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Discussion Starter · #1 · (Edited)
Does anyone know, or have a sets of flywheels on which they can compare or degree the timing marks between knuckle, flattie, and pans?

I'm familiar with timing procedures and what the manuals say, which got me wondering whether the timing marks on knuckle, pan, and flatties are in the same location on the flywheels relative to degrees. Id like a definitive and quantitative way of measuring timing in motors with swapped flywheels, especially if assembled (ie heads on).
 

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The mark is relative to the stroke of the flywheels. There is a longer advance on longer stroke flywheels than shorter ones. Therefore an 80SV mark is more advanced than a 74FL, and a 74 is more advanced than a 61EL. But as was mentioned, they are all in about the same point as far as degrees. And so are Triumphs, BSAs, BMWs , and virtually all other engines!The marks are in the right place for the stroke, no need to change them! If you are running really radical components you need to advance a little more. I always ran my strokers at 42 degrees. But that was with real gas!!
Robbie
 

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Discussion Starter · #8 ·
The mark is relative to the stroke of the flywheels. There is a longer advance on longer stroke flywheels than shorter ones. Therefore an 80SV mark is more advanced than a 74FL, and a 74 is more advanced than a 61EL. But as was mentioned, they are all in about the same point as far as degrees. And so are Triumphs, BSAs, BMWs , and virtually all other engines!The marks are in the right place for the stroke, no need to change them! If you are running really radical components you need to advance a little more. I always ran my strokers at 42 degrees. But that was with real gas!!
Robbie
Robbie: I missed this reply, but i'm still curious.

I understand that a timing mark at 35 degrees will always be a 35 degrees, regardless of the size of the flywheels or the location of the mark on the flywheels. And that's why my question was about where the timing mark for Knuckleheads and big flatheads are. I never found a numerical reference, relative to degrees (I have for pans), and I'd still love to confirm the location of said marks for mix/match applications (like flathead wheels in a panhead, for example). if they are all 35 degrees, then fantastic.
 

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When I get back to the shop this week. I'll check. There's all of them down there.

I understand what Robbie is saying, and he is right. Depending on stroke the mark will be farther or closer to the TDC mark.

One thought, wasn't the hot setup to swap wheels around. Seems like 35* is 35* and TDC is TDC, so depending on stroke length, say 61,74,80 all of them would be the same to say. 61 is the same as 61, 74 the same as 74, 80 same 80, regardless of top end. Pinion shafts and such I know are different per wheel design, but stroke and degrees, I can't see being different.
 

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Scott,
Knucklehead and Panhead wheels (through '54) are the same part, so consequently the timing is also the same. And the marks remained in the same place on the wheels after the shafts changed for '55. And since the Panhead service manuals put it at 35 degrees BTC, then you are pretty safe in betting that a Knuckle is as well.
And if you want to send me a set of UL wheels I'll degree then for you.
Robbie
 

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Discussion Starter · #11 ·
Scott,
Knucklehead and Panhead wheels (through '54) are the same part, so consequently the timing is also the same. And the marks remained in the same place on the wheels after the shafts changed for '55. And since the Panhead service manuals put it at 35 degrees BTC, then you are pretty safe in betting that a Knuckle is as well.
And if you want to send me a set of UL wheels I'll degree then for you.
Robbie
Good point on the part number sharing on the knuckle and pans. I assumed they would be the same but hate relying on assumptions. but the flatheads are really what I'm curious about. for example, I'm not an ironhead guy, but as I recall they are marked at 40 or more degrees

If I had a set of flathead wheels, it would be no problem to degree them. Just don't have any and I can't justify buying a set only for the sake of satisfying my curiosity, at this time.
 

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i have my knuck apart (which has flathead flywheels), waiting on flywheel thrust washers to put it back together, so i'll try to get out in the garage tomorrow to measure them for you and let you know.

take care,
-dan
That would be great, Im very interested in this also. I have a set of flathead wheels (shaved left side) that they did not put a timing mark back on. :confused:
 

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ok, sorry to be a bit slower than i said, but here are some pics for you guys.

my wheels, which are according to Mr. Palmer's book, 1937-48 74 and 80 Sidevalve wheels, only have one timing mark present (unless the little round depressions mean something). this being the case, i took some photos of just the sprocket shaft side wheel by itself, and the same with a degree wheel aligned with the only mark at 0, and another shot with the 0 mark aligned as best i could in a straight line with the centerline of the sprocket shaft and centerline of the crankpin.

don't know if these help or not, but if you'd like me to measure them some other way, let me know and i'd be glad to do it for ya.

take care,
-dan
 

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Im heading to the shop today.

Down there is a flattie, knucks and pans and gennie shovels, complete and apart.

If I'm no mistaken, the timing mark for TDC of the front hole, shouldn't it be when the crankpin is at it's highest rotational point directly inline with the front cylinder, and showing through the timing hole? Isn't the timing hole directly above the crank pin, between the two cylinders? Effectively splitting the "V"?

It's my thinking that all the bigtwins are the same degree V. That being true, shouldn't it be simple enough to "degree" the wheels and find out where the marks are. I'm thinking the TDC marks will have to be the same, but depending on stroke, the timing marks will be different.
 

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well they are different part numbers, but i find it odd that they want you to measure one at the back of the hole and another in the center.
True on the part numbers, but they all have sight differences. I'm getting at the basics of design as far as degrees.

Why they measure one at front or back of the whole, that is an interesting question. I wonder if OEM cam profile/timing differences comes into play here.

They all are 45 degrees, right? So placing the timing mark in the center at O, would put the front rod and crank pins in alignment at exactly 22.5 degrees. Is my thinking on this correct?
 

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I made it down, but didn't take any shots. Its a friends shop, and when he gets over his head he'll call for some help. I got stuck doing a motor and trans swap. Next is a rewire job. Oh well, we did chat some about the wheels and the differences. He knows them pretty well.

I'll get some shots.

Which ones exactly do you want to compare? He's got a hotrod flattie up and running in a bike. In the same room is two knucks and a couple pans. I could pop the timing plug on each and shoot the marks. I know he has some wheels for each up in the "stash" room. Maybe you want it both ways? In running bikes and on the bare wheels?
 
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