- Steve PASCO
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How to check and adjust my valves on my TM Racing 250/300Fi ?
It's never been easier to check and adjust the valves on a tm 4-stroke motorcycle engine. Indeed, TM Racing SPA brought with the new TM Racing 250Fi engine block, now also available in 300Fi cylinder from 2020, a "mixed" timing chain/gearing, this system allows to check the valves of its tm engine without even need to remove the timing chain.
Here we explain you step by step the process you can do simply at home with a little need of tools. As a reminder, it is important to check the valve clearance of his tm racing every 20 hours approximately. A non-optimized valve clearance will shift the engine cycle by as much, and cause non-optimal performance.
The process can be done with the engine in the frame, or on an engine support, in the case where the engine is in the frame of the motorcycle, it will first be necessary to remove the air box in order to have access to the cylinder head of your tm. For obvious reasons to facilitate photo-shooting, our tutorial is made with an engine on engine support.
1 - Unscrew the screws (1) from the head cover (2)
2 - Remove the cover (2) using the corresponding gaskets (3) and (4). Check the status of the gaskets (3) and (4), replace them if worn.
5 - Remove the cap (8) from the generator cover (9). Check the status of the gasket (10), replace it if worn. Position the gearbox in neutral.
6 - Using a socket wrench (11), turn the crankshaft to position the piston at top dead centre, as indicated by the timing points (12) parallel to the edge of the head present on the intake (13) and exhaust (14) camshaft gear.
7 - Remove the comparator (7).
8 - Use a thickness gauge (15) to check the play between the cams (16) of the intake camshaft (13) and the valve pad is 0.15mm (0.006 in.).
If the valve clearance noted is within the values shown, go to step 23.
Otherwise, go to step 10
10 - Unscrew the screws (19) of the clamps (20) and (21).
11 - Remove the clamps (20) and (21).
12 - Remove the camshafts (13) and (14).
13 - Lift the rockers (22) and remove the pads (23).
14 - In case it is necessary to replace the spring of the valve lifter pin, work as follows: After dismounting the exhaust camshaft (1), unscrew the screw (2) and remove the plate (3).
15 - Extract the spring (4) and the pin (5); check the status of the pin (5), replace if worn / ruined. Replace the spring (4) and remount all the components working in the opposite direction.
16 - Mount a comparator (1) on the head and position the piston at top dead centre, rotating the crankshaft via the closed-end spanner (2).
17 - Before remounting the camshafts, check that the gasket (3) is not worn, replace it if necessary.
18 - Mount the intake camshaft (4) and the exhaust camshaft (5) so that the tuning points (6) are parallel on the edge of the head.
19 - Mount the clamp (7) by inserting the centering pins in their corresponding seats.
20 - Remove the comparator (1).
21 - Mount the clamp (8) by inserting the centering pins in their corresponding seats.
22 - Screw the screws (9) alternately without tightening, then tighten the screws with a tightening torque of 10 Nm (1,0 kgm, 7,37 ft/lb).
23 - Check that valves play is correct (see “Valves play check” paragraph). Spread some LOCTITE sealing paste onto the surfaces of the two crescents (10). Check that the gaskets (11) and (12), located on the head cover (13), are not worn. Replace them if necessary
24 - Mount the head cover (13) by screwing the screws (14) crosswise and then tightening them with a torque of 10 Nm (1 kgm/ 7.37 ft/lb).
25 - Mount the spark plug (15).
26 - Check the gasket (16), replace it if worn, then remount the plug (17)screwing it with a tightening torque of 5 Nm (0,5 kgm, 3,69 ft/lb).
Your tm 250 fi mx, tm 300 fi motorcycle is ready to ride again. The tm racing engine is perfectly adjusted. All you have to do is open the gas on the whoops of your favorite track or on the woods next weekend.