MK3 Restomod

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
Working in the shop keeps me sane (or at least less insane).

Ken
 

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
A little more progress. I cut the 83 mm pistons down as low as I could and still keep a deck thickness I felt safe with. This is a shot of one of the pistons next to a 79.5 mm piston that with the same deck height as the original 83 mm item.



I also need to re-balance the crankshaft, since it was originally balanced at 78% for use with Carrillo rods and unmodified pistons in a rigid mount frame. I need to get closer to the 52% Commando balance factor. I'm shooting for 62%, but the exact factor isn't that critical with isolastics. I need to take a fair amount of weight out of the flywheel. This is the setup I'm using in the mill to drill the flywheel. I'm being very careful to drill in precise locations and to the same depth on each side of the center line, so I don't introduce asymmetries that would affect the dynamic balance of the crank. I'm considering also moving some of the mass from the flywheel to the cheeks by adding heavy metal slugs, to get the forces closer to the main bearings, but haven't decided yet if I want to go to that level for a street bike engine.



Once the crankshaft is done, I can mock up the engine to see where I am in terms of compression ratio. Because of the 4 mm longer stroke, I'm going to have to use a combination of copper head and base gaskets to get the CR down, even with the shortened pistons. I'd like to run something between 9.0 and 9.5 when finished.

Ken
 

Attachments

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
So, next step is partially assembling to check for rod bolt clearance in the crankcase. I expected maybe a little interference, requiring some slight grinding for clearance, because of the long stroke. This is a shot of the assembly. There is a piston on the left rod to guide the rod appropriately. I'll eventually do the same with the left side crankcase half, with a piston on the right side rod.



The problem is worse than I expected, with significant interference. You can see the bolt head hitting the case in this picture.



This shot shows the area (between the marks) at the front of the case that needs metal removed to clear the rods. There's a similar area at the rear.



I hadn't expected this much problem, but after looking at it, I realize part of the problem was the rods I was using. Instead of Carrillos, I'm using a set of Don's (madass) rods, which are pretty much copies of the Carrillos, and very nicely done. Unfortunately, they have 3/8" bolts, instead of the 5/16" bolts Carrillo uses, so the heads are larger diameter, and also a little further out from the center-line. Both rods use ARP 2000 bolts, but Don chose to go up one size. Great for strength, but not so hot for clearance. They might work fine with stock or short stroke, but with the 93 mm stroke, there just isn't room for them.

I'm still working on a solution. One option is to order a set of Carrillos, and hope they have them on the shelf. I'll check with them and see. I don't want to have to wait till they do another batch of Norton rods, because I need to get this project done in time for the rally in July. I might still have to grind some clearance, but it would be a lot less. Another option is to tape up the crank, and grind the heads of the bolts at 45 degrees for clearance. I've actually done that before in a race Commando, and it worked fine. Even then I might have to grind the case a bit for clearance. The problem is that every time you tear it down, you have to use something like vise grips to remove the bolts, and you have to put in a set of new bolts, and then grind them to fit. I'm hoping to not have to tear this engine down for a long time, but you never know. Using stock rods is also an option, but I've already balanced the crank for steel rods, and don't really want to go through that again. Besides, it is 1006 ccs, with cam and big valves, etc., so that might be a bit much for the stock rods.

Stay tuned to this station for further developments.

Ken
 

Attachments

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
Looking a little better today. I taped up the crank like this



and ground large bevels on all four nuts. First try gave me .039" clearance at the closest spot. I bagged the crank up again and took off a bit more. Didn't manage a picture before closing up, but will take one tomorrow. I now have .060" clearance at the tightest spot. I have no experience with this, but I doubt very much that the crank will flex that much at the rod journals, so I think I'm good to go. I could get another .010", or maybe even .020" with some very careful grinding, but I don't think I need to. On the other hand, if I get paranoid about it tomorrow, I could take that little bit off, and also get some more clearance by machining the inside of the crankcase.

Ken
 

Attachments

grandpaul

VIP MEMBER
Joined
Jan 15, 2008
Messages
11,119
Country flag
I would have gone at the cases with a mill after marking a nice clean arc.
 

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
grandpaul said:
I would have gone at the cases with a mill after marking a nice clean arc.
Thought about it, but didn't want to risk weakening the cases. I've cracked enough of them over the years to be a little leery of removing material. In this case, if I hadn't ground down the cap screws, I'd have had to remove at least .125", and maybe more, to get clearance, and I wasn't comfortable with that. The best solution would have been to buy a set of Carrillo rods, but I didn't want the additional delay and expense at this point.

This is a picture of the crank after grinding the bolt heads. It may look a bit ugly, but it doesn't really take anything away from their clamping strength, just makes them more difficult to remove.



Ken
 

Attachments

Joined
Feb 5, 2011
Messages
1,920
Country flag
lcrken said:
................it doesn't really take anything away from their clamping strength, just makes them more difficult to remove......Ken
Well I don't have anywhere near the experience you do with these bikes, but it seems to me that you should be able to get them apart fairly easily, like you said, because you really only need to hold the bolt head still and keep it from turning while you (or someone else helping out ) turns the nut to undo it. Good looking crankshaft assembly you've got there, I especially like the way you lightened the center and added the heavy slugs to the outer cheeks. Thanks for posting and best of luck with the rest of the build. I bet it is going to be a beauty to ride! Which carbs are you going to use to feed those thousand cubes?
 

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
cjandme said:
lcrken said:
................it doesn't really take anything away from their clamping strength, just makes them more difficult to remove......Ken
Well I don't have anywhere near the experience you do with these bikes, but it seems to me that you should be able to get them apart fairly easily, like you said, because you really only need to hold the bolt head still and keep it from turning while you (or someone else helping out ) turns the nut to undo it. Good looking crankshaft assembly you've got there, I especially like the way you lightened the center and added the heavy slugs to the outer cheeks. Thanks for posting and best of luck with the rest of the build. I bet it is going to be a beauty to ride! Which carbs are you going to use to feed those thousand cubes?
There are no nuts. The bolt threads into the upper half of the rod big end. That's why it's more difficult to remove. Not impossible, just more difficult. The only issue here is the need to buy new ARP bolts each time the assembly is apart, and then go through the grinding process again. But they are readily available, and not all that expensive.

Ken
 

grandpaul

VIP MEMBER
Joined
Jan 15, 2008
Messages
11,119
Country flag
Ah, so.

I, too, was misguided in thinking it was nuts and threaded bolt ends being ground down.

Proceed.
 

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
Finally some more progress. Life keeps interfering with my plans. This is the engine lower bits mocked up to check the compression ratio. The piston is .030" below the deck. That's a bit more than I planned, and would make the CR only about 8.7 with the normal .040" thick copper gasket. Jim Schmidt supplied me with a .016" coper gasket. That will bring the CR up to just over 9.0. I had originally planned for something closer to 9.5, but 9.0 should be fine for a street bike on pump gas.



I'm using an Axtell cam ground for BSA radiused lifters, with adapters from JS Motorsports. The bronze adapters are held in place by a combination of stock lifter retainers and socket head set screws. This is a shot of the setup for drilling the cylinder base for the set screws.



This is a shot of the engine bits with the pistons in place and the cylinders ready to install. The head is complete, and ready to fit.



Or at least I thought they were ready when I took the picture. Turns out the lifters are way too tight in the adapters when the adapters are installed in the cylinder. What has happened is that the adapters are about .0015" larger in diameter where the slot for the lifter bases is milled than for the rest of the adapter. The adapters are a nice, tight fit in the bores, so when they are pressed all the way in, the slot gets slightly compressed, and pinches the lifter bases. I suspect that what has happened is that the adapters are turned to a very accurate diameter, but the force of milling the large slot for the lifter bases expands them slightly. It looks like I have two choices to get the fit right. I can chuck the adapters in the lathe and turn down the slot end just enough that it does't get squeezed tighter when installed, or I can just open up the slots a bit more so they are the right fit when installed. More details in a future installment.

Ken
 

Attachments

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
12,590
Country flag
Looking good Ken, as I would expect!

Is it the Axtel # 3 version you're running aka JS#1 ?

Are you going to run Jims pushrods too? Any thoughts on tappets clearances with the alloy pushrods and alloy cylinder block?

Please keep the updates and pics coming...
 

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
It's an Axtell #3 that I talked him into grinding for me years ago when I first started using BSA lifters. I had bought an ex-factory dirt track bike to get the short stroke 750 engine in it, and found it had a Sifton 460 cam with BSA lifters. After running it in my PR for several races, I tore it down, and discovered that the BSA lifters and cam lobe still looked like new, unlike what I had seen with cams and stock flat lifters. I thought it was pretty slick, and wanted to try the same setup with an Axtell cam. I had been using his #3 grinds with stock Norton lifters in my race bikes for some years by then, and really liked them. Axetel converted the flat tappet profile to suit the radiused lifters, but I was only able to get him to grind one cam to that profile for me. It's got pretty close lobe separation at 102 degrees, so I still have to check to be sure I don't have valve interference problems with the stage 3 Maney head. Steve re-angles both the intake and exhaust valves in the stage 3, so I should be ok.

I've never tried the #3 in a street bike, but I think the extra displacement will mellow it a bit, and I'm looking forward to seeing how well it works.

I make my own pushrods, so that won't be a problem. I've already made some for Norton engines with BSA lifters, so I have the basic dimensions, and will make a set to suit this engine.

I've always run the same valve clearances in alloy cylinders as in iron, so I'll run Axtell's recommended .006" clearance. That's always worked well for me in the race bikes. If it gets too noisy when hot, I can always tighten them up a bit.

Ken
 

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
A little more progress. This is one of the EMGO tanks that I just finished spraying epoxy primer on. I cleaned up the welds a bit, then cleaned and acid etched it before priming. It has to cure for 24 hours before I can spray some high fill polyester primer, and then it's just sanding and filling until it's ready for paint.



Actually, I'm doing two tanks, one for this bike and one to convert my grandson's Interstate to a Roadster.



I've also got two sets of side covers almost ready for paint. This bike isn't going to be done in time for the rally, so I think I'll focus the painting on getting the Interstate converted in time for the rally. The Roadster riding position is better for my back, and my grandson also likes it better. He picked "British Racing Green" with silver lettering for the color scheme, so I think I'll go with that. For mine, I'm probably going to do something a little more flashy.

I've made some more progress on the engine, too, but don't have pictures yet. It's almost done.

Ken
 

Attachments

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
12,590
Country flag
Now you really are a tease...

Engine pictures please sir... and look sharp...
 

Jerry Doe

Admin
Joined
May 21, 2003
Messages
1,534
Country flag
You cant beat those EMGO tanks. I have them on my 750 and on my 850 and am very happy with the results..
 

lcrken

VIP MEMBER
Joined
Mar 15, 2009
Messages
4,138
Country flag
They look pretty good to me too, Jerry. Because they are formed in dies, not by hand, the shape is much better than the usual Indian tank. The welds are not as nice as on original steel tanks, but will be fine with a little bit of filler and some sanding. The surface texture of the metal is also not as smooth as factory tanks, but perfectly acceptable. Some primer surfacer and a little sanding, and they will be perfect.

As far as final paint goes, I'm planning on some form of red with gold lettering. I'm trying to decide between a simple solid color "Roman Red", or a metallic, or candy apple, or even a metal flake finish. The flashy ones are appealing, but there's also something I like about a simple solid color paint. I sometimes think the flashy ones are a bit pretentious, but then, this whole bike is going to be a bit pretentious. Besides, the solid color is easier to get right when you're spraying out of doors like I am. The picture below is the bike back before I started this project. I had painted it a simple solid red a few years back, and it's tempting to just do the same for the new tank and covers. It's been something like 40 years since the last time I painted anything in candy or metalflake, but I do have memories of sanding out a lot of flaws, particularly small bugs, in the process. A solid color basecoat/clearcoat finish is definitely easier if you don't have a spray booth. I won't get to the final painting till after the rally, so I have time to ponder the choice for a bit.



Ken
 

Attachments

Top