MAICO engines

MAICO engines.

Much of the maico fame is due to their engines and power output. The open class 440 and 490 engines have a reputation for having the best and most usable powerband of all bikes all times. Maico actually has several engines but we will focus on two: the old engine of the 70's and early 80' with a chain primary drive and therefore one shaft more than most bikes. And from 1983 the smaller compact more conventional engine that however never gained the same fame. It's an excellent engine though.

The older engine design has been called the best powerband ever, slickest shifting mechanism ever made and everything from good to bad. This engine is easily recognized by it's shape. From the ignition (right) side the engine case is long

but very thin. This engine has a few special features that makes it both durable and easy to rebuild but there are a few drawbacks to. We start up front. These engines are air cooled. The huge radial shaped fins with their rough casting generates a whole lot of sound. There is no head gasket, only a copper ring that can be used over and over again. The trick is to heaten it up on the stove and put it in cold water fast. This makes it softer and as good as new. The cylinder has no reed cage intake until 1981 (250cc) and 1982 (490cc). The piston controls the intake timing. The cylinders have a steel sleeve that can be rebored several times. The piston is a forged Mahle single ring. It's famous for beeing expensive but worth every single dollar. The piston is a quality unit that should last for a long time. There is a forged steel connecting rod with needle bearings on each side. The first problem area is the needle bearing and wrist pin in the crank. The big bores produces and enourmous pressure on the wrist pin. Therefore the lubrication in the pre-mixture is crutial. Normally a two stroke motocross engine can very well operate on 2-2.5% oil ratio. This is not sufficient for the 400,440-490 engines. The problem is not the cylinder but the lower bearing. They require high quality oil with 3-4% ratio. The crank rolls in two huge hefty main bearings that simply cannot wear out from riding. Remember that these bearings cannot deteriorate from the mechanical forces created by the engine. This is unique in two stroke history. On the right side is the ignition which is a Motoplat electronic unit. We won't discuss them more at this moment. On the left side is a sprocket wheel with either two or three rows. This sprocket can wear out if the chain is worn and the owner doesn't perform regular oil changes. This is however not likely to occur. The wheel should be ok even if there is some visible wear. The 250cc normally has a duplex (two row) chain whereas the 400,440 and 490 has a triplex (three row) chain. This chain is the main problem with this engine design. The chain has to be changed now and then and requries fresh oil at all times. Once the chain has strechened a bit it will hit the clutch cover and produce a crack in it. Newer engines has a nylon piece in the cover that can withstand this problem for a short while. The primary gearing ratio makes the clutch rotates at a very high speed compared to practically all other engines on the market. The clutch basket has a small diameter but is made of steel and therefore stronger against wear. The clutch basket filing shouldn't be necessary as it often is with aluminium baskets. The sprocket on the clutch basket can wear just like the front one but can almost always be reused with a new chain. The clutch has spring washers instead of normal springs. This is a bit complicated but works once correctly adjusted and mounted. There are normally 20 spring washers that should be mounted like this: (())(())(())(())(()). In pair of two against each other. This will result in the correct pressure to prevent the clutch from slipping. The gearbox is in some perspective different from most other engines too. First and foremost there are mostly needle bearings instead of roller bearings for the shafts. The gearwheels are constantly engaged which is called constant mesh. Once moved sideways the blocks on the side of the wheels hooks into each other and locks that particular gear. The shiftforks are good quality pieces but like most others they wear out. This is something one can expect to change if the oil changes has been neglected. The shift forks are guided by a flat steel plate instead of a drum with grooves like most engines. The shifting mechanism is somewhat complicated when it comes to transfer the shift lever movement to the guide plate. Keep an eye on that in order to achive a good working gearbox. All in all the gearbox is made of good quality steel and should last a long time. Like always the important thing is to give it clean oil since the sintered clutch plates contaminates the oil turning it to an effective grinding paste. And the next problem is wear on the bearings which allows movement on the shafts and can damage the gearwheels and shiftforks. All bearings in the maico engine is standard sizes and can be bought in any hardware store.


BEARINGS, SEALS & CHAIN (1980 model)