Distributer (motorcycle ralated) sorry

37chief · Dec 10, 2016

What does it mean when I see 12 degrees on the advance weight plate on a distributer? I have distributer that has 10 degrees in the same spot, it is no good. I found a new 12 degree distributer I want make it a 10. If I put the advance weights from the old dis in the new one will that make it a 10 degree distributor? Any thoughts, Stan

Earl-IL · Dec 10, 2016

You can only tell by using a timing light with a adjusting knob or a flywheel with degrees marked off. I do a lot of dist. & mag repair and most of the time they check out with more advanced than they are suppose to have. It is not the springs, it is the wear on the stop pin & slot on 2cyl Deere Delco dist. The worst I have seen was 55deg.advance range. The magneto's, the wear is in the impulse coupler. I have a old SPLITDORF off a old 4 cyl. Indian.Replaced Coil, Cond, Broken wire. I have fire. The Indian belongs to a friend.

MarkB_MI · Dec 11, 2016

What's this off of?

Just a wild guess, but I suspect the marking means the limit to total centrifugal advance. If that's the case, then if you swap weights and springs the new distributor will still achieve the same 12 degrees advance, but not necessarily at the same rpm as with its original weights and springs.

crawlerjohn · Dec 11, 2016

You need to know at what rpm the total advance of 12 degrees is taken it might work fine as is or you could set initial advance back 2 degrees to reach desired total advance. It might start easier. John

Bob · Dec 11, 2016

Actual advance measured at the crankshaft will be twice the distributor advance, or 20?.

As to the difference between the two distributors, in addition to any difference in the "advance curve", likely there's a difference in the weights or the weight carrier or both that limits the travel of the mechanism, in other words some sort of mechanical stop.

Geo-TH,In · Dec 11, 2016

Stan I would try it and see what happens. Too much spark advance will cut down on performance. If needed just retard the spark and see if it will still start and run properly. Let us know how it works. geo

notjustair · Dec 11, 2016

I don't know cycles, but air cooled VW engines don't like too much advance. That's the only time they overheat. They will literally melt main bearings. Don't ask how I know.

37chief · Dec 11, 2016

Mark. I am working on a 61 Triumph TR5C. All the hardware including the distributor sat in a bucket. Every time it rained, the stuff sat for months in water. I finally found a new distributor in the UK, but it was 12 degrees. My other challenge is finding Whitworth nuts, and bolts. This stuff even used different wrenches, not US or metric, its Whithworth. Why didn't everyone get on the same page years ago, and make wrenches, nuts, and bolts the same? Stan

dr sportster · Dec 11, 2016

Wouldn't total advance be the same amount of degrees for any engine? Full advance is where it runs . Why would one set advance 10 and another 12 . What does the book call total advance. The degrees may indicate a rate of advance where full is achieved?

MarkB_MI · Dec 11, 2016

> Wouldn't total advance be the same amount of degrees for any engine?

The faster the engine turns, the more total advance it's going to need. Remember, the reason advance is needed in the first place is to time the maximum combustion pressure to occur roughly at the mid-point of the stroke, when piston velocity is greatest. Of course there are plenty of variables that factor in, including compression ratio, octane and initial advance.

MarkB_MI · Dec 11, 2016

> I am working on a 61 Triumph TR5C

Sounds like a great project. I would use the new distributor as-is; it's not like you're going to be racing your vintage bike and two degrees difference isn't much. If you're concerned about pre-ignition, run premium gas to be on the safe side.

> Why didn't everyone get on the same page years ago.

Well, everybody DID back in the seventies when ISO fastener standards came out. Everybody, that is, EXCEPT our beloved US of A.

dr sportster · Dec 11, 2016

Most engine have a spec for initial advance [ maybe 5 Degrees] and total advance when the weights are fully spun out by centrifugal force. Maybe 35 degrees. Working off those specs he should be able to determine what this distributor is doing.

Steve@Advance · Dec 11, 2016

Stan, after reading the rest of the post, about the rusty parts in a bucket, about the only choice you have, (and what I would do), is to cull the best parts you have, put it together, and see what you come up with. If there are unusable or missing parts, then start searching for what you need to complete it.

There are so many different advance curves and limits, unless you have everything exactly as it was when it was born, a few degrees one way or the other will not make a noticeable difference.

I work at a machine shop, if there is anything I can do, let me know.

Distributer (motorcycle ralated) sorry

37chief

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Earl-IL

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MarkB_MI

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crawlerjohn

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Bob

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Geo-TH,In

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notjustair

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37chief

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dr sportster

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MarkB_MI

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MarkB_MI

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dr sportster

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Steve@Advance

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