The TRX Project: Cylinder head II. Verifying valve stems and cam dimensions I.

Once I´ve dismounted and classified all the pieces from the cylinder head (Read here) I must to start to check his status verifying all the distribution and comparing the values obtained with the Yamaha TRX 850 service manual. To do this measurements I recommend use a good condition micrometer 0 to 25 mm, another one 25 to 50 mm, caliper and measuring square or goniometer. To store and compare all this values I do the following tables to note the measures.
With right buttom click on " target as...." to get a copy on your computer.
1.Valve stem diameter. Measuring the stem valve diameter with the 0 to 25 mm micrometer, I can know the wear of the stem valve comparing this measures with the values of the service manual (Yamaha service manual page 4-16 & Haynes manual 2-2 2nd chapter page2). These values are the followigs:
Stem outside diameter Intake valve: 5.475 to 5.490 mm, limit value 5.445 mm. Stem outside diameter Exhaust valve: 4.460 to 5.475 mm, limit value 5.43 mm.
Measuring all the valve stems I´ve a medium diameter of 5.483 with all the diameters obtained within the tolerance, this is a good signal but I don´t have measured yet the internal diameter of the valve guides to know the valve stem-to-guide clerance. 2. Measuring the springs. With the caliper I measured the free length of each spring and taking note of all the values on the table. These values must be:
Intake spring 37.29 mm, limit value 35.2mm. Exhaust spring 37.29 mm, limit value 35.2 mm.
Once I have measured all the free lengths I measured the spring tilt limit using a square or a goniometer and a feeler gauge, I used my goniometer set on 90º , keeping the base of the spring against the vertical face of the square & rolling the spring with my fingers to find the maximum clearance beetwin the spring to the horizontal face of the square. This clarance must be within 0.5 to 1.7 mm. Because I don´t have cleaned and polished the valves I prefer wait to have it done before measure the head diameter, face width, seat width and margin thickness. In my next post about the cylinder head I will show it done. 3. Measuring the cam dimensions. To measure the cam dimensions I used a 25 to 50 mm micrometer , and clamping the cam by the sprocket wheel (with the rubber clamp protection) in a bench clamp to make me easy the job. In this position I measured the two values that I must to take note. Intake/Exhaust cam "A" dimension 35.95 to 36.05 mm. "B" dimension 27.95 to 28.05 mm. The "C" dimensions results from the diference from "A" & "B" dimension and must be within 7.9 to 8.1 mm. In this cylinder head all the cams are within the admissible clearance and I take note of all measurements for a futher analysis. ....coming soon the finished veryfication and status analysis .....

1 comentarios:

Zhu Y | July 21, 2015 at 3:21 AM

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