October 28, 1997
Dear Ralph:
What is your recommended procedure for removing stickers from snowmobile hoods without damaging the hood? Is there any quick and easy method?
Whatever you do, keep razor sharp blades and such away from your sled. The best method of removing plastic and vinyl decals is by using a hair dryer to slowly heat up the decal. Start slowly by lifting up one corner (this is the hard part and requires a fingernail that has some length to it) and pulling slowly. As the decal gets warmed up from the hair dryer, you will be able to slowly pull the decal off from the hood. Do not get the dryer too close to the surface as you can overheat it, and start with a lower setting and work your way up in heat until you find the coolest possible setting that will work.
The sticky residue left over can easily be removed with a mild solvent, but you need to find one that will not damage the plastic. This is another trick. Try WD-40, no kidding. It will dissolve the adhesive used in the decal backing, but (likely) will not damage the hood surface or finish. Be sure to apply a new coating of wax to the surface after this procedure, as the solvent will strip any protective coating from the area.
October 28, 1997
Dear Ralph:
My ’94 Vmax 500 has a continual leak at the Y-pipe area. Oil is dripping down into the belly pan and sure makes a mess. I’ve already installed new gaskets, but still have the problem. Any suggestions ?
Even though new gaskets are used, you will sometimes have annoying leakage around the Y-pipe to cylinder surfaces, as well as around the ball joints where the Y-pipe fits to the Y-pipe. First clean the surfaces with brake or contact cleaner to insure a flat mating surface, then apply a thin coat of hi-temp silicone (available at any auto parts store) to the surfaces. The same can be done to the ball joints if they are leaky. Use caution when re-installing the Y-pipe and only torque to 15-17 ft pounds.
October 28, 1997
Dear Ralph:
Are there advantages of the rotary intake that Rotax uses on many of their twin cylinder engines ? Are rotary equipped engines more powerful than piston ported or reed intake designs ?
First let’s compare the rotary intake to a piston ported engine. The advantages of the rotary intake are that the intake port is positioned directly into the crankcase, and that the opening and closing of the intake port is controlled by a rotary valve disc instead of the piston. The use of a rotary valve enables a very short inlet path. This design gets the fuel/air mixture into the engine without any kind of obstruction that would impair the volumetric efficiency. This intake position also enhances the lubrication of the lower connecting rod bearings. The use of a rotary valve allows a longer duration of intake and the opening of the intake starts earlier. This results in better filling of the crankcase. In addition, the rotary intake closes earlier helping to avoid fresh charge spitback. The rotary valve gives the engine designer complete control of the intake duration. This basically gives the engine greater torque at lower rpms, more peak power, and easier starting, all other factors being equal, of course.
Reed intakes provide substantial improvements in torque when compared to piston ported designs, but also have disadvantages. Reeds tend to separate air from the fuel. Since the crankcase “vacuum” must first open the reed to allow intake, this force is not fully applied to the actual intake operation of fuel & air – resulting is a partial loss of intake potential. At higher speeds, the delay in closing the reeds affects the reopening of the reed (referred to as “float”). Again, potential volumetric efficiency is affected. Stiffness of the reeds, size of the cage, and potential for breakage are also variables to deal with.
October 28, 1997
Dear Ralph:
I have a 1995 Indy XLT and the head gasket keeps blowing out. What is the solution to this problem?
You’ve got one of two problems. Most likely is that the water (coolant) filter is partially blocked (plugged) and the coolant flow is reduced. This reduction in coolant flow causes the water temperature in the engine to get too hot. The temp light comes on, and not too much later the head gasket blows. Coolant flow may only be reduced by 40%, and this may take a while to happen, but the filter is the first place to check.
Take a look in the coolant overflow bottle for some black stuff (residue left over from blown head gaskets). If there is black stuff in the bottle the filter is probably plugged full of the same debris (filter is located between the overflow bottle and the water pump). Drain and flush the entire coolant system, replace the filter, and refill with fresh premix.
Also check the cylinder head and block for warpage. Head and block surface should be within .003″ variance. Never seen a warped block though.
October 28, 1997
Dear Ralph:
I have a flooding problem with my engine. If the sled sits for a while without turning off the gas, the crankcase gets quite a bit of gas in it.
J. Barsness
One of two things is happening. We had a similar problem on one of our sleds this year. A foreign particle hung up in the needle and seat in the float bowl causing the floats to stick. Gas was running into the carb and engine all the time. The solution was to pull the float bowl off the bottom of the carb, remove the floats and inlet needle. There above the needle we found a chunk of material that had caused the problem. We are to the point that before every season we are going to remove and clean the carbs on our sleds. Too many cases of “carb related problems” are showing up and this is cheap insurance. The other possibility is that the needle and seat have a poor seal and are slowly allowing the fuel to pass. Pull the carb on the offending cylinder and have it pressure tested (most servicing dealers should have a pressure tester).
October 28, 1997
Dear Ralph:
What is “tunnel porting” ? Is this only a Ski-Doo thing ?
Lee Kempffer
To be accurate, tunnel porting is performed on rotary valve intake engines, and since Ski-Doo is the only sled maker using this type of intake, it is a “Ski-Doo thing” . This procedure refers to the grinding out of the crankcase from the rotary valve inlet towards the transfer ports at the cylinder base. This procedure streamlines the flow from the rotary valve inlet to the cylinders. This modification really only benefits engines running above 8000 rpm. When installing larger carburetors, opening of the rotary valve cover and the crankcase openings may also be included in a tunnel porting job to match the new carburetor bore. However, when installing carburetors larger than 42mm, do not enlarge the opening at the valve side of the cover beyond 42 mm. Taper the opening smoothly from the carburetor flange down to 42 mm on the disc valve side. The opening in the crankcase should match it at 42 mm and “trumpet” out towards the transfer ports. Also, tunnel porting should only be done by accomplished engine modifiers.
October 28, 1997
Dear Ralph:
What is the difference between Mikuni VM38SS and VM38AL carbs ? I thought that the XLT Special and XC 600 were using the same engine, but the SP specs say it has SS carbs, and the XC says AL – what gives ?
Nothing more than an oversight. According to our sources at Polaris, all of the high output versions of the 597cc monoblock engine use the same VM38SS carbs, which are aluminum. The AL designation was used in the past, but no longer applies and was listed in error on the specs.
October 28, 1997
Dear Ralph:
I’ve heard somebody say that it is nearly impossible to get over 110 horsepower out of an engine with a single pipe. If this is the case, then how are we to believe that the MX Z 670 and SX 700 produce around 115 hp ?
It’s a fact, the MX Z 670 and the Vmax 700 SX both produce a certified 115 (or so) hp. Credit recent advances in pipe designs, mostly due to computer aided design software that allows pipe makers to “test” several different designs in a far shorter period of time.
October 28, 1997
Dear Ralph:
My Indy Classic seems to have a problem with the throttle override kicking in at low rpms which causes the engine to backfire. Is there any way to unhook or disconnect this system ?
Under no circumstances (other than in an emergency to make it home) should you render the throttle safety system inoperable. You should check the throttle cable tension and free play before messing with the safety system. If proper cable tension does not fix the problem, hold the throttle lever stationary and press the throttle. If the system is working properly the engine will die. Another possibility is the kill switch which can cause erratic low rpm running. The connector for both of these systems is under the handlebar pad (brown and black wires). If everything still works after you unplug this coupling, there definitely is a problem. If the problem is in fact the safety switch and not the cable (highly unlikely), replace it.
October 28, 1997
Dear Ralph:
I’ve heard that these new “Nicasil” cylinder liners have a longer break-in period than do the cast liners. How many miles should I wait before I change jets and expect full power from the engine?
It isn’t so much breaking in the cylinders as it is to get the rings to “seat” and come up to full compression. Since the nicasil cylinder liners are harder than those of cast iron, they will require a longer period of time for the rings to seat. How much longer ? This depends on who you ask. Maybe an extra tank of fuel. This business about it taking 500 miles to break in the engine (before you change the jetting) is likely nothing more than an attempt to keep warranty claims down. The first 150 miles is when the majority of improvement will occur, and you should be able to jet accordingly for the conditions.
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