Valve lash on aftermarket cams

[renobruce]

The info I have on my Andrews cams says to set the lash between .004-.006 inches, which converts to approx. .10 - .15 mm. Why such a large gap? You would think that with higher lift cams you would want to set the clearances tight so as to help eliminate the possibility of spitting a shim. Unless someone can tell me why I shouldn't, I'm going to set them at the factory .03-.08mm gaps. They are Andrews 2S cams, .390 lift.

Any input, my fellow GS gurus?

[Steve]

Has anyone bothered to measure the height of the lip around the bucket in which the shim resides?

I haven't, either, but I'll bet it's a LOT more than 0.15mm.

I don't have experience with "high-performance" cams, either, but it might have something to do with the way the base circle of the cam starts going into the lift ramp that determines how much clearance you need. If you run your clearances too small, it will start riding up the ramp sooner. If the base circle starts growing before the ramp, the valve might open too soon, then close too late on the closing ramp. This might enhance breathing a bit, but it also minimizes heat transfer time when the valve is closed.

Just a couple things to ponder.

.

[Nessism]

I'd do what Andrews says. All the aftermarket 8V cams spec more clearance than stock so I'd just go with it.

[salty_monk]

I don't know about bikes but on 4 cyl cars I've worked on Lash has always increased with a performance cam...

Dan

[BadBillyB]

Hey Bruce, When a shim gets "spit out", it always happens at just past max lift when the valve "floats". Good springs and proper seat pressure are what prevent this. The rule of thumb is anything over .400" lift requires shim under buckets. So basically you are right at the threshold. A quality rev-limiter would be good. The valve lash has a large effect on the duration of the cam (opening and closing) so stick with the figures from Andrews. You could lose some mid-range and bottom end power by running them tighter......Billy

[salty_monk]

Dyna 2000 has a rev limiter that you can set built in....

Dan

[renobruce]

Hey Bruce, When a shim gets "spit out", it always happens at just past max lift when the valve "floats". Good springs and proper seat pressure are what prevent this. The rule of thumb is anything over .400" lift requires shim under buckets. So basically you are right at the threshold. A quality rev-limiter would be good. The valve lash has a large effect on the duration of the cam (opening and closing) so stick with the figures from Andrews. You could lose some mid-range and bottom end power by running them tighter......Billy

I'll be using heavy-duty springs from WebCams, and I have a Dyna 2000 with rev limiter.

Thanks for all your repsonses. I'll go with what Andrews says.

[Dan Ruddock]

What clearance to run depends on the design of the clearance ramps(first .010" of lift). I have spent a lot of time with dial indicators following the profile of air cooled cams. The first .010" is soaked up very slowly to keep things quiet and once it is past that things speed up quickly.

I use valve clearance as a tuning tool. I like setting it up as loose as I can without the noise which is the most efficient. Don't worry about spitting a shim that is caused by over revving it or weak springs and not by loose valve clearances. Dan

[renobruce]

What clearance to run depends on the design of the clearance ramps(first .010" of lift). I have spent a lot of time with dial indicators following the profile of air cooled cams. The first .010" is soaked up very slowly to keep things quiet and once it is past that things speed up quickly.

I use valve clearance as a tuning tool. I like setting it up as loose as I can without the noise which is the most efficient. Don't worry about spitting a shim that is caused by over revving it or weak springs and not by loose valve clearances. Dan

So how much lash are you setting yours at? Should I go with .004, .005, or .006?

[Dan Ruddock]

Not knowing what the ramps are like on the andrews .004 is a good starting point. If they are still quiet at .004 try .006 which will slightly help the low end torque. I am running .004 on my 151i webcams with a small amount of noise just the way I like it. Dan

[bellucci]

My motor was set up with Andrews cams. I uploaded the build instructions that came with my bike. If you look under historical documents in the search feature, you will see what he recomended... granted mine is a 16v, but his setttings were 003-004 on intake and 004-005 on exhaust. This was in a 1327 cc that made 180 hp on the dyno... very sharp builder.
Curt

[BadBillyB]

Hey Bruce....I would shoot for .005" and settle for a loose .004" or a tight .006"......A perfect valve adjust would require grinding the valve stems. Funny, I have actually done that, but I have a valve grinding machine in my garage......Anyway, I was thinking back when I had some large cams in my motor (.455/.425 lift) the things that I had run into making them fit. I know your cams have less lift, but some things should just be checked. My cams were ground on the stock factory base circle and would not turn freely in the cam saddles. They hit the top of the lifter bores. No problem, just grind a slight relief notch for them to clear....Second problem was the cam boss for the sprocket was rubbing on the side of the tunnel for the cam chain. No problem, I ground the cam down in this area to where it no longer was rubbing. Got to realize these performance cams were only made for a year or two as the GS1100 was now in the limelight. Parts were never perfected because of this. The last issue I had was the lobes were actually striking the valve cover in numerous places. A die grinder and a few hours later this was overcome........ Just wanted to share....Good luck on the build....Brings back some great memories for me .......Billy

[renobruce]

Thanks for the advice, Billy. I don't see any interference at the buckets, she turns over nice and smooth. I'll check for any problems regarding the valve cover. Everything is installed..just need to adjust the clearances and do the degreeing.

Thanks again, everyone. Here's some pics. Sorry she's a bit dusty!

[Nessism]

Just like me to come in with a comment after the valve cover is on...but shouldn't those cam sprocket bolts have a hardened washer under them?

[renobruce]

Just like me to come in with a comment after the valve cover is on...but shouldn't those cam sprocket bolts have a hardened washer under them?

The cover is just resting on top to keep unwanted stuff out of there. I have some new bolts/washers for them. I'll install them when I do the degreeing.