Project Bender Viper Clutch and Jet Work plus

A Head Gasket, Heat Exchanger and a Hood Shim

Nov. 01, 2005 By Matthew Baynard

The last installment of the Project Bender Viper was expected about two months ago, but a host of delays plagued the staff at Snomobile Online. The biggest delay was a lack of snow for any testing and we also wanted to wait for some key components from Bender. All the parts arrived and have been installed. One of the key components that we've been waiting on was the Bender designed and manufacturered rear heat exchanger. This Editor feels the exchanger should have been a factory installed item like on the SRX, but that was not the case.

Regardless if you plan to install triples on your Viper or not, the addition of the Bender OPTICOOL head gasket and rear heat exchanger may be the best investment you can make. We haven't make up our minds if the stock Viper has cooling issue or not, but you do seem to see more than a few at the dealers having cooked cylinders replaced. Keep in mind that this year has been a real bummer with the snow condition across North America.

Just click on the links below to jump to topic that most interests you.


The Bender jetting for the Viper is center and mag cylinders 162.5 and the PTO cylinder 167.5. The pilot jets are 55. The air/fuel screw is set at 1 7/8th screws. None of the needles or needle jets need to be modified. The PTO cylinder can also be jetted to 162.5 like the others if you are experiencing an over-rich mixture. So far we have not had to so this. Our Project Vipers have been running a full synthetic Spectro oil.

The jet installation was pretty straight forward. The photos below show some of the key steps. If you remember from the pipe installation, the airbox is already removed at this point since it has to be modified. The photos have all been taken after the airbox was removed.

jetkit_small.jpg carbs_small.jpg
Bender packages the jets in individual compartments so you don't get them mixed up.
Click picture for larger image
Looking down on to the engine the airbox is removed and the carbs will need to be removed so the jets can be installed.
Click picture for larger image


removefuellines_small.jpg removecarbs_small.jpg mainjet_and_pilot_small.jpg
Remove the fuel lines so you can flip the carbs up on top of the cylinders to install the new jets.
Click picture for larger image
Once the fuel lines are off, remove carbs from the cylinders by loosening the rubber boots that connect the carbs to the cylinders.
Click picture for larger image
You can now get at the main jet and pilot jet that will be replaced.
Click picture for larger image

Back to top


The initial clutching that was supplied was not 100% due to the poor testing conditions in Alaska this year. The kit did hit hard and it was ok, some thought it was perfect. The original setup did prevent the engine from reving like it should and it shifted a bit too hard. That's not the case with the new setup and it's really made the Viper come alive. The new setup has proved to be perfect for the trails and gets the most out of the Viper. The shift RPM is 8700 while the clutch engages at about 4000 RPM.

You'll notice in the series of photos below, that we did a few things different that what the instruction sheets detail. All the springs and rivets are installed to Benders recommendations, we just did the work with the clutch still attached to the Viper. We didn't have a clutch puller at the 'barn' in upstate NY, so we had to improvise a bit. I'll give Tom Baynard the credit where it's due for this one.

clutchkit_small.jpg clutch_cover_removed_small.jpg loosen_set_screws_small.jpg
The new springs, rivets, shim, and helix from Bender.
Click picture for larger image
With the belt cover and belt removed, remove the bolts that hold the clutch cover on. Their under tension so be careful.
Click picture for larger image
With the clutch cover removed, you need to loosen the set srews that hold the clutch weights on. You'll need to remove the outer rivet on each arm.
Click picture for larger image


install_shim_small.jpg install_new_spring_small.jpg
The outer rivet removed from the arm. Use a grinder to grind the rivet head flush. Be careful not to grind the weight. Install the new rivet in a vise. Be sure their is no slop in the rivet hole. Reinstall.
Click picture for larger image
Install the new 8mm shim below the primary spring and then the new spring.
Click picture for larger image
After the 8mm shim the new primary spring needs to be installed..
Click picture for larger image

In the next set of pictures you can see the 'cheater bolt' that were used to re-install the clutch cover. It would have probably been easier if we used a clutch puller, but if you don't pull alot of clutches this is a nice little shop trip.

Using a 2" bolt you can compress the spring and cover back on if you don't have a press.
Click picture for larger image
After you draw the cover onto the clutch, you can reinstall the stock bolts one at a time. Torque the cover to 87 ft/lbs.
Click picture for larger image

Once the primary clutch has been modified and reinstalled, the secondary needs to removed. Be careful not to loose any of the spacers on bolt that fastens the clutch. Once the clutch is removed, remove the three bolts that hold the helix. The spring under the helix will be replaced with the Bender kit also.

Install the new spring. Refer to the Bender instructions, but the 30 degree helix will use holes 3 and 0. Set the new helix over the spring, and turn the helix clockwise until the studs line up with the stud holes on the helix.

Reinstall the secondary clutch on the jackshaft. Make sure that all the spacers and bushings are used. Tighten the bolt, but remember that there will be play where the secondary fits on the jackshaft. Once the belt is put back on and the clutch cover added, your all done. The change will impress.

Back to top

Exhanger and Head Gasket

The stock Vipers have been cooking PTO cylinders all season and some are wondering if Yamaha didn't make a mistake and undercool the Viper. The issues are probably more related to the poor snow conditions this year, but one thing is certain, any modified Viper will need cooling addressed.

The Bender solution is twofold, a new OPTICOOL headgasket and a Bender manufacturered rear heat exchanger. The new headgasket will alter the flow of coolant around the cylinders to help cool the PTO cylinder better. We've captured some of the highlights of the installation below. We skipped most of the heat exchanger installation, but the instructions are extremely well done by Bender. One tip is that when you drill the bottom of the exchanger for rivets, remove the bumper so you can get a better angle on the drill. Another key point it to make sure that you bleed your cooling system so that no air bubbles remain in the lines. You may also want to put a piece of duct tape over the hole that was left from the stock cross over line that connected the two running borad heat exchangers. You'll be drilling a new one for the Bender rear heat exchanger.

headremoval_small.jpg new_gasket_in_position_small.jpg
The Bender OPTICOOL gasket is on top. The stock gasket below provides the identical cooling for all cylinders. The OPTICOOL gaskets alters the coolant flow.
Click picture for larger image
Remove the head bolts after you've drained the coolant from the motor. The stock gasket is still on the heads. Notice the carbon on the pistons, our Viper was running a bit rich at first.
Click picture for larger image
The new gasket installed. You can see the differences in the openings for coolant flow.
Click picture for larger image


The head bolts get torqued to 20 ft/lbs. Be sure to follow torque sequence that is in the instructions.
Click picture for larger image
We jumped ahead on the exchanger installation and here's the final results. The cooler looks almost identical to a SRX unit and installs without major difficulties. In the picture you can see were some of the tunnel protectors have been removed.
Click picture for larger image

Back to top

Hood Shim

The Bender update kit that included the new clutch settings also provided an aluminum shim that will eliminate the hood rubbing on the triples. Installation is 'greatly' simplified if you have a buddy help you. The shim only lifts the front of the hood about an eight inch, but its enough to keep the cowl electric lines from getting melted and keep the pipes away from the foam where the heat tape is installed. You may still want to bend, by hand, the air vent screen on the lower right of the cowl. It had a tendency to rub the paint off the pipe on the trails.

Back to the Project Viper Main Page.

The Bender Triple Pipes are available at most dealers throughout US or directly from Bender Racing, Canadian Distributors Magneto Sales 780-469-2807, and Bender Racing Canada 705-694-2620.


For more infomation contact Bender Racing at:
General Business Line: 716-941-5010
Order Line: 716-941-5010
Fax Line: 716-941-5990

E-Mail: [email protected] , [email protected] , and [email protected] Newsletter
Join our Weekly Newsletter to get the latest off-road news, reviews, events, and alerts!