top end work and lapping

hi, i have my engine off the bike, im replacing the head gasket.
i have measured valve clearances and they need a bit of adjusting. i havent taken the compression readings, but the bike ran ok before i started to tear it down, so i suspect things to be pretty all right, so maybe i would get by with replacing the gasket and valve adjustment. and cleaning things up of course.

so my friend told me to lap the valves while i have the head off. as i said, i dont really know if there is need for lapping, since i havent taken compression readings and the head is still on. theres no oil in the engine so i suppose turning it with the starter enough to get readings would not be a good idea?

id hate to replace the gasket and adjust valves just to get sucky readings and need to take the head off again? so the question is would you guys lap the valves just to be sure?

 

Heads off???

Lap the Valves.
Replace Valve Seals.

The Lapping of the Valves is going to give you a NEW Gas-tight Band on the Valve Faces and Seats.
Combined with New Seals and De-coking the Combustion Chambers and Valve Stems, ... renewed performance.

When you have the Head OFF, ...
DO everything you can do with the Head Off.

Clean Valves
Knurl Guides
New Seals
De-carbon
Port
Polish
Plane
Piston Crowns
De-ridge Holes

 

thanks for the advice rick,

that seems like a thorough list!

i do like the 'while youre at it'-mentality. maybe that is why im not riding this summer.

off to get some compound.

but off with the head first, its very stuck. ive been tapping on it for a while

 

Why are you replacing the head gasket?

 

Yes at least lap those valves. You did not say how many miles are on the bike, that would help determine how much other work it may need.

 

What does all this mean? Lap the head?

 

"Lapping the valves" is where you use lapping compound between the valve and valve seat on the head, and spin the valve around to polish the areas of contact and get a good seal -- if that makes sense.

The lapping compound is just like a rubbing compound which come in different grits.

I've got the head off my Seca right now as well, and for the life of me I cannot find my valve spring compressor. Probably one of those things I let someone borrow and never got back.

 

I kinda get the feeling you are not talking about the head gasket. I think you are replacing the valve cover gasket and if that is the case you will not be able to lap the valves.

 

I think this winter I'll over haul the engine. I'll be hitting everyone up on that job

 

I get that feeling too.

Are you pullling the HEAD (as in removing cams, tieing up camchain, etc.,) or are you removing the COVER on the head (the valve cover?)

Removing the valve cover to check valve clearances and replace the cover gasket is a whole different "ballgame" than pulling the head. One is a normal "maintenance" procedure; one is major surgery.

Which one are we discussing after all?

 

yes we are talking about pulling the head, replacing the head gasket and lapping valves. apologies if i wasnt clear enough on that.

the head was VERY stuck, i tapped it for an good time - nothing. i had to start prying carefully but careful wasnt good enough so i managed to break the cooling fins on two locations before i got it off. even when the head was clearly off the block, the gasket was loose from the top side on some sections and from bottom on others, and it took a good time to break the seals.

so the head is off, should i take it to a proper headwork or should i fiddle with it myself?

 

waldo the head gasket was leaking oil under the 1st cyl exhaust, thats why im replacing.

there was 84000 km on the clock, but the odometer had been toast for i dont know how long..

by the way since i have the head off, do you think i should replace the piston rings while im at it

 

ok i just called a nearby shop they said they would machine the seats and valves for 50 euros and blow the whole thing with glass.. im there.

 

84,000Km = 52,000Mi.

You should probably have the Rings done and the Timing Chain Replaced, too.

 

thanks rick, im sure my timing chain has been replaced at some point, since there is skidmarks under the valve cover(!!!) yes by the looks of it the earlier cam chain has been up there.

by the quick look i took the cylinder walls look mint.

those rings are hard to find. im having an eye on a yoshimura 820cc kit, while trying to figure out the cost of boring my block

 

Boring-out might not be necessary.

You may only need to have the Cylinders honed and move to an Oversize set of Rings.

The decision gets made after the Cylinders have their Inside Diameters measured at varying depths.

 

what got me thinking was that i could get my hands on the whole yoshimura kit for much less than the oem piston ring kit from a reputable vendor.

that tempts me to inquire the costs of boring from couple of places.

 

option 1: full sh*t

boring the four cylinders: 120€

valve and head work: 150€ (they quoted me for 50 because they thought we are talking about 2 cylinder bike.)

yoshimura piston kit: 100€ (without head gasket)

custom head gasket: loads of €




option 2: DIY

get everything clean, lap valves: not that much €




may have to bid on that kit anyway for later use