what to consider when rebuilding an engine?

[MrAtom]

Im picking up a project bike tomorrow, and the engines messed up and needs to be rebuilt, needs new crankshaft. What all should i do while im in there?

[Ghostt]

What kind of bike??

[ninjamunky85]

Stay organized - I like to put small nuts, bolts, and misc parts in envelopes and label what's in them

Take detailed pictures as you progress. This makes reassembly easier.

Take your time and check your work. This is an area where one little mistake can be very costly both time and money wise.

[garth285]

Originally Posted by Ghostt

What kind of bike??

Looks like from his user info it could possibly be a 03?

One big thing to consider is buying a complete engine off someone, if the crank is bad you may need just a crank and bearings but if its a main bearing and ruined the cases you might be in some deep water.

I know I can pick up a 08-12 250 motor for about 300-350 locally so it might be worth it to just pick up an engine and do a swap?

[Ghostt]

Personally I consider both the 250 & 500 ninja engines, to be like a Bic lighter, disposable.

Not worth the time and money to rebuild, especially if a crank is needed, if it was just lapping the head, then okay, otherwise save yourself the time, money, effort, and aggravation and pick up a low miles replacement for it.

[MrAtom]

Its a gs500e.

[dcj13]

Originally Posted by Ghostt

Personally I consider both the 250 & 500 ninja engines, to be like a Bic lighter, disposable.

Not worth the time and money to rebuild, especially if a crank is needed, if it was just lapping the head, then okay, otherwise save yourself the time, money, effort, and aggravation and pick up a low miles replacement for it.

Gotta concur with Scott on this one.

[cookiebug79]

While your bottom end is apart, and your looking to sink money into the motor, deck the head, hone the cylinders, lap the valves, replace the piston rings, gaskets, and cam bolts, get new o-rings for the water pump.

All of that is about $500 of parts and a little bit of machinist time on a ninja 250 engine, but it's a fun learning experience if you're in for the project.

[crazymadbastard]

Originally Posted by Ghostt

Personally I consider both the 250 & 500 ninja engines, to be like a Bic lighter, disposable.

Not worth the time and money to rebuild, especially if a crank is needed, if it was just lapping the head, then okay, otherwise save yourself the time, money, effort, and aggravation and pick up a low miles replacement for it.

yep $300 for a good runner versus $500 to rebuild and possibly screw it up.

[cookiebug79]

This has been my project on and off since last summer:
https://www.ninjette.org/forums/showthread.php?t=189221

[spooph]

I would do it just for the experience.. Sure, you're probably going to screw something up. That's what learning is. We all do it our first time around.. Compared to trade school, messing up a free engine is super cheap. Gotta pay for your education somehow....

[Ghostt]

Buy a replacement engine, then experiment with the old one at your leisure, problem solved.

[dcj13]

Originally Posted by Ghostt

Buy a replacement engine, then experiment with the old one at your leisure, problem solved.

Once again, sage advice.

You'll enjoy disassembling the old bad engine. You can make a cool table lamp out of the crankshaft or something.

[MrAtom]

I don't wanna rebuild it because I think its the most efficient way to get a new bike. I wanna rebuild it for fun

[alex.s]

Originally Posted by MrAtom

What all should i do while im in there?

bore it out and throw in high compression pistons with a stroker crank and shorter rods, clean out all the oil passages, replace the pumps, put an oil heat exchanger on, get better cams and do a port job on the head

[JohnnyBravo]

Mainly