Nrrrow case mach 1

[Ken Lippett]

How much resistance should ther be when closing the crankcase halves??

[darnold]

They should go together with a two handed push. I drilled a hole in my work bench so the crank can pass through and the cases rest flat.

Here are some suggestions you might try. Remove the two dowels or better yet get a spare set of dowels and make them a little under size so they slip in easily.

Start by fitting the each side case to the crank. Use some emery on the crank so that slips into bearing with some resistance with a little oil. Then close the cases on the crank and check the end play.

Then remove the crank and do the same with each trany shaft. Then with the complete trany installed make sure each gear can be engaged with no drag on the forks.

Take a piece of steel flat bar and drill holes in it so you can bolt it to the case. Put a magnetic base and dial indicator on the bar to check end play.

You can also wet the paper gasket so it stretches a little and becomes flexible.

-dan

[Rocket Rick]

I thought I might add a few things to Dan's response. First, I hope you replaced all the bearings (except the loose roller bearing behind clutch, unless required), and split the crank to examine and measure the rod & pin, true the rod, install new rollers, and replace the cage & thrust washers if necessary.
Now check the fit of the empty crankcase halves (nothing installed), and clean up, or dress down the locating dowels if necesssary to obtain the desired fit. It's normal for the halves to hang up on the dowels, requiring rocking back & forth to separate. The original centre gaskets had an installed thickness of .007". Make your new gasket as close to this as possible. You should be able to find an art paper which will compress to .008". Next, install the the crankshaft (fitted as Dan described), close the cases with the bolts & screws, and check both run out, and end float on the crank. It must not exceed .002". End float is adjusted by shims, run out is more complicated, get Phil Irving"s "Tunining for Speed" and read the section on crakshaft truing.
When the crank is right, the next job is shimming the lower bevel gears. The timing shaft gear has to be in the hole in the casting before the crank is installed. The bearing carrier should be a push fit in the casting (sand it if required). You have to get the mesh set with no free play (backlash) at the tightest spot, no end float on the timing shaft gear, and prefectly even across the grinder mark on the gears. The lower shaft cover is also shimmed, and must exert a slight pressure on the top bearing in the carrier, otherwise the whole assembly will float up & down. These jobs can take hours to do correctly, and can't be done without a supply of the shims.
The transmission shafts, gears and shifter drum are shimmed as well, and both will benefit from being set up tighter than stock. The shafts as installed have no end float (it's taken up by the clutch and sprocket nuts), but shim the gears & drum for .015" end float, Then with the crank removed, transmission installed and cases bolted up, check the mesh, and the shift action by looking through the cylinder spiggot. Again, it takes hours, and can't be done without a supply of shims. When everything is shimmed & trued, you can install all the parts & close the cases, and then shim the camshaft gears in the head. These are a little easier because usually no bearing carrier shim is needed. All this bolting & unbolting is lot's of fun. If you do it correctly, it will result in a quieter, excellent shifting, virtually unburstable motor.
Good luck, Rocket Rick

[Ken Lippett]

Thanks to both of you for the replies,very helpful.
Engine is now closed up, frame going to powder coater this week.
I do however, need some decent (polishable) engine side covers, I have three complete (1-160,2-250) engines but all side covers have major flaws(pitted, scraped etc.etc.).
Finally, is there a good or repairable Mach 1 type tank available out there???
Thanks again, Ken