1987 Yamaha SRV 540
Crankshaft gear removal / installation
Removal of the power take off end's interference fit gear. This
gear runs the oil pump and tachometer. It needs to be heated so
that it expands and allows easy removal and installation. About
1/4" away from the gear is a rubber & metal seal. We didn't
care to protect the seal during gear removal as it was going to be
replaced - but upon installation we did care to protect it.
Here is a short video of the gear removal. Tri-finger gear puller
is attached to the gear with a resonable amount of pressure
exerted. The gear is heated and when it's hot enough it expands
and readily slips (notice the gear puller dropping near the end of the
video). We heated the gear only once during removal - but perhaps
could have reheated it as during the pull off it was starting to cool
and contract making the pull off difficult. The rubber seal was
destroyed. I did not have much concern for the ball bearings
behind the seal as they did not receive direct heating (the metal
backing of the seal deflected most of it - but they did get warm).
WMV, 480 KB, 22 sec
We had fun here - a Rube Goldberg
In the end - most of it was discarded and we just made it happen.
The goal was to 1) have even heating of the gear and to 2) quickly get
the hot, expanded gear onto the crankshaft before it would cool.
We did not want to exert force on the crankshaft by pressing it
on. We also did not want to damage the new rubber seal from the
heat in this process.
So we needed a device to rotate the gear at an even pace. In comes
the cordless hand drill (with a zip tie to hold the trigger at a set
speed - easier said than done). Now we need to support the
process so that the gear is sitting, roughly, over the end of the
crankshaft - to quickly drop it on and perhaps give it a quick tap to
make sure it's seated (rests against a shoulder) - in comes some string
from the ceiling to hold the drill. Now we need to fasten the
gear to the drill but not too close as a torch will be aimed at it -
sacrifice a metal hanger to make an extension hook. We also need
to hold onto the gear - perferably so that it'll still slip onto the
crankshaft - so we need to hold onto it externally - more hanger
wire. Now, would the hanger wire, when the gear is to be heated,
overheat and melt away dropping the gear, or worse become fused to the
gear (fortunately neither of these was an issue). Heating torch
needs to be fastened and pointed to the gear (that "even heating"
desire plus that would leave my hands free) - in comes the foot ladder,
a couple 2x4's and some trusty duc tape. Now, one item not
mentioned was a small 2 inch lenght of string between the drill's chuck
and the first metal extension hook. Its purpose was to provide a
flexible coupling between the "stationary" drill and the moving
items. The goal was so that the moving items would always be
hanging straight down without any influence by a not perfectly aligned
drivetrain. The string in this project proved some weaknesses -
but before that - how about proteting the seal from heat?
The gear sits about 1/4" inch from the seal. With the motor
sitting on end the seal was a bit of a cup. We filled it with
water in hopes that any heat near the center where the gear is would be
dissipated. On top of that we placed a barrier - fiberboard soaked
in water. This might have been overkill but it was quick and easy
and I certainly would not want to have to pull the motor apart and
re-do the process due to a damaged seal.
Now, what about that string... First, the string suspending the drill -
there was perhaps 3 to 4 feet of it between the drill and the
ceiling. When the drill was activated that amount of string
started to spin - either to counteract the drill's torque or to simply
"unwind" under the weight of the drill. With the drill
spinning it would wobble. The suspended gear would thus
really wobble. The quick fix was to pull the shop press over and
fasten the drill to it (more duc tape) to keep it stationary - now
things are looking up. Drill moving, gear moving - but not quite
moving in a nice circle but perhaps good enough (out of balance??
It's low speed but that string from the chuck is quite flexible).
Let's turn on the torch. Now life gets way out of whack.
The force of the flame blows the gear away. Watching it oscillate
for 30 seconds or so and it's evident that the gear typically swings
back at the same point each revolution - heating really only one spot
on the gear. Trials to manually influence the extension hook to
be steady made life worse. This isn't going anywhere. What
to do - replace the short chunk of string at the chuck and go solid
metal? Nope - scrap most of it and go manual.
We removed the torch from the stationary setup and left the drill
turned off - I'll hold the torch and heat the gear manually. Dad
held the extension hook stationary to keep the gear from being pushed
about by the flame's force. When the gear was showing a dull red
Dad pulled the hanger from the extension hook and dropped the gear onto
the crankshaft - one could hear a solid click as it rested against the
shoulder. He pulled the hanger wire off of the gear and I tapped
down onto the gear with a section of pipe - the gear was already fully
seated. Wait for the gear to cool and then remove the fiber board
and water (which were warm). Project done.
Drill suspended from the ceiling via string.
Showing the connection to the shop press to keep it stationary.
Suspended gear with the fixed torch
Fiberboards soaked with water
(they were sliced in half so that they could be pulled out from the
side with the gear installed)
Well, down here I should
have a picture of the installed gear....