Lighten & knife edge flywheel assembly

[Mattls6]

Sending my stock M8 flywheel assembly to Darkhorse to be beefed up. For $200 they can lighten and knife edge it (-1.5lbs.).

Has anyone had that service done? If so, what are your interpretations?

I spoke with DH but they were neutral on it, looking for some real world feedback.

Bike is a solo ridden Street Bob, will be a little bit of a hot rod. I could myself liking slightly quicker revs but I'm sure it comes at a cost.

[RTMike]

Keep them heavy!

[Mattls6]

Yeah, leaning towards keeping heavy, but would be nice if it revved quicker...

 

[BigT]

Yeah, leaning towards keeping heavy, but would be nice if it revved quicker...

 

Up the cubic inches...that will make it rev faster!

[JSD]

Moonshine harley had a discussion on this on Utube . What ya got 4 3/8 "?

[Ohio HD]

Yeah, leaning towards keeping heavy, but would be nice if it revved quicker...

 

You want faster revs, use a cam with moderate overlap and duration, and set the compression on the top side of the cams needs. Less overlap aids in combustion efficiency.

[hrdtail78]

IMO With flywheels having nothing to do with getting oil out of the bottom end, or splash lube, on TC's and up.  The flywheel really shouldn't be in a puddle of oil anyway.  So, I really don't see the advantage.  BUT maybe I am missing an advantage to it.

[SP33DY]

IMO With flywheels having nothing to do with getting oil out of the bottom end, or splash lube, on TC's and up.  The flywheel really shouldn't be in a puddle of oil anyway.  So, I really don't see the advantage.  BUT maybe I am missing an advantage to it.

The flywheels in a Twin Cam or M-8 behave just like the earlier Big Twins. They spin up and act like the impeller in a centrifugal pump, and the scraper plate cast into the bottom of the case halves scrape the "ropes" off the edge of the flywheels and direct the oil to the scavenge port of the oil pump.

[hrdtail78]

IMO With flywheels having nothing to do with getting oil out of the bottom end, or splash lube, on TC's and up.  The flywheel really shouldn't be in a puddle of oil anyway.  So, I really don't see the advantage.  BUT maybe I am missing an advantage to it.

The flywheels in a Twin Cam or M-8 behave just like the earlier Big Twins. They spin up and act like the impeller in a centrifugal pump, and the scraper plate cast into the bottom of the case halves scrape the "ropes" off the edge of the flywheels and direct the oil to the scavenge port of the oil pump.

Yes, but earlier big twins relied on flywheel to get oil to piston walls and pistons, and remove 99% oil in the engine.  From the return from heads and lower end oiling to a scraper that is at the 10 oclock position.  This includes the oil running off the side walls coming out the main bearing.  Which in a TC or M8 could drain to bottom and into sump without touching a flywheel.  I don't think the TC or M8 should be running through a bath of oil.  The earlier models have to, to remove oil.  This is why a knife edge flywheel can cut through this pool and still get oil to cling to it to move it.  This is the reason I don't believe there is a great advantage to a knife edge fly wheel in the later models. 

[Hossamania]

Probably not necessary for the street, but would it help on a race bike, cut elapsed time in the 1/4 mile, or a road course?
Every advantage, you know!

[turboprop]

Some engines for land speed bikes have weight added to the wheels during the balancing process.

[FLDavetrain]

Sending my stock M8 flywheel assembly to Darkhorse to be beefed up. For $200 they can lighten and knife edge it (-1.5lbs.).

Has anyone had that service done? If so, what are your interpretations?

I spoke with DH but they were neutral on it, looking for some real world feedback.

Bike is a solo ridden Street Bob, will be a little bit of a hot rod. I could myself liking slightly quicker revs but I'm sure it comes at a cost.

I've had that exact service done on late model TC and have builds very similar wout. So I think I can compare somewhat apples to apples on the street. I vote yes on the lightening, that bagger wheelies easier than the other with similar power delivery and maybe those DH wheels contribute. At .0003 runout it's just an awesome product, go for it.

[Ohio HD]

I've had that exact service done on late model TC and have builds very similar wout. So I think I can compare somewhat apples to apples on the street. I vote yes on the lightening, that bagger wheelies easier than the other with similar power delivery and maybe those DH wheels contribute. At .0003 runout it's just an awesome product, go for it.

Can you share some pics of the wheels? I'd like to see how they deal with the teeth when knife edging

[FLDavetrain]

I've had that exact service done on late model TC and have builds very similar wout. So I think I can compare somewhat apples to apples on the street. I vote yes on the lightening, that bagger wheelies easier than the other with similar power delivery and maybe those DH wheels contribute. At .0003 runout it's just an awesome product, go for it.

Can you share some pics of the wheels? I'd like to see how they deal with the teeth when knife edging

No clear shot of it, came back in the cases

[SP33DY]

I've had that exact service done on late model TC and have builds very similar wout. So I think I can compare somewhat apples to apples on the street. I vote yes on the lightening, that bagger wheelies easier than the other with similar power delivery and maybe those DH wheels contribute. At .0003 runout it's just an awesome product, go for it.

Can you share some pics of the wheels? I'd like to see how they deal with the teeth when knife edging

I don't have pictures, but I have had TC flywheels "knife edged" for some of my builds.
 
The term "knife edge" is a little misleading if you take it literally.

On Twin Cam flywheels, the timing teeth are on the outside half of the left flywheel, about 1/2" wide. They cut a bevel on the insides of the flywheels and the bevel stops at the teeth on the left flywheel, and they also stop within about 1/2" from the edge of the right flywheel.

On M-8 flywheels the the timing teeth are on the inside edge of the flywheel. I haven't had any M-8's knife edged, so I don't know if they just cut the outsides of the wheels, or if they take a little bit off the inside too.

[Mattls6]

I don't remember the convo exactly but I do recall them mentioning some cranks get beveled on the inside, some the outside.

Didn't dawn on me before, but the lightening holes seem counterintuitive to beefing up the stock flywheels since the existing hole is being plugged and welded. I'm not an engineer but I could see how that may weaken the assembly.

I'll need to speak with them about it again. Perhaps the placement of the holes makes it a non-issue. Maybe I'll split the weight difference and have the flywheels edged only, I dunno.

If it were one of my track bikes I'd have it lightened without question. Since this one is 90% street / 10% track I've been torn. I do ride the hell out of my bikes.

[Deye76]

Brian, from the DH FB page.

[Ohio HD]

Can you share some pics of the wheels? I'd like to see how they deal with the teeth when knife edging

I don't have pictures, but I have had TC flywheels "knife edged" for some of my builds.
 
The term "knife edge" is a little misleading if you take it literally.

On Twin Cam flywheels, the timing teeth are on the outside half of the left flywheel, about 1/2" wide. They cut a bevel on the insides of the flywheels and the bevel stops at the teeth on the left flywheel, and they also stop within about 1/2" from the edge of the right flywheel.

On M-8 flywheels the the timing teeth are on the inside edge of the flywheel. I haven't had any M-8's knife edged, so I don't know if they just cut the outsides of the wheels, or if they take a little bit off the inside too.

Thanks, I did know that from Talking to Andrew at DH with my last crank he built. The M8 they chamfer the outside as there are no teeth located there. The teeth are on the opposite flywheel as well. 

[Ohio HD]

I don't remember the convo exactly but I do recall them mentioning some cranks get beveled on the inside, some the outside.

Yes, the same info that Andrew gave me last spring when I had a TC stroker crank built.

[Ohio HD]

Brian, from the DH FB page.

Thanks John