I guess we'll just have to
find something to keep the guys down in JIMS R&D occupied. When most
folks would rest on their accomplishments JIMS just keeps breaking new
ground, and this time it's a 95 inch barrel kit for twin-cams. This kit
contains barrels, pistons, rings and gaskets, everything you need. The
cylinders are made of aerospace quality 356-T6 aluminum, with high-grade
cast iron sleeves. The pistons are made by Arias to JIMS exacting standards,
and use a compression ratio of 10:1. JIMS tells us you can expect your
horsepower to increase to between 85 to a 100. The kits are available in
either black or plain aluminum finish.
We met up with Tom, at JIMS brand new R&D
facility, and he managed to pull himself away from the hectic development
pace long enough to go through this unbelievably easy install with us.
As with just about any engine modification,
the seat and exhaust comes off first, (Photo 1) and, for safety's sake,
disconnect the negative battery cable from the battery.
Once the fuel line to the carb is disconnected
and the tank bolts removed, the tank can be raised, and a block of wood
placed in the tank well to hold it out of the way. This can be done with
the crossover still attached, if you're careful. Be sure to use a small
bungee cord to stabilize the tank (Photo 2).
The carb comes off next, remove the cables
(Photo 3) and set the carb aside.
Unbolt the manifold retainers and carefully
remove the connector to the MAP sensor (Photo 4) before removing the manifold.
Now it's time to get down to business.
Tom recommends marking the rocker boxes (Photo 5) because, even though
they're interchangeable, it's best to re-install them on the heads they've
The rocker covers are now removed, and
we're ready to pull off the rocker arms. Always pull the breather bolts
out first (Photo 6), this is VERY important.
These bolts extend into the heads, and,
if taken out last, will strip the bolt holes in the heads. The rocker stand
bolts are now removed, along with the rocker assembly, and we're left with
the lower rocker boxes (Photo 7).
Pop the rest of the lower box bolts and
the head bolts are exposed (Photo 8). The four head bolts on each head
come out and the heads can be laid on the bench.
You're now ready to pull off the old cylinders,
but you've got to watch out for anything falling into the case. In order
to keep foreign material out of the case, ease the cylinders up, part way,
and stuff a couple of shop towels around each rod (Photo 9).
Once that's done, go ahead and pull the
cylinders the rest of the way off (Photo 10).
The old pistons can now be removed. The
pistons use full floating pins and, once the snap rings are taken out (Photo
JIMS pin tool can slide them right out
The new Arias pistons can now be installed
on the rods (Photo 13).
Making sure not to slam the new pistons
against the head studs, install the piston rings (Photo 14).
New o-rings are included with JIMS kit
and are installed now (Photo 15).
Place the new base gaskets on the new cylinders
(Photo 16) and then the new cylinder o-rings (Photo 17).
We used a Snap-On detachable ring compressor
to get the slugs into the cylinders (Photo 18). With both cylinders in
place, it's time to get the heads back on.
With the heads in place, lightly coat the
case bolts and bottom face of the cylinder head bolts with clean 20W50
oil. Start the head bolts onto the studs, short bolts on the left side,
long bolts on the right. Tighten the four cylinder bolts with the left
side rear first, then the left side front, next the right side rear, then
the right side front to 7-9 foot pounds. Following the same sequence tighten
each to 12-14 foot-pounds. Finally tighten each bolt, in the same sequence,
90 degrees (Photo 20).
The rocker boxes go on now. Replace the
gaskets and set the lower box on and tighten the bolts (Photo 7) in a cross
pattern, starting with the right front first.
Be sure to use a small dab of medium strength
Locktite on the bolts first. Tighten the bolts to 10-14 foot-pounds. The
push rods and tubes are now put in place and the rockers are installed
and torqued down using the Snap-On wrench shown (Photo 21).
Make sure to replace the o-rings before
the shaft assembly in put in place. The rocker arm shaft assembly bolts
are tightened, a quarter turn at a time, using a cross pattern, until they
are at 15-18 foot pounds, The breather bolts are tightened, also to 15-18
foot pounds. The rest of the rocker boxes can now be installed, remember
the front and rear (Photo 22) and the bolts tightened in a cross pattern,
starting with the middle bolts and torqued to 9-12 foot-pounds.
Put the push rod tubes in place, replace
the manifold and carb and spiff up your work, as we see Tom doing here
(Photo 23) and you're done.
You've now got 95 inches of serious v-twin
power (Photo 24).
Now it's time to take this puppy out and
thrash it around a little.