Billet Tappet Cuff Kit M8

[Ohio HD]

I came across this kit on Fuel Moto's site. An intermediate plate that acts as a lifter cuff, and then a shorter (I assume shorter) lifter cover to complete the assembly. They're pricey, but might be worth it to some when a tappet cuff bolt breaks off.


Billet Tappet Cuff Kit M8

[FSG]

I like the idea .....  but I don't like the o-rings and they are spendy, very spendy   

[Ohio HD]

Yeah I was wondering about the o-ring. But I guess it's to get a metal to metal fitment. Probably less likely for the plate to shift without a gasket there. Assuming the o-ring is the bottom of the plate to the case.

[FSG]

yeah .....  need to see the underside of the plate and the screws

[Ohio HD]

Found the answer FSG, it's the bottom of the plate.



O. F. Performance

[FSG]

 

If it was me I'd bee getting Apple Rubber Products (or similar) to do a molded o-ring that shape to make it even better

[Ohio HD]

After thinking this through, the o-ring is needed instead of a gasket. A gasket at the case and the intermediate plate would most likely not pull down evenly, and would put the lifters in a bind with the cuff section of the plate. The compressed o-ring allows a metal to metal connection between the intermediate plate and the case. Allowing the cuff section to stay in line with the lifters.

[biggzed]

Nice piece. I have to wonder though, how weak of a link are the stock plastic parts HD uses on a basically stock bike with a cam upgrade? I'm at the point of placing an order for a cam in the next 30 days or so. Going with the CR480. I had the S&S replacements in mind, but really started to question if they were necessary. Now these come along and I'm asking the same question.

I can see if I were going to a more max effort 128", then it becomes the "while you're in there" part of the conversation.

Zach

[Ohio HD]

I think the preferred upgrade if you want better than stock is to use the S&S Cuffs. Considerably less expensive. The OF Performance kit is when you break a cuff bolt and can't remove the broken bolt. Or don't wish to try to remove it.


S&S 330-0655

[Hossamania]

After having a friend break a cuff bolt and going into complete panic mode, this seems a simple solution that would relieve a lot of stress. It might relieve a little weight from your wallet as well, but if you don't have the skills or tools to remove the broken bolt, this solves the problem easily.

Correction:
Ok, I just looked up the price. It will relieve a LOT of weight from your wallet. You might want to figure out how to drill out that broken bolt...

[biggzed]

Those are the ones I had in my plan, but now I'm questioning if they are necessary. Are the stock pieces really a weak link, or did the aftermarket identify an opportunity to take our money. Do we know of real world cases of the lifters twisting in their bores because of the factory plastic cuffs?

It's not like $80 is that big a deal, but IF that bolt snaps it becomes a situation that gets considerably more frustrating (if extraction is the path) or expensive (if these new $575 Fuel Moto parts are the path). Makes me wonder if I should even mess with the stock cuffs. Again, this would be a cam only upgrade. Not talking about a max effort big bore kit here.

Zach

I think the preferred upgrade if you want better than stock is to use the S&S Cuffs. Considerably less expensive. The OF Performance kit is when you break a cuff bolt and can't remove the broken bolt. Or don't wish to try to remove it.

S&S 330-0655

[Hossamania]

The cuffs are made for stock cam lift, and look to me that any increase in lift has potential for issues. Might be fine too, of course. Have you seen them in person, they sure seem "fragile" to me, but I am just a dumb amateur when it comes to real motor work.

[Ohio HD]

Those are the ones I had in my plan, but now I'm questioning if they are necessary. Are the stock pieces really a weak link, or did the aftermarket identify an opportunity to take our money. Do we know of real world cases of the lifters twisting in their bores because of the factory plastic cuffs?

It's not like $80 is that big a deal, but IF that bolt snaps it becomes a situation that gets considerably more frustrating (if extraction is the path) or expensive (if these new $575 Fuel Moto parts are the path). Makes me wonder if I should even mess with the stock cuffs. Again, this would be a cam only upgrade. Not talking about a max effort big bore kit here.

Zach

Yes the purpose of the cuffs is to keep the lifters from rotating back and forth in the bore. How much of a problem is this? I don't know. But I always used oversize pins in the TC cases to tighten the fit against the lifters. More than once I saw dings and wear marks in the OEM pins that allowed the lifter to rotate in the bore. These all were with larger than stock cams. I assume the plastic used in the M8 is designed to be non-marking.

If you follow methods like Fuel Moto suggests the bolts can be removed without drama. And then the new bolt can be used with Blue Loctite which is easily removed.

H-D Milwaukee 8 Lifter Tappet Cuff bolt removal tips

[biggzed]

Thanks Ohio - I hadn't seen that tip on FM website. They have a lot of good information in there.

I'm like you Hoss - Just an amateur trying to not make life more frustrating than it is. I know the S&S part is far superior to the stock plastic part, was just questioning the necessity. I'll probably still go with the S&S cuffs and take the chance on the bolts (with the heat gun).

Zach

Those are the ones I had in my plan, but now I'm questioning if they are necessary. Are the stock pieces really a weak link, or did the aftermarket identify an opportunity to take our money. Do we know of real world cases of the lifters twisting in their bores because of the factory plastic cuffs?

It's not like $80 is that big a deal, but IF that bolt snaps it becomes a situation that gets considerably more frustrating (if extraction is the path) or expensive (if these new $575 Fuel Moto parts are the path). Makes me wonder if I should even mess with the stock cuffs. Again, this would be a cam only upgrade. Not talking about a max effort big bore kit here.

Zach

Yes the purpose of the cuffs is to keep the lifters from rotating back and forth in the bore. How much of a problem is this? I don't know. But I always used oversize pins in the TC cases to tighten the fit against the lifters. More than once I saw dings and wear marks in the OEM pins that allowed the lifter to rotate in the bore. These all were with larger than stock cams. I assume the plastic used in the M8 is designed to be non-marking.

If you follow methods like Fuel Moto suggests the bolts can be removed without drama. And then the new bolt can be used with Blue Loctite which is easily removed.

H-D Milwaukee 8 Lifter Tappet Cuff bolt removal tips

[hrdtail78]

If the stock cuffs fit down to the plain of the lifter block cover gasket surface.  The S&S fits down to the gasket surface and these new design also fit to the plain of the gasket surface.  How will one allow more cam lift over the other?

The pic in reply 4 shows the underside.  I see no clearance for the lifter to go any higher than the stock piece does.  There is no relief in the S&S ones either.

I have heard of zero issue with stock no matter what the effort the engine is built to.  I hear about people having problems while performing maintenance.  Maybe more youtube is needed to realize some loctite needs heat for ease of removal?  Are the LS guys getting rid of their plastic lifter guides?

[Ohio HD]

I'm sure there is a potential lift limit to any of the cuffs, whether it be S&S or OEM. When I asked S&S some time back they said that the limit was 0.600" lift. I assume they mean by their cam design and base circle. Other cam manufactures that may not be the same lift due to base circle size. 

[Hossamania]

But the S&S cuffs are so pretty!

[Ohio HD]

Just out of curiosity I contacted OF Performance and asked about maximum cam lift. They're replay was 0.610" lift based on stock M8 heads. So I assume stock rocker arm ratio and stock valve protrusion, unmachined head gasket surface, etc. And some static cam base circle.

Maybe all M8 cams are using the same base circle.   

Like anything else, one needs to measure things before closing up the motor.

[hrdtail78]

I have seen most at 1.5 and have seen some at 1.45.  Measure roughly with calibers and not micrometer.

[les]

Does FuelMoto give you grade 8 or grade 5 screws for the lifter cuffs?

[SP33DY]

If the stock cuffs fit down to the plain of the lifter block cover gasket surface.  The S&S fits down to the gasket surface and these new design also fit to the plain of the gasket surface.  How will one allow more cam lift over the other?

The pic in reply 4 shows the underside.  I see no clearance for the lifter to go any higher than the stock piece does.  There is no relief in the S&S ones either.

I have heard of zero issue with stock no matter what the effort the engine is built to.  I hear about people having problems while performing maintenance.  Maybe more youtube is needed to realize some loctite needs heat for ease of removal?  Are the LS guys getting rid of their plastic lifter guides?

Take another look at the S&S cuffs. They definitely have a relief in the underside for higher lifter travel. If I could remember how to post a photo, I would add one. Maybe someone else could?

[hrdtail78]

For the m8?  I'll have to take a second look.  I don't have any in stock at this time.

[ziggy24]

Not to mention, when using a high lift cam, by default allows the lifter to travel higher out of the bore. I would guess at some point the tolerances in the lifter bore, being what they are, would let the lifter become unstable, with a hot piece of plastic trying to keep them from getting a little hinkey.

[Ohio HD]

Cycle Rama also got into the lifter cuff business this year I think it was.

[biggzed]

So S&S says .600 lift for their cuffs and OF says .610. Safe to say either is good to go from a cam lift perspective. I only see 2 .600 lift cams on the spreadsheet Ohio created for the specs on M8 cams.

At this point I'll probably take my chances and replace the stock plastic with S&S using the Fuel Moto recommendation and hope for the best.

Zach