Engine tear down: What would you replace?

Aside from any parts that are out of spec, what would you replace as a precaution? Valves? Cam chain? Crankshaft end bearings?

You should go with cam chain, cam chain gears and guides, all seals and bearings. I would also go with the extra money to toughen up the bottom end like welded crank, APE studs, main cap support, back cut tranny and so on. If you have the bottom end apart and do the upgrades you can always go bigger later when you get bored with it.

donthekawguy wrote:

You should go with cam chain, cam chain gears and guides, all seals and bearings. I would also go with the extra money to toughen up the bottom end like welded crank, APE studs, main cap support, back cut tranny and so on. If you have the bottom end apart and do the upgrades you can always go bigger later when you get bored with it.

ditto

What are you planning on doing with the bike? Racing it? Just a daily driver? Makes a difference as to how much should be done and/or needs to be done. If you are planning on racing the bike or seeing how fast the tach can move on a regular basis, then all the stuff mentioned is a very good idea. If you are just planning on a daily driver, then some of the work and parts, although they wouldn't be a bad idea, aren't really necessary. Consider the studs, crank cap, back-cut tranny, welded crank as over-build on a daily driver but good insurance if you can afford to do it. Personally, I would either way if possible, just for peace of mind. Absolutely do it if you plan on rotating the earth from time to time, but optional on a daily driver. Have the head freshened up with springs, guides and seals. Have the clutch taken apart and inspected. Have the steels and fibers cleaned up and deglazed. Springs will probably be ok but they can be changed if weak. Cam bearings should be fine also but have a look. They last forever for the most part. If plans call for a bigger motor later, do the bottom end work now while it's apart. If not, it's a judgement call only you can make for your situation. I, myself, like to over-build my stuff...for possible future upgrades and also for the added insurance against normal stress of operation.

Good info posted above. At least the cam chain and valve stem seals. How many miles on the bike? Is it a daily rider or do you lead foot it? On my last top end job I was lazy and did not want to pull the engine to change the cam chain. However, it measured well within specs. Pulling a shaftie out of the frame is a PITA....chris3

LeeLewis7 wrote:

Aside from any parts that are out of spec, what would you replace as a precaution? Valves? Cam chain? Crankshaft end bearings?

Depends how many miles are on it and how long you want to ride it.

The engine is out of a '84 KZP w/ 39k miles before tear down. Someone's been in the engine before, if that matters. I'd guess it was whoever did maintenance for the Atlanta PD fleet.

I originally intended for it to be a touring and weekend bike, but with gas prices rising it'll probably see use as a commuter. Whatever miles it does see, they'll be conservatively ridden. For Earth rotation duty, I've my eye out for a mint '93 VMax I'd like to pick up one day.

I don't intend to ever race it, and budget is limited, so welding up the crank, back-cut tranny, etc. seems a bit much for the intended use, though I can see the advantages.

Thanks for the input so far. Great info! Please keep it coming.

If it was me and it's running good I wouldn't replace anything. I know "preventive maintenence". My preventive maintenence has always been replace something only after it's worn out, and as strange and out in left field that sounds, that has always worked for me.

racer54 wrote:

What are you planning on doing with the bike? Racing it? Just a daily driver? Makes a difference as to how much should be done and/or needs to be done. If you are planning on racing the bike or seeing how fast the tach can move on a regular basis, then all the stuff mentioned is a very good idea. If you are just planning on a daily driver, then some of the work and parts, although they wouldn't be a bad idea, aren't really necessary. Consider the studs, crank cap, back-cut tranny, welded crank as over-build on a daily driver but good insurance if you can afford to do it. Personally, I would either way if possible, just for peace of mind. Absolutely do it if you plan on rotating the earth from time to time, but optional on a daily driver. Have the head freshened up with springs, guides and seals. Have the clutch taken apart and inspected. Have the steels and fibers cleaned up and deglazed. Springs will probably be ok but they can be changed if weak. Cam bearings should be fine also but have a look. They last forever for the most part. If plans call for a bigger motor later, do the bottom end work now while it's apart. If not, it's a judgement call only you can make for your situation. I, myself, like to over-build my stuff...for possible future upgrades and also for the added insurance against normal stress of operation.

ditto