Can-Am 370 Mx-4
CAN-AM 370 MX-4
CYCLE WORLD TEST
From the beginning Can-Ams have been fast. They have also drawn attention because of their insistence on rotaryvalved power plants. While other manufacturers were producing reed-valve and
piston port engines. Can-Am kept on building rotary valved motors that usually out-powered Europe’s and Japan’s best designs.
Can-Am’s latest missile is a 370cc open class motocrosser. It is their first attempt at building a production open class bike. It is also their first departure from the rotary
The 366cc power plant is a completely new engine. Fuel is fed from a 36mm Bing V-54 carburetor into a piston ported cylinder. Mid-w'ay between the carb and piston a case reed feeds the crankcase, much like the successful system that Suzuki has employed since 1975 on their RMs. The reed cage is a large four petal design that uses plastic for the reed material.
The oversquare piston is connected to a beefy rod via a caged needle bearing. The rod’s lower end also uses a large caged needle bearing. The crank assembly pivots in huge main bearings. The size of these bearings (which Can-Am ir?TTJT* engineers felt
necessary for engine reliability) prompted the new case reed designed power plant. With such large bearings there simply wasn't room for their normal rotary valve. Also a more narrow engine case width is possible. Although the internal transmission gear ratios are the same as the 250 MX-4, the gears and shafts have been made larger to handle the load. All of the gears are big. bullet proof pieces that even hold up under Can Arn's factory riders without failure.
A large, hollow shift drum moves one of three shift forks to select the proper gear. The 370's clutch uses the same plates as the 250 but has more of them.
The cylinder is a squarish shape with eight large fins. These fins have stepped outside edges to increase cooling efficiency. The 370 has a bore that measures 84mm (3.30 in.) and a stroke of 66mm (2.59 in.). This is an extremely short stroke design, being not much longer than the 250’s stroke of 61mm (2.40 in.). One would think the motor would require high revs to get power but almost the opposite is true. Can-Am claims 42 rear wheel bhp at only 7000 rpm. Low end power is good.
A Royal Canadian Bullet for the Motocross Wars
Ignition is a Bosch CDI, rated at 30,000 volts. The front drive sprocket is located close to the sw ing arm pivot and has a case saver installed as stock equipment.
Throughout our test period the engine proved as reliable as it looked. Pro motocrosser Steve Bauer bashed the 370 around DeAnza’s MX course for the better part of two days without a failure or problem. Quite an accomplishment fora new engine design.
With the engine removed the machine is nearly identical to the 250 MX-4.
It has the same huge backbone, double dow n tube chrome-moly frame that is very strong but looks over-designed in the area under the seat. Three large tubes form double triangles on each side of the frame in this area. These heavy tubes give the frame an indestructible but busy appearance.
A long and curved swing arm pivots on needle bearings and incorporates a snailtype chain adjuster. Like the frame, it is heavy duty.
Footpegs and rear brake lever are heavily cleated and function flawlessly.
A nice die-formed exhaust pipe snakes over the engine and dumps the exhaust into a modified Super Trapp silencer/ spark arrester. The Trapp has been modified by removing the bolt that holds the discs and assorted pieces together and replacing them w ith four external springs. These springs allow some movement, which keeps carbon from building up and makes removal or addition of discs (for tuning purposes) simpler. This mod is something Super Trapp should change to. We have had problems trying to keep the Trapp discs tight on long rides. The CanAm mod eliminates all of the problems and produces a reading of only 86 dBA on the sound meter.
Like the 250, the 370 uses 38mm leading-axle Marzocchi forks and gas-charged Girling shocks. Ten in. of travel is stock at both ends and should be enough for most folks.
Petty MX fenders are used front and rear. The rear fender has been modified bv> cutting the sides to remove the droopy look.
The side number plates and odd shaped tank are also plastic but are made by a Bombardier owned company. The CanAm has a long squarish looking seat. It is thick and does its job well but the shape of seat and tank definitely subtract from salesroom appeal. The frame color drew almost as many negative comments—gray, a plain non-metallic Navy gray. The paint is nicely applied. A silver like Husqvarna’s would be better and not look so, ah . . . military. Otherwise there is little to fault on the machine.
Peg, seat, bar relationship is correct. Bars are the right shape, grips are good, hand controls are Magura, pegs and brake pedal grip secure.
The pipe brackets are nicely gusseted, all bolts and nuts are quality items. The axles are large hollow jobs that look strong.
The kick lever is located on the left side, somewhat awkward to some but it turns the engine over so easily that most riders quickly adapt to the location. One or two easy kicks will usually bring the motor to life anyway, so the placement isn’t too important. Like all Can-Ams, power is abundant. It’s interesting to note the engine has been detuned by some ten horsepower when compared to the original prototype. The prototype had so much power that test riders had difficulty getting past third gear without looping the machine. Even Jeff Smith pulled it over backwards the first time he rode it. So . . . the production version has been detuned so normal people can use the power that it produces.
Power output is smooth all the way to the 7000 max but like most sub 400cc twostroke Singles, it is happiest when revved.
Clutch pull is easy and the transmission ratios and operation are perfect. The cylinder finning is massive and will certainly cool on even the hottest days.
The big Can-Am handles a lot like a 390 Husky. The front end is light and may be lifted at will in almost any gear. The 370 has a rock solid feel to it. Even whooped > corners don’t flex the big forks and heavily triangulated frame. Rider trust is further enhanced by the strong, progressive brakes. The rear is full floating and doesn’t chatter or lock when braking hard on downhill whoops. Steering is accurate but a little slow for an expert with the delivered 31° head angle. The stock steering head cones can be rotated to give 29° if the rider wishes. Can-Am has optional steering cones available that allow an owner to set the rake angle from 26° to 32°. (See the accompanying article on Can-Am’s adjustable steering rake for a more complete explanation.) We turned the stock cones to give 29° and changed the character of the machine from a stable, somewhat slow steering bike, to a quick inside line goexactly-where-pointed expert bike.
Can-Aitfs Adjustable Steering Rake
Rake and trail on a motocross bike probably affect handling (quickness, straight-line stability, etc.) more than any other single thing.
Pity the poor manufacturers who have to decide at what head angle their products will be produced. For a short, tight, stadium-type event, 28 or 29 deg. may be right. For the ultra-high-speed track, 31 deg. might be best. If they set it at 31 deg., the buyer who races mostly on tight tracks will be dissatisfied. Set at 29 deg. the highspeed user is dissatisfied and is often in tank slappers at speed. Most companies are currently setting their motocross weapons’ rake at 30 deg. and trail at around 5 in. These figures seem to be a good compromise. Many of the newest MXers also have long fork tubes that allow up and down adjustments. These adjustments allow the quickness/slowness to be altered some.
The engineers at Can-Am came up with a solution to everyone’s problem: Make the rake/trail adjustable. The frame’s head angle is set at 29 deg. The steering stem rotates in large cones that contain caged needle bearings. By making cones that have different offsets, the rake can be adjusted from 26 to 32 deg. The cones that come stock set the rake at 31 deg. By rotating the top one Í80 deg., the rake can be reduced to 29 deg. By purchasing optional cones the rake can be changed in one-half degree increments to suit virtually any rider preference. This cone change only takes about 20 minutes to accomplish, so the bike can be adjusted to suit almost any track situation. By dialing the bike’s steering to suit the track, a definite advantage can be had. E8
The following table gives a list of cones to be used to attain a given fork angle.
Suspension compliance is good, and most riders will be happy with the supplied spring and damping rates.
The long, thick seat is narrow at the tank junction, allowing easy movement and good comfort.
Can-Am has added an excellent large bore MXer to their line. It is competitive and sensibly priced. Supply this first year is limited but those who find one will surely be glad.
CAN-AM 370 MX-4
These 38mm magnesium-slider forks are extremely good units. Long travel with plenty of engagement provides good action with little flex. Spring rate is right, and, for most applications, 5 wt. oil will provide proper damping rates.
Excessive compression damping makes the stock shocks too stiff for all but the all-out MX racer. Control is good, but comfort and fatigue factor can be improved by swapping the stock shocks for an aftermarket pair.
$1899
Tests performed at Number 1 Products
