Timing lesson for Yabby / another of C.T. engine competed

Finished up today another one of C.T. 's engines ---- The Kustom Kraftsmanship engine.
This one was a lot of work as the piston was "really" stuck!

Before and After:


There was so much rust and corrosion that it took a while to find different ways to ge the engine appart.
The prop driver was stripped out and just slipped onto the crankshaft.




The venturi screen was full of "junk" to where it looked like it was corroded over with something?
So, I installed a new screen after I buffed out the inner cone of the venturi.




With the prop driver removed, the needle valve assembly also removed, and I was able to remove the venturi body and the nut holding the body on (the red plastic part) and that is far as I got as the rest of the engine was not cooperating.

So, I threw the assemble into my sonic tank for cleaning for 20 minutes to see what could shake loose?
Well, the cylinder loosened up, the crankshaft could turn but the backplate and piston/cylinder assemble was stuck.
I then tried my hot plate and antifreeze and let the parts simmer over night.
I was able to get the backplate unscrewed but it was iffy as I unscrewed it the backplate was making a terrible squeaking sound.
I'd unscrew it a little until it felt it was tightening up, spray some Liquid Wrench (lubricant), screw the backplate back in then back it out again until it tightens up again, then repeated the spraying of the Liquid Wrench until I finally got the backplate off.

What the problem with the backplate is the anodizing. With the aluminum and the anodizing (dissimilar metal), it oxidized and filled up the threads (like using Loctite on them).
With the backplate off and the crankshaft free to turn, I was able to unscrew the cylinder (piston still stuck in the sleeve) and with the crankshaft turning, I was able to disconnect the connecting rod from the crankshaft.
And, I took a photo of the piston/cylinder underneath side and also how bad the corrosion is on the engine housing.





Here is what the piston looks like now after one day in a solution weak solution for a day in C/L/R (calcium/lime/ rust remover)


As I have marked on the photo where the rust was and what caused it to have the rust there is where the exhaust port was, and the piston exposed to corrosion.

Onto the rebuild of C.T.'s Kustom Kraftsmanship engine (for you Yabby and C.T.)

After I cleaned the entire engine in my sonic tank (excluding the "plastic" parts -- the red venturi body)
Buffed up the parts a little and re-blued the cylinder.

Now for the rebuild.
1st was to replace the old needle valve seal on the KK needle valve body as it was cracked.






Simple enough job and with the special channel locks (with no serrations) to damage the new seal.
And I had plenty left over so I have shipped the extras to C.T. when they need replacing.



I assembled the venturi body (red) onto the crankcase, and then threaded on the screw that holds the venturi body and tightened up to finger tight, then used the wrench and gave it an 1/8 of a turn (you don't need to really tighten this up as the aluminum will expand (the plastic won't -- tightened too much and it will crack later on!)
Next was to press on the new prop driver onto the crankshaft (don't forget the thrust washer!).
I use my little hand press to do this.
On the base is a pin that slips into the intake hole on the crankshaft (tight slip fit -- for different engines) and on the ramming end is a flat plate that presses the prop drivers on.
Lightly press it all together until the prop driver and thrust washer stops at the shoulder on the crankshaft.

Next is to use my Turbine oil to oil up the piston (even the underside where the socket ball is at) and assemble it to the crankshaft.
now oil the treads on the crankcase and backplate and screw them together.

For Yabby:
Here is how I check the deck height for the piston timing.
I oil the cylinder and screw it onto the crankcase (piston sliding into the cylinder sleeve)
I install my glow plug shoulder plug at the top.




Install my "glow" head adapter (or you can use an old burnt-out glow head with the glow area drilled out?)
This is only hand tightened like the cylinder sleeve.



Now I rotate the crankshaft until the piston is at TDC.
Now, "IF" your piston hits and stops at TDC, then you know that shims are needed between the crankcase and the cylinder sleeve.
I put the "black" marks on the engine for help here (for a guide)





Now, if you can't turn the crankshaft past TDC, then slowly unscrew the cylinder until you can.
What I do then is using a feeler gages I try to slip a shim between the crankcase and the cylinder sleeve.
This will get you the approximate size shim needed to shim the cylinder up.




I purchased from Cox International the "FOUR" shims that burnie sells when I ordered the additional engine parts.
If you can't make your own, these will be acceptable for shimming.
Of the four in the set, I used three of them on the three engines I rebuilt.
One I used was the correct thickness at .010" (0.254mm) (for this Kustom Kraftsmanship engine. (in the photo with the caliper)
Another one I had to sand down to .008" (0.203mm) for the Tee Dee .049.
So that left me with "two" .015" (0.38mm) for the Tee Dee .051 R/C and I had to sand that down to .009" and reduce the outside diameter as well to be the same size as the cylinder sleeve diameter (you will see why later)

So, "if" you need some shims, they will work.

Interesting fact on this engine when I took it apart. It had "three" glow head shims on top.





When checking the deck height with these shims, the piston would swing past without touching the piston (Hello Yabby?)
Knowing this, this engine was not hand built by Kustom Kraftsmanship ---- just the backplate was added by the previous owner, probably for fuel tank pressure?

Back to the timing:
When the cylinder is unscrewed to where the piston can go by TDC, you should feel a very slight "BUMP" -- a bump to where there is none at all (this will be explained later).
Now with the gap measured (and if you purchased the "4" shims from Burnie - Cox International / Matt - EX Model Engines)
What size will be close to the feeler gage?
If the sizes in the 4 are too thick, you can sand the thickness down using 400 grit sandpaper (also nice to have a pair of calipers handy too to see how much you sanded off?)

In my case with the "three" glow head shims, I used my calipers (get a pair from Harbor Freight) and measured the three together and got my shim thickness.



So out of the four from the shims I purchased from Burnie, the .01" could work for me.
One thing to remember on measuring the three shims is that it is not one piece of metal and there will be a measuring error (bigger) because of that.




And I installed the shim between the crankcase and cylinder:



Last thing to do now is to tighten the cylinder to the crankcase to check an see if the shim is the correct thickness.
This is where when you had everything finger tight comes in.
I told you that when the piston comes to TDC and you should feel a very slight "BUMP", when you tighten down on the cylinder, that very hardly noticeable "BUMP" will be more noticeable after things are tightened down.

See the photos below:

Piston Before TDC --- with shim installed



Piston At TDC --- with shim installed



Piston After TDC --- with shim installed


If you have a hard "BUMP" after the TDC, then you shim needs to be just slightly thicker.
The bump you feel as you turn the crankshaft is the "crown" of the piston hitting the slug (stop).
The deck height (shoulder) where the glow plug stops, and the side of the piston is a few thousands (microns) below that.
If you take a ruler across the top of the piston you will see that the center is slightly higher, that is why yoy want to feel a very slight "BUMP" hitting the slug/stop.

Now you will have an engine that will give you the correct compression/SPI and you can then also decrease the compression by adding shims under the glow head.

To finish up ---- here are photos of an engine that can be called a Kustom Kraftsmanship engine.
C.T. ----- I'm giving you one of the boxes from my collection from engines I use to purchase from Kustom Kraftsmanship.
The three glow head shims are in the box as well. To be used on other engines -- if needed?

KK engines were more expensive, but they were the best! (hand built)