head/base gasket thickness selection? overhaul; seized piston removal?

[Chuck78]

After the last ride, I have to retire my 1977 GS750B's 78 750 engine that has been seeping oil out all over slowly for the past few seasons. I got home Friday night with my left boot toe covered in oil...

I want to build up a spare engine to swap in with a fresh head and some overbored '79 gs850 cylinders and NOS M.T.C. Engineering 920cc 10:1 pistons that I've had for 2 years. I have an unknown but good looking 79 gs750n engine I could build, but also a 78 frame & engine with rusted/stuck valves& pistons/rings. Bike was last registered on the road (plated) in 1985, sold in 89, sat until Witttom here parted it out last year. I'd like to try & use this one, as it seems good that the original owner only rode it '79-85, likely to have the best condition gearbox in my mind. 79 engine looks good, no head or clutch, no clue on mileage or history.

I suppose the only way to get the bottom end freed from the shot head/pistons/jugs is to unbolt the rods from the cranks underneath, and remove the jugs with seized pistons and rods. After that, does anyone have any tips besides heat to remove the rods (&pistons) to reuse the rods? Cams & bottom end looked great, I think the bike just sat in a barn forever needing some repairs, & moisture in the open valves got the best of the rings & most of the exhaust valves (they look pretty bad).


My other question is - are there different thicknesses available typically in head and base gaskets? In musclecar engines, proper quench height (piston to head distance) is very critical/fussed about in maximizing a high compression engine & reducing chance of detonation (pre-ignition).

I will be running a GS850 base gasket (probably have to go OEM if Cometic doesnt make one), and either a 73mm bore GS1100G MLS head gasket for like $117 (thicknesses?), or get a custom Cometic GS750 head gasket for 72mm bores for $80-90, which I suppose I could get made any thickness I wanted.
I'd prefer to go standard on the custom head gasket thickness (to get it sooner) & have some selection of oem base gaskets to adjust the height, but I wasnt sure what options I have & how critical this quench height was. RapidRay, blowerbike, anyone???

[rapidray]

Chuck, too many questions to type answers to. Call me at 714--356--7845. Ray.

[Old guy]

I'd adjust the compression ratio higher with the pistons or milling the head. You're going overbored so you're going to have more squish area, probably making squish clearance more important.

[Old guy]

Stuck motor, pull the cams, add acetone and ATF, use a leak down tester to pressurize the cylinder. If the head is off, acetone and ATF, heat a block of wood and a big ass hammer

[Chuck78]

Ray, I may give you a call here in the next few days after 4PM-ish EST for some advice on the whole engine rebuild if you have time.
I've messed around with lots of V8 engines in Camaros, Firebirds, GTO's, etc, but this will be my first japanese inline 4 motorcycle engine. I have the factory service manual and clymer's and a large work bench to tear the engine(s) down and inspect everything, but wasn't sure on the quench height and gasket thicknesses, if it was considered as critical since there is such a limited selection of thicknesses if I recall from other posts.

Any other tips on a total engine overhaul would be much appreciated. It's a roller bearing bottom, so I am expecting the cranks to be pretty great, not sure if it is frowned upon to reuse the bearings on a low mileage engine or not, and looking for pointers on spotting common wear and tear in the gearbox. Thanks to all of you for all the help over the years, and to come yet.

[blowerbike]

press pin crank...can't unbolt the rods.