Replacing head gasket, anyone know what parts needed (besides head gasket)?

R-III-R Turbo

R-III-R Turbo

Registered
Hi guys, newbie 'ere.
My bikes are a Rocket III and a 2004 Busa. The Busa has become increasingly hard to start, this is due to low compression.
So I am going ripping the head off to investigate. BTW clearances were checked too all good.

Just to save me bother, has anyone who's had the head off know of any parts needed (besides a new head gasket) or likely to be needed, for the job?

I've had other bike engines apart many times so comfortable with the type of work, just would like the tips of anyone who's done it on this particular engine.

thanks
 
Technically just a head gasket and probably coolant, it’s easier to drop the motor and do it. Actually u might have to drop the motor regardless. But I can’t remember, I no longer have a stock frame.

And get a manual and take pics if it’s your first time. Helps.
 
R-III-R Turbo said:
Hi guys, newbie 'ere.
My bikes are a Rocket III and a 2004 Busa. The Busa has become increasingly hard to start, this is due to low compression.
So I am going ripping the head off to investigate. BTW clearances were checked too all good.

Just to save me bother, has anyone who's had the head off know of any parts needed (besides a new head gasket) or likely to be needed, for the job?

I've had other bike engines apart many times so comfortable with the type of work, just would like the tips of anyone who's done it on this particular engine.

thanks
Click to expand...
What @Kiwi Rider said,a leak down test is the proper way to find out where the compression is going and we're kind of nosey like that and want to know :lol:. I know that's not what your asking about and the head gonna have to come off for just about any reason anyways but it would be good to know before you get it tore apart. Aside from the head gasket I would get the other gaskets (valve cover,spark plug tubes,etc.)your gonna have to pull even tho most can be reused just a good practice to replace them anyway. Welcome to the org and be sure to post some pics,we like pics of all bikes around here and you won't find a better more knowledgeable group of people to help you with your busa issues.
 
Kiwi Rider said:
Welcome along, what did you find with the compression test results? Numbers?
Have you done a leakdown test?
How many kms/miles on the bike?
Post up a pic if you can….
Click to expand...

Cranking compression results were 142psi on 1, 152 on 2, 147 on 3, and 150 on 4.
Squirting a drop of oil into the cylinder brought compression up by about 10psi.
So not a massive jump, could well be rings but not entirely certain.

Last compression check was 46K miles, they were all around 160psi then.
I didn't go tearing it apart at the time because it started ok and ran perfect, lots of power, but did note that it was below the spec but not quite at the service limit.

But then it got harder and harder to start, at the point now where it won't unless I got a real good fresh battery. So time to do the needful.
I might do a leakdown test for the lols before ripping it asunder.

49k miles on it. Oil changed every 1500-2000 miles in my ownership (since 39k miles). Castrol 10W40 4T Racing, Suzuki filter.
Oil always spotless coming out.
Always well warmed up before giving it much throttle, and I wouldn't be into burnouts or wheelies but will not shy away from some doucher who thinks he's fast and wants to prove it to me :-)

1660846042328.png


1660845626769.png


BTW them Nissins were put on by previous owner, they're not much better than the stock 6 pot Tokico, the pic was taken shortly after I got it but a set of €1000 Brembo caliper/disc/lines/fluid have gone on since, which aren't bad.

VIPER said:
Um, little confused here. You said low compression. How do you know its the head gasket? Coolant missing? Pressure in the crank case? How do you know its not a valve issue or potentially rings? Smoke test would seem to make alot of sense to me.
Click to expand...

It could be head gasket, rings, valves, I don't know, but in any case the head has to come off to sort it, hence the head gasket requirement. Yes the coolant level did drop a little.


Soooo.. anyone know of a reasonably priced parts supplier (in Europe, preferably.. avoid import tax) :-)
CMSNL are good but not cheap I find.
 
Last edited:
Ok so finally got some time off work to go ahead and tackle this.

I bought the bike used in 2015, started and ran well, performed as good as any stock gen 1, but doing a compression test for the fun revealed a 160ish psi across all 4 condition.
Spec was 171 - 228psi, service limit 128psi.
I left well enough alone as the bike worked fine.

But cut forward 5 years and it was gradually becoming harder and harder to start.
By 2021 it wouldn't start at all, unless you hooked up a really strong battery and spun the bejesus out of it, then it would just about start.
Anyway did another compression test and found all four were down around 142 - 152 psi cranking.
This rose a shade with a drop of oil in cylinder.
Figured it was time to rip the head off.

Cut to 2023 when I got the time;

1683576982287.png


Indeed you can remove the cylinder head and the cylinder block from the crankcase without removing the engine from the chassis, but I will wager that it is probably easier overall to just remove the engine in the first place.

Found that no special tools are required (unless you're measuring bore diameters) except a couple of castle nut sockets.
Lucky I had the 30mm but I had to make the other from a 14mm socket.

Anyway I found the valves to be in very clean & in good nick (apart from left hand intake valve on cylinder #1 which was coked up for some reason but still closed perfectly from what I could see - cleaned and lapped it anyway).
The head gasket was good.

So this left only the piston rings or something in that regard to be worn in order to explain the low compression.
I pulled the block and checked rings.

1683577004562.png


I found the ring gaps to be significantly larger than spec.

Top ring
Specification: 0.08 - 0.20mm (service limit 0.50mm)
As Found: 0.36 - 0.41mm

2nd ring
Specification: 0.15 - 0.30mm (service limit 0.50mm)
As Found: 0.36 - 0.53mm

1683577101792.png



So I thought, woohoo, that explains the low compression etc.

But then when I popped the new, straight from Japan, Suzuki rings in, the gaps came back not much better!!
Top ring 0.31 - 0.36mm
2nd ring 0.28 - 0.33mm

What the eff.
So I measured up the bores, even though they looked good with no scratches or wearing signs.

Found the bores with this gauge, and also a telescopic bore gauge, to be about 81.06mm.
Specification 81.000 to 81.015mm.

Checked too at very top directly with a calipers, to be the same. And this is above where the top ring actually touches.
The bores had literally zero variability off the 81.06mm, up down left right, no change. Dead straight, but a bit above spec.

1683577061616.png



It is like the large ring gaps are caused by the cylinder bores being too large, and they were that way from factory as I can't see how the cylinders could be worn given they are dead even top to bottom, even where the piston doesn't go.
But it doesn't make sense that they would be too large from factory.

Anyway, I put it all back together and after a bit of work priming the fuel line, it started and ran good.
Stopped and restarted it a few times, all good.

Not broken in yet and no compression test done since rebuild.
 
Last edited:
you said
"
But cut forward 5 years and it was gradually becoming harder and harder to start.
By 2021 it wouldn't start at all, unless you hooked up a really strong battery and spun the bejesus out of it, then it would just about start.
Anyway did another compression test and found all four were down around 142 - 152 psi cranking.
This rose a shade with a drop of oil in cylinder.
Figured it was time to rip the head off."


when you put it back together make SURE you have good voltage to the coils while cranking
my pet peeve but it sounds EXACTLY like a problem I had

Voltage feeding coils goes thru a bunch of switches and relays each caused my voltage to drop a little
by the time it got to the coils under cranking it was too borderline low

cut that lead and cranked when I touched a wire to 12v and she kicks instantly
went back and forth between factor feed and my 12v 6-8 time unable to belive the difference
I mean at one point I was 24v start 8-1 comp bike and still hard start
 
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