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Polaris 700/800 Crankshaft Upgrade Kit
While the Polaris “big block” 700 & 800 twin engines
have proven to be extremely powerful and dominant engines, a problem
with premature failure of the PTO end of the crankshaft has surfaced,
particularly on the 800 twins. The primary clutch and the PTO end
of the crankshaft can snap off, rendering the vehicle unable to
move under its own power.
What has been witnessed is the deformation of the crankcase line
bore. The amount of bearing to crankcase bonding area on the PTO
end appears to be less than perfect to be able to endure the tremendous
load and thrust of the primary clutch. The crankcase line bore and
PTO bearing mating areas can actually become warped, allowing an
increasing amount of crankshaft wobble, eventually leading to PTO
bearing and/or pin failure.
Allsport Polaris of Spokane, Washington, home of one of the largest
Polaris parts inventories in the world, has developed an upgrade
kit that greatly improves the longevity of the PTO end of the Polaris
big block engines. The kit consists of increased bearing support
area with a wider inner PTO pinned bearing and spacer, a new outer
PTO end bearing, required crankcase modifications, improved oiling
ability and a final crankshaft realignment. If the deformation to
the crankcase line bore is sufficient, replacement could be necessary.
Total cost of the kit with crankcase modifications is $295 plus
shipping. The crankshaft and crankcase must both be sent together
for the work to be done. For engines that have already suffered
a failure, the costs will be more to repair the damaged components,
so why take the chance! This kit has been developed over the past
few seasons and has all but eliminated the PTO end failures, and
is virtually a must-do step in the modification of 800 twins for
the best in long-term reliability.
The Allsport Polaris Crankshaft Upgrade Kit replaces the
stock PTO bearings (lower) with a wider inner PTO bearing (upper)
that is pinned, along with several detail changes to improve crankshaft
reliability.
If you have the engine apart for any reason, this should be done
to improve the reliability. Mountain riders who don’t want
to take the risk of going down have started to do this during the
off season as a preventative measure, but more casual riders seem
to wait until the engine is apart or being serviced and then get
it done. We’ve seen this twice in a matter of four years on
our test sleds, so it is fairly common. Polaris seems to have improved
the crankcase manufacturing since the introduction of the 800, but
it was still occurring on some stock 2004s.
This cutaway of the PTO end of a stock crankcase shows the
porosity (voids) in the aluminum that can lead to the deformation
of the crankcase line bore and crankshaft failure.
Left as is, most failures occur within 2000-3500 miles on the engine.
Allsport has found excessive crankshaft run out and out of balance
primary clutches to accelerate the failure rate, as does modifications
that increase the amount of stress to the PTO end of the crankshaft.
Even bone-stock engines can and do experience PTO end failure, thus
the need for an expertly developed fix to this growing problem.
Having this service performed as a preventative measure is highly
recommended, along with the precision balancing of the primary clutch.
Allsport recommends Kinetic Balance and Machine of Spokane, Washington
for expert clutch balancing (509-534-8722).
Even if your big block engine has experienced crankshaft PTO end
failure, or some other crank related issue such as a broken rod,
bad bearings, or something similar, don’t throw it away! Allsport
offers expert crankshaft repair and can get you back up and running
with their huge parts inventory when others can’t.
If you own a Polaris 800 twin and want to take steps to enhance
the durability of your otherwise excellent engine package, give
Allsport Polaris a call and talk to Bob at 800-359-4884 or e-mail
them at allsport@sisna.com
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