X-Mozilla-Keys:
Anderson Ed wrote:
Hi Paul and folks,
Just getting back to my e mail and saw a couple of posts about
overhauling a 13B.
Between selling and buying houses and getting ready for the move, time
has been at a premium. However, I did find the time to put my 13B back
together.
I thought I would relay my experience having just completed a first time
overhaul of a 13B. I had a leak between the rear rotor chamber and the
coolant system that required a tear down. I found that the rear rotor
housing had apparently "shrunk" due to overheating in the early stages
of my engine testing.
Using Bruce T's 13B overhaul video and the Haynes RX-7 repair
manual, I
am happy to say that my initial hesitation to tear into the 13B was ill
founded. I order new rear rotor housing, new apex seals and springs,
side seals etc., for the rear rotor (the one that had overheated) left
the front rotor seals alone as they all measured near new specs. I also
got the high performance inner coolant "O" rings from Hayes and Bruce T
provide a high volume Turbo II oil pump as well as two eccentric shaft
oil jets to replace the ball and spring stock ones. I also took some
"Steel" manifold epoxy putty and contoured the aux intake ports of
the end housings (turns out they had no contouring and in effect present
the airflow with a dead end subway tunnel in which the air in effect had
to back up from the end to get into the combustion chamber). I also
contoured my 90 degree sharp corners of my homemade intake manifold with
the same putty. I hoped that contouring those two 90 deg bends from
sharp to smooth that it would promote airflow. I convinced it has bound
to have helped.
The tear down was simple once you remove the flywheel nut and
tension
bolts, it comes apart like a stack of pan cakes. It is important to keep
track of the 66 plus parts for each rotor so you can put them back
exactly where they came from. I had the Mazda rotary parts box which
enables you to keep the parts for each apex and side seal segregated.
Also, I strongly recommend you uniquly identify the rotors and their
apex sides. I used the metal alpha/numeric stamps to identify each apex
and rotor apex side.
Getting the eccentric shaft lifted upward in order to get the
intermediate (center housing) off without a helper was a little
awkward. I ended up raising the eccentric shaft approx 1 " and placing
a wood block under it to hold it there until I had the intermediate
housing off.
Reassembly it involved using liberal amounts of petroleum jelly
(Vaseline) to hold the side seals in place on the rotors. Rubber band
around the rotor to hold the apex seal parts in place (without the apex
springs installed) and Hylomar? sealant to hold the coolant "O" rings
in place. I did use Crazy glue to glue the triangular part of the apex
seal to the top apex seal and recommend it. The triangular part should
always be to the flywheel side of each rotor.
The Hayes coolant "O" rings are considerably stiffer than the
stock ones and tend to hold their round shape, so coating the "O" ring
grooves in the side housings with hylomar is needed to keep them in
their channels while reassembling. Once you place the front rotor on the
front housing meshing its gear teeth with the front stationary gear is
critical. Close is not good enough, you have to put it on exactly the
right tooth to tooth alignment. This is not too tough because if you
try rotating the rotor and if any apex end crosses the coolant "O" ring
boundary, you know its not positioned correctly. So had to reposition
the rotor a couple of times until I got it correct.
One little difficulty is when you order the gasket kit from
Mazdatrix
it comes with a number of "O" rings of various sizes and they are all
black in color in one bag. Some are not used unless you are rebuilding
the engine
for an automobile, but trying to guess which ones are the dowel pin "O"
rings (for example) was done by simply seeing which ones seem to fill
the recesses for the "O" rings in the rotor housing the best. And then
identifying that little $&#@* "O" ring that seals the oil galley between
the front cover and front rotor housing was interesting- but more on
that later.
I suggest that when you take off the smaller old "O" rings lay them
aside and identify them so you can compare them with the new "O" rings
and more likely pick the correct ones out of the bag. Now if you order
such things separately, then I assume they will come each in its own
identifying plastic package, but Mazdatrix they all come together in one
bag.
I took off the Ross PSRU and replaced the rear seal(it had a minor leak)
and set it aside.
Be certain and mark the three legs of the flex plate (the one with the
four heavy duty springs) relative to their position on the flywheel.
Also note that the concave side of the flywheel faces outward toward the
PSRU. Also note, that when you go to put the flex plate back on the
flywheel, I suggest you stick the spline end of the drive shaft into the
spine socket of the flex wheel and make certain it sets down into the
socket (approx half of the length of the splines on the drive shaft will
be down in the socket)
and then tighten the bolts that holds the flex plate to the flywheel.
Or else you will find, as I did, that without this alignment procedure
the flex plate spline socket may be off set enough to keep the end of
the drive shaft from setting into the hollow end of the eccentric shaft
(pivot bearing hole) and will bind and keep the PSRU from touching the
rear housing by approx 1".
You also really need some dental probes to get at the small
springs and other pieces of the rotors. Be very careful about losing
small parts as some will pop out. Also little parts like the key for
the oil pump shaft and gear are verrrry small and hard to find on a
hangar floor. Don't forget to get the two rotors assembled as much as
possible before you start putting it together as you will need to put
sealant on the legs (oil pan side) of the rotor housing and side
housings and want to assembly the entire engine housings before the
sealant sets.
If you are working by yourself, I strongly recommend a air
torque wrench as it makes getting the flywheel nut and front eccentric
shaft bolt off a piece of cake.
Also, when reassembly, I had a 150 ft/lb torque
wrench but the flywheel nut calls for 300+ ft/lbs of torque. Bruce T.
explained about how to torque the flywheel nut to 150 ft/lb (the max for
most common torque wrenches) and then to get the required 300+ ft/lbs
needed to turn the nut another sixty (60) degrees with the air torque
wrench. 60 degrees is getting one vertex of the nut to rotate to the
position where the previous vertex had been. I just marked the
reference vertex on the nut and marked on the block the next vertex
position CW to the reference vertex and then when the air wrench had
moved the reference vertex of the nut to the mark on the block I had my
300+ ft/lbs. Thanks Bruce.
Well, once I had it back together I decided to manually turn
over the engine to see what kind of compression I would get. Those of
you who have seen Bruce's video will recognize his procedure of counting
the
number of "Whomps" as the apex seals go past the exhaust port to see if
the apex seals are sealing. Well, I manually cranked the eccentric
shaft and while the front housing was "Whoamping" the rear (New housing)
was NOT. What was the problem???? Was I going to have to tear the
engine down again to find out the problem?? Well, it was late and I was
tired so I am not too embarrassed to admit that once I realized the new
housing did not have spark plugs in place whereas the front housing did
that problem turned out not to be a problem. Whew!
It took me approx 3 hours to put the engine back together. It
took me another hour to hang the PSRU (see above about PSRU) and
another hour to get the engine positioned back on the motor mount. I
hooked up the oil lines and starter wiring wanting to make certain I had
oil pressure before I hooked up everything else (another 3 hours of
work). Well, gents, I
remove a spark plug from each chamber and cranked that sucker with two
25AH batteries keeping a close eye on the oil pressure. I was somewhat
concerned about the effect that the two eccentric oil jets and the new
higher volume turbo II oil pump would have. Well, I cranked and cranked
and that oil pressure gauge move not one PSI. I checked the connections
to the gauge, I pour oil down the oil outlet on the front cover trying
to "prime" the pump, but nothing - not one PSI on the gauge. So I then
unscrewed one of the oil fittings to see if oil was really pumping and
if perhaps there was some problem with the oil pressure sensor of
gauge. Nope - not one drop of oil flowed.
Well nothing to do, but take the engine back off the aircraft
while
wondering if I installed the oil jets incorrectly, or perhaps the oil
pump or oil pickup. So I hung the engine from the host and took off the
front cover and there on the bottom was that $%#*& 0.20 cent "O" ring
that was suppose to seal the front cover and front housing. It had
apparently become dislodged when I had replaced the front cover. Well,
I took off the the distributor drive gear in order to make certain that
the thrust bearings had not slipped down and being clamped by the thrust
spacer. Rechecked the oil pump chain (which I had replaced), put the
"O" ring back into position sticking it there with some Halyomar sealant
and watching from the oil pan side of the engine as I slipped the front
cover back on and watched with a flash light as the front cover boss
compressed that *&%#$ "O" ring and tightened down the front cover bolts.
I walked around the front of the engine (PSRU end) and about dropped in
my tracks - did I mention I was tired and it had been a long hot day-
there was the distributor drive gear laying in the cup I had placed it.
SOOOOOooooo, off comes the oil pan, water pump and front cover AGAIN!
This time I managed to get it all back together with no left over
parts. But, before I installed in back on the motor mount. I connected
the starter and cranked it over while the engine was hanging from the
host and got oil flowing out of the oil exit hole. I then rehung the
engine on the motor mount, connected the pressure gauge, and cranked it
over. I got 26 psi at cranking rpm so felt at least it was on the right
track.
Spend another three hours hooking up manifolds, radiators, hoses,
wiring, etc. and went home for the night. Did not try to fire it up as I
was afraid if I had another problem I might light a match to the whole
thing.
Hauled the aircraft out of the hangar the next morning and started it up
holding my breath hoping not to see it trailing smoke or coolant/oil
leaking.
Well, no problems on that account. However, I could not get the engine
to run over 2000 rpm as over that rpm I got a lean surge condition with
the engine revving up to 2500 rpm and dying back to 1800 rpm. However,
this was not necessarily bad as it indicated (I believe) that my
contouring of the intake ports and manifold was resulting in more
airflow at those rpms than my injector timing was set for. So next day
I brought out my laptop and reset the injector timing for approx 10%
more fuel flow and the lean condition disappeared. I did notice that
even thought it the OAT was 98F that the oil temp did not climb above
150F. This may be as a result of the greater oil flow to the rotors
with the eccentric shaft oil jets (webers) and the higher volume oil
pump. Of course, will have to wait until the first flight to see how it
really pans out.
So I need to break in the engine with another hour of ground time and
find a cooler day to take it flying - hopefully this coming weekend.
But, thanks to all the helpful suggestions from many on the list the
overhaul went well and is not to be feared. Total cost of overhaul
parts including new gasket set, new rear rotor housing and new apex and
side seals for the rear rotor came to $950.
So, I am back on the list for the rest of this week and then will
be shutting down for approx 2-3 weeks. After this Friday, you should
next hear from me from my North Carolina address once I get an e mail
account set up from there. Hope my account shows that the 13B overhaul
is not to be feared, just respected {:>}
Ed Anderson
Vienna, VA
Very comprehensive report Ed. Thanks. Glad to hear everything
is now working fine.
Not to worry. The list is shutting down around tommorrow until
after Oskosh so hold those cards and letters folks. Get your questions
in in the next 24 hours or so as I am heading out all over the place :-)
Off in all directions? :-)
Paul Lamar
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