Crank Case Inspection

[Pushrod Twin]

Has anybody compiled a comprehensive list of inspection criteria, dimensions & tolerances for inspecting crankcases in preparation for assembly? Or is this the beginning of the process where we meander around the half dozen revered publications looking for the answers?
I am only hours away from completing the crankcase-gearbox hookup work that connects the Commando box & clutch to my Twin engine. The next step is to wash out the swarf & start the engine build.

BTW, is a Twin with a separate gearbox a Twin cylinder Comet, should the engine prefix read F5+5/AB/1/ ????

 

[Pushrod Twin]

Based on the overwhelming silence, I will assume the answer to the first is NO? In which case I must start into the process of 2, read up the revered publications & start my own list!
I have vague recollection from many years ago that the Good Professor wrote a series of articles in MPH regarding the preparation of crankcases before engine build, can any body remind me how far back I should go looking in my collection?

 

[Peter Holmes]

Has anybody compiled a comprehensive list of inspection criteria, dimensions & tolerances for inspecting crankcases in preparation for assembly? Or is this the beginning of the process where we meander around the half dozen revered publications looking for the answers?
I am only hours away from completing the crankcase-gearbox hookup work that connects the Commando box & clutch to my Twin engine. The next step is to wash out the swarf & start the engine build.

BTW, is a Twin with a separate gearbox a Twin cylinder Comet, should the engine prefix read F5+5/AB/1/ ????

I do not think that because your bike has a separate gearbox that makes it a Comet, what you have is a Rapide or Black Shadow which has had its gearbox hacked off, with regard to checking out your crankcases before reassembly you would need some pretty good equipment and the knowledge of how to use it, bearing alignment and correct interference fit, flywheel and conrod assembly checked for wear, alignment and balance with pistons attached, cam spindles checked for wear and interference fit (are they tight and correctly positioned in the timing chest) really a great deal to get right if you want a nice reliable engine. Good Luck.
Peter

 

[greg brillus]

Check all threads for damage and clean them out of old sealant, repair any that need it straight away, using the correct taps and helicoil inserts where necessary. Then check all flat mating surfaces are flat and free from burrs, using a surface plate works very well ( flat sheet of glass with some sheets of emery paper glued down, need a good sized sheet of glass). I assemble cases and other joints with Threebond sealant, available in grey and black......best sealant you will ever use. When assembling the case through bolts through the timing chest...be sure to use some of said sealant under the heads of the bolt heads, or else oil will leak along the studs, and come out the other end. This is a good starting point.......Cheers......Greg.

 

[davidd]

You might try:
MPH 468 8-9
MPH 471 and 473 for Neville's articles
MPH 303 for a Tony Maughan article 21-24
MPH 305 Comment 21
MPH 309 Comments 21-24

I have not looked at these recently, but I have them in my notes.

David

 

[Pushrod Twin]

Thank you gentlemen. Peter, Greg, yes, all of these things must be checked & inspected for serviceability. Having been an aircraft technician early in my career, then an aeronautical machinist for the next 30 odd years, I am vaguely familiar with inspection techniques, which is why I ask for dimensions & tolerances. We all know the case mating surfaces need to be flat, how flat? If I place them on a surface plate, is a .005" feeler gauge blade acceptable? When I measure the mains bearing bores, what should the diameter be, how much out of round, if any, is acceptable? When I torque the case halves together, what is the dimension of the cylinder throats, variation in flatness of the decks etc? Timing case spindles, we know they are an interference fit, I dont expect to pull them out for a measure, has anybody calculated a torque test with a nut pulling over a sleeve to determine how much torque indicates acceptable "tightness"?
I guess as a long time Moto Guzzi owner I have been spoilt, while not quite up to aircraft standards, they do at least have understandable tables of dimensions & tolerances.

David, my MPH's start at 533, June 93. I am only a pup in this organisation! But thanks for the steer, I do have 40 Years on & will clearly need to spend the time looking there & the 10 year sequel. I will also need to laboriously look back through what I do have to find Neville's later articles.

So, conclusion; it appears that I will need to write an inspection list, fill in the dimensions & tolerances, then publish it.
I will be asking for help where I cant find answers elsewhere.
It wont start this week, I still have a shaft to finish machining which will drive the alternator. That is the last job to complete for the Norton gearbox hook up to my die cast Series C cases, would you like to see what I have done?

 

[Chris Launders]

Please don't publish this document, you'll frighten the rest of us to death, we'll all think our motors are scrap. I don't think Vincents were made to this sort accuracy.
Are all the holes in the back of the cases to mount a plate carrying the Norton Box.

Chris.

 

[b'knighted]

Didn't some Enfields have their gearboxes bolted on like that?

 

[davidd]

Roy,

Nice photos! On the spindles, if they are not worn you can warm up the area to running temperature and see if they wiggle around. I don't do a test. I usually have to replace them. If they are not worn, they are usually set to low in the case. I use a slide puller with an adapter on the end to screw on the spindle. I measure and go to the oversize if it is edgy. So, I would assess the height as well as the wear on the spindles when developing a plan.

David

 

[Pushrod Twin]

Thanks Guys.
Chris, you will only think your cases are scrap if you measure them! If your engine is together & running, take the "it aint broken, no need to fix" attitude & ride on.
Yes, all of those holes are tapped to hold the rear plate to the back of the cases. The kick starter hole has alloy plugs loctited in place & tapped 1/4"x 20 TPI Whit, & have a spacer plate bonded above them for support, the rest are 3/16 x 24 TPI. Because these are die cast cases the wall material is thinner than my B cases & the top row are at an angle parallel to the rear cylinder deck. When the cases were machined flat some of the gearbox trapdoor bore remained, I had it welded, you can see it from the inside at the kick start hole. There was also some chain case support missing at the bottom from the chain adjuster rearward, that has been welded back in and the piece at the top where the g/box oil dip stick penetrated was repaired too. I will attach a photo of the back plate soon.

Chris, yes, I have seen Enfields with boxes mounted similar, but not with an outrigger bearing on the sleeve gear as I have with this one.

David, how do you measure your spindle heights from the mating face? My first thought is to place the case back on the mill table & set a DTI with a fine nib onto the face, zero it, then transfer it to each spindle in turn, winding the knee until the DTI zeros & read the readout?

My thoughts for the first inspection detail are as already suggested;
Visual, much of which I have done during the machining phase.
Damage to mating faces, nicks & burrs.
Bolt/stud hole faces for cracks & burrs. Both to be dressed as required.
Stud hole threads for damage, helicoil or solid insert repair as applicable.
Mating face flatness, gauged on surface plate.
Measurements & tolerances required;
1,Mains bearing bores,
2,Cylinder bores,
3,Oil pump bore

More tomorrow.