Cam chain for 500 Lav

seagreen said:
Thanks for your comments and jests. It is my view that if we can garner enough potential demand then Regina or another may consider it commerically profitable. Until we reach the numbers - no idea what that might be - we stand very little chance. I agree that it may end up being cheaper to do as you propose, Piranha-bro2, but it is a supply and demand relationship - more chains produced = lower item cost. If the chain manufacturer is after the sort of money that competes with the crank/cam mod then it is probably a non starter and they will need to look again at their costs - and we who want/need a chain will have to consider our options.

So, what are the numbers of 500s that might potentailly require a new camchain?

Please keep your comments (constructive preferably) coming.
Adios,
Charles
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Hi Charles, if its true they are the same as the small block guzzi then why is it a manufacturing problem?
The only difference is the length of and the guzzi small block engine is still produce today in models such as the 750 breva and the new v7and 85 models.
This don't mean the new ones are the same but I an trying to find out from the guzzi folk.
Regards Andy 😁
 
a good way to seal the deal would be to have an individual pre-purchase them, or at least send a formal letter of intent through solicitors in the form of a contract, once price and delivery period have been arrived at, the trouble is there is no one who specializes in either the Breganze 500/Atlas/early Breganze 650's/668's (how many I doubt more than 10) or later Zane assembled, re-purposed (ex Breganze stock) or even scratch built built bikes as far as I know, even Mike Waugh had to go back to work after trying his Monty Dons full time for a short period, might have even been less than two years, I cant remember, he and I were never close (in reality we disliked each other) and I only owned a Monty for the two and a bit seasons that I was racing which was before he was involved and there were plenty of active dealers. The buyer of such a batch, would very likely have to wait years for it to even return his costs, which would have to be 30% of the batch, maybe 50%
 
I resurrected this thread as the issue is still an issue. So I was wondering if anybody had heard of any body finding an alternative supplier?
 
I've become aware that many car engines (notably BMW/Mini) use 8mm pitch camchains with designation G53HR/HC. Presumably this option has been investigated and rejected? What is the geometry difference between C107 and G53?
 
breganzane said:
I've become aware that many car engines (notably BMW/Mini) use 8mm pitch camchains with designation G53HR/HC. Presumably this option has been investigated and rejected? What is the geometry difference between C107 and G53?
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We've looked into this... I think, not entirely sure, the roller diametre is different.

5/16" works out to 7,9375mm, pretty close, the sprockets may even tolerate 8mm.

No cigar Steve, sorry. ;)

Talked to one of the major M-G dealers (Agostini) in Mandello last summer, timing chains for the little Vees seem to be NOS, packed and boxed long ago. I was hoping they'd have the chain in bulk lengths. Guzzi people are apparently aware that the chain will become a problem in the very near future.

piet
 
Obviously a bit more investigation is needed of chains that are close to the original size to see if, with suitable adaptations to the crankshaft and camshaft sprockets, they can be used as a substitute.
Earlier today I visited a metal printing company in Norway with my friend Rune Vangen, to ask if they could repair parts of a damaged Zane 750 crankshaft. The answer was yes. Following further discussion they also said they could also modify the sprockets to take a different size chain. Therefore, if a workable, alternative chain can be identified we may be back in business for future repairs and servicing of Breganze and Zane built bikes fitted with the 5/16 chain.
 
Easier to manufacture new sprockets (to more std dimensions so you can actually buy chain!) than manufacture new chains. Do the 500 and Zane cranks have a pressed up centre with the cam chain sprocket machined into it (a la SF/C)?
 
There's also this thread on the subject. Another 10 pages of discussion.

Future for Zane bikes?

A couple of questions to Piet and then my opinion. You said you have about 40 Zane' bikes in destroyed condition. Sounds like a lot without context but 40 of the 5000+ built is less than 1%, not a huge proportion of bikes sold as sport toys. Among those, can you guess what proportion were...
laverdaforum.com laverdaforum.com
 
piranha-bro2 said:
Easier to manufacture new sprockets (to more std dimensions so you can actually buy chain!) than manufacture new chains. Do the 500 and Zane cranks have a pressed up centre with the cam chain sprocket machined into it (a la SF/C)?
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I have a hunch there is a genuine reason that prompted Mr. Alfieri to use this specific type of chain.

One of the restraints when designing an engine is its overall physical size, especially so with motorcycle engines. Crank and cam position are laid down very early in the design phase, which in turn determines the size of the cases and covers, etc. All Laverda overhead cams are driven through a 15t-30t ratio. This allows for a "hunting tooth" to even out chain and sprocket wear, chain links and sprocket teeth constantly alter their relative positions during rotation. A 14 tooth crank would mean the cams would have a 28 tooth sprocket, the same chain links would run on the same sprocket teeth over and over, causing premature wear. Using the common 06-B type chain as in the big twins and triples is out of the question, the cam sprockets would be simply too big to fit under the cam cover with the conventional 15-30 drive. Comparing a triple cam sprocket with a 4-valve item shows the difference clearly! The 4-valve 500 is overall far more compact than the triple or 750. Even the later Zane 750, which is based on the 500, is also physically lots smaller (and lighter!) than its earlier SOHC counterpart, despite the cylinder head being drastically revised to accomodate a narrower valve angle.

If redesigning the cam drive, a chain close to the dimensions of the original C107 must be used, which leaves the G53 as the only real option. As it is widely used in auto engines, supply will be ensured for quite some time to come. If my suspicion is correct and the major difference is the roller size, it may be as simple as re-grinding the crank and cam sprockets to suit. Exact chain specifications would determine if this is a possibility, or if completely new components are required.

Many designers of the 1950s-60s used quite a number of (now) odd-ball/obsolete chain sizes. At the time the design was on paper, they were most probably very readily available.

An example to observe the advantages of a hunting tooth is the #530 19t drive sprocket of our clunkers. Over time, each tooth will show wear on the side from the chain side plates. In the case of the 16-34 tooth ratio of the #630 chain, wear will only show on every second tooth. Possibly the reason why the supposedly superior #630 chain doesn't really last any longer than a #530...

Drivetrain design is anything but simple. ;)

piet
 
As Piet says, C107 and G53 are almost the same. They're the same pitch (8mm) but there are slight differences in roller diameter and width between inner plates. There are a couple of options for replacement of the original chain with an alternative 8mm pitch chain. Here's the size comparison.

Roller diameter (mm)Width between plates (mm)Average breaking load (N)
C107 (original)4.775.7212,300
G5354.78,500
05B5312,300

Fortunately, the dimensional differences are in the right direction for removing material from the sprockets. The roller valleys in the sprockets need to be bored out slightly for the larger diameter rollers, and the sides need to be machined down for the narrower width. It's a simple re-machining job for any workshop equipped to do it (basically just milling machine and lathe). That's all it needs to convert the sprockets to G53 or 05B. These chains are readily available, so that seems the obvious way to go for the future of these bikes. No re-manufacturing of the centre crank section is required, although the crank will need to be pressed apart so the centre pin can be machined.

Before anyone raises the issue of the "weakness" of using a narrower chain, it's more likely to be an improvement than a disadvantage. There are a lot of engines that run G53 cam chains (I didn't find any examples that use the narrower 05B, but I didn't spend much time looking for them). The load is carried by the side plates and pins. Most of the load on cam chains is dynamic load at high revs when the chain links have to change direction quickly around the crank sprocket. It's the dynamic loads that can bust cam chains. The narrower chain has an advantage in that respect because it's lighter, so the dynamic loads are reduced. On the other hand, a narrower chain will have higher roller pressure for a given tensile load, which could lead to more rapid wear on sprocket teeth. But cam chains operate at a fairly low power transmission load, so that's probably not a major issue.
 
So standard sprockets slightly changed by machining and that Hunting Tooth still applies. Still the cost of a bottom-end strip as well as machining. Better than not running at all I guess.
 
Taking into account that the bikes using these chains, in general, don’t do particularly high mileages per year the wear issue isn’t probably an issue.
As I have a number of engines in various states of repair I will buy a couple of chains to experiment with.
 
Hi all,

Very interesting topic. However as I understand, adapting the cranckshaft sprocket requires opening the crankshaft! Isn’t it?
Even if we find a good chain candidate, opening a crank must be a real challenge, and re-assemble even more, probably skills only available for a very few people here (not me).

When we started this topic, while I was restoring my 500, I was very motivated of learning how to open and close a crank, I even bought a 30T press and found a few old cranks to play with.
I could not find enough documentation nor people who could teach me, then I found 3 chains, that I keep in the Bank of Spain in a safe box, and I left the crazy idea.

I have to admit that despite many people prevented me not to rebuild the cylinder head, I finally did it with an spare one and the result was great, runs smooth and good, thanks to the redax ignition also of course.

I have a couple of complete 500 spare engines, and I would be happy to participate in the project if more people do, I would finally have an excuse to use my MEGA press🤣🤣 in a real job.

I upload some photos as a tribute to this bike and the project, I have to say I love this bike, and the engine despite what many people thinks is a great engine (from my point of view)

Best regards,
Miguel

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