Timing Gear Set - Replacing timing chain

[swooshdave]

Do not assume parts manuals or workshop manuals to ever be flawless. Nor have the actual updates from production. Those books are assembled well ahead of production and production specs can change.

The only way to verify a spec is to test it.

[andy york]

If its any consolation, I have 125,000 on my LeMans. Original timing chain,tensioner,oil pump, etc...etc...etc...

and it still has the 2800-3000 rpm hiccup !!!

I think I will keep her

[Lucky Phil]

7 hours ago, swooshdave said:

Do not assume parts manuals or workshop manuals to ever be flawless. Nor have the actual updates from production. Those books are assembled well ahead of production and production specs can change.

The only way to verify a spec is to test it.

Yes good points, but I have 2 manuals from different eras with the same specs and the "5" stamped on the valve housing. Also applying the rule of thumb that's been around for 100 years and still holds true of  approximately 10 psi/1000 rpm and with the high cam engines turning max rpm of 8400rpm then a 5 bar or 70psi relief valve sound about right.

Also there's no guarantee with a relief valve that the original spring hasn't sagged so measuring its crack pressure wont necessarily give you a baseline.   

Ciao

[swooshdave]

20 hours ago, Lucky Phil said:

Also there's no guarantee with a relief valve that the original spring hasn't sagged so measuring its crack pressure wont necessarily give you a baseline.   

Ciao

Oh, it's sagged. Everything sags after a while.

There are three specs; what the engineer designed, what the factory made and what you actually got. 

I'm not saying you don't try to go off the first one but just don't get into fisticuffs over it. I've seen people try to argue paint colors from a marketing brochure. That marketing brochure was probably made 6 mos before production. Nowadays they have to put something in the fine print about "subject to change". 50 years ago they didn't worry about the legalese.

[po18guy]

Way old thread, but back to timing setups. First cup of coffee musing here. HQ gears should last the life of the engine, but such gears - think transmission quality or above - would cost near the value of the bike. Straight cut gears are more efficient than helical (no thrust), but give you that "NASCAR" V8 sound. Lovely for around town, but tiring when droning along. Alloy gears? If we go back 60+ years to the Studebaker car V8s, we find a fiber cam gear! And I know of no failures driving 16 valves for 100K. Rather mild cam profiles I'll grant you, but their performance "Avanti" cam gear was helical alloy. The engineering on the Studes was such that there was crank gear directly meshing with cam gear - nothing in between and no tensioner needed.

Where does that leave us? I tend to think that racing engines (fairly frequent tear downs) need gears, while street engines need a good tensioner. Being an owner,  have prowled the Kawasaki EX500 forum for many years and cam chain tensioners were a big issue on the gen1 ('87-'93) motors. Fortunatel, the bulletproof gen2 unit swapped right on. They have the silent hy-vo chains and many of them go 100K miles if properly maintained. Says something about the chains in what was essentially a commuter/throw away bike. And this is with the lumpy 180º/540º firing interval they have.

I am of the mind that a good aftermarket tensioner will serve me well.

 Timing setup that Andy Granatelli used to go 168 MPH in a 1963 Avanti.  https://www.youtube.com/watch?v=YG8pdR6VAXw    

 

[Lucky Phil]

29 minutes ago, po18guy said:

Way old thread, but back to timing setups. First cup of coffee musing here. HQ gears should last the life of the engine, but such gears - think transmission quality or above - would cost near the value of the bike. Straight cut gears are more efficient than helical (no thrust), but give you that "NASCAR" V8 sound. Lovely for around town, but tiring when droning along. Alloy gears? If we go back 60+ years to the Studebaker car V8s, we find a fiber cam gear! And I know of no failures driving 16 valves for 100K. Rather mild cam profiles I'll grant you, but their performance "Avanti" cam gear was helical alloy. The engineering on the Studes was such that there was crank gear directly meshing with cam gear - nothing in between and no tensioner needed.

Where does that leave us? I tend to think that racing engines (fairly frequent tear downs) need gears, while street engines need a good tensioner. Being an owner,  have prowled the Kawasaki EX500 forum for many years and cam chain tensioners were a big issue on the gen1 ('87-'93) motors. Fortunatel, the bulletproof gen2 unit swapped right on. They have the silent hy-vo chains and many of them go 100K miles if properly maintained. Says something about the chains in what was essentially a commuter/throw away bike. And this is with the lumpy 180º/540º firing interval they have.

I am of the mind that a good aftermarket tensioner will serve me well.

 Timing setup that Andy Granatelli used to go 168 MPH in a 1963 Avanti.  https://www.youtube.com/watch?v=YG8pdR6VAXw    

 

No to the cost and no to the noise. My bike has Joe Caruso steel gears and neither of those comments apply.

Ciao

[po18guy]

Well, I stand corrected! Thank you. As always seems to happen, I should have specified that my experience is limited to V8 car engines.

[pete roper]

Not a fan of alloy or alloy/composite gear sets. No doubt one of the shouty brigade will be along in a minute to tell me I'm wrong.

[luhbo]

Pete, what oil pump is used with these gears? Here they sell these gears for the V11, too, but none of these sets has the pump gear small enough to be fittable with the standard v11 pump. Is it necessary to buy a Centauro pump or do they just relabel Centauro gears as V11's?

[Lucky Phil]

3 hours ago, po18guy said:

Well, I stand corrected! Thank you. As always seems to happen, I should have specified that my experience is limited to V8 car engines.

Although car/multi cylinder engines have more valve springs to drive the load on the gears is more evenly distributed and the gears generally have more real estate inside the engine which means they can also be wider. Car engines by and large also spend much of their working life at much lower rpm. My previous Chev gen111 engined car used to cruize at 1750 rpm at 110kph. The Guzzi is turning around twice those revs at the same speed. 

There are of course many other factors but I agree with Pete in that aluminium isnt a great choice for cam gears. I wouldnt have changed the chain for alloy gears.

Ciao

[Pressureangle]

Just to toss a bit more clarity into the mix;

Gears are one of the most difficult systems of mechanical engineering.
Purpose, environment, shock, expansion, duty cycle all calculate into the mix. Tooth profile, materials, loads, lubricants.
Heavily loaded gears are always steel, with heavy, high-additive lubricants. Lesser loads can be handled by lesser materials; but Aluminum is at best a poor bet in any case. High-speed gears subject to high heat demand specific lubricants; think your rear drive unit with Red Line heavy, etc.

Well your engine doesn't have Red Line heavy. Your engine has motor oil, which is *not* a very good gear lube. One solution is to use very high quality, ground-profile gear teeth that don't clash. What you hear in your straight-cut gearbox is actually each tooth bashing into the next one as the gears rotate. That's a lot of abuse. To eliminate the noise, the teeth have to be finish-ground rather than hobbed (cut) to have the correct profile and finish, and the clearance needs to be within a very specific range. Aluminum is not out of the question here, with the caveat that gears have a minimum threshold for load capacity, obviously, and metals have the very odd property of disliking mating gears with the same hardness. One gear must always be harder than the other, unless both are hard enough to have zero deflection and adequate lubrication to keep them apart. So by the time you create an aluminum gear of high enough quality and finish, and mate it to a steel gear of sufficient hardness, you may as well just go with steel anyway, which is what Joe Caruso has done. 

I would also wager that if you could watch the cam gear on our engine with a strobe light, you'd see it flopping all over in a wobble as the camshaft deflects, which leads to edge loading the gears, multiplying the problem. I wonder if Joe has a tiny bit of camber built into the teeth to prevent that edge loading. 

Pay no attention to the man behind the curtain, I'm tired and rambling.

[pete roper]

3 hours ago, luhbo said:

Pete, what oil pump is used with these gears? Here they sell these gears for the V11, too, but none of these sets has the pump gear small enough to be fittable with the standard v11 pump. Is it necessary to buy a Centauro pump or do they just relabel Centauro gears as V11's?

There are all sorts of sets, or there used to be. I've had long arguments with a lot of people who claim that one or other manufacturer's gears are good and all the rest are crap but in my experience they are all crap, untrustworthy and I wouldn't put them in my two stroke lawnmower! As far as what pump is used? Most of those sets use the stock pump with bearings and a straight shaft.

The gears used in the Hi-Cams which are also failure prone tend to shatter before they gall up and fall to pieces but this is more because the pumps don't have bearings supporting the driveshaft,the pump bodies are machined with poor tolerances and the shaft and it's attached gear flop about until the gear shatters. Engines that get a lucky good set of gears and pump seem to last a long time but Guzzi use some weird toothform that hasn't been used by anyone else since Noah was building the windlass's for the Ark! Whether that is relevant though I have no idea?

If I had an early Hi-Cam though I'd piss the gears off and go to a well tensioned chain.

Pete

 

Edited October 9, 2019 by pete roper
More info.

[po18guy]

Hmmm... let's see: air cooled cylinder, high cam, short pushrods opening valves via rockers - something about it is just so familiar. Ah yes! It seems that Giovanni Parrilla might have had the idea first. But bevel gears* (see correction - thanks Pete) and shaft was his choice of drive. Back in the day, I lusted after a 250 Wildcat scrambler.

 

 

[pete roper]

No bevel gears on Parilla. Hi-Cam design with cam driven by a gear train, one of which was a fibre gear.

[po18guy]

15 minutes ago, pete roper said:

No bevel gears on Parilla. Hi-Cam design with cam driven by a gear train, one of which was a fibre gear.

Quite right! I had just been viewing the Parilla DOHC diagram. Did the Guzzi V8 have so many gears? I must say that 11 years and 20 different chemo drugs have scrambled my egg, so to speak.