head warped (how many grinding?)

dirk · Post by **dirk** » Mon Sep 15, 2008 8:02 pm

Hi folks,

how many mm can i grind the surface without rework the combustion chamber or squish?
my head need around 0,2mm, so that it is flat.

thanks

regards
dirk

mgtkr1 · Post by **mgtkr1** » Mon Sep 15, 2008 9:50 pm

if the head is std then i think .2 mm will be fine. use genuine gaskets and torque the head in the correct sequence 3-4 times min. i do this and have not had a problem. im sure someone will clarify how much can be removed before it affects reliability. cheers matt

dirk · Post by **dirk** » Mon Sep 15, 2008 10:50 pm

hi matt

thanks for your answer.

i hope you are right and the pistons don`t kiss the head..... [-o<
think my cylinderhead is std.
have two heads and both are same thick and same warped...

around the combustion chamber is a edge.
if i grind the head (0.2) this edge is away.
that`s ok?

cheers
dirk

mgtkr1 · Post by **mgtkr1** » Tue Sep 16, 2008 7:27 pm

another way of doing it is getting a flat plate of glass with wet/dry paper wrapped round it. using water as lubrication, rotate the head in a figure of eight and keep checking for flatness. time consuming and monotonous but effective if done right. i think elf knows the ins/out as he did a post on the very subject. my head on my race motor doesnt have the ''step'' around the combustion area and uses taller tz pistons aswell without a problem. the shape matches the dome and uses diffrent fuel but i think you will be able to safely remove the material so long as it just is enough. if the head is only slightly warped your ok. you could have the combustion chamber reworked to compensate so its same as std but for the effort you may as well up the compression slightly in order to sharpen her up a bit but remember kr's DONT like high c/r so dont get carried away. dont rely on my info as guaranteeing your gonna get 20000mls trouble free though, my experience with std kr's is quite limited as i dont have one on the road. are you desperate for a cyl head dirk?

the-elf · Post by **the-elf** » Tue Sep 16, 2008 11:29 pm

Posted a lot of info on this for scobble (i think under "engine" topics) . The standard sqish is about 1.6mm +/- a big manufacturing toleranace. Idea is around 0.7-0.8mm. Measure it with some soft solder as I discribed in the previous posts. If its standard then it won't matter as it'll need alot more skimmed off it than 0.2 to get it correct.

the-elf · Post by **the-elf** » Tue Sep 16, 2008 11:29 pm

Posted a lot of info on this for scobble (i think under "engine" topics) . The standard sqish is about 1.6mm +/- a big manufacturing toleranace. Idea is around 0.7-0.8mm. Measure it with some soft solder as I discribed in the previous posts. If its standard then it won't matter as it'll need alot more skimmed off it than 0.2 to get it correct.

dirk · Post by **dirk** » Sun Sep 21, 2008 5:53 pm

hi folks

thanks for the tipps

many hours later with sandpaper i think the head is 95% flat.
it was around 0,15mm.
if the head leak again i wish a new from Santa Claus or i throw the bike away.

..dont rely on my info as guaranteeing your gonna get 20000mls trouble free though...

my h***a cb500 pc26 is the only bike that manage 20000mls without trouble......

i have no basic trust to the kr.
if the bike run more than 1000mls without trouble than i am happy. [-o<

cheers
dirk

SHimmer45 · Post by **SHimmer45** » Sun Sep 21, 2008 8:22 pm

have faith in the old girl

good motors i have absolute faith in them (not run the new one but im sure it be fine

dirk · Post by **dirk** » Sat Sep 27, 2008 8:27 pm

hi

fuc... head

my work was for nothing.
i have tried many times torque the head and every time the valves stick.
I tried each powervalve in each cylinder and the same thing happened
think my head is still warp.

next week i go to a grinding shop and hope it cost not to much.
@matt

are you desperate for a cyl head dirk?

yes i am.
have you a good warp free standard head?

dirk

scooble · Post by **scooble** » Sat Sep 27, 2008 9:49 pm

I had exactly the same problem with a non standard head gasket. Check the head again by torquing it to the cylinders without the head gasket to see if the valves still stick.
I also took a few thou of the disk section of each powervalve.

dirk · Post by **dirk** » Sun Sep 28, 2008 5:06 pm

hi folks,

next question...

if the head must grind more than 0.2mm is it possible to use two head gaskets?
if i loose a little bit compression with two gaskets ..that is ok.
for road use i don't need the last pony and perhaps a bit less compression is better for the stability under load.

@scooble
nice workaround, but i am sure the head is not 100% flat and i don't need the next water leak.

Dirk

the-elf · Post by **the-elf** » Mon Sep 29, 2008 6:10 pm

Don't bother with two gaskets as a) they arn't needed and b) they will leak.

Have you have polished the head on a very large sheet of 500 grit wet and dry glued on to a piece of glass (use WD40 as a lub)?

I've had the problem with the valves a few times. Make sure the valves and the cylinders where they sit are clean. Dip the valves in new 2 smoke oil and assemble. Don't use after market head gaskets as I've had problems with some of them and tighten the bolts up a little bit, first hand tight, then a quater of a turn each in the correct order.

dirk · Post by **dirk** » Mon Sep 29, 2008 8:32 pm

hi elf

thanks

with two gasket...it was only an idea....

Have you have polished the head on a very large sheet of 500 grit wet and dry glued on to a piece of glass (use WD40 as a lub)?

yes but only with water.
perhaps the glass was not thick enough and bent or i am to stupid?

however
the head is now in the garage.
grind cost around 40 pounds.
not cheap but then i am sure thar the head is flat.

my new cylinders was deliverd with a set after market gasket kit.
the gaskets are the same as from pj.
you think the head gasket is not good?

this bike eat me out of house and home.
if the bike in next time don't run without trouble an needs more new parts my girlfriend kill me.
i spend much more time and money in my 2strokers as in my girlfriend....
for me it is ok but.......

Dirk

Red Devil 777 · Post by **Red Devil 777** » Mon Sep 29, 2008 8:41 pm

dirk wrote:the gaskets are the same as from pj.
you think the head gasket is not good?

In my experience get a genuine one, cos you'll end up putting one in any way. I've just ordered one from z-power, think it was about £16.00 + del.

dirk · Post by **dirk** » Thu Oct 02, 2008 8:26 pm

hi

today i assemble the head.
no sticking valves

but the squish is now ~0,65mm

need only the squish band restored or the whole combustion chamber?
the 0.8 squish is good only for race?
is a little more better for road use (durability)?

how much is a new cylinder head in uk?

dirk