Cheap top end rebuild

[Franco]

I’ve been contemplating how I want to rebuild my top end, I don’t want to put a ton of money into it since it’s kind of a beater. I went with a cheap $200 rebuild kit from 50 caliber racing in North Las Vegas, and a $50 cheap head from ebay. This is basically to show others what I got out of a budget rebuild kit vs quality machine work just to help others decide where to put their money when it comes to a top end rebuild. What I got in the box was 2 cylinders, 4 cylinder dowels, 2 moly coated cast pistons, piston rings, wrist pin, wrist pin bearing, retention springs, 10 head studs, and a crap gasket kit. 

Pictures: https://imgur.com/a/blaw69e

Things I didn’t like: The top of the pistons are rough and irregular, and the area just above the wrist pin has minimal material in a place where I would think there would be a need for strength. The coolant passage ways are very rough and the ones on the inside of the cylinders are extremely narrow and blocked. The rings don’t have the little cut out for the alignment pins, instead they are curved to fit the pin. I don’t have any carbide burrs bits to clean up the coolant passage but I might pick one up just to clean up some of the casting burrs. No new coolant plugs provided for the bottom of the cylinder. 

What I need help on:

I’m mechanically inclined but I’ve never rebuilt a banshee engine before, any tips, tricks, or advice would be appreciated. I’ve read that the use of high temp silicone around the water plugs to assist with leaking. On the startup I’m putting fresh gear oil, and distilled water for coolant, going to do 3x15min heat cycles before rolling around the neighborhood. I’ll change the oil and switch the water for coolant after I take it out for 2-4 rides. 3 years down the road I’ll probably get a good port put on them, back to the wiseco piston, and maybe 4mil stroke.
 

Things I’m concerned about:
The old wiseco piston looks to be cut a little bit short, so I’m going to check for crank case clearances before torquing down the cylinder. I measured with my dial calipers close to 54mm stroke but I kept getting different readings. I figured if my readings are always close to 54mm it wasn’t stroked. The connecting rod and crank shaft have 29L markings on them.
Some water may have made it down into the crank case but I didn’t see anything out of the ordinary when I drained the oil. No hole in the piston just a little piston vaporization near the side wall. 
 

If you want to read the back story:
I had been doing some trail riding in and around the Panguitch / hatch area in Utah, the elevation is about 6k+ feet. The shee ran ok, not great but good enough, idle was good, mid was lacking, wot was good. Yes I know pilot jet is for idle, needle jet for mid range ( I’m at 2nd from the top ring ), and main jet is for wot. So I wanted to lean up the air to fuel ratio a bit since there’s less altitude up there to see if that helps any. I went down from a 35 main to a 32 main, I couldn’t really tell a difference at my house just riding on the streets. I took a little ride in the desert and the head gasket gave out and locked up the motor. After if cooled down it kicked over with ease. I’m sure it was the head gasket cuz I could hear the coolant boiling in the cylinder, and there wasn’t much water left in the radiator when I tore it down. 
 

Bike spec and set up:
91’ shee bought for 2k on craigslist wasn’t expecting much out of it.
Stock parts: carbs, head, reeds, new stator, new ignition coil, and new cdi, original clutch basket with deep ass grooves, and missing the air box. 
Aftermarket parts: uni foam filters w/ custom hack job 8” long radiator hose intake runner, 35 main, 2.7 pilot, no markings on the needle, +2mm bore, stock 54mm stroke and probably dune port on the cylinders, wiseco 66mm pistons, fmf gold series pipes, +2 or +3 chrome rear swing arm. 
I’ve only ever liked riding 2 strokes and this bike rode like it had really bad turbo lag, probably due to the type of port job it had. It really ripped if you kept the rpms up like in the dunes, no problem walking 450s, and wasn’t too far behind a fat guy on a cr500. The lag would catch me off guard at first and took some time to get used to, but I learned embrace it.
 

[Keno]

What caused your previous setup to fail?

[Franco]

I'm taking a guess that it runs hot since it's bored over +2mm. Less metal to absorb heat plus more volume of

fuel to burn. I think the head gasket was leaking a little, the plug on the cylinder that melted always looked fouled but I couldn't figure it out. It might have had a small leak for some time. 

[yamaha04]

What side was the cylinder on.  Might have had a crank seal sucking air.  Or tranny fluid.  Depending on the side 

[Franco]

It was on the right side. 

[Keno]

You probably had an air leak. You'll for sure want to pressure test it before running it. If it were me, id go ahead and replace crank seals and intake boots.

[Franco]

I had an air leak a while back, fixed it and I've had no problems since. 

[the boris]

Very interested in this topic as I'm planning to buy cheep cylinder kit to practice porting.

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[Franco]

Boris,

I don't know what kind of grade the aluminum is or if that would affect how the material reacts when cutting into it. I would try to find some used ones for practice. 

[Keno]

Last i knew Herjuggs has used cheap cylinders to port with good results

[the boris]

Boris,
I don't know what kind of grade the aluminum is or if that would affect how the material reacts when cutting into it. I would try to find some used ones for practice. 

I know but most used ones around me are so far gone that you can't do anything with them any more and, as I live in the very asshole of the world, shipping to here is quite expensive from USA. USA is only place where you can still get decent used set of jugs.
Anyway I wouldn't really use it much, once I figure out what to do I would probably go 421 and welded crank, and do my port job to it, but now I'm talking in 2-3 years time.

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[the boris]

By the way, I would use just cylinders, wouldn't use their pistons.
When it comes to pistons I would definitely go reputable route.

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[Franco]

I agree welded crank, solid piston, and a good port can get you good power.

 

Update on the cheap build, ran a few heat cycles, ripped around the block a few times. It doesn't pull as hard as it did before but has a more predictable power band. Running a 310 main, 27.5 pilot and middle clip on the needle, 2000'elev. This summer I'll be back in southern Utah at 6000' I'll provide another update then.