Reassemble Questions for engine

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Predator303

Predator303

New Member
Apr 26, 2012
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San Juan, Puerto Rico
hi guys. im at the end of my patience with a series of breakdowns every day or at least week something else broke on my bike and it would have been better to buy a new kit instead of start with a used bike. anyways. i decided to buy a new bottom (engine block) with clutch and everything else. i took the old engine apart (again) completely and just had a couple questions. i used to build up turbo engines but its a long time ago and a 2stroke is not the same.

1. when reassemble the engine, especially pistons, should i use pure 2stroke oil to get the parts together to avoid damage or the fuel/oil mix? i would go for pure oil as with a 4stroke.

2. same question for the new crank and bottom. should i put oil first before i assemble it with the head so when it turns its already lubricated?

3. anything i have to take care of when mounting the piston back on the new crankshaft? especially about the rod bolt and the clips. any special i have to do with the clips maybe?

4. i also ordered a new nt carb. do they come set up already to some sort of basic setting?

5. i have heard stories that in new engine kits, nuts and screws where not tightened. anybody have experience with that? going to take off all covers at least to check everything.

right now i cant think of another question. thank you
 
bairdco

bairdco

a guy who makes cool bikes
Aug 18, 2009
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living the dream in southern california
i lube the parts with 2 cycle oil when i rebuild an engine, and if the engine's gonna sit for a while i usually pour a capful into the spark plug hole.

when mounting the piston, take your time. all you need are some needle nose pliers to get the clips back in. if you scuff up the piston by accident, you can use a scotch brite pad to clean it up.

when installing it back into the jug, squeeze the rings with your fingers and again, take your time. make sure the rings gaps stay where the pins are, and DO NOT force anything. it takes a tiny bit of effort to get the piston in. if you're hammering on it, you're doing it wrong.

NT carbs are super-simple. i set the idle screw for the first time by looking into the carb, and turn the screw till i see it barely start to lift up the slide. once the engine starts, you can adjust it where you want the idle.

the needle clip setting will depend on your altitude, oil mixture, etc. at sea level, i run mine on the second notch from the top.

check ALL the nuts and bolts. all the stories are true. every engine i've had has loose bolts.

after the first 15 minutes or so of riding, tighten the head nuts again. CAREFULLY. with the engine hot, it's easy to strip the studs in the case, but just go easy with your wrench. a 1/4 turn or less should be all it takes.

the reason for this is when the engine heats up, everything expands, contracts, or wiggles into place, head gasket seats, etc.

after your first ride, check all your mounting hardware again. if it's loose, tighten it. if it's not, don't force it. you should check your hardware now and then, not force it tighter all the time.

good luck.
 
Predator303

Predator303

New Member
Apr 26, 2012
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San Juan, Puerto Rico
Thank you a lot, that helps.

I just forgot to ask one question that I remember now. Since the crank is new, I will need to break in the bottom part of the engine. DO I need to use more oil for this too in the beginning or is that only for new complete engines and the cylinder and piston? Pretty sure I need to use more oil again here too. As I said, I used to build up engines but this a 2stroke and I am not too proud to ask ;)

As for the altitude. I am at sea level, literally. I live right at the beach but there is not much oxygen in the air. Really hot air here even at night and humidity - tropical climate at its best. But the old carb was setup on the second notch.
 
Last edited:
uniblab

uniblab

New Member
Jul 12, 2012
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Sheattle, WA
While I'm no exspurt (SIC on porpoise) I would advise against retorquing while the engine is hot. I personally would allow it to cool down completely, overnight it you can. Reason is that you'll get a false torque reading and as mentioned by bairdco you have a very good chance of pulling threads.

Once it's been heat cycled (cold/hot/cold) the gaskets and related hardware will have taken a set (the gaskets will have squished down and the studs will have stretched). The recommended torque values where based on a cold engine. Tightening bolts by a quarter turn can induce quite a bit of stretch which can then conspire against you later.

Think of it this way: studs are like rubber bands, they have a finite amount of elasticity. That's to say, you can stretch them only so far before they snap...add to the mix the potential for pulling the threads out of the case.

All of this is compounded by the chinesium alloys used in both the engine castings and the fasteners. It boils down to a crappy crap shoot with genuine crap. Too bad they don't have this sign in the engine factory: "All employees must wash their hands before returning to work (or before going home)"
 
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