72 cc LC bbk installation tips

[Triesandluth]

My kit arrived in the mail today.  Sport style with cast iron cylinder and two ring piston.
I've done a piston, rings, and gasket change on this before,  but not the kit. So I thought I'd post up for any tips.  Zombie says he has something,  but anything else is appreciated.  I'll also post along with with little things that I come across,  like do's and don'ts.
I've already filed the ports smooth and came across the stubborn temperature sensor and lower coolant hose nipple bolt thing. 
Thanks in advance!  Links are appreciated!

[zombie]

The bottom edges of the cylinder skirts should be beveled at 60* to allow oil to wick.
Same for the skirts on the piston. Also on the piston drill a pair of 1/8th " holes allowing the wrist pin to get oil. Make sure to smooth the inside, and chamfer the outside of these holes.

It also helps to smooth and or polish the pistons dome. The lumpy factory casting will hold carbon.

The rings should be gaped 2 -3 thousandths for the top, ans 3-4 for the bottom.

The Squish is VERY important. I use note parer if I have to to shim or replace factory gaskets.
Shimming the jug base changes timing so it is better to shim the head if you can. If not... No big deal.
You will want about 1mm squish for most sport cylinders.

Break in is common sense. Add approx 2 ounces to the fuel tank (2t oil), and baby the bike for the first 150 miles. Nothing more than 1/2 throttle. You will never even find out if the main jet is correct till then.

Just listen for detonation. Any funny pops in the pipe or tinging / crackling sounds are too lean. Stay on the rich side for another 50 - 75 miles, and then you can beat the snot out of it.

Jetting is a bitch so go slow, and easy till you get it nailed. 4-5 new plugs will help narrow down the mix

[Triesandluth]

No homo,  but I love you man!  That's some great advice.  When I get up later (working twelve hour nights :-/  ) I will see what I can do.  All of what you recommended is great and makes perfect sense.  Except the half throttle break in.  I'm not sure if it has half throttle.  Anytime I tried to use it I would give up and gun it.  If so it's just barely a sixteenth of a turn lol. 

Findings after tearing down the original cylinder...  I've only been running with 2/3 of a bottom ring.  I never noticed any problem.  Hopefully I broke it while I was putting in the new piston and rings in late November and it's not in my case.  I peeked around but didn't find it. 
Also,  that bottom brass coolant house connector bolt is a @$#*@$* and I can't seem to break it loose.  I'm taking it with me to work tonight to take advantage of the fancy tools.

[zombie]

If the ring snapped in the groove the ONLY reason would be the end gap was too tight. It fit in the cylinder but heat expansion took care of the rest.

there are a couple Utube vids on gaping rings. Use the piston to push the ring SQUARE in the bore, and measure. I use a diamond nail file to gap. Just squeeze the ring and pull the file out Slowly. It takes off material fast.

Heat is all you need o get the banjo bolt out. Heat the aluminium all around it. Not the bolt. Someone may have used LokTite on it.

Good luck Bro.

[Triesandluth]

It's a cast iron head,  I'm not thinking that's going to make a difference except for time to heat. 
Yeah,  I didn't take any time to properly learn how to replace rings.  I've done a little research on gaping since then but assumed it was fine since I had no mechanical issues. 
Definitely going to try to do this as right as possible,  which means as an end result everything will fail and my bike will burn up,  lol.

[zombie]

Cast iron is odd for a LC engine... It will take longer to get up to temp, and it will also maintain a steady temp longer ie: stop lights ect.

I read an article about Cart Racers that stated the engine runs at temp but heats up in corners. Reason turned out to be the cool fuel is shut partially down, and the cyl. head temp increases.
For the longest time they assumed it was an airflow issue.
Maybe I read that here?

Anyway, Yes! Take your time, and cover all the bases. The engine can last for years or minutes. It's all in getting their junk trimmed up into proper gear.

[chaz35]

I used a dremel to file ring ends.  Place dremel in a vise to hold, and grind off the end of the ring on flat side of the stone.  Never used a diamond file.  I checked on line to buy, what grit do you use, any diamond nail file OK?

[Triesandluth]

I have a little precision file set with different types and shapes and sizes.  I was really gentle and only made inward strokes. 

Okay,  got it all set up.  Proudly put it together this morning after work.  But instead of putting the piston in with the arrow pointing toward the exhaust port,  which I knew from previous piston changes,  I decided today that arrows should point up.  I got all the coolant in, etc,  and ran it horribly for a minute before realizing that I'm slightly retarded.  So, now I'm better with circlips than I was...

I did a squish area check and it seemed okay.  At idle I hear nothing.  But as the rpms increase I can hear a distinct ticking that rises.  I only heard this after I had already went out for a quick test ride.  So I'm going to check it again later.  It felt great though,  more power,  and it hates half throttle, but I kept it there.

Okay,  notebook paper to shim squish height?  I don't think it's off enough to use a whole extra head gasket,  the old one is in great condition and could be used. 

And what would be a good rpm to use as a maximum during break in?  I stuck around 6k because any less and my throttle wouldn't even be opened.  I'm going to make marks on my throttle grip that show the positions, but wanna make sure that it'd I'm going downhill it doesn't climb into the danger zone. 

I now need sleep.  I have about three hours of sleep to get that is supposed to last me until tomorrow morning at about eight....
Damn scooter addiction...

[zombie]

I used a dremel to file ring ends.  Place dremel in a vise to hold, and grind off the end of the ring on flat side of the stone.  Never used a diamond file.  I checked on line to buy, what grit do you use, any diamond nail file OK?

Dollar store find... Whatever grit "Pink" is.

They all looked the same. I think you would have to exert some effort to even remove skin but it cuts like a bastard (file) on metal.

[zombie]

You really have to measure the squish w/ a piece of solder to get it right.  but since you are hitting go to 2 head gaskets until it is broken in. Lower compression will add some safety.

Have you up jetted yet? MANDATORY!!!!! Rich-en the idle mix, and go up at least 2 sizes on the main.

Dont worry about down hill rpm. There is no load on the engine.

[Triesandluth]

I was sure it was good,  but this surety was also at the same time I decided to put the piston in upside down. I also could've over torqued it, but it made no difference.
Okay great.  I'll add the other gasket.  After it's broken in I should then maybe work with proper shimming?
I upjetted before,  running 93 if I remember correctly.  Took the plug out and it was gray so I'll go up in size again as well. I put the air fuel screw all the way in and backed it out only enough to keep it running a little smoother.  I'm sure after the extra gasket is installed that I will need to adjust all that stuff again.

[zombie]

Yeah. After break in do the shimming.

Order a couple base gaskets, cut a couple from printer paper, and get a couple head gaskets.

I use Indian Shellac on all of those. You HAVE to be sure NONE can squeeze out into the cylinder so a tiny amount is used, and ONLY near the outside edges.
It turns into a polymer coating on the metal, and you don't want it on your piston.

Gray is lean so yep! Up it another 2 sizes. Rich is good for now. The gaskets won't effect jetting so no worries there.

[Triesandluth]

I didn't take into consideration that the extra gaskets I have are for the fifty head,  and they don't cut easily.  So I just found a heavy weight paper and cut one out.  Sadly the noise is still there and after checking again it seems like the piston isn't hitting anything. Sounds lower,  which worries me.

I'm going to tear it down again. Is the needle bearing at the wrist pin supposed to be a little loose or should it be snug?  When I took it out to inspect it, it seemed like it had a lot of play. 

[zombie]

That's your noise Bro!

No play at all ... That is a precision fit bearing.

Don't run it like that any further because that noise is actually hammering the bearings (pins) out.

[Triesandluth]

Good deal.  I had a feeling.  Can't believe that it became so noticeable after putting the new kit on. I guess from the tightness of the new junk. I guess I'll find a place to get one in town.  If not I'll message b&w