Engine stripdown of DT175MX 1978

[RobboM]

Hi I wonder if anyone can advise me of what is "Normal" tolerance for the movement "Side to side" of the conrod once the head and barrels have been removed.

I have had this bike in the back of my garage unused since I bought it apart from starting it once a couple of years ago, but remember that the engine made an unusual noise when running, not that it would run for long. (Mainly due to carbs I think?).

I have decided to get it going at last and have removed the top end to clean/paint it properly and thought that while it was apart that I should check out the condition of the engine. On removal of the barrel the conrod seems to move from side to side more than I would have expected and therefore wondered if this waqs "Normal" - hence asking for "Usual" tolerances. If anyone could advise then I would be very grateful

Thank you

[Airhead]

Yamaha DT175MX

Checking Cylinder, Piston, Rings and Crankshaft

Piston rings end gap (Both rings) 0.3 – 0.5mm

Ring groove side clearance, Top 0.02 – 0.06mm, 2nd 0.03 – 0.07mm

Cylinder maximum taper 0.05mm (0.02in)

Cylinder maximum out of round 0.01mm (0.04in)

Piston clearance: Using an outside micrometer, measure piston diameter. The only core measuring point is at right angles to the piston pin holes and about 10mm from the bottom of the piston. Compare piston diameter to cylinder bore measurements.

Piston clearance is Minimum cylinder diameter minus maximum piston diameter.

Min 0.035mm, Max 0.04mm

Piston pin and bearing, Apply a light film of oil to pin and bearing surfaces. Install in connecting rod small end to inspect for wear. There should be no noticeable vertical play. If play exists check connecting rod small end for wear. Replace pin, connecting rod and/or bearing as required.

Connecting rod Cylinder Specs

Con rod axial ( C )

New 0.8 – 1.0mm , Maximum 2mm

Con rod side ( D ) Big end clearance

Min 0.02mm (0.008in), Max 0.8mm (0.03in)

...Paul