Checking Spark Plugs

Since no one else seems to have anything to post, I'll continue.
Here's my luck with the new bike.
Friday, I go to check spark plugs before going for a ride and then delving into a potential air leak(surging at slow cruising speed). It's a two-stroke thing.
Right plug is galled from the start and i'm rolling out alu. threads with my pinky.
I'm tempted to just replace the plug but I pulled the right head.

Good thing I didn't just try to run it. BTW, this is called galvanic corrosion and it can happen to you too - anywhere there are dissimilar metals in contact.

I have a spare head but I had better pull the other to check both heads - in case that potential air leak was there.
Well one of the left cylinder studs came out of the block rusted to the sleeve nut!
Now I have to pull the unaffected cylinder to reinstall the stud correctly. I could have just screwed it all back in like a bolt but I'm a glutton for punishment!
Look what I see!

All this rusty grit falling onto the crank and into the case from all eight studs!

I found an RD350 gasket kit from a few years back (and a bunch of NOS cables I forgot I had!) so I can wrap this up this weekend.
Okay, that was easy. Now I see I have a missing exhaust stud. Made a new one. Looking at the rubber carb manifolds, I see they don't line up very well. Better port match those to eliminate that edge. A simple scribing shows the mismatch.


But look deeper. It's upside down but see how the iron cylinder sleeve has a lip at the intake port? I'll remove that while I'm at it.

Be careful as this is the intake valve of a two-stroke. Grind all the way into the cylinder, raising the opening even 1mm, and you can make the power very peaky. Modifying the height of the intake and exhaust ports is how you "recam" a two stroke. Simple to do but easy to make it unrideable.

Here you can see the port opened up.


You don't want to hog out the whole runner - just radius it at the offending part. I want to leave it rough in there as this helps with the fuel mix. Polishing intakes runners provided little gain and maybe even some loss. Also note how I ramped the cylinder sleeve to transition the runner to the port without a step. I never actually ground into the opening.
These things are how one would "blueprint" an engine. All is still stock but you gain all the possible efficiency possible before making other mods. The ports leading down into the crankcase can be matched as well BUT not without the case all apart so forget it. You 4-strokers will want to add a three angle valve job, a balance, and degree the cam.
Well I might as well pull the pistons, clean them properly and take a bunch of measurements. Regardless of the numbers, I'm not reboring this thing.


After hunting down a spare head in the shed, I decided I should paint the cyls and heads while it's all apart. See where this is all going?!
JP1 satin paint and bake at XXX for XXX minutes(turn off and go watch a James Bond movie). I like the new Bond as he kills indescriminately. The Walther PPK returns as well. Hey, anyone wanna go shooting? Anyway,

Common advice is to do this when the wife is away. My sis' redid her kitchen a few years ago so I combined her broken top and bottom ovens together to get one good one for the garage. Great for powder coating small parts - and this.
I had to sand off the fins but this is how it turned out.


Here's a before and after of the pistons.


3am. This is not to measure the rings but to show you the taper. These are known as keystone rings. The taper forms a wedge so that the cylinder pressure forces the rings against the cylinder wall. This also greatly reduces ring sticking.



New oils pretty much obviate the need for ring expanders. Both of mine in the top grooves were broken. I ended up leaving them all out even though I like to use castor-type oil. You 4-strokers can toss them all together. This is what the expanders look like.


Put the pistons back in before turning in.
Today, I broke a ring when reinstalling the right cylinder. Guess what? I'm now running one ring in the top groove of each piston! This wasn't my plan but was common in race motors of the time - this is my justification. And I'm NOT dumping $50 on stock rings when oversized piston/rings are $150. Not today, friends. Hack on! I have several other bikes to build before I go that deep on a new one!
Here she is back together. Not very snappy off throttle - needs some tuning - or is that just new blowby? ;)> Feels fine when gettin' on it. Break-in period? Screw that!