Timing Chain Tensioner

[Ganzo]

I recently needed to remove my timing chain cover to reseal it due to an oil leak. I had done this with a past Guzzi (SPII) and it was easy. My 2003 V11 Rosso Corse has 17K miles on it which is low, but I thought I would take a look at the chain tensioner issue while I was in there. I ordered all the replacement seals and an after market chain tensioner just in case I decided to use them. The following is what I learned:

1. The side stand has to come off so I put the bike on my lift.

2. The alternater rotor is on a straight shaft not on a tappered shaft like my SPII was. I was all prepared with the puller.

3. The frame on a 2003 V11 is a buger! It has additional bracing near the top of the casing which gets in your way. I can deal with that, but the voltage regulator mount is welded to the frame and is definately in your way. I had to bend it up to get the neccessary clearance to remove the cover. It's a real shoe horn fit! Next time I will grind it off and make my own bracket.

4. This was taking me longer than I wanted so I didn't want to do it again anytime soon. I was having no problems with the timing chain tensioner, but it was worn some (17K). (see picture) I estimated that it had maybe 40K max life left. The sprockets and chain were in great shape. There was very little slack in the chain. I decided to replace the chain tensioner.

5. I took a look at the after market tensioner that I purchased from Moto International and thought that it was flimsy. The friction surface is very thin, mayby 3/32". I don't know it's manufacture. (see picture) Maybe someone can help me with this. I decided that I could make a better product than the original and the after maket item. Now the project time just doubled to two weeks.

6. I'm a fairly busy person and don't sit still much so I had no time to research all this stuff. Maybe some of you can fill in the holes.

7. I decided to use polycorbinate for my material. It was the toughest stuff I could get my hands on. I did a quick test in the oven at 350. I cooked the original and polycarbinate part in oil and found both to hold up great. At 350 both were still hard to bend and file. I know this is not very scientific. I'm not sure what material the original on is made from.

8. The only significant difference between the original and home made part is material and area of friction surface. It's the friction surface area that I though was lacking on the original. (see picture)

9. Now to increase the surface area I had to increase the length and shape of the arm. I planned to reuse the original tensioning spring. It's a good design. But now that the arm is longer mechanical advantage is lost. I can increase the spring tension with the original spring so I decided to add a spring. (see picture)

10. Everything works like a champ. I have only 300 miles on the mod so I can't recommend it to anyone.

 

There's nothing like making a simple project hard.

Enjoy,

Gonzo

[Ganzo]

Attached are 2 more pictures that wouldn't fit on the first/original post.

 

Gonzo

[Guest ratchethack]

OUTSTANDING, Kurt. Nice job. I've been wondering for years on this board why someone hasn't done something like this. I agree, it just seems to be pretty obvious that something like this would be better than the stock setup (where the weak spring seems to be completely useless)?! Unless there's something going on here that yet remains to be seen?!

 

Coupla observations and a Q or 2:

 

Don't know what kind of polycarbonate you used, but Ridout Plastics here in San Diego carries Dupont Delrin, commonly used for rubbing blocks on chain guides, tensioners, and swingarm pads on moto's. The stuff has formidable properties of abrasion resistance and lubricity, and is well proven long-term in internal engine applications, so it can take the heat and petrochem environment. I've purchased the stuff in small block sizes for various moto projects and have had great results long-term. If you notice relatively rapid wear on the one you fabbed-up, you might consider trying it. Here's Dupont's link: http://plastics.dupont.com/myplastics/Mediator?id=30

 

As was suggested to me (I think it was Docc?) when replacing my tensioner, you can test the effectiveness of the tensioner with a timing light on the flywheel to look for signal scatter -- the tendency of the point on the flywheel that the strobe picks up to "wander" about, an indicator that the tensioner is allowing the chain to "whip" at the only critical section of the chain, that being the few links between the crank sprocket and cam sprocket. You have to find or make your own reference point on the flywheel, because there are no marks on it for timing. Prior to installing my new tensioner (same one you got from the same source), I was getting intermittent scatter up to 6-7 mm in one direction from a relatively steady point at idle on the flywheel. Not good. The scatter would disappear at 3K RPM and under any kind of acceleration, suggesting that higher RPMs eliminate variances in angular velocity, smoothing out sources of chain whip. I haven't tested the new tensioner with the timing light yet, but it runs perfectly, and seems to lack the occasional dropped signal at idle I'd been experiencing with the stock tensioner. It'd be interesting to get a read on yours.

 

I can't quite make out the detail in your photo, but it looks to me like you've put an adjuster through the timing chaincase? This seemed most logical to me also when I (briefly) considered making up my own, and why it wasn't done at the factory remains a bit of a challenging question -- at least for Yours Truly?? Unless it presents an oil leakage problem, and you haven't indicated that, so I reckon it's not a concern? How does this work? Do you have a locknut or stack of washers under the head of the adjuster on the outside to adjust it, or is it simply acting as a keeper for the spring you added?

 

FWIW, here's a shot of the same aftermarket tensioner you purchased from MI as installed on mine.

 

And the stock tensioner for comparison.

[dlaing]

FWIW, here's a shot of the same aftermarket tensioner you purchased from MI as installed on mine.

 

And the stock tensioner for comparison.

Dang that tensioner stretches out!

I suppose Valtek knows what they are doing, but I trust Ganzo's design more!!!

True it is more work to drill and tap a hole, but only a few minutes more work.

[callison]

Dang that tensioner stretches out!

I suppose Valtek knows what they are doing, but I trust Ganzo's design more!!!

True it is more work to drill and tap a hole, but only a few minutes more work.

 

 

The pressure surface of the Valtek is quite a bit longer than stock so I wouldn't expect it to wear quickly. How long is an unknown. Since it flexes, it can adapt to the chain position to avoid a high contact area. The polycarbonate one won't do that but as Gonzo says, the results aren't in yet. To me, it looks like viable alternative. Ideally I suppose, the stock chain tensioner would have enough tension to allow starting the engine but have the pressure adjusted by a pneumatic cylinder fed by engine oil pressure. Like that's ever going to happen. <_>

[Ganzo]

You're right, the bolt's only purpose is to keep the spring in place. The engine casing is drilled and taped. The bolt is lock tighted and sealed. There are no leaks. The spring provides the additional tension needed for the longer arm. There is no way to adjust the tension from the outside of the motor. The spring that I used was cut to a length that I felt suitable for proper tension. I know it's not very scientific, but I wanted to get back on the road.

 

Gonzo

[Guest frankdugo]

gonzo,you can,t say you did not have a good time.

[pete roper]

Ideally I suppose, the stock chain tensioner would have enough tension to allow starting the engine but have the pressure adjusted by a pneumatic cylinder fed by engine oil pressure. Like that's ever going to happen. <_>

 

Well, not for the old motor but its exactly what has been done with the chains on the 8V.

 

I've been using Valtek tensioners since the dawn of time. The commonest problem with them is that the spring snaps and Ive heard of one instance of the blade snapping but generally they are a long lived thing. Once the chain has worn out though you'll find that the blade of the tensioner hardens with use and it may well snap if you try to re-use it. I treat them as a 'One Use' item and replace them with the chain, lets face it they're dirt cheap!

 

Pete