Cub engine queston?

[smokinj]

I think I went to 400, but others online quote anywhere between 120 - 600. I'd guess 220 is fine, but maybe wait for MasterMech to come in.

The torque pattern is critical on these, and there are two different K301 torque patterns. Google (or the folks at onlycubcadets) is your friend, here. I gave my Kohler manual to the guy who bought my cub, so I don't have it anymore.

I have the service manual. IT IS 25-30 LBS WITH TORQUE PATTERN.

 

[Jags]

Jay - hit 220. If you have it and the extra 45 seconds to spare, finish with the 400, but that is probably not a requirement.

 

[Ashful]

Cool. The torque pattern in my manual was apparently for a real old (1965) cub, and I remember they had a newer torque pattern. The guys over at onlycubcadets seemed to think that following the pattern was a huge issue on these.

The one thing that was a real PITA was that most of them will tell you to torque everything down, put a few hours on the engine, and then re-torque those head bolts. That means pulling off the gas tank and sheet metal a second time.

 

[Jags]

The one thing that was a real PITA was that most of them will tell you to torque everything down, put a few hours on the engine, and then re-torque those head bolts. That means pulling off the gas tank and sheet metal a second time.

If you are using OEM head gasket, then yes, you will want to re-torque.

 

[smokinj]

Cool. The torque pattern in my manual was apparently for a real old (1965) cub, and I remember they had a newer torque pattern. The guys over at onlycubcadets seemed to think that following the pattern was a huge issue on these.

The one thing that was a real PITA was that most of them will tell you to torque everything down, put a few hours on the engine, and then re-torque those head bolts. That means pulling off the gas tank and sheet metal a second time.

Not on a 128 you don't. Its even got holes in the heat shield for the head bolts.

 

[Ashful]

Cool. They obviously learned from the past!

 

[charly]

Never re-torqued any Harley head bolts.. Actually by re torquing a bolt , the initial inertia used to get the bolt moving again winds up over torquing the bolt , etc. Your better off backing off and then coming up to the torque spec you wanted.. This was mentioned in service school for Harley and also by a DOT trainer on heavy trucks concerning checking wheel nut torques... I would just go 10 -20- 30 ft lbs and let it be..Use the proper torque pattern.. On the New EVO Harley they wound up going to two increments of torque, like 7 ft lbs, then 18, and after that a 90 degree turn at the end on each head bolt.. Been a long time so can't remember exactly the first two specs , but that was their sequence.. 30 ft lbs will still give you a 5 lb variable for the head gasket crushing down.. Then some later stuff had you did the first two torques, back them back off and then re tighten the head back up as normal.. That precrushed the gasket. I'm surprised they just don't do something like that instead of taking everything back off to check..

 

[MasterMech]

two increments of torque, like 7 ft lbs, then 18, and after that a 90 degree turn at the end on each head bolt​

That's a Torque To Yield fastener. Different animal. They are designed to be put under a certain amount of pre-tension (the torque spec) and then streched a certain distance like a spring. (that's the 90 deg spec. If you had 16 threads per inch [std for a 3/8" head bolt/stud] 90 deg would be stretching that bolt 0.015625". )
The point of coming up in steps rather than just torqing to spec is so that the clamping force remains even as the final bolts are torqued down. Say you torque one side of the part to spec, as you move towards the opposite side, the part can act as a lever and actually increase the clamping force in the area where you first started torqing fasteners.

 

[smokinj]

Ok grit how fine o a grit should be used?

 

[charly]

That's a Torque To Yield fastener. Different animal. They are designed to be put under a certain amount of pre-tension (the torque spec) and then streched a certain distance like a spring. (that's the 90 deg spec. If you had 16 threads per inch [std for a 3/8" head bolt/stud] 90 deg would be stretching that bolt 0.015625". )
The point of coming up in steps rather than just torqing to spec is so that the clamping force remains even as the final bolts are torqued down. Say you torque one side of the part to spec, as you move towards the opposite side, the part can act as a lever and actually increase the clamping force in the area where you first started torqing fasteners.

I realize you would never torque one bolt to it's full spec and then start the others.. Just saying how you have to know what the specs are for torquing down a particular application..

 

[Ashful]

I realize you would never torque one bolt to it's full spec and then start the others.. Just saying how you have to know what the specs are for torquing down a particular application..

Yeah... but the Cub shop manuals were written at a time when a certain amount of intelligence was assumed (something our litigious society has forgotten) on the part of the owner / mechanic. It simply gives the pattern (eg. fasteners 1 thru 8), final torque value, and states "torque in steps up to final value". Less detailed than a modern Harley shop manual, for sure.

 

[smokinj]

Yeah... but the Cub shop manuals were written at a time when a certain amount of intelligence was assumed (something our litigious society has forgotten) on the part of the owner / mechanic. It simply gives the pattern (eg. fasteners 1 thru 8), final torque value, and states "torque in steps up to final value". Less detailed than a modern Harley shop manual, for sure.

Yep I think the that pattern and torque is pretty simple stuff. With manual in hand. Now back to the grit factor. How high should I go?

 

[Jags]

Yep I think the that pattern and torque is pretty simple stuff. With manual in hand. Now back to the grit factor. How high should I go?

400 or 600 - whatever you got - will get the job done and shiny.

 

[smokinj]

400 or 600 - whatever you got - will get the job done and shiny.

I am at 220 now. Got any ideas to make Velcro stick to granite?

 

[Ashful]

Hah... I already gave you my answer! I went to 400 (or maybe higher), but that's because I already had paper on-hand to at least 2000 grit. I see folks on Cub forums posting anywhere between 120 and 600 grit, as the final surface. I basically look at the surface, and make a call on whether or not I think it's scratch-free enough for the head gasket to make a good seal.

Having only done this a few times in 40 years, but I guess Jags has done a bunch of these, and he says 240 is good enough. I would guess that if you go too coarse, you'll see evidence of blow-by at the aluminum ring on the head gasket, next time you have the head off. Then you'll know.

BTW... don't use that velcro chit! It's not flat enough. You'll end up with a convex (not flat) surface on the head. Your local body shop supplier will have the flat SiC paper I use, and they sell single sheets (it's expensive, for sandpaper).

 

[Ashful]

Here's a suitable paper. This 5-pack has one sheet of each grit you'll need.

http://www.mcmaster.com/#4680A112

 

[smokinj]

Hah... I already gave you my answer! I went to 400 (or maybe higher), but that's because I already had paper on-hand to at least 2000 grit. I see folks on Cub forums posting anywhere between 120 and 600 grit, as the final surface. I basically look at the surface, and make a call on whether or not I think it's scratch-free enough for the head gasket to make a good seal.

Having only done this a few times in 40 years, but I guess Jags has done a bunch of these, and he says 240 is good enough. I would guess that if you go too coarse, you'll see evidence of blow-by at the aluminum ring on the head gasket, next time you have the head off. Then you'll know.

BTW... don't use that velcro chit! It's not flat enough. You'll end up with a convex (not flat) surface on the head. Your local body shop supplier will have the flat SiC paper I use, and they sell single sheets (it's expensive, for sandpaper).

I think you said wait for reply from master small engines. I have Norton wood and metal up to 220 grit and everything else I have over 220 is Velcro (Auto body paper) and trying to figure out how to make it stick?

 

[lukem]

You don't want velcro. An old timer machinist friend of mine had a certified flat granite slab for doing just what you are doing. He would spill a little of his coke on the slab, wipe it around, and put down the sand paper. Wait a few minutes...bingo...your paper is stuck to the slab...and cleans up with a little soap and water.

 

[Ashful]

I think you said wait for reply from master small engines.

Always a safe bet. Did you see my link for SiC paper from McMaster? At $5, I'd pick up a pack, and use that. They probably have some other hardware you need, anyway... so you can combine shipping on a few items.

 

[smokinj]

Always a safe bet. Did you see my link for SiC paper from McMaster? At $5, I'd pick up a pack, and use that. They probably have some other hardware you need, anyway... so you can combine shipping on a few items.

Yea trying to use what I got on hand. I have draws full of sand paper but most is for my 1,2,4,6 inch Velcro system.

 

[Ashful]

The trouble with the velcro is that you're trying to be flat within a few thousandths of an inch, and most Velcro loop backing will compress and conform to a few hundredths of an inch. No way it's staying as flat as you want.

 

[smokinj]

The trouble with the velcro is that you're trying to be flat within a few thousandths of an inch, and most Velcro loop backing will compress and conform to a few hundredths of an inch. No way it's staying as flat as you want.

Nor can I get it to stick!

 

[Ashful]

I like lukem's suggestion, and will have to try that next. I have a bunch of heavy glass plates around, and I usually either just use water (which helps it stick a little, but you still have to hold it in place by hand), or spray adhesive. The spray adhesive is great for keeping it in place, but it's tricky to get that stuff perfectly flat. The soda would be about perfect.

Another idea I just came up with is hair spray. I always have a can of Aqua Net in the shop, which I use for things like installing handle-bar grips on bikes. Slippery lube when wet, sticky as all heck when dry.

 

[Jags]

Don't use the velcro backed stuff, Jay. It will have too much give or "sponge" to it. Heck - you are at 220, get a sheet of wet/dry 400 or 600 from any store you can. Wet the back side slightly (it will help it stay in place) and then wet the surface of the grit. Get-R-Done. It won't take but a couple of minutes.

 

[smokinj]

Don't use the velcro backed stuff, Jay. It will have too much give or "sponge" to it. Heck - you are at 220, get a sheet of wet/dry 400 or 600 from any store you can. Wet the back side slightly (it will help it stay in place) and then wet the surface of the grit. Get-R-Done. It won't take but a couple of minutes.

Yea that's what I am going to do. Cant believe 5 draws full of sandpaper up to 3m's 1500 grit that I don't have the paper to finish this. (Head held low)