Replacing the chain tensioner

[Guest ratchethack]

. . .

Now the last example, and this I think is probably relevant to Ratch's observations of his bike's behavior, is what is happening on a light or feathering throttle. Here too is a situation where the scatter WILL be apparent. IMHO though the hesitation that he's experiencing is probably much less to do with any variance in cam timing per-se, (Although the observed scatter will prove that the timing is shifting about a bit.) but is Far more likely to be the result of instability in the signal from the 'Phonic Wheel' due to the 'floatation' of the timing due to the slack chain. This may well confuse the ECU so that it periodically says 'F@ck it! and givs up the ghost for a revolution or two until it can get it's bearings again.

. . .

Pete, thanks for the superb description and analysis (2 times, even!) . I b'lieve my observations above in this thread fit exactly here to confirm wot I've been openly observing on this Forum for years:

 

I've noticed (up front and personal) that many V11's, mine included, have exhibited an annoying tendency to erratically drop a signal -- or even two successive signals -- and then snuff out at idle as a result, as well as to cough and misfire on trailing or steady low throttle underway. Very early on, I'd suspected the signal sensor and eliminated this from consideration. Next, I'd immediately improved, but not by any means eliminated these symptoms by opening up valve clearances first to World Spec, then got more improvement yet at .006" and .008". Careful balancing of the TBs improved it more yet, and finally, installation of a PC III improved it even more again, until it was "tolerable" but not entirely absent. At this point it had improved to the point where at least it wouldn't snuff at idle at stoplights. Again -- under engine load, as you and I have both noted many times in this scenario, none of these symptoms are ever present wotsoever -- exactly wot might be expected from a wonky tensioner (as opposed to the entirely separate consideration of retarded valve timing due a worn, aka "stretched" chain!). My Guzzi has just lately been getting "worse" in this regard at 34K miles, which may also have something to do with warmer weather. I'm no subscriber to the "single magic bullet theory" here! Wotever combination of diverse Physics is at work (and who cares exactly, as long as it can be effectively dealt with?!), the "team of conspirators" seems to all be pulling in the same direction lately.

. . .

As has been observed the later model Guzzi tensioner has a pissweak little spring and IMHO it probably won't have the strength to combat the chain-flap on the over-run but I know of CAlis that have done best part of 200,000 miles without replacement of the chain or tensioner so?????????

As many people know I'm not a fan of any of the available alloy or composite gear sets available for converting to gear drive. I'm not willing to embark on another long and tiresome debate on the subject here. If you want to see how the other half thinks, if somewhat irrationally, go and have a look on the timing gear thread on Guzzi Exchange. I can't be arsed going through all that shit again!

. . .

Pete, I have no doubt that many riders could well tolerate the symptoms I'm experiencing now. But then, there are many riders who seem to tolerate lots o' things that I consider horrifically intolerable. Call me picky, persnickity, or even a perfectionist -- I don't much care, even when "sensitive types" somehow get offended by care and attention to Guzzi's evidently beyond their own comprehension, and lash out irrationally , I've been called lots worse and couldn't care less. I can't speak for others on this, but I happen to believe there's an excellent chance that at least my own riding enjoyment can be improved greatly by some additional study and maybe some focused attention to chain tension, that's all. I think of this thread as part of my "additional study", for which I thank you and Raz (for opening and continuing this thread) and Docc, and others again.

 

Unless I miss my guess, none o' this is new, and it's been as common as dirt on Guzzi's for about 4 decades now. Unless I miss my guess, Part II, some have taken it upon themselves to "remedy" the situation described here with timing gears -- and while I'm sure this solves one problem, the new ones it opens up by way of trade-off hold no attraction for Yours Truly. Nope -- don't want any part o' any consideration of timing gears, no need to go there! You're welcome.

 

The big Q's still remaining unanswered for me are:

 

1. Is it possible, without too much mechanical histrionics and cost, to improve the "scatter" that I've directly measured above by replacing and/or modifying the tensioner? I've progressed in my understanding (with your guidance and confirmation, thanks again!) to the point where I believe that if I could reduce the erratic jumps of the strobe on the flywheel of up to ~7 mm I observed to half that or less, it would make a considerable improvement on the road, and be well worth considerable effort, if necessary.

 

2. If it IS possible to achieve the above, wot's the best way to go about achieving it?

 

I have almost enough feedback now to have the timing cover off for a direct exploratory analysis of me own. With just a little more knowledge, experience, and input from our esteemed Forum (the Royal Plural, as it was described recently in the depths of the current perennial Timing Gear Brouhaha at Guzzi Exchange ), it'll put me over the edge, and I'll consider meself properly outfitted for spelunking in wot for me are heretofore unexplored recesses of the mighty Guzzi donk.

 

Can't hardly wait, Gents!

 

More dialog, por favor!

 

And gracias, in advance.

 

EDIT: I b'lieve the still unanswered Q that Raz is most interested in (not fully addressed clearly and directly unless I missed it -- if so, pls. accept my apologies) is one I now have meself:

 

Is it necessary to remove one or more sprockets in the set to replace the tensioner, and if so, wot if any special tools and/or procedures are required for a proper job??

 

I'm also very curious to learn wot Raz might discover to be the source of the noise from his timing chest, since I don't seem to have any of this at all??

[raz]

I b'lieve the still unanswered Q that Raz is most interested in (not fully addressed clearly and directly unless I missed it -- if so, pls. accept my apologies) is one I now have meself:

 

Is it necessary to remove one or more sprockets in the set to replace the tensioner, and if so, wot if any special tools and/or procedures are required for a proper job??

 

I'm also very curious to learn wot Raz might discover to be the source of the noise from his timing chest, since I don't seem to have any of this at all??

I now got the answer from a fellow Swedish Guzzisti. The bad news: there is no way you can remove the chain without removing all three sprockets (at the same time, see). And to clarify, there is no way you can replace the tensioner without taking off the chain.

 

The good news: it should be doable (not saying it's easy) without any special tools. A rattle gun is a good help for the cam sprocket, I'm not counting that as a special tool.

I'll probably try it out this weekend, and keep you posted. Thanks all of you!

[Guest ratchethack]

I now got the answer from a fellow Swedish Guzzisti. The bad news: there is no way you can remove the chain without removing all three sprockets (at the same time, see). And to clarify, there is no way you can replace the tensioner without taking off the chain.

 

The good news: it should be doable (not saying it's easy) without any special tools. A rattle gun is a good help for the cam sprocket, I'm not counting that as a special tool.

I'll probably try it out this weekend, and keep you posted. Thanks all of you!

Thanks again to YOU, Raz.

 

I sincerely b'lieve you're on to something here, my friend.

 

If you have access to a timing light, it'd be interesting to see if you get the same read as I did above.

 

It'd be even MORE interesting -- potentially even compelling! -- to see wot kind of DIFFERENCE in scatter you get before and after replacing the tensioner.

[raz]

If you have access to a timing light, it'd be interesting to see if you get the same read as I did above.

 

It'd be even MORE interesting -- potentially even compelling! -- to see wot kind of DIFFERENCE in scatter you get before and after replacing the tensioner.

Yes, I'll get a timing strobe and check scatter before and after. I'm totally convinced my reading will be at least as bad as yours. Carl's description of the sympthoms is actually the best, it stops as it is trying to change direction completely! I'm sure he meant his Sporti and not the Norge...

 

I'm going through this in my head at the moment. Looking at pictures from last winter, I can confirm the crank sprocket nut is an ordinary one, not the peg nut described in Pete's excellent Engine Strip PDF.

 

I'm looking for torque spec's right now. The "Nut, gear to camshaft" must be the cam sprocket nut, right? It's listed as 15 kgm so just below 150 Nm. The other two I can't find, neither in WHB or that Roper PDF. I have some good listings of standard torques for various threads and grades of steel, and bigger sizes than listed in the Guzzi manual so I hope I can choose something sensible unless someone here has them in his head?

 

The alternator nut is 8 kgm so just below 80 Nm.

 

This article is a bit help too (it describes installing timing gears , but the first half is right). No torque spec's there either. I'll just have to revert to feel and Loctite

 

Apparently the crank nut is 32 mm and it needs a deep socket to swallow the shaft.

[John A]

I reduced the clearance between the sensor and the cam wheel to maybe make the timing more stable,I'm sorry I don't remember how much but I remember the first time I did it I didn't have the cover off so I measured and guessed and got it a little tight because it actually rubbed.That didn't seem to hurt anything and you could see on the sensor a rub mark so when I had the cover off I set it less than the book says.I don't know if it helped or not but I think it did.The problem was I did so many things at that time it's hard to tell what did what.I've had the same tuneup now for at least 60K miles so all I do now is clutches and tires with the occasional brake pad change.Raz, I like your attitude!

[Guest ratchethack]

John, the clearance between sensor and phase sensor wheel is critical. The gap tolerance is 0.7-0.9 mm, and is shimmed up by a soft aluminum shim set (4 shims) that comes with the part.

 

SOURCE: p. I-30, Moto Guzzi S.p.A. Service Manual, Cod. 01 92 01 31

[John A]

John, the clearance between sensor and phase sensor wheel is critical. The gap tolerance is 0.7-0.9 mm, and is shimmed up by a soft aluminum shim set (4 shims) that comes with the part.

 

SOURCE: p. I-30, Moto Guzzi S.p.A. Service Manual, Cod. 01 92 01 31

Yeah I know but I reduced it with no ill effects,Took out one or two shims.I think it runs a little better.As the block heats up it expands moving the sensor farther away.I did not measure that but I did take it into consideration.I'm just saying I did it and I believe I achieved what I was trying to do.Others may not be so lucky and so should stick to the factory specifications.

[raz]

John, the clearance between sensor and phase sensor wheel is critical. The gap tolerance is 0.7-0.9 mm, and is shimmed up by a soft aluminum shim set (4 shims) that comes with the part.

 

SOURCE: p. I-30, Moto Guzzi S.p.A. Service Manual, Cod. 01 92 01 31

Interestingly enough my WHB (for a Sporti) says 0.6-1.2 mm. I'll set it to your spec's as they are subrange of mine.

[Greg Field]

Raz, I for one will be watching your project here with with keen interest.

 

I've been getting more noticeable symptoms of what I believe is a loose timing chain lately myself (33K miles).

 

Does any of this sound like wot you've been experiencing:

 

The symptoms only show up at steady, low throttle openings. As long as there's load on the motor and even a little throttle, it runs 100% perfectly. But whenever conditions that would cause a loose timing chain to jump and whip, it acts like it's picking up a mis-timed, or more often, an absent signal. <_>

 

Since the signal is taken off the camshaft, I reckon the valve timing is thrown off just enough to conspire with the dropping/mis-timing of a spark signal to cause an occasional backfire, balk, or simply dead miss.

 

When I'm in traffic, it's the worst, and it's startin' to drive me bats. If a wonky tensioner ain't it, I ain't got the first clue wot it is?!

 

Any comment -- Raz and/or Pete?

 

I would look for a subtle exhaust leak, and then at the TPS.

[Guest ratchethack]

I would look for a subtle exhaust leak, and then at the TPS.

Thanks f'er the input, Greg. My TPS is spot-on, and I rule this out with confidence.

 

I do have one relatively tiny exhaust leak at the junction of my Stucchi crossover and left-hand muffler, where exhaust finds it's way thru one o' the "clamping slots" in the muffler inlet pipe. Your comment is well taken -- but to me, this seems an unlikely contributor to my symptoms. Please advise if you disagree?

 

Any comments about the aforementioned erratic scatter I observed of up to ~7 mm on the flywheel via timing light?

 

TIA

[John A]

I went out to the shop to have a look at my notes,I had set the reluctor gap at .6mm before the trip to Doug Lofgren's dyno.It makes sense to me to set that gap at the minimum.I see from my notes that I did try it at less than .6 for a while but ended up out to .6 because of reliability concerns.

[nose2wind]

I would look for a subtle exhaust leak, and then at the TPS.

 

The Group,

 

Mike at MPH cycles in Houston has my bike. It is there for a Tranny recall and to solve the mystery of the stumble!

 

He said from the start he did not think chain tensioner is the issue.

 

He wants to go back and check basic set up etc.

 

I will keep you posted.

 

Also while in the Transmission he found a bad bearing and the clutch in bad need of replacing. My bike has 50,000+ miles. Docc I know you are not far behind and may need a clutch soon.

 

:Later

[Guest ratchethack]

I went out to the shop to have a look at my notes,I had set the reluctor gap at .6mm before the trip to Doug Lofgren's dyno.It makes sense to me to set that gap at the minimum.I see from my notes that I did try it at less than .6 for a while but ended up out to .6 because of reliability concerns.

Now this is just me, but it seems to me that generally the engineers who spec and test these kinds of parts spec ranges of adjustability that cover real-world conditions that allow for such normal considerations as variance due to expansion and contraction with heat, etc.

 

My inclination would be to go for the mid-point of the spec'd. range in this case.

 

BAA, TJM, & YMMV

[John A]

I agree but in this case I was trying to make the erratic running better when all along it was a software problem.

[raz]

 

I would look for a subtle exhaust leak, and then at the TPS.

Could a tiny exhaust leak render such sympthoms? Why?