Pushrod position
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Cruiser
Joined: May 2017
Posts: 162
Likes: 32
From: Linton, IN
Pushrod position
So I’m assembling the rockers after changing tensioner shoes.
I have followed the book step by step. Verified cams were in alignment, then installed driver gears with dots in alignment.
Sitting with pushrods and pushrod covers installed, ready to install the rocker supports and arms.
Starting with rear cyclinder? I rotate the back tire to find TDC, watching the pushrods poking through the top of the rocker box bottom....
It looks like there is a point on BOTH cylinders where the pushrods are at bottom of their movement.
I KNOW I’ve done everything correctly up to this point, but I wanted to make sure this sounded correct.
I soaked rhe lifters in new oil prior to installation. So then need to bleed down?
You install the rocker arms and supports with cylinder at TDC, in compression stroke. What should the other cylinders pushrods look like at that point?
I wish i coukd find some sort of animation that shows BOTH cylinders pistons and valve or pushrod operation so I could better understand how the parts on both cylinder move in relationship to each other.
Can anyone provide an insight? I’m probably my just being paranoid but I want to make sure when I fire up the bike I can ride it.
Thanks.
I have followed the book step by step. Verified cams were in alignment, then installed driver gears with dots in alignment.
Sitting with pushrods and pushrod covers installed, ready to install the rocker supports and arms.
Starting with rear cyclinder? I rotate the back tire to find TDC, watching the pushrods poking through the top of the rocker box bottom....
It looks like there is a point on BOTH cylinders where the pushrods are at bottom of their movement.
I KNOW I’ve done everything correctly up to this point, but I wanted to make sure this sounded correct.
I soaked rhe lifters in new oil prior to installation. So then need to bleed down?
You install the rocker arms and supports with cylinder at TDC, in compression stroke. What should the other cylinders pushrods look like at that point?
I wish i coukd find some sort of animation that shows BOTH cylinders pistons and valve or pushrod operation so I could better understand how the parts on both cylinder move in relationship to each other.
Can anyone provide an insight? I’m probably my just being paranoid but I want to make sure when I fire up the bike I can ride it.
Thanks.
Seasoned HDF Member
Joined: Mar 2012
Posts: 100,455
Likes: 19,811
From: Centennial, CO
Don't worry about the front cylinder yet. When you get done with assembling the rear completely and wait for bleed down so you can spin both p-rods easily, rotate the wheel so that the front cylinder p-rods get to the same position, neither moving at the same time and then assemble the top end on that one.
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Joined: Jul 2015
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From: SF Bay area
Concentrate on one cylinder at a time.
The pushrods on the cylinder you're working on should both be all the way down & NOT moving as you turn the engine over. There is a point in the rotation that one pushrod will be all the way down while one is starting to go up... this IS NOT the correct spot to install the support plate. Both need to be all the way down & not moving. Spin the engine over few times & you'll see what I'm talking about.
__________________________________________________ ____
For ROCKOUT information & purchasing please click HERE For all Twin Cams and Evo Big Twins & Sportsters
The pushrods on the cylinder you're working on should both be all the way down & NOT moving as you turn the engine over. There is a point in the rotation that one pushrod will be all the way down while one is starting to go up... this IS NOT the correct spot to install the support plate. Both need to be all the way down & not moving. Spin the engine over few times & you'll see what I'm talking about.
__________________________________________________ ____
For ROCKOUT information & purchasing please click HERE For all Twin Cams and Evo Big Twins & Sportsters
__________________
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Ordering & info http://www.rockout.biz On ebay! ... CLICK HERE
Also on amazon.com...
Imitated, never equaled... ROCKOUTS!
Thread Starter
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Cruiser
Joined: May 2017
Posts: 162
Likes: 32
From: Linton, IN
Just to clarify.... I’m not trying to assemble both cylinders at once. I just had noticed that it looked like there was a spot where both cylinders had closed valves, or pushrods all the way down. Was curious to see if this was correct, or if something is off....
and pkease clarify avout bleeding down...
are you you saying that when I start on the rear to go ahead and install support plate at TDC, with final torque and breather, cover ect, THEN wait for bleed down before I go to rotate engine tondonthe front cylinder?
please give detail regarding bleed down. What it is, why we do it, ect.
Thsnks.
and pkease clarify avout bleeding down...
are you you saying that when I start on the rear to go ahead and install support plate at TDC, with final torque and breather, cover ect, THEN wait for bleed down before I go to rotate engine tondonthe front cylinder?
please give detail regarding bleed down. What it is, why we do it, ect.
Thsnks.
Seasoned HDF Member
Joined: Apr 2015
Posts: 10,060
Likes: 5,316
Just to clarify.... I’m not trying to assemble both cylinders at once. I just had noticed that it looked like there was a spot where both cylinders had closed valves, or pushrods all the way down. Was curious to see if this was correct, or if something is off....
and pkease clarify avout bleeding down...
are you you saying that when I start on the rear to go ahead and install support plate at TDC, with final torque and breather, cover ect, THEN wait for bleed down before I go to rotate engine tondonthe front cylinder?
please give detail regarding bleed down. What it is, why we do it, ect.
Thsnks.
and pkease clarify avout bleeding down...
are you you saying that when I start on the rear to go ahead and install support plate at TDC, with final torque and breather, cover ect, THEN wait for bleed down before I go to rotate engine tondonthe front cylinder?
please give detail regarding bleed down. What it is, why we do it, ect.
Thsnks.
Club Member
Joined: Sep 2010
Posts: 1,690
Likes: 457
A pumped up lifter has a layer of oil inside of it. When the cam pushes the lifter, there is a “cushion” of oil between the roller of the lifter and the plunger that pushes on the pushrod. To my knowledge, this makes for a quieter valve train and the layer of oil can become a little thicker or thinner as the cylinders heat up or cool down. The cylinders will expand and contract very slightly, making them taller and shorter, again very slightly.
When you put your valve train back together, the proper pushrod length pushes down on the lifter from the valve spring tension, to position the plunger inside the lifter at about half stroke. If the lifter is full of oil, the plunger inside of it cannot push down to this halfway point so instead the valve opens a little. If left sitting for a time, could be 10 minutes, could be a half hour, the lifter will bleed down and the valve will close as the lifter should be on the base circle of the cam for assembling the valve train.
Once a lifter bleeds down, it can easily be spun with your fingers. If it’s not bled down, you can’t spin it because of the tension placed on it by the valve spring. This is why, even with non adjustable pushrods, you should leave the pushrod covers collapsed until the end so you can make sure the lifters on one cylinder are bled down.
Before the lifters bleed down, the valves will be slightly open with the cams on their base circles. If you rotate the engine at this point, the valves will be open farther than they should be when the cams are at the peak of their lift. This could cause a couple things to happen that end in damaged and bent valves. The valves could contact the top of the cylinder, or the valves could contact each other.
When you put your valve train back together, the proper pushrod length pushes down on the lifter from the valve spring tension, to position the plunger inside the lifter at about half stroke. If the lifter is full of oil, the plunger inside of it cannot push down to this halfway point so instead the valve opens a little. If left sitting for a time, could be 10 minutes, could be a half hour, the lifter will bleed down and the valve will close as the lifter should be on the base circle of the cam for assembling the valve train.
Once a lifter bleeds down, it can easily be spun with your fingers. If it’s not bled down, you can’t spin it because of the tension placed on it by the valve spring. This is why, even with non adjustable pushrods, you should leave the pushrod covers collapsed until the end so you can make sure the lifters on one cylinder are bled down.
Before the lifters bleed down, the valves will be slightly open with the cams on their base circles. If you rotate the engine at this point, the valves will be open farther than they should be when the cams are at the peak of their lift. This could cause a couple things to happen that end in damaged and bent valves. The valves could contact the top of the cylinder, or the valves could contact each other.
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HDF Community Team
Joined: Nov 2012
Posts: 6,189
Likes: 2,419
From: USA
Just to clarify.... I’m not trying to assemble both cylinders at once. I just had noticed that it looked like there was a spot where both cylinders had closed valves, or pushrods all the way down. Was curious to see if this was correct, or if something is off....
There are two times the piston is at the top. Once is in between the compression and power stroke. The valves are both closed. The other time is in between the exhaust and intake stroke. Both valves are open, though not fully.
You can use the likes of a wooden dowel in the spark plug hole to help you see when the piston is up. Just use a little care ax the dowel will need a little jiggling from you owing to the angle and the threads in the spark plug hole.
Bleeding down the lifters is important for the proper torquing of the rocker shaft bolts. You need the valve train slack in order to properly torque the rocker shaft bolts down properly.
You let the engine sit with the valves open, slowly bleeding out oil from the tappets (top of the exhaust/intake cycle), squishing them down.Then when you rotate the engine one full spin you’ll be at the top of the compression/power cycle, and everything will be slack. Then you can properly torque the top end bolts.
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