More Horsepower for the “Fat Rod”

By Joseph “Joey D.” DiGiovanni, www.UTVUnderground.com

In January of 2009 I begin a complete overhaul of my 2006 Yamaha Rhino 660.  Together with Magnum Off Road and other UTVUnderground.com members and sponsors I cut the car down to the bare bones and built a complete 1 off 5 seat chopped and dropped UTV. After months of laboring over the car we finally had our sites set on Glamis Dunes for Halloween as our official virgin run on the new build.  Photo shoots were scheduled and with the Dune Tour in full swing I was really looking forward to showing the car off to all of the UTV community in attendance.  Unfortunately fate had other plans.  On the first day of the Halloween trip my original stock 660cc motor took a crap on me.  I essentially drove that motor into the ground while trying to make it to a friends camp about 1/2 hr into my first ride of the trip.  Apparently the motor got way to hot due to clogged spark arrestors causing an extremely volatile situation inside my motor and because of my unwillingness to want to shut off the oh so good tunes pumping out of my Rugged Radios head sets I couldn’t hear the marbles that were being tossed around in my motor.  The ride ended quickly with a poof of smoke from the intake after I was reduced to about 20mph.  As you could imagine I was super bummed! This was the first trip for the “Fat Rod”; it wasn’t supposed to end this way!!!

So while sitting about 1/4mile from Gecko Road, oil dripping from my PBS breather onto the sand and waiting for my rescue vehicle I called Jason Weller of Weller Racing in Chandler, AZ.  He and I had already agreed to build my motor but we weren’t going to do it until closer to Thanksgiving.  I told Jason what happened and asked what my chances were of getting a motor sooner and possibly that weekend?   He called me back within minutes just as I was towed to the Bakersfield Rhino Motorsports trailer for further evaluation.  Jason told me he had a motor he could build me that day and bring out to Glamis with him that weekend.  It was then up to me to get the motor swapped in which I had never done.  Thankfully the boys at Bakersfield Rhino Motorsports were ready and willing to help out and had the skills and tools to get this done.

So on the morning of Halloween my freshly built Weller 720cc Stroker Motor was delivered to me in Glamis by Jason and Corry Weller.  Talk about awesome customer service!  Jason brought with him the motor full of 10w – 40 oil and ready to drop in.  He also brought me a K&N Intake and some bottles of Engine Ice just in case I needed either one.  I had to make the call to “Bronco” Dan Kelly for a new clutch and without question he got me dialed in with a brand new Bronco Dry Clutch out in Glamis!   After about 6hrs of work my old 660 was out and my new 720 stroker motor was in and by that evening we were trick or treating with the kids and riding to the hill for an evening of fun.  Weller Racing with the help of BRM and Bronco saved my weekend and doubled my horsepower all in one shot!!!

Fast forward one month and Thanksgiving 2009 had arrived.  We were heading to Ocotillo Wells for this trip which is my favorite riding area due to the high speed and rugged terrain.  For 4 days I ripped the Fat Rod around flawlessly but due to me using a slightly modified stock carburetor the motor really wasn’t able to live up to its full potential.  Although it was noticeably more powerful on the bottom end I could tell I was really restricting it.  But at the same time I was just thrilled to be out riding with friends and family in my new car with no problems.  The Fat Rod was all I had dreamed of it being!

Upon returning home I had one goal and that was to now get that motor dialed in with a new carburetor.   One call to Jason at Weller Racing and he had me lined up with a Mikuni HSR45 jetted and tuned for my motor with my intake and Muzzys exhaust set up.  The carb came in the mail with a brand new throttle cable and I got right to work.  It took me about 1.5hrs to pull my stock carb and put this new one on having never done it before.  Now having done it I think I could perform this swap in about 1/2hr, even for a motor illiterate guy like me this was no heavy task.  Once it was put on the car I called Jason and Jeff Weller for advice on setting the accelerator pump and dialing in the A/F adjustment.  They held my hand and walked me through the process step by step.  After a quick run up and down the street I was ready to roll!

Now it was time for the New Years trip to Ocotillo Wells and I was PUMPED!  Just feeling how the car drove down my street I couldn’t wait to tear the desert up.  The car was now in tip top shape performance wise and I couldn’t wait to flex the motors power on all the other UTV’s in our group.  Once camp was set up I couldn’t wait to drive.  I got loaded up and went off to do a little riding and testing around camp and with a huge cloud of dust I slid off into the Ocotillo Wells desert terrain.  After cruising around our camp area (not within 100ft of camps of course) I decided to test the suspension a bit and fired off into a large whoop section.  As I blasted through the whoops all of a sudden a loud and strange vibration came from inside the motor……NOT AGAIN!

What was weird here is the motor would run and it had full compression unlike when my 660 went, but this awful clanking sound was not very pleasing.  So again while being towed back to my camp which thankfully was only about 200 yards away I call Jason.  I tell him you’re not going to believe this but I think I blew the motor up.  After some discussion he feels confident the motor isn’t blown but is definitely broken.  He states that I will need to get the motor to him for repair and tells me if I am willing to drive to AZ to his shop he will do what he can to get me back in the desert for the rest of New Years.  So after a little bit of thought I borrowed a flat bed trailer from UTVUnderground.com member Rusty5150 and off I went to Weller Racing in Chandler, AZ at 5am on New Years Eve.

Upon arriving I discovered another So Cal friend and UTVUnderground.com member Gary “MotoGary” Thompson who was there picking up his new Weller SR1 Race Rhino.  Once his car was complete (parking lot burnouts and all) and on the trailer Jeff Weller dove strait into my car and within about 1/2hr he had my motor out and on the bench.  First off was the head which appeared fine and was a good sign.  Next off was the cylinder which immediately showed our source of failure.  The cylinder sleeve skirt had cracked and broken off.  Not only was it a freak part failure but it was a first for Weller.  It is easy to try and or want to point fingers when something like a motor breaks but at the end of the day these are machines.  Some break sooner than others, some due to mechanical failures, and some due to mechanic failures.  In my case it was purely bad luck with a faulty part, no ones fault but Weller took the bull by the horns and now it was full rebuild time.  Not taking any chances Jeff split the cases and completely rebuilt the motor from top to bottom. I was learning a ton watching the motor come apart, I also learned Jeff does not like to be stood over and asked about every nut, bolt, and washer but he answered my questions and in good fun told me to back the heck up so he could finish! All reusable parts were thoroughly cleaned and inspected.  Everything was put back together to spec and by 6 pm that night was reinstalled back into the Fat Rod.

I was ready to jet back to Ocotillo Wells but both Jeff and Jason were not letting that motor out of their site without a good dyno shake down and tune session.  So after about an hour of dyno tuning the car was ready to rock with a little over 50hp at the rear wheels on pump gas, that’s about double what a stock Rhino 660 has!  As I loaded the car onto the trailer and fired up the diesel we noticed my lights on the trailer were out….WHAT ELSE CAN GO WRONG?  Mind you this was now 8pm on New Years Eve, Jason and his wife (also a UTVUnderground.com member 450grl) Corry hadn’t even loaded their trailer for their weekend Glamis departure that night and instead of sending me off they popped the hood on my truck to check for blown fuses.  They then found the burnt fuse and spent at least 5-10 minutes searching for a new one so that I could have lights on my 5 hr ride back to California. These guys just don’t ever quit.

Needless to say the weekend ended on a high note.  I was back at camp at 1am and just in time to party the rest of the night away (and sneak in one quick ride of course).   I was able to spend the weekend and do a little riding with my wife in the Fat Rod which was the best part.  Other than needing to upgrade my fuel pump to a high volume pump the car and motor are amazing.  Weller Racing are not only good people; they are knowledgeable, and committed to their customers.  I am proud to have chosen them as my motor builder but I am even prouder to call them friends.  They have gone far and above the call of duty to help me out.  On race weekends Jason works tirelessly to ensure Corry’s car, and all the Weller Racing powered cars are taken care of and dialed in.  Without a doubt, Weller Racing is my builder of choice!

Now the next trip should be the BEST trip ever!!!  We shall wait and see!!!

www.WellerRacing.com

RHINO 720 STROKER KIT

• 50+ HORSEPOWER
• PUMP GAS
• FORGED 102mm 10:1 COMP PISTON
• COMETIC TOP END GASKET KIT
• WELLER RACING CAMSHAFT
• HEAD STUD KIT
• CAM PINS
• VALVE SPRINGS TI RETAINERS
• VALVE SEALS
• BORE AND HONE CYLINDER
• PORTING & POLISHING
• +1 VALVES
• SHORTENED CENTER GUIDE
• CRANKSHAFT REBUILD
• CRANKSHAFT BALANCE
• CRANKSHAFT STROKE 88mm
• CRANKSHAFT BEARINGS / PIN
• CRANKSHAFT KEY MAG
• WELLER RACING DIFF PLATE
• WELLER RACING OIL MODS
• NGK SPARK PLUG DPR8EA-9
• OIL FILTER (KN303)
• ENGINE ICE x 2
• DYNO TUNE

Weller Racing Dyno Sheet - 720 Stroker Yamaha Rhino

More Fat Rod photos and information:

• December 2009 UTV of the Month
• Build thread on UTVUnderground.com

Tags: UTVUnderground.com, Weller Racing, Yamaha Rhino

Category: Featured, Product Reviews, Yamaha