the factory manual, I have removed/cleaned/rebuilt/installed the assembly back onto the engine and released the set-screw by 1/4 turn, then locked it up with the locknut. I heard the tensioner ping into place when I undid the set-screw, so I'm happy it extended out and should be pushing against the tensioner blade.
Using a 19mm socket on the crank/points end, the engine rotates smoothly by hand, with no new or undue noises, catches or knocks etc.

Going back to the big knurled wheel/spring, and being very careful with applying finger pressure only, I can now see that the knurled wheel will not rotate in either direction - it appears to be locked in position.

Is this how it should be if the tensioner is working/set correctly?

[Gorminrider]

If you mean the big knurled knob won't turn, No. there's something wrong. Properly, it can easily be turned by hand against the spring that's coiled around it.

I think you'll have to take it apart. Refer to bwringers nice take-apart page....and there's probably more at BikeCliff's Website . It's really a clever device and defies a description that isn't hard to read but once you play with it in detail, (and I think you'll have to in this case) it's easy.

[GS400B]

ok thanks - back to the drawing board!

hang on - scrub that. I was being very tentative with the hand pressure, and I have just had another go at turning the knurled knob but with slightly more pressure. This time, the knob moved in an anti-clockwise direction, and the spring pressure returned it to 'full lock'. It will not turn clockwise once the spring returns it.

[Gorminrider]

Like you Gormin, I've not noticed or read about this before. Been scratching my head trying to imagine what's happening.

I've heard of it before here on the forum with a youtube video attached but I don't remember if it was resolved in detail...I do remember trying to help so it might have been in the last year.

[GS400B]

That seems to be the problem, gents - there does not seem to be any detailed final follow-up or resolution published to the original video query, or elsewhere.

BTW, it is so very helpful to have your inputs on the problem, though, and the links do explain the procedures in great detail.

The bit that's missing is what the knurled wheel should actually be doing if all is working correctly when its back on the running bike. From reading your responses, it looks like your opinion is that the wheel should be non-moving when the engine is running, and I would totally agree with that - I've never ever seen a camchain tensioner physically moving while the bike was running, and there's scant few GS400s around here to go have a look at for a crosscheck!.

Question is, once the rebuild/installation is done, should it be possible to turn the wheel in one or both directions when the engine is switched off, and is it safe or detrimental to do so?

I think that's the part of the conundrum the OP of the video was trying to find out - the links explain the process, but if he/we know what that dang wheel should be doing, then we would be more 'comfortable' that we had rebuilt the tensioner correctly, and it was safe to start the engine.

Ahh the joys ... !.

[rphillips]

The wheel will turn one direction whether eng is running or not. If the eng is running, you turn the wheel slowly, when it goes far enough, you will start to hear the rattle from the chain getting looser and looser. That's on the larger bikes, I've not worked on a 400, but imagine it's the same.

[GS400B]

OK another quick thought - on the bike in question, would there be any risk/effect in turning crank to TDC mark and then releasing/re-locking the set-screw and locknut? Taking the set-screw right out would at least allow me to see(with the aid of a bright light) if the pushrod has rotated off the flat area, as suggested by Gorminrider.

As of right now, I have not attempted any adjustment or removal of the problem tensioner, and I am wondering if the problem lies with an incorrectly adjusted set-screw. Too far out, or not out at all?

I have also checked to see which way the knurled wheel rotates - it will only turn anti-clockwise, then the spring returns it to full lock.

[rphillips]

TDC or not, you can loosen the lock nut, screw the set screw in till it bottoms, then back out 1/4 or so, then retighten the lock nut, being sure you aren't turning the set screw while tightening the nut.