Copyright 2008/2012 - ATVRE Media Group / www.atvre.com - All rights reserved
Who Can Build A - National Caliber - CVT Race Engine?
Part 2
"Preparing Your Cases For Assembly"
xxx
Gasket matching the cases requires a Dremel or similar grinding tool and a little patience but to get the most out of your high-end cylinder kit it will be necessary. This is one of the techniques that can be best explained with some pictures so here are a few to look over as I discuss the objective. I have chosen to picture an example using the R/T 70 base gasket because it is so dramatic as to the changes that need to be made but all size engines and brand of kits will follow same steps. Start by putting one bolt in the cases to hold the halves together securely, then install the base gasket out of your kit to the cases with a couple of spare bolts (as shown below).
ARCHIVES: 2-Stroke Power - "It's All About The Exhaust / Heart Of The 2-Stroke - "Choosing A Cylinder" /
Last month we discussed cleaning and checking our cases to verify their suitability for a dependable high performance race engine, so we will pick up from there assuming we have a known good foundation for this build. Certain procedures can be performed with cases split or bolted together but you will be smart do as much as possible while the halves are separated, much less bulky as well as more working clearance.
Today’s installment will be covering the following procedures;
1. Installing engine rubber mount bushings
2. Gasket matching cases
3. Installing crank bearings
4. Installing transmission bearings
5. Installing rear engine mount
The rubber engine bushings are a pressed fit and can be easily installed with a shop press or even a vise by simply lining up the bushing to the opening in the case(it will only enter the opening from one side) and sandwiching it between the 2 vise jaws, tighten the vise until bushing has bottomed out. The job will be made easier by using a socket that matches the O.D. of the bushing as a driver so the rubber will not be damaged. The oem cases are made of cast aluminum and very easy to crack so never force or bind the cases during install, the bushing must stay level and centered. I do not recommend it but the bushing can be installed with a hammer and again a socket of the correct diameter but be careful to lay cases flat and have proper support to equalize the load.
I like to use a Sharpie and follow the edge of the gasket marking all material that should be removed, remove the bolts and gasket and it should appear similar to the picture below. (also so notice that these cases have been machined”enlarged” at the cylinder skirt area to accept the oversized r/t cylinder)
Your finished cases should look like this …
There are a variety of tools that can be used in your grinder such as grinding stones, carbide bits, sanding rolls etc, but whatever you use be patient or your nice new cases can be ruined. Split the halves and work on one at a time for better results. Below the pic shows one half of the cases complete , you see the amount of material that was removed is significant. Use to make the transition from the gasket surface to the interior case as smooth as possible(polishing is not necessary or recommended).
Now we are ready to install our crank bearings, I suggest dropping the bearings (while still in their plastic) into the freezer at least 24 hours before installing, this will make the metal contract and install with less effort, remove the bearing right before you intend to install, spray a little WD-40 on the outer contact surface to dissipate any condensation and protect from rust, now its ready to go in. I also heat the case halves with my heat gun (you may put in an oven at 200 degrees) for about 5 minutes, this will slightly expand the metal case and the bearings can be bumped with slight tap of a hammer. I assume most of you will not have a bearing driving tool but do not hit the bearing directly use a brass drift or wood block, my favorite is again a socket that matches size of bearing OD. Drive the bearing in until it bottoms out, while putting the majority of the load on the outer steel bearing case.
Each of the transmission bearings can be installed at this time too, they will simply drive –in without freezing taking care to not damage the bearings, once installed take your finger and spin each bearing to make sure it works freely and does not bind.
Taking advantage of the split case convenience, you can install the rear engine mount with the its unique oem hardware.
This wraps up our case prep and we can move on to installing the crankshaft and sealing our cases in next segment.
