Author Topic: Idler pinion  (Read 134 times)

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teebee67

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Idler pinion
« on: 22 October, 2020, 11:57:26 »
Does anyone know if there are more than one idler pinions (half time pinion) available for the A65 to suite different  valve timings. The one on my Spitfire has a number 3 stamped on it and this made me wonder if there is a 1 and 2 or more with different keyway positions. 
Any info much appreciated.

wardy

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Re: Idler pinion
« Reply #1 on: 26 October, 2020, 20:53:07 »
Do you mean the idler pinion or the cam pinion? Idler pinion on my A65 has no keyway

DAVE BRADY

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Re: Idler pinion
« Reply #2 on: 26 October, 2020, 21:37:50 »
Hi,

Although the A65 idler pinion is a very tight fit on its spindle it does have a key/keyway.  It is quite hard to see as it is very small.  The parts book shows only one part number for all models including the A50.  I would think that differences in valve timing would have been built in to the cam with specific cams for A65 and A50.

Dave.

teebee67

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Re: Idler pinion
« Reply #3 on: 26 October, 2020, 21:45:28 »
Thanks for the replies/info, it is helpful.

craigc11g

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Re: Idler pinion
« Reply #4 on: 27 October, 2020, 08:57:29 »
if im thinking of the correct gear it would NOT have a key , what would it be keyed too ? the marks are for crank to cam timing , on some bsa singles they do make a crank gear with a altered key position not sure about the unit models .

DAVE BRADY

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Re: Idler pinion
« Reply #5 on: 27 October, 2020, 09:29:39 »
Hi,

The idler gear and the shaft it fits to are separate probably for ease of manufacture and although a tight fit the key is to ensure no movement that could occur.  Any movement would upset the valve timing and the ignition timing as the points are attached to the idler shaft.
The 1970 parts book shows the pinion and shaft as one part number, 70-9104 and a key as part number 27-1386.
The 1965 parts book is similar but the keyway is shown in the illustration.
I would imagine that really only having one part number would imply that the idler pinion, shaft and key would always be treated as one component.

Dave.

wardy

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Re: Idler pinion
« Reply #6 on: 27 October, 2020, 11:50:52 »
Fooled me too. Catalogue shows a key but it may not be evident looking at the part! Feels one-piece