Alloy Idler Gear

Puddle jumper

Well Known and Active Forum User
Non-VOC Member
Hi Guys,
Hope someone can help me with a small problem on my V twin, I am rebuilding the engine and have a slight problem with the washers for the alloy idler gear, mainly should it have a washer each side, if so I will have to reduce the width of the gear boss because at the moment with no washers it's flush with the spindle face.

Cheers
 

chankly bore

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Non-VOC Member
If you are planning to use your machine, throw out the alloy idler and fit a steel one.Flog the alloy idler on ebay.Many alloy idlers made in the 70s and 80s were of sub-standard material and/or manufacture and I wouldn't trust a one!
 

Puddle jumper

Well Known and Active Forum User
Non-VOC Member
Hi,
I think the idler I have must pre date that because the engine has been sitting under a bench for over 50 years which make it 1960 at the earliest! Do you know if any alloy gears where fitted as standard? And can you tell me what was wrong with the manufacture of the 1970/80 ones.

Many thanks
 

Ken Tidswell

Well Known and Active Forum User
VOC Member
It is sound advice to use this as a loss leader on ebay, or as a paper weight. It should have a shim behind it and a large washer outside.
If the idler boss is 2 piece , you could heat it and tap out the spindle, to accomodate the washer. Have you put a straight edge across the spindle to check the height
with all the others. Again most 2 part idler bosses are loose at this age. Or become loose when at running temperarture. Ned Ludd
 

Bazlerker

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Non-VOC Member
I had 2 alloy idlers self-destruct ..then I changed to steel. The fitment can be a bit fiddly, but I have had no problems for almost 15,000 miles.
 

clevtrev

Well Known and Active Forum User
VOC Member
Hi,
I think the idler I have must pre date that because the engine has been sitting under a bench for over 50 years which make it 1960 at the earliest! Do you know if any alloy gears where fitted as standard? And can you tell me what was wrong with the manufacture of the 1970/80 ones.

Many thanks
Pretty well all Comets were supplied with alloy idlers, twins from maybe mid 1950.
 

roy the mechanic

Well Known and Active Forum User
VOC Member
As all the others are steel, why mess with "aluminum", as for spacers, get it to align nice+ central with it's mates+ work-out the spacers from there. Regards, Roy.
 

Tom Gaynor

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VOC Member
My Shadow was built February 1951, had an alloy idler. It failed by losing most of a tooth, by chance exactly at 34 BTDC on the front pot with the marks aligned. For a few minutes (I was checking timing) I thought I had a 55 degree vee-twin...
The other five alloy idlers I subsequently found in a box, with five clapped out ATD's among other things, had each lost a tooth. Which I think tells anyone all they need to know about the wisdom of replacing alloy idlers with steel, and Lucas ATD's with one of the better made alternatives.
 
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