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800 Etec cylinder cut to show thin areas when bored to 880 bore size
After Years of developing the Rotax 800R to a Big Bore with over 800 872 builds on the snow we have submitted the following facts and findings!
News - Check out our new 872 piston just released in Febuary 2014 on above heading (New 872 Piston) for more information.
The largest bore size the cast 800R & Etec cylinder can be bored to and make the most power and remain durable is our 872 bore size. We started with a prototype 890 size piston and even tried to offset bore the cylinder to accept this size and also the 880 size product with our durability testing on our SuperFlow 901 Dyno, (And we were not easy on it, )believe me! Many problems became apparent with those piston sizes in the Rotax 800R monblock cylinder! We have come up with our 872 Bore Size to be the best product available for horsepower and durability by far and that is what we produce and provide to our customers today and in the future to come!
Note: We no longer build and have not for over 6 years build the 860 style BB. The cast pistons do and will fail due to thin skirt design and always ruin the cylinder and most of the time take the crancase and crankshaft also!!
This is a well know fact some try to hide with this application.
We bore our cylinders in house and have overbored the cylinder to see what it is capable of and have found the following, With the 880 bore size the cylinder walls are paper thin in certain areas, Lower intake transfer areas are lost to bore size and cause performance loss and piston skirt support which leads to early piston failure, Rear intake transfer port is too thin to support piston and ring pressures causing failure in that area.
Welding O-ring area at cylinder head sealing surface causes many problems, These cast cylinders are heat treated by Rotax and when welded it removes temper from that area causing soft bolt holes and major cylinder bore size distortion which leads to bolt hole failure, causes cyl head bolts to loosen, coolant leakage at sealing surface. In the 880 bore size after running for a short period of time we have used a Sunnen Bore Gauge and see major distortion in the cylinder wall areas which cause performance loss and early piston failures. Sound familiar to anyone?
We only use Cast pistons in all our Rotax engines developed in house- race and trail and Big Bores. FORGED pistons cause many problems in two-cycle high performance engines, Cylinder wall to piston clearances have to be greatly increased due to expansion of forged products which cause performance loss and major cylinder and piston wear. Ring locator pins fail due to major expansion and contraction of forged materials. Forged pistons do not hold lubricating oil as well as cast style pistons, We have seen many of these failed forged piston -cylinder projects to establish our facts.
Note-not one major snowmobile engine manufacture uses forged pistons for there 2-cycle engines! This is not for cost reasons, This comes from years of R&D by there engine development teams. The forged piston issue is a well know fact with the high performance ski doo engines of today, Only reason some use forged is for there easy availability and lack of knowledge of the above facts, Forged pistons also make great ashtrays, you see a lot of them serving that purpose!
Our respected Canadian engine builders have all basically abandoned the 880 bore size Big Bores for the same reasons that we have established with the above facts!!
We continue to replace the 880 big bores for the customers that have the inherent problems with that product, replacing with our proven 872 for an increase in performance and the reliability which our product line offers, We also update the 860 Bore size to our 872 depending on extent of porting previously done, (some porting we can not correct) Call for pricing on these specific applications,
Our 872 BB Rotax Engine Kit Specs
All Machine work is done in house. Cyl boring, Porting, Dome designs and ratio development, Development and durability testing done on in house SuperFlow dyno. We never stop working with porting and other changes to make our product the best available.
We have in stock over 1000 872 pistons at this time and always will have them available for rebuilds and 10 plus years in the future!!
Cylinder bores are torque plate (cylinder head simulated) diamond honed to prep for small amount of distortion by cyl head bolt installation.
We have at this time 30 plus Specific dome ratios available for the 872 (custom requests available) Race inspired porting designs, Some areas of our cylinder porting are being done by CNC equipment.
We have been building this great package for 7 plus years now with many very satisfied customers. Also our race versions have dominated the Hillcross, Hilldrags across the midwest to Eastern circuits, Jackson Hole RMSHA event Open Improved class was won by Tom Roby in 2011,2014 just to mention a few.
800 ETEC BIG BORE FACTS
We have many of these failed Forged Wossner pistons to establish our facts on piston types and designs as we will never install a forged piston in any engine that leaves our Rotax Engine design facility! We get the calls daily on the failures caused by these Wossner inferior line of forged pistons. Wiseco's are the worst forged piston line ever offered for the Rotax engine!
*Not one OEM installs FORGED PISTONS in there 2 cycle engines.
*Interesting how some claim they are the best?
A few of our customer Big Bores in progress!