Flywheel welding
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3rd Gear
Joined: Jul 2014
Posts: 7
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From: Minnesota
Flywheel welding
Looking for some advice here about stock flywheels. I am in the planning stages of building a 117 for my 07 ultra. Question is are trued and welded flywheels with a timken bearing sufficient enough for a high output 117 build? I already have a stock set of flywheel sitting in the shelf that needs reworking, but if they are still going to be a problem Ill just build a 124. Building a crate style engine on the bench when done will put it in the scooter so down time not a issue.
Road Captain
Joined: Mar 2020
Posts: 650
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From: Sierra foothills
If building a high output 117, you are going to need to either have your flywheel rebuilt or replaced with a S&S flywheel. I recommend S&S. I have purchased two and both were within 0.0005 tir pinion side, and so far bullet proof.
I don't think welding is necessary on properly rebuilt/built/plugged flywheels. I had a flywheel rebuilt and welded once and was less than impressed with the weld quality. Came back with crater cracks on welds and I could tell not enough penetration to really make any difference. Any welding substantial enough on its own to really hold on a flywheel is likely to pull assembly out of true. Welding induces stress
High output 117 or regular 124 cost about the same. You can get 135hp on a 117 with a bit of work. You can get 135hp, probably 140 on a 124 pretty easily.
I don't think welding is necessary on properly rebuilt/built/plugged flywheels. I had a flywheel rebuilt and welded once and was less than impressed with the weld quality. Came back with crater cracks on welds and I could tell not enough penetration to really make any difference. Any welding substantial enough on its own to really hold on a flywheel is likely to pull assembly out of true. Welding induces stress
High output 117 or regular 124 cost about the same. You can get 135hp on a 117 with a bit of work. You can get 135hp, probably 140 on a 124 pretty easily.
Last edited by tdrglide; Nov 28, 2022 at 11:55 AM.
Grand HDF Member
Joined: Sep 2017
Posts: 4,359
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From: Dubuque, IA
+1 on the S&S. No welds to worry about and save your money on the Timken setup too. The lefty bearings have never been an issue and the guy from S&S that did did mine for me won't take your money for the timken conversion either.
While I'm only running a 107, I am doing just under 130ft lbs of torque running a 30 tooth compensator eliminator and run it hard with no worries.
While I'm only running a 107, I am doing just under 130ft lbs of torque running a 30 tooth compensator eliminator and run it hard with no worries.
Club Member
Joined: Mar 2009
Posts: 66,102
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From: Niles Canyon Ca.
Little welder input, they put enough penetration weld on to actually hold the heat expansion will warp the wheels and it's two very different hardness metals which leads to stress cracking in the welds. Some higher end shops do it right but most welds you see are shallow surface blend tig , not deep penetration work. There's a youtube vid where they did a torque test on welded versus pressed wheels. The welds let go not much above the pressed.
S&S bigger crankpin wheels are the way to go.
S&S bigger crankpin wheels are the way to go.
Seasoned HDF Member
Joined: Dec 2005
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From: poway
Little welder input, they put enough penetration weld on to actually hold the heat expansion will warp the wheels and it's two very different hardness metals which leads to stress cracking in the welds. Some higher end shops do it right but most welds you see are shallow surface blend tig , not deep penetration work. There's a youtube vid where they did a torque test on welded versus pressed wheels. The welds let go not much above the pressed.
S&S bigger crankpin wheels are the way to go.
S&S bigger crankpin wheels are the way to go.
Club Member
Joined: Mar 2009
Posts: 66,102
Likes: 51,361
From: Niles Canyon Ca.
Yes, not sure of the sizes per say but the bigger pin means more surface area to hold things true.
Road Captain
Joined: Mar 2020
Posts: 650
Likes: 351
From: Sierra foothills
Just a poor joint design for weld. In a lot of ways. Although I'm sure some shops can make a pretty looking weld
When I pulled out the welded flywheel a few years later, one of the welds had completely cracked, right down the middle. Cosmetic weld at best. And sloppy at that. Don't know what they used for filler metal. Should have done it myself or just not at all
When I pulled out the welded flywheel a few years later, one of the welds had completely cracked, right down the middle. Cosmetic weld at best. And sloppy at that. Don't know what they used for filler metal. Should have done it myself or just not at all
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Seasoned HDF Member
Joined: Jun 2017
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From: Granville New York
I have a darkhorse man o war crank in my 117 with lefty bearings on both sides and so far no problems. I don't thrash it at the drag strip but I make use of the power. You'll be fine with S&S crank...they sure are purty lol...its a shame they get hidden inside of the motor.
HDF Community Team
Joined: Apr 2018
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From: Ohio
Looking for some advice here about stock flywheels. I am in the planning stages of building a 117 for my 07 ultra. Question is are trued and welded flywheels with a timken bearing sufficient enough for a high output 117 build? I already have a stock set of flywheel sitting in the shelf that needs reworking, but if they are still going to be a problem Ill just build a 124. Building a crate style engine on the bench when done will put it in the scooter so down time not a issue.
By the time you send your set somwhere, pay to have it worked & pay shipping both ways you probably could have just bought an S&S.