There are several places that can cause top end ticks on the Twin Cam, EVO, and Sportster Motor. These motors share the same Rocker arm, shaft and same basic design of the rocker arm plate.
The main cause of top end noise it the rotation of the rocker arm shaft hitting the bolt, this is because of the gap between the bolt and the shaft, this problem is fixed with the installation of Rocker Lockers.
Another problem with the rocker arm assembly is the excessive end play of the rocker arm between the towers.
(The Factory calls for .003 to .013)
We commonly see gaps of .015 cold
Due to the differences in the coefficient of thermal expansion between the two different metals steel and aluminum the gap grows about .004 changing from 32 degrees to 350 degrees and you can frequently see gaps of .019.
Shimming the rocker arm endplay was a common thing in the past, but has lost favor due to the lack of improvement, simply because most ticks were caused by the rocker arm shaft hitting the bolt and no one knew this.
This end play tick can still be a factor in SOME bikes.
If you have seen the video of the end play cutter.
In this video we were using our endplay cutter that was in its experimental stage, since then we have found a better way to cut the end play by using a stationary sanding station. Instead of cutting the towers we take the excess off of the rocker arm itself. The measurement are the same as in the video, so is the fitment.
Before we remove the rocker arm assembly we want to check end play with a feeler gauge, check it on the non-load side at the bottom (this is where the clearance it tightest.)
From Zippers, on a twin cam non load is, left side on intake, right side on exhaust), this is the side where the cutting is done and the shims are installed.
If you look at the push rods on a twin cam motor you can see that it has two cams, also that the lifters are side by side on that cam.
Since the rocker arms are in line with each other in the rocker arm assembly this puts the push rods at an angle, this angle puts a side load on the rocker arms. The exhaust (in the rear) is leaning in; this pushes the rocker arm in. The intake is leaning out, this pushes the rocker arm.
So you want to check the end play on the non-thrust side, where the gap is. This also determines where the shims go. You do not want the shims on the thrust/wear side; you want the shims to be shims not act as bearings.
It’s also important to measure the end play at the bottom not the top. Every rocker arm that I have checked the rocker arm was tighter at the bottom or slightly longer on both ends on the bottom.
It is also important to mark the plate front and rear; once the shims are installed they need to be replaced on the same head. It is also important to mark the plate because the shim location is different on the front head and rear head (load side of the rocker arm changes the shim location front head to rear.)
Due to the coefficient of thermal expansion between the aluminum and steel parts, being that aluminum expands more than steel the endplay actually expands with heat. If you put it in the freezer the gap shrinks. This is where we get our minimum, clearance of .003, cold starts.
Pull your rocker arm shaft out if it has Rocker Lockers installed; simply tap them out with a punch from the bottom.
Our new target gap is .020+.003. Subtract your gap from .023 and we have the amount needed to be removed from the rocker arm.
You should consider what side of the arm you want to remove the excess, check your alignment of the rocker arm foot on the valve stem, and decide if you want to move the arm one side or the other.
Measure the rocker arm and subtract the amount to be removed and we get the new length to be measured periodically as we cut.
When using the sanding station, you do not want to use too course of a sand paper, we want to sneak up on the fit as we cut, when we get within .02 of the final length we want to check our clearance with the rocker arm and shaft in place with the feeler gauge. To take it down the last couple of thousands use the fine paper. It is better to err on the loose side instead of being too tight.
I like to start out with 220, finish with 330, but check your work frequently to get a feel for your cutting speed.
On the sanding station it is important to align your shaft so that the material is taken off evenly using the factory edge as a guide. The factory edge is not perpendicular to the shaft, but longer on the bottom than the top on all the shafts that I have checked.
I adjust the table for the right angle, and then use a scrap piece of aluminum to align the shaft.
After cutting make sure your parts are clean, don’t hesitate to wash them in the sink with soap and water and well lubed before installing your Rocker Lockers and installing them on the bike. After installation on the bike, recheck your endplay to make sure torqueing the plate did not change the gap.
Last place that you want to check is see if the push rods are rubbing the push rod tubes, especially with the use of thicker adjustable push rods.
A lot of times with rubbing tubes you can grab the tubes with your fingers and push them back to feel the rubbing. Another way is by looking down the tubes from the top and using something like a straw cut in half as a feeler gauge to see if there is clearance.
In the majority of the time we have found that with the installation of Rocker Lockers that center the plate better rubbing of the tubes is not a problem.
We have seen instances of where the lower rocker housing was not centered on the head and can cause the push rods to rub. When installing this plate it should be centered on the head, and might need to be realigned if you see a problem. We have seen customers use the rocker lockers as a guide on the bolts then removing them before torquing the housing down.
For final assembley remember to use your manual for final installation.
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