Valve Adjustment Specs

[BrianG]

If I had my 'druthers the MG cam would be driven by a cog-wheel/toothed belt in an oil-free chest like most new automotive engines, which could also house the oil pump and alternator drives.

[pete roper]

Carbon fiber is even lighter & stiffer! Unfortunately, epoxy doesn't like extended exposure to hot solvents, & you really, really wouldn't want stray bits of CF floating around the engine scoring things...

 

 

Amadeo and various other people tried using CF pushrods back in the '80's. Apart from having to set the valve lash to negative clearances they found that the CF rods were prone to 'Greenstick' type fractures which, oddly enough, tended to have a bit of a derogatory effect on race placings!

 

 

That's something that gets me every time I read it: where's the thrust washer to take up all the end forces these helical gears are putting into the cam, crank & oil pump? Yeah, o.k., so helical gears are quieter than straight spurs, but the added friction and end thrust certainly makes a simpler approach worth looking into, doesn't it? Why am I the only one thinking about this? And Pete, if you're done w/ those gears, can I have'em? I need diametral pitch measurements &etc if I'm ever going to figure out how to make some straight gears on my hobby lathe [don't worry, I won't make'em out of aluminum: that's the stupidest thing I've ever heard! These aren't sewing machines or computer plotters, they're IC engines w/ big honking pistons! It's all brass for me, at least until I get the kinks worked out... ]

 

The *important* one is the cam. that has a brass/bronze thrust face on the cam retainer. Likewise the crank has a thrust face on the back of the front main bearing. The oil pump? In theory yopu're 100% correct, but I've not seen thrust related problems on gear driven pumps with helical gears so I just assume it isn't an issue

 

Pete

[Ryland3210]

.... And Pete, if you're done w/ those gears, can I have'em? I need diametral pitch measurements &etc if I'm ever going to figure out how to make some straight gears on my hobby lathe ...

 

Careful there. If Pete's gears make lots of noise, even though they are helical, the diametral pitches are likely to be too loose. Assuming you are serious, as long as you are making your own gears, better to accurately measure your engine's shaft center to center distance, and calculate the exact pitch diameters required. A common problem on Yamaha Ventures, which use spur gears for the primary drive is excessive noise. The engine and transmission are in a combined casting, so there is no adjustment possible. It appears Yamaha solved the center to center variation by cutting the gears with enough clearance to fit all engines. Consequently, some whine more than others. Mine was on the loose side, and whined annoyingly. To their credit, Yamaha will install a driven gear with a large pitch diameter under warrantee. It helped, but again, it is a one size fits all approach which is not optimum. I've considered make up my own gears as well.

 

Cheers,

John

 

If I had my 'druthers the MG cam would be driven by a cog-wheel/toothed belt in an oil-free chest like most new automotive engines, which could also house the oil pump and alternator drives.

 

Is the V11 engine an interference engine?

 

If so, my preference is a chain. Some of the automakers have switched back to chains. Too many customers complaints about trashed pistons and head from broken timing belts and a 4 figure bill. Chains are more likely to skip a tooth when they get really worn. The effect on performance is obvious, and the engine may simply refuse to start. Replacing a chain is cheap and fast compared to a set of heads and pistons.

[quazi-moto]

I had a Ford Escort once and I must have gone through three timing belts in less than 100,000 miles. Fortunately, the valves cleared the pistons. My '68 Galaxie had a 390 and at approx. 120,000 miles the timing chain started jumping. Funny thing was it would skip a tooth, run like a dog and sometimes die, and then it would skip back to normal and run great. Needless to say I couldn't continue to drive it this way as it left me stranded more than once. I prefer chains or gears for driving the cam(s) although a belt driven primary can be a nice thing. I better shut up now because I'm straying from all things Guzzi.

[mike wilson]

Quote Ryland

"Careful there. If Pete's gears make lots of noise, even though they are helical, the diametral pitches are likely to be too loose. Assuming you are serious, as long as you are making your own gears, better to accurately measure your engine's shaft center to center distance, and calculate the exact pitch diameters required. A common problem on Yamaha Ventures, which use spur gears for the primary drive is excessive noise. The engine and transmission are in a combined casting, so there is no adjustment possible. It appears Yamaha solved the center to center variation by cutting the gears with enough clearance to fit all engines. Consequently, some whine more than others. Mine was on the loose side, and whined annoyingly. To their credit, Yamaha will install a driven gear with a large pitch diameter under warrantee. It helped, but again, it is a one size fits all approach which is not optimum. I've considered make up my own gears as well."

 

Whereas MZ, a properly innovative company instead of merely copycats like Yamaha [8-))] provided primary gears of slightly different diameters so that play could be properly measured and minimised. This on a poxy little go-to-work machine. No wonder communism went bust.