78 Lift and Duration Specs From Down Under

[Orange4]

For anyone with extreme patience contemplating higher revs and lower valve train inertia I give you drilled bucket cam followers:



This was apparently done on the MV Agusta 500 triple racing engines. (Teardown documented in Classic Bike Magazine Sept 2013)

[IanDMacDonald]

Followed procedure to the T. They are not out. I put them out accidentally while I was monkeying with it before the cam was bolted down so I know how far they look when out by a tooth. ACCT is installed too.

Okay, one more question: following the install to the T as you said, when you installed the cams, did you manually align the dots with the wrench on each cam? And if so, is the alignment of the cam boss dots in the pic the current alignment after the wrenching?

[Orange4]

Didn't need to wrench because only helper springs are installed and only two valves. They have been rotated several times by the crankshaft and now very accurately to TDC using a dial indicator.

[DGXSER]

Just taking a stab in the almost dark have you checked your not off a tooth on the crank? One tooth on the crank is roughly half the distance of one tooth on the cams.

[IanDMacDonald]

Didn't need to wrench because only helper springs are installed and only two valves. They have been rotated several times by the crankshaft and now very accurately to TDC using a dial indicator.

Keep in-mind that I am the novice to this bike, so absolutely no disrespect is intended, but . . . is my point clear about wrenching on the cams to manually align the cams? I'm talking about once your timing wheel shows TDC, and your cams still show the cam boss dots are off a little, you may stick a (17mm?) open-end wrench on the cam and rotate it slightly to align the dots prior to tightening down the cam caps, etc. This corrects the alignment after you hand-rotate the engine.

If you already knew this, forgive me for looking too far into your words.

[IanDMacDonald]

Oh . . . the chain is off, and only Cyl # 1 has torpedoes in the tube. Gotcha, lol. Well, I guess I'm out of my league at this point with an answer. I never messed with clearances when the head was off.

[DGXSER]

Ian, what I understand is that he only put a couple valves back in, and has the head mounted to the cylinders with no gasket underneath it. So the spacing of the gasket will change the timing slightly. Valves or no valves the dots should still align though. As is typical of four stroke engines, the crank turns twice for every one rotation of the cams. So one tooth off on the crankshaft will move the cams half as much as one tooth off on the cams.

[Orange4]

Just for fun... let's try some crank sprocket misalignment . If nothing less we will have a comparison of what each sprocket misalignment looks like.

I'm also sure I'm aligned because I measured the valve to piston clearance and it's roughly equal between them. If I was off a sprocket on either end there would be an uneven distribution.

P.S. My head gasket is in but my cylinder base gasket is out.

[Dan Hodges]

A Hole In Your Bucket

For anyone with extreme patience contemplating higher revs and lower valve train inertia I give you drilled bucket cam followers:



This was apparently done on the MV Agusta 500 triple racing engines. (Teardown documented in Classic Bike Magazine Sept 2013)

You certainly have an eye for detail my friend because this little trick lightens the valve train by an amount similiar to that typically seen when using titanium retainers from Kibble-White and the weight reduction from drilled buckets is free.

[Orange4]

Hole in my head too.

Can't tell if that's a compliment or...

You know that saying "we aren't building pianos here"? Well when you say that to me I reply: What? We aren't? because I literally come from a family of piano builders so we tend to be a bit on the persnickety side when it comes to detail. And hey, We are talking about Yamahas after all.

[Dan Hodges]

Piano Man

Can't tell if that's a compliment or...

You know that saying "we aren't building pianos here"? Well when you say that to me I reply: What? We aren't? because I literally come from a family of piano builders so we tend to be a bit on the persnickety side when it comes to detail. And hey, We are talking about Yamahas after all.

I don't know diddly about Piano's other than I like to listen to the sound they make depending on whose tickling the Ivory and so consquently I was complimenting you on your mechanical aptitude not your ability to portray yourself as another Van Cliburn or Billy Joel caught in a New York state of mind.

[Orange4]

No Billy Joel from me, I promise.