Size gentlemen please!

[Alastair Gregg]

What size is the nut that holds the pully on the end of the crank on a Jav/Jup please. I have got back a rebuilt engine and best practice decree's that every few months you turn the engine to save the bearings. I tried with the starting handle but have insufficient purchase on a new (tight) engine.

[rob needs]

Is that with the plugs still in?

[Alastair Gregg]

Yes it is I would expect it to be stiff but not impossible.

[paul wilks]

Hi Alastair.

I have a spare Javelin engine (rebuilt by Roy Braddock many years ago) which I turn over every so often using a large 3/4" Whitworth ring spanner. Although spark plugs are inserted (and Roy insisted they be kept in place in the engine whilst out of use) the engine does turn over showing a good compression but not so difficult that I need to use a huge amount of force.
Hope this helps.

Paul

[Alastair Gregg]

Thanks Paul,

My Socket /spanner set does not go to that size, but very shortly it will. Thanks for your help.

[Forumadmin]

Be careful I once broke the bolt. Sometimes the bearings are such a good fit that they suffer from stiction. Once moving, the engine turns; but very difficult to initiate. I have also relaxed the crankcase tie bolts slightly to overcome what might be an overtight engine. Of course that may indicate poor alignment of the main bearing housings or dirt under the shell or poor tolerance on grinding. Anyway it is a way of telling which bearing is causing the problem.

[TedAllen]

Further to above, I once broke the bolt trying to turn over an engine I had bought. I thought I was in trouble but found the remains of the thread came out quite easily just using a small screwdriver to push the shaft round by the rough end of the break.
I don't think the threaded shaft actually bottoms in the crankshaft but relies on the inner face of the starter dog to tighten against the pulley and end of the crank.

Ted