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MP RacingSerious about speed.  The connotations of that statement imply a great degree of enthusiasm, dedication, knowledge, and experience.  Each of those factors can be found within MP Racing in Salem Oregon.  Serious about speed is MP Racing’s motto.  They believe that each engine they do is a representation of them, and therefore must run hard and do such for a long time.  However, MP Racing takes it a step further and on most weekends can be found out riding in the dunes.  Testing and improving upon existing designs as well as creating new and exciting creations.  Those very test rides and thoughts have lead MP Racing to their newest line of engines.

Profile of Polanda EngineTheir new engine, whose nickname is now The Polonda, has emerged and proven to be a potent engine indeed.  Team Source met up with the MP Racing Team for a great weekend of riding at the Oregon Dunes National Recreation Area in Florence Oregon.  Our objective; test ride the new Polonda engine.  Polonda?  Well, the name halfway gives it away.  A Honda ATC/TRX250R is the donor engine.  MP Racing skillfully crafts a Polaris Scrambler 400 cylinder to fit upon the 250R bottom end.  Current displacement ranges from 389cc’s to the latest generation of Polondas at an astounding 440cc’s.  No replacement for displacement is indeed true.

The actual conversion itself is rather simple when compared to other hybrid engines.  In most true hybrid engines, case welding and repositioning of case bolts and studs is required which does not allow for retro-fitting the stock 250R cylinder back on the bottom end.  In the case of the Polonda this is not required.  The majority of the work to allow the fit up of the Polaris cylinder is done to the cylinder itself.

Dave Moore, owner of MP Racing, explained in great detail to Team Source what all was involved in creating this hybrid.  A straightforward procession of steps involving welding, machining, and ultimately porting and head configuration alterations.  The engine is completely disassembled, and with any big bore cylinder, the case halves are machined larger to accept the larger sleeve to slide down into the cases.  With that complete, Dave then begins to work over the cylinder altering it to what he has found to be the best configuration.  The cylinder water outlets are re-positioned and welded to better accommodate the 250R cooling system.  The cylinder itself is built up and welded around the stud holes and exhaust port for much greater strength.  Additionally a spacer plate is fitted to the cylinder to get the port opening heights corrected.  The 389cc variant utilize the stock Polaris piston at 83mm’s, whereas the 440cc variant that has been built uses a Yamaha YZ490 piston at 89mm’s.  Currently Dave is researching using the new Aaen piston which is 91mm’s, which would take the displacement out to 490cc’s on the stock stroke!

The next steps in creating a Polonda are considered normal in any high output modifications.  The porting arrangement is skillfully re-worked to suit the power delivery needs of the customer.  Additionally the head configuration is re-worked as well.  Dave recommends running 100+ octane fuel due to the larger bore size.  In our conversation he did say that it could be ran on pump gas, but for the best in performance and reliability, higher octane fuel is preferred.

With the greater displacement of the Polonda, a tuned pipe that can handle the greater exhaust gas volume is required as well.  Dave through many test rides has found that there are 2 commonly available pipes that work best with the Polonda.  The ESR TRX5 Centermount works extremely well for all around power, where the ultimate in top-end power is needed, for instance a greater proportion of drag racing, then the FTZ fat in-frame drag pipe is used.

The intake side is handled by an MP Racing worked over Mikuni TM 39mm carburetor coupled with a Moto Tassarini V-Force reed cage.  The advantage of the Mikuni TM carburetor is that with some additional modification the carburetor can run both gasoline and methanol.  Once converted to run alcohol, unlike Keihin carburetors, the Mikuni TM can be easily swapped between the two fuel types.  The V-force reed cage is as designed for the Scrambler cylinder.  No re-work of the intake is required.  The intake angle and direction is handled via a custom intake plate and boot.  MP Racing also offers nitrous systems for the Polonda(or any engine that you wish) as well.  The intake system is simple and efficient; again designed, tested, and perfected by MP Racing.

The Polonda utilizes the stock stroke of 72mm’s.  Dave has found that a modified YZ250 rod is stronger for increased strength and longer service life.  Dave is currently in development with a newly designed and custom-machined rod that far surpasses any rod available to ensure the ultimate in crank and rod life.  This ensures that the higher output generated does not reduce the reliability or increase the maintenance required.

The MP Racing Team had arrived in the campground the evening before and we all had the chance to sit around and chat quite a bit about everything.  However, as most that have ridden the ODNRA know, the weather can and does change for the worse, and often.  Saturday morning arrived under grey skies but no rain.  Lets go!!!  We all get geared up to ride as a few light sprinkles begin to fall and as we rode out the rain really started to come down.  We had hoped that it was a passing squall.  We got out to the flat and I watched as Dave and several other guys lined up for a quick drag race or two.  Dave and another member of the MP Racing Team touched wheels about 40 ft out and Dave wound up taking a hard digger over the bars.  Living up to his moniker of Krazy Dave, he chose to ignore the fact that he likely had broken a couple of ribs in the crash.  Dave gingerly stood around and regained his breath.

The rain wouldn’t subside and with Dave all sandy from his crash we headed back to camp to get dried out and let Dave clean up some.  Later that afternoon the skies cleared some and the rain stopped.  Capitalizing on the break we headed out again to the flats.

Gang Green RHS ProfileThe first generation Polonda that MP Racing did was for their good friend Jason Maisel.  His bike is named Gang Green for it’s very bright green paint job. This would be the one we were going to review.  I had Jason line up and race some other of the MP quads and make several passes for me and I noted how easily the front end would lift even with a 10 inch over swingarm - View Mpeg Video (size 125 kbytes).   After Jason had made several good passes, I took over the controls and lined up to drag race a couple times myself.  I was surprised at how potent the engine really was.  It launched out off of the line extremely hard, and as Jason had demonstrated getting the front end light with such a long swingarm was still easy.  The weight transfer was excellent, the rear squatted, the front end got a little light, and it rocketed off.

I was very impressed with how well this engine pulled.  Not only did it have that great large displacement torque to moving well; it had excellent hi-rpm’s too.  The contention that some people hold is that bigger bore engines will not rev out as nearly as high as a smaller displacement engine.  In the case of the Polonda engine this is not the case.  It revved up and out very well.  In this MPEG video watch the comparison in shift point between the hi-revving Banshee on the left, and myself on Gang Green on the right.  This really is an excellent real world comparison - View Mpeg Video (size 125 kbytes).

Not everyone drag races all the time, so to see how the Polonda would ride for a dune rider oriented engine I headed off towards the trails and small hills to rip around a bit.  I was very surprised to see how well the engine performed.  The power delivery was consistent and smooth.  While at times the corner would come up faster than I had expected –BRAKES!!!  I found that riding it in the tight trails was equally as impressive.

A true testament to Dave’s testing and development- an engine that could do very well drag racing, and then cruise off to go play ride in the dunes.  It would not be a stretch to say that this engine could be suited for just about any type of riding.

Jason later demonstrated the hillclimbing ability of the Polonda engine.  He lined up deep down in an hillclimb on the edge of the dunes and showed how well it could climb.  Here Jason rips it up pretty hard coming out - View Mpeg Video (size 240 kbytes).

Overall, Team Source found the Polonda to be a truly great engine.  A hybrid engine, whose cost is on par with all the other big bore engines, yet having the capability to go straight from drag racing to trail riding.  The amount of modification required to the engine is an asset to the Polonda as well.  The engine can be retro-fitted with the stock 250R cylinder if you chose to, whereas with other hybrid engines that is not the case, it’s a one way deal.  This engine is easily above the performance levels achievable with a Pro-X engine set-up.  The Polonda we rode was only 389cc’s; Dave has built a 440cc, with plans for even larger displacement engines sure to come.  Our test rides and the dyno graphs both support that notion.  The engine is potent, but very rider friendly as well.

MP Racing can build these engines for all applications and years of experience and many hours of testing and developing the Polonda becomes apparent with how strong these engines run.

[This company is no longer in business]
MP Racing
1550 4th Street   
Salem, Oregon  97303
Phone: 503.361.7666

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