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-   Ironhead Sportster Motorcycle Talk (1957-1985) (http://xlforum.net/forums/forumdisplay.php?f=7)
-   -   Ironhead Shovster build take2 (http://xlforum.net/forums/showthread.php?t=2077210)

Maxeffort 13th July 2020 18:38

Quote:

Originally Posted by wedge (Post 5836401)
So, doesn't this crank lower the compression again?

I read it as going to a longer stroke

The longer the stroke, the more compression (assuming chamber size, bore, piston dome, etc.. stay the same)

billeuze 13th July 2020 18:54

Quote:

Originally Posted by wedge (Post 5836401)
So, doesn't this crank lower the compression again?

Yes, I’ll have to deal with that by milling the heads and/or the cylinders

billeuze 13th July 2020 18:56

Quote:

Originally Posted by Maxeffort (Post 5836407)
I read it as going to a longer stroke

The longer the stroke, the more compression (assuming chamber size, bore, piston dome, etc.. stay the same)

The bigger t&o wheels I purchased would have increased the stroke and compression. But I broke them do I am back to my s&s 4-1/2” wheels.

davixlrtt 13th July 2020 19:55

Bill, I know that the crank assembly fell from the bench, but what part about it has actually been damaged enough to render the wheels useless?
........Davi.

billeuze 13th July 2020 20:59

Quote:

Originally Posted by kitabel (Post 5836420)
Where is your quench clearance?

I don't have my notes with me. But that will be dealt with and accounted for at the same time as milling the heads to increase compression ratio

Quote:

I've no contact with one of these engines, the throttle response must be great with the small OD (7-7/16" vs. 8-1/2") and light weight (20 lbs? vs. 25 for S&S BT).
I hope so, we'll see...

wedge 13th July 2020 21:05

Davi asked my next question. I'm not even involved and this is driving me nuts. I have been in your place once and it just drains the blood from your brain. In my case the wife and I were installing a very expensive redwood sign that was already attached to the posts. We leaned it against a tree for me to take a quick survey of the holes to be sure we were ready and I heard that same sickening sound as it hit the ground after a gust of wind knocked it over. Split the face into a few pieces, so we loaded it back into the truck and went straight into making another one.

In your case, I think we all want for you to find a solution that has you using the new wheels.

billeuze 13th July 2020 21:12

Quote:

Originally Posted by davixlrtt (Post 5836422)
Bill, I know that the crank assembly fell from the bench, but what part about it has actually been damaged enough to render the wheels useless?
........Davi.

Good question. Maybe they do still have a use.

I cannot get the crankpin anywhere close to true on them anymore. I can force it to true but then as soon as I apply more torque it goes way out of true again. I don't remember how much they are out but it is definitely closer to .01" than .001"

So what has been damaged? I think the tapers. I assume that with the momentum of the assembly landing on the floor, something had to give, or break, or bounce. So with the hard steel crankpin in relatively softer cast iron flywheel tapers, it is the cast iron that gave, deformed. I also assume that if we tried to correct the taper by re-machining that would make the taper bigger so the crank would go in deeper pinching the connecting rods.

If anyone knows otherwise or would have a use for these "damaged" flywheels, let me know.

needspeed 13th July 2020 22:52

Diameter of stock sportster flywheels = 7-7/8"

brucstoudt 13th July 2020 23:25

good looking video bill.when i was taught to check flywheels it was to hold the rods across your fingers in an open hand and turn the flywheel assy with your opposite hand.doe's anyone else do it that way?

Ferrous Head 13th July 2020 23:51

Paperweights ?

If it helps any, with the 4.5 inch wheels you don't actually have to move the oil holes.

And in theory the shorter stroke will allow higher revs which the Shovel Heads will be able to feed.
You should probably always skim alloy heads in any case so not really any extra cost there.

With the alloy heads you can up the compression more than you can with the cast iron Sportster version.

How much to take off ?

Dunno about that with Shovel heads. I would do a dry assembly and do a measure. Your also going to need to cc the combustion chamber to get a ball park figure.

It's not going to be "Super" critical either way. Too little of and you wind up with less compression than is optimal which you can correct by skimming again.
Too much can be alleviated by running thicker head gaskets.

The real go would be to try for some quench area. Then accept whatever clearance is required for that.


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