JRM

CODY RACING PRODUCTS
North American Distributor for JRM
13821 West Street
Garden Grove, CA 92843
Phone: (714) 265-1576
Fax: (714) 265-1582
E-mail: codyjawa@sbcglobal.net


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Description of JAWA Engine Type 884 and 888

Single cylinder, single OHC with a swept volume of 500 ccm. Air-cooled, four valve with a bore of 85 mm and a stroke of 87 mm, or a bore of 88 mm and stroke of 81.2 mm. Engine oil sumps, head and cylinders are made from aluminum alloy. The big-end and main bearings are of caged needle-roller type. The camshaft is seated inside the head on needle bearings and is chain driven. Valves are at a 35 angle with one tapered helical spring per valve. Valve seats are hot pressed into the head. The forged piston is made of light alloy with two piston rings. The engine has a circulation lubrication system. The oil tank is situated in the valve gear cover and right hand crank case. The engine holds .6 litre of oil. The oil can be checked at the oil level gauge. A 34 mm carburetor is used with electronic ignition.

Technical Data

Model 884 bore / stroke 85 mm / 87 mm
Model 888 bore / stroke 88 mm / 81.2mm
Swept volume 493 ccm
Maximum power / RPM 63-70 bhp / 8500-10500 RPM
Compression ratio 13-15:1
Carburetor Dellorto 34 mm
Ignition advance 30 -33
Ignition PVL Electronic
Spark plug Champion G55R / G57R
Valve / cam timing 10A 13A 17A 01 02 03
Ex. valve open / close 69 /31 69 /31 67 /30 62 /30 66 /33 62/30
In, valve open / close 37 /67 34 /67 39 /62 31 /68 39 /62 37/68
(measured at a valve lift of 1 mm)
Valve clearance Int / ex .004" / .006"
Fuel Methanol
Oil (.6 litre) Silkolene Castorene R-50

Instructions for operation

These items must be checked before the engine is started. * Valve clearance.
* Timing chain adjustment. Tighten the screws on the cam gear.
Check and tighten all cover screws.
* Adjustment of the primary and secondary chains.
* Clutch adjustment.
* Oil and fuel levels.
* Function of the ignition cut-off switch.
* Function of the carburetor.
* Use the right temperature range spark plug.
For long tracks use colder Champion G55R;
For short tracks use a warmer Champion G57R.
* Engine must be properly warmed up before running at higher RPM's

* Starting the engine is accomplished by pushing the motorcycle or rotating the rear wheel. Cold engines should be started with the choke on and without using the throttle. Starting the bike is made easier by "tightening" the engine before pushing the bike. This is accomplished by gently pushing the bike backwards until resistance is felt in the engine.

Adjustment of the carburetor

Main jet 205-230
Needle jet 290-300
Needle position 2 slots from the top
Slide number 8

A portion of the track is driven at full throttle. After a rapid stopping of the engine, the condition of the main jet is checked, do not run at idle. If the jet has been chosen properly, the piston bottom is lightly moistured with traces of oil and gilded. If the needle is small, a lean mixture, the piston will be dry and greyish. These symptoms are evident at the spark plug also. If the jet is too, it is a rich mixture, there are patches of fuel at the piston and spark plug. To determine a proper jet, which represents the most important part of the carburetor setup, the carburetor transition is adjusted by means of the proper idle jet and the proper adjustment of the slide needle. The highest engine power output can be achieved if the carburetor is adjusted in this way. To prevent burning up of the piston, it is recommended to be one size bigger on the main jet, engine output will decrease only slightly. At this adjustment there must be the right plug installed.

Setting the ignition timing

Peak engine power also depends on proper ignition timing. Advanced ignition occurs before top dead center according to the performance data spec listing. To adjust, the screw, at the inspection hole on the left side of the engine case, will need to be loosened. Rotate the crankshaft so the advanced ignition mark is in the hole center. with the adjusting screws loose, rotate the stator until the checking mark is behind that of the rotor. Tighten the adjusting screws on the stator. When using the PVL standard ignition, the recommended ignition advance is 30 to 33 degrees. When using the PVL Digital ignition, the recommended ignition advance is 27 degrees. The shaft of the ignition rotor is located separately in two bearings and is connected to the crankshaft.

Engine lubrication

A circulation lubrication system is used. It is recommended to completely replace the oil after five or six heats. The recommended oil is Castrol R SAE 40 (M) or Silkolene 50 weight Casterene.

Dismantling, assembly, adjustment and service life

Head and cylinder

In the mounted state the valve springs must have a minimal tension of 28 kg to obtain an engine speed of 9000 RPM.

Width of the valve seats 1.2 mm.
Valve and seat edges should be rounded off in the head.
Rocker arm rollers must rotate smoothly and be frictionless.
Camshaft axial clearance .3 mm.
Valve pans need to be replaced after about 30 races.
Replace cam chain after about 25 races.
Replace piston after every 10-15 races. Pistons sizes are std., +.10" and + .20" for boring.
Piston pin clearance is .03 mm.
Clearance of gudgeon pin in piston must be .005 - .015 mm.
Clearance in piston ring lock .25 - .3 mm.
Clearance of gudgeon pin in connecting rod .01 - .02 mm.

Crankshaft

Repair work of the crankshaft is recommended to be done by specialized repair shops with the correct tooling. The crankshaft is pressed at the cylindrical surfaces. Before disassembling the crankshaft, the pressed sizes of the diameters should be checked. The pressed fit of the main pins should be .11 mm minimum and the crank pin should be .1 mm minimum. The crankshaft can be pressed three times without using oversize parts. Axial clearance of the crankshaft in the crankcase is 0.5 mm. Minimum. The balancing of the crank mechanism for vertical engines is 68% of balancing masses, for horizontal engines it is 52% of balancing masses.

Assembly of crankshaft

Clean all parts before assembling. The right main pin is pressed into the flywheel on wedges to ensure a proper position and exchangeability of the mechanism. Lightly coat the openings and pins with oil or an anti-seize coating to prevent jamming when pressing. The crankshaft must be balanced after assembly. Measurements are made in points and untrue running is measured 5 mm from the faces of the flywheel, and should not exceed .03 mm. The connecting rod dimensions should be checked after 15 races as a safety precaution. Replacement of the needle cage and rollers should be done after 15 races.

Valve adjustment

The camshaft is driven by a chain driven directly from the crankshaft. Valve timing is made very easy. All adjustment is made at the cam chain wheel by means of 4 oval holes on the wheel, which is held by 4 screws.

Specifications for the valve clearance can be obtained in the performance data section.

These instructions will give you a guide for longer service life, but it is needful to take into account the riding style of the rider, his weight, light or heavy, the quality of the rider, if he is a top rider or a beginner and what size tracks he rides on.


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