TOPIC:

My bike has 12,000 miles on the odo, and
in my brief ownership it has
smoked slightly when cold.
The other day I fire it up and let it warm up
when oil starts to drip out of a small hole in
the exhaust collector. In a matter of 5 minutes
the puddle was the size of a grapefruit.
After taking off the exhaust I see #2 &
#3 exhaust ports are wet from oil.
So I did a compression test last night
(WOT on cold engine)and #1-130, #2-124, #3-110, #4-130. I oiled #3 and it jumped to 130.

So I am assuming I am looking at rings.
Now this bike seems to have been used as a
drag bike by a previous owner so one of my
concerns is have any internals been changed.
First would be the piston. I will have to
measure the cylinders and pistons to see if
they are still OE size. Now if they are stock
size how can I tell if they are OE piston.
Does anyone have pictures of the stock crown?
Or will the part number be on the piston
somewhere? Should I just take a pic of mine
and post them up?

Post reformatted (not edited) for readability

Post edited by: steell, at: 2006/04/24 11:37

Unless you are determined to go to oversize
pistons I don't think I'd make any plans just yet.
20 lbs is not much of an increase in compression
after injecting oil into the cylinder,
the pressure will increase 10-15 psi just
by warming the motor up. If you have not done so, shimming the valves may bring the compression
back up to where it should be, and the oil burning
could be due to bad guides or seals. So the problem could be the head and not the rings
It would be best to check things out prior to
planning to buy parts.

But if you have the money and the desire, a Wiseco piston kit would be cool

All posts reformatted for readabilty.
I don't know how to shrink pics located off site.

Post edited by: steell, at: 2006/04/24 11:39

Yeah, it's beyond smoking now, the oil just pours out.
I guess when I get everything apart I might be able
to see where the oil is coming from. I'm not trying
to throw money into it, so if I don't have to do
rings I won't. I was going to check valve clearance
and replace the seals while I was in there. I
honestly doubt I will put an money into hp mods
since I have my gixxer for speed. The only thing
I've bought so far was cam seals and a top end
gasket kit. I'm sure I'll have a lot more questions
as I start to dig into this thing.

Post edited by: steell, at: 2006/04/24 11:42

Yeah, it would take a lot of money and work to make the
650 as fast as the Gixxer

Pull the head and take a look at it and the cylinders,
then you will have a better idea where you need to go.

Post edited by: steell, at: 2006/04/24 11:58

The OEM pistons were manufactured by a company
called ART (a Japanese company). They had ART
stamped on them somewhere I think. First, the
oil you have coming through may not be caused
by worn rings. It may be a cracked ring or
piston to bore clearance may be too great.
You will have to do more than remove your
cylinder head... you will have to remove the
cylinder and MEASURE the pistons and measure
the bore and inspect the rings. THEN you can
make an intelligent decision as far as what
needs done. It might possibly be that you have
a cracked or broken ring. You need to measure
the slots the rings sit in to ensure they are
within spec. If they are and the piston to
cylinder clearance is within spec, you can
get by with rings and honing the bores.
If it is outside spec, new and oversized
pistons will be needed (with new rings of course).
If you are on a tight budget, you might want to
find a set of matched used pistons and a cylinder
and just rering this combo if it is within spec
(and hone) as the piston kit and cylinder boring
will run $500-600 I think. I would also clean up
the head/valves and replace the valve stem oil
seals at the same time.

Post edited by: steell, at: 2006/04/24 11:44

Cliff notes, details below:
What motor is a 650-C3 out of?
Dirt piles around 4 inner studs on cylinder, normal?
How much play should piston rings have?
Valve clearence 0 with 2.10 shims, where to start?

I got everything torn down today and have run into some issues and concerns. First I knew my engine
and frame vins didn't match but I read my motor
is a 650-C3 and I'm not sure what that is out of.
I measured my valve clearance and all 8 where
0 and pretty snug against the cams. I tried
the method where you rotate the cams a little to
see if the feeler slips in but nothing. So I have
no clearence and of all the shims only one
is readable and it says 2.10. I lined all the
shims up and they all appear the same size but
I have to get my micrometer back so I can
measure them. I m going to measure them again
when everything is put back together but if
I'm still at 0 where do I go from there?
I read in another thread someone recommended
starting with 2.000 shims.
Ok, next concern when I pull the cylinder off
there where little piles of dirts around the
4 inner studs, is this normal? The engine is
pretty clean and I can't see how the dirt would
get in there. All the gaskets where in decent
shape so I don't think it was deteriorated gasket. Next is the rings, how much freeplay should they
have in the grooves? If they are flush on one
side they stick out far enough on the other side
to make a tiny gap. The cylinders look pretty good,
very smooth and I can still see cross-hatching.
The pistons are ART and don't appear to have any
cracks and the ring lands look good. I still have
to measure the cylinders and pistons though. To
remove the valves do you really need the special
tools or will a c-clamp and some dexterity do it?
I'll try and get some pics of some things to help
you guys out.
Sorry my camera sucks.
The dirt around the studs


Piston ring play


Post edited by: puckaveli, at: 2006/04/23 16:14

Post edited by: steell, at: 2006/04/24 11:48

First, you should have measured valve clearances
BEFORE taking the cylinder off. I suspect your
compression woes will be just fine once you set the
valve clearances correct. Clean off the crud that
tends to fall into the stud wells and scrape off your
base gasket mating surfaces and reinstall your
cylinder. Next, you will need an adapter with your C
clamp and you will also need to weld a nut onto the
end of the clamp. You will not disassemble your
cylinder head otherwise. Contact roy-b-boy-b for an
adapter. He might be able to help you out. Last,
since the rings SEEM to be OK, measure your cylinder
to bore clearances since you took it apart this far
to ensure that there isn't general wear that is not
allowing your rings to scrape as they should.

If you take apart the head, measure valve stem
lengths as they are the BEST indicator of seat wear.
If they are within spec, lap the seats/faces and
install new valve stem oil seals. Also check guide
wear by wiggling the valve in the stem. It is pretty
hard to use a small bore gauge effectively and the
wiggle test works about as well.

Post edited by: steell, at: 2006/04/24 11:50

What do the bores, piston skirts and bottom of pistons
look like? If OK....

I would pull the pistons out, clean the carbon off by
soaking with Marvel Mystery Oil(that stuff will clean
burned rice out of a rice cooker!) or with fine wire
brush. Then measure your bores and piston diameter at
the skirts, front to back.

That does look like a lot of slop in the top ring.
There should be a spec in the manual for feeler guage
between ring and groove. Not something I've done
enough to have in my head

That brown stuff on the sides of the pistons looks a
little weird, but some pistons are made with a
coating in this area. Once you have them out, you can
see if they are original or not.

Bore measurement will give you a clue here too.

Post edited by: steell, at: 2006/04/24 11:52

I had to reformat everyone's post so I could read them
because the pics are to wide (took a while for me to do)
So, when posting in this thread, please hit "Enter" when
you get to the end of the editing window, at each line,
so the text will stay in the white part where people can
read it.
If I knew how to resize pics that are located off site
then it would be easier. Or people could limit their
pics to 550 wide

My valve measurements where taken before the head was removed.

I'll get the piston, bores, and such measured and we'll see what those reveal.

In the manual it says not to clean the carbon build up around the edges of the crown of the piston because it will promote oil comsumption. Any truth to that?

That's common when using the original rings and bore, but if you are using new rings and honing the cylinder, then I'd clean all the carbon off the piston.

Just my $0.00002