117 and 124 differences
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Road Master
Joined: Jun 2012
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From: Mo
One thing about long strokes not discussed much is the "side load" on the cylinder when the crank is at mid stroke. A guy I used to go to the track with had a BAD *** Ironhead stroker. 4-3/4" T&O wheels, IIRC. Ran a 4"slick, was a HOT little street/strip bike. This thing blew the side of the front cylinder out and took the spigot and case with it during a run. The long rod/long stroke puts a lot of force perpendicular to the piston's direction of travel.
Now, case castings have come a LONG way since Ironhead days, but the longer strokes still push the pistons hard against the cylinder walls. This causes cylinder/piston wear more rapidly than in a lesser stroke engine.
That said, the 124" has been around for a while, now; it's not as if it ain't a proven combination... Just thinking about it in light of what I know about long arm strokers, it seems to me that an equally prepped 117 should outlast a 124.
Now, case castings have come a LONG way since Ironhead days, but the longer strokes still push the pistons hard against the cylinder walls. This causes cylinder/piston wear more rapidly than in a lesser stroke engine.
That said, the 124" has been around for a while, now; it's not as if it ain't a proven combination... Just thinking about it in light of what I know about long arm strokers, it seems to me that an equally prepped 117 should outlast a 124.
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One thing I'll mention about long stroke engines, ie, 4 3/4"-5" applications, is that TDC dwell, and BDC dwell time is increased as well.
With a 5" arm, when mocking up an engine, or checking with a degree wheel, you can certainly witness how FAST that piston moves once the flywheels are rotated from either postion, TDC, or bottom center.
Scott
With a 5" arm, when mocking up an engine, or checking with a degree wheel, you can certainly witness how FAST that piston moves once the flywheels are rotated from either postion, TDC, or bottom center.
Scott
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Road Master
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From: Mo
I'm sticking to my original plan of the 117. PLENTY enough motor for me. If that doesn't work, there is little nitrous kits for just incase I ever need to play catch up. Very good info about the two motors!!
Ultimate HDF Member
Joined: Jan 2008
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From: SoCal
I just had a long chat with my guy. I have a 107" that is leaned on pretty good for a street bagger so I am preparing for the inevitable. 117" is the way i'm gonna go. I like 'em closer to square than where a 124" gets me. Good thing is I have the cams, TB, heads and exhaust already on my 107" that will work great on a 117". So I am giving up some low end tq currently but she is still pretty darn fun.
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