Questions about tear down, rebuilding a Seca engine

Since my new to me Seca is not the get on it an ride bike I was hoping for; I have choices between rebuilding my engine, or replace it.

From a rebuilding perspective, studying the factory service manual I've already run into discrepancies, as in valve clearances.

Len of XJ Forever recommends replacing rod bolts , FSM says nothing about that. I don't have a problem replacing them, as it looks like their torque procedure reminds me of torque to yield head bolts in cars, though there is no corresponding resize of the big end after replacing the bolts. Car experience has me having the big ends resized after a bolt change due to change in clamp load.

Bearings, are they even available??? And I still don't quite understand sizing procedures, I'm used to, measure the journal, pick the bearing; grind the crank if too warn, pick the bearing. Only one bearing was/is position specific, and is self explanatory.


Replacing engine is an option, it's just every used engine ran great when it came out of the donar frame, before you put it into your frame.

 

I am fitting a new starter clutch starter chain the guide for the latter and a new cam chain. The XJ engines are very tough your motor will probably not need a rebuild but other forum members will keep you right on bearings and rod bolts.

 

I'm thinking rebuild due to the following; compression test dry, low70, high 90; wet 90 to 110, leak down test is 10 to 15%, all into the crank case. This engine is sick.

 

All you need is a hone (maybe a rebore) and new rings (maybe pistons if you have to bore oversize).

How long have you had the engine running? It's not uncommon for the compression rings to get stuck whn a bike sets for years. A 50/50 mix of acetone and ATF generally will unstick them if that's what's going on.

The bottom end is pert-near bulletproof. No need to touch it unless the alternator chain guide breaks up, and even then you don't need to mess with the rods and crank. There is at least one member here who had over 200,000 miles on the engine before rebuild.

There are discrepancies and typos in all of the manuals, which is part of why we have so much information in the DYI section to correct those errors.

 

the factory service manual is printed more for the trained mechanic and leaves out the little details

 

I would try soaking it as kmoe stated with 50/50 acetone/atf

 

this may be of interest to you
XJ750 Engine removal and split - Pictures.