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By Craig Castleberry, eXtreme Outdoors
On Sunday 08/20/06 we took a new bone stock Rhino 660 with 1/2 hour of run time on the engine and went to work to increase horsepower and top end. By the end on the day we had our Rhino at 59 MPH, quite an increase from the stock 41 MPH.
We wanted a day without wind for top end testing and outside the shop we have a nice level road to test.
Our test subject is a 06 Yamaha Rhino 660, the cheapest Rhino we could buy, we had the digital dash installed as an option, our Rhino was the one with the green body. We tested it with stock tires and wheels. Temp 90 to 95 degrees, Elevation 2300 ft approx. Driver 6'3, weight 312 lbs.
Parts being tested; Dynatek Rhino CDI, Rhino Re-Machined Sheave, Billet End Cap for the stock exhaust, Extreme Flow Intake kit, air box lid removed, our larger diameter head pipe, Dubach Racing exhaust, with the spark arrestor removed. Oil breather siphon break.
Our 1st run was completely stock. Top speed 41 MPH and we hit the rev limit.
We installed our Dynatek CDI and top speed was 50 MPH. The Dynatek CDI is capable of speeds over 70 mph but at this point our motor is out of horse power.
Next we installed the re-machined Rhino sheave. This was pretty easy and no special tools were required. Installation time was about 1.5 hours.
After we got the Sheave installed our top end increased to 56 MPH! Not bad! Amount spent at this point, 199.00 for the CDI and the Sheave was 120.
Note on the sheave, the bottom and mid range is not changed one bit, just top end is increased.
We installed a billet end cap for the stock exhaust. We were hoping for a few miles an hour, as the stock end cap of the stock exhaust is pretty small. We topped out at the same 56 MPH with the billet end cap.
At this point it is time to get serious. We are now ready to re-jet and install the Extreme Flow intake kit, Rhino siphon break to stop oil from leaking into the air box from the crankcase breather, larger diameter exhaust header, and Dubach Racing slip-on exhaust.
The Extreme Flow intake kit consist of a CNC machined filter mount, K&N high flow filter, and Outerwears pre-filter. Removing the air box is pretty easy and installation took about 45 min.
The Extreme Flow kit is used for 2 reasons, to allow un-restricted air flow to the air box and to allow the lid to be removed without the slip on stock filter falling off. The K&N filter is secured to the Extreme Flow base plate with a stainless hose clamp.
The stock head pipe outside diameter (OD) is 1.25" and inside diameter (ID) is 1.12" Our new header is 1.369" OD and ID 1.25" Our new head pipe is also ceramic coated. It is designed to be used with either the stock exhaust or any slip on exhaust. There is supposed to be a 2 HP increase with the larger header and the stock exhaust and the larger flowing billet end cap, however we did not test this combo.
We removed the 145 main jet and installed a genuine Mikuni jet. Our final size after testing several was a 170.
We drilled out the air fuel mixture plug and increased the turns to 2.5
We also installed the new siphon break. This is not for performance but to stop oil from running into the air box from the crankcase breather. Since we are not running an air box lid this would be a mess. This is one of those items all Rhino's need to keep your air box clean of oil.
Now we installed the new head pipe and Dubach Racing exhaust. Installation of the exhaust took about 1 hour. Having everything dialed in we were ready for our runs.
Our 1st run, we used a 157.5 jet. This jet was way to lean, however top speed was 60 MPH however when we returned to the shop, the exhaust core was glowing red hot. We increased jetting over several runs and finalized at a 170 main. We never got to 60 MPH with the other jets, however we did reach 59 on the long runs. 57 MPH was easily attainable in a block and 1/2
We ran a friends stock Rhino against the modified one and in 200 feet our Rhino was out over 2 lengths.
Check out our tested Rhino performance products.
If you have any questions we are always happy to discuss options with you.
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