Petter PH 2 Troubleshooting Questions

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meleager
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Real name: mark ashford
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Petter PH 2 Troubleshooting Questions

Post #1 by meleager » Thu Aug 27, 2015 9:25 pm

The PH2 in an old Thwaites dumper is hunting badly and over a very long period, perhaps as much as 6-7 seconds per cycle.

I suspect the governor pushrod/s are gummed up with dirt in the camshaft.

1) Is this the/a likely cause? What are any others?

2) Can the short pushrod be extracted without removing the flywheel?

3) How free should the fuel pump rack be to move? Do I expect it to need quite a push to move it or should it slide freely with little resistance?

4) Should the Speeder spring pull the rack towards/to the high speed stop with the rack when unopposed by the accelerator and governor? Or does it only move that way when the engine is running?

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FOWLER MAN
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Re: Petter PH 2 Troubleshooting Questions

Post #2 by FOWLER MAN » Fri Aug 28, 2015 5:09 pm

Hello Mark,
Let me try to answer some of your questions.
1) I have worked with Petters engines since the 1950s and have never known a problem with a push rod sticking in the cam shaft though I suppose it could happen.

2) The short push rod at the flywheel end can be easily withdrawn, (flywheel in place), after removing the rack opperating arm and housing.
To remove the long push rod from the other end of the cam shaft you would need to open up the timing case and remove the governor weights.

3) The fuel pump racks should move with the lightest of finger pressure when springs are removed.

4) Yes the spring should pull the rack against the stop when the engine isn't running.
To set this up release the cold start to allow the rack(s) to move to the end of their travel in max.fuel position. Carefully move the racks back 1/16 th. ins. and hold in position. Adjust the bolt provided in the opperating arm so that there is no clearance between it and the rack extension then lock up.

The Governor opperates by creating a ballance of forces between the governor weights and the speeder spring. This can be established or corrected by adjustment of the spring tension.
Also check that the fulcrum pin on the rack opperating arm is free.
Other causes of hunting can be an engine moving on loose mountings and/or the throttle opperating rod or cable being too tight.

Regards
Fred


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