When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
In my stay at home boredom, I'm checking my valve clearances and doing some other fiddling. Wouldn't I get the best measurements with the cam lobe 180Deg from the tappet? I already have the covers and chains off for other reasons and while waiting for parts I was just thinkin'......
I do the same; my understanding is the cam consists of the base circle and the lobe; as long as you are on the base circle and not the lobe you should be measuring the clearance accurately, and pointing the lobe away from the valve does exactly that.
Any place off the cam lobe ramp is good, but best practice is center of the base circle....just do that visually, if you anyplace near 180 off the lobe top, your good
Thanks people, The next random (read boredom) question; If it will still be in spec.tolerence, is it better to go on the tight side or the loose side?
Depends. My idea of tight vs your idea of tight when checking the clearances may differ a bit. I prefer to use a "go, no-go" method of valve clearance using next size up "feely" gauge. If I can force the next size up in it's close enough for gov't work. Valves rarely loosen, mostly tighten, especially the exhaust.
I had a Ducati 851S that I raced. Ducati said, check the valves every 1500 miles. I did it every 8 race hours . Rarely had to change a shim.
Thanks people, The next random (read boredom) question; If it will still be in spec.tolerence, is it better to go on the tight side or the loose side?
The valve train of a cam above valve/ shim / follower gets tighter as parts wear... so you do not really want to be at the tight end of tolerance for a street bike.
On a Race bike you want max valve lift from you might shim to the tight end.
BUT here is reality... unless you have a large selection of OEM "1/2" size shims.. You are stuck with the more comn "whole" size shims the aftermarket sells...
And even with OEM shims if available is not uncommon to be at a point of , in spec is all you can do.
If your not very good with feeler gauges, and have a choice between at min spec, or next thinner shim but still in spec ..do that thinner shim and still inspec.
If the mileage is high, as in, well beyond initial break-in 10k+, I set to the tighter end of the spec. I do this because most of the valve stretch and seat wear has already occurred and the spec won't change much after that point, It is way better to have a tighter spec than a looser spec because you will have better valve control. If you have to choose due to limited shim selection or limited patience, go loose on the intake side and you will potentially make a bit more power. This happens because the lobe becomes, in effect, more aggressive in its ramp as a result of the lifter contacting the ramp later when more lift has begun. To be clear I'm not saying to run exhaust valves tight...that will burn a valve and it's bad. I'm saying that if you have to choose, and choose wisely, go with a looser intake valve.
That being said, use your digital caliper to measure your feeler gauge and make sure you worn out set of feeler gauges that you got from your grand daddy, or harbor freight, or snap-on, are actually what they are etched as. Do the same for the shims, .0005" here and there makes a big difference.
I generally mic all my feeler gauges prior to use. Tight vs loose; EX. Spec .31mm - tight = .30, loose = .32. My engine has 48k miles and has changed tolerance (tighter)on a couple of exhaust valves by .02- .03mm. I check them about every 10 -12k miles (because I like to and I like working on her as much as riding her). Heck I've pulled the engine 3 times just to clean it.
Last edited by CaryDG; 04-05-2020 at 10:49 PM.
Reason: additional info
Thanks for all the input. I've got her all buttoned up and the new ETL MCCT's installed. I like them as they are double O-ring sealed on the adjustment shaft and don't need a gasket as they are milled with an O-ring as well. I've had good luck with these in the past. They even include the release tool for OEM ACCT's
Here's some pics. Sorry about the focus, the camera looked but I didn't have my glasses on.LOL
Last edited by CaryDG; 04-07-2020 at 09:47 PM.
Reason: Additional info
Thanks for all the input. I've got her all buttoned up and the new ETL MCCT's installed. I like them as they are double O-ring sealed on the adjustment shaft and don't need a gasket as they are milled with an O-ring as well. I've had good luck with these in the past. They even include the release tool for OEM ACCT's
Here's some pics. Sorry about the focus, the camera looked but I didn't have my glasses on.LOL
Nice! That's a new design to me. Looks good though.
I've been using them on a couple of different bikes and really like them/ They're about $130 shipped from UK They don't need thread sealant, gaskets, Etc. and they come with the ACCT removal tool, if needed
04-02-2020, 12:10 PM
