What compression do you get on your GS ?

[ukjules]

I have another thread re an oil leak but start
this as want to know what others get
when doing a compression test ?

I attach my results but I get 180-200psi
on my GS550E 1980.
This throttle open , dry

and 200 - 225 throttle open , with oil.

(throttle shut i get round 120 area)

Not I think this points to my rings gone. (likely too)
but my question is do others get 200psi
area when running test ?

20201106_134058_resize_19.jpg

[Rob S.]

How does the bike run? Does the bike run?

[tatu]

I have another thread re an oil leak but start
this as want to know what others get
when doing a compression test ?



[ATTACH=CONFIG]61944[/ATTACH]

Those numbers look pretty good to me, engine should be hot with throttle wide open. But if you do decide to deal with the base gasket leak just stick in some new rings while you're at it.
I used to gather them a bit at a time from ebay as OEM are a mad cost, now I just order from cruzin image, very low cost and ( I'm pretty sure), are NPR (Nippon Piston Ring) which are OEM. I think I paid $50 for a full set for my 1000 resurrected wrecker.
Valves can always do with a lick round if you do decide to open the engine.
Is this in preparation for your next outing?

[ukjules]

Ok understood and noted.

The bike runs fine. BUT I ride it like an old woman...
and have been told off for doing so!
Starts fine , cruises at 70/80 all day.

It seems to lack power I reckon but I dont use it !
mad but poor "herbs" (the name of the bike)
needs to be saved ....

Re oil leak. still no idea where it comes from !
but there are for sure oil leaks on rocker cover,
tacko and tensioner. poss a stripped helucoiled
bolt in rocker cover not allowing perfect
torque on 1 or 2 bolts.

but more oil is being lost that could come from
those areas. thus it must be and comp test
points to rings.

[tatu]

but more oil is being lost that could come from
those areas. thus it must be and comp test
points to rings.

Your compression test says rings are ok, adding oil made a little difference. I would say it's your guide seals that are seeping oil.
Does it puff a little blue smoke on start up after standing for a while? or slightly on overrun? Get a mate to ride behind you and look.

[ukjules]

Yes it does puff a bit of smoke at start up.
I will have to find a friend ...

one thing about comp test it says
if it increases 3-17% it is likely to be using oil
and be the rings. another book says if 20%
difference. I am on 15% increase.
so it looks a small increase but it's right where
it says (cant recall where ) an issue is.

But I agree seals need replacing ... I have
no stats on which head i did them last.

all I do know on this engine it's time for a
full and proper strip down to base gasket and back up
and address all !

being unemployed , homeless and a lockdown due to
global pandemic it's the ideal time to test engine
no 2. (this was rebuilt by a oldy obsessuonal
ex engineer).
I start this on monday and will add a thread or results
so all can enjoy the saga !

[tatu]

A puff at start up is leaky stems seals. Possibly, but unlikely guides as well.
I couldn't find the seals that i liked in the UK so I brought this kind from the States, (They have all the good stuff there)

https://www.ebay.com/itm/SUZUKI-GS550-GS650-XN85-GS-550-650-VALVE-SEALS-VITON/303024258656?epid=0&hash=item468da73e60:g:ejYAAOSwkGVZub20

These are the kind that are available in UK nothing wrong with them, they're the same as in my Kawasaki.

https://www.ebay.co.uk/itm/Fits-Suzuki-GS750-77-79-7mm-Viton-Valve-Stem-seals-set-of-8-The-best/362257426842?hash=item545839a99a:g:D6gAAOSwFMdaVdh0

Just that I preferred the first type they look better made and very similar to pattern of OEM.
I would/do only use Viton seals on the stems.

Cruzin Image : https://www.cruzinimage.net/2017/08/...ings-included/

Nowt wrong with their stuff.

Robinsons for the gaskets Michelle there is a delight and very helpful. Only OEM for gaskets and the oil seals (pear shaped ones)
Just as an aside, Three bond is what the manufacturers use, i used to not use it but really as an insurance a smear both sides of the gasket saves a heap of heartache. I wouldn't use anything else on such a place.

[ukjules]

All noted down....

It is mad that the bikes I restored
- the other three I have I have all records
and took my time.

My beloved GS that iv had as the main bike
the longest I have neglected terribly.
An outrage but it is due to it just keeping
going on and on regardless .....

The other 3 sound now I turn to the GS.

This engine is the winter project but
next week I'm gonna swap engines.
I am sure the guy I bought it off
was a genuine engineer obsessive so
it will slap straight in with every
clearance spot on.

Fingers crossed and will do this by next
weekend.

Hopefully one way of stopping oil leaks
is to use another engine.

p.s anyone want a Gpz750r1?

[ukjules]

Update and compression data for new engine:

New engine just put into gs550e 1980
Compression test

1 2 3 4
Dry 150 148 150 150

Wet 165 162 168 165

This with engine at normal temp, throttle open.
This engine is considered to be rebuilt, valve clearances set and possible pistons, rings and valve seals.

Suzuki spec: 128 – 171 and say compression must be over 110 and 150 is ideal.
I am told that a 20% increase (between dry and wet) points to worn rings and it would burn oil. The increase here is 9-12%.
No increase would point to valves not seating correctly or head gasket issue.

So basically, am I right in thinking that this is almost a perfect test on the new engine? It goes with what I assume to be the case it was rebuilt by an obsessive engineer?

Old engine – out due to oil leak

1 2 3 4
Dry ? 180 190 200

Wet 198 200 220 225

This taken as per guidelines, engine at temp, throttle open.

Q) What do these stats tell us? Remember it chugs along fine, has an oil leak, not a great deal of power, possible bodged base gasket, possibly head and cam cover gasket at fault. Knackered can tensioner gasket. I did the valve seals and lapped the valves …….

If the new engine is perfect – we must assume so !!! how is the psi so high on the comp test of this old one?
Clearly out of spec but I assumed as it wore it would be lower? What on earth would make the test psi increase?

Id be so interested on thoughts

[Grimly]

150 is fine - it's what I get after re-ringing and valve-seating mine.
Likely your new engine might increase its readings as it runs in.
Try again in a thousand miles.

[ukjules]

I agree that new engine is clearly in good health.
150 is ideal . The stats backup what the PO
engineer said.

But the question is how on earth is my old engine 180-200 psi ?
How can an old leaking engine have a psi
that no other bike has ? I bet no one on here has
a coomp' pressure that high ? indeed I dont know anyone
in the entire world who has ?
If it was 90 like a worn engine I'd understand.
or does a worn engine increase psi ?
suzuki tolerance is 128-171

what causes low psi and what causes high psi .
I cant believe my lapping of valves , Athena
gaskets , oil leak .. caused my old engine to
have a psi of a grand prix bike ?

[londonboards]

The higher readings in the old engine may have been due to the head being skimmed or non-standard pistons being installed. Something that would physically reduce the size of the combustion chamber. Maybe?

I am very dubious of compression testing in general. More people seem to get anxious about their figures than is necessary. Throw it together and take it for a spirited ride. That'll tell you if it's working well enough.

I did a carb job on a 550 recently and noticed that the engine is very sensitive to the set up in the airbox, especially if you are using one of the foam filters that has been soaked in oil. We cleaned the oil out and the bike took off like a bat out of hell. But, according to your earlier post about your riding style, you do need to spin these motors up. They really take off over 7,000 and were designed to operate up there. Don't be afraid of opening it up. It will appear to be pretty guttless below that rpm number. The 550 is not a machine inclined to sedate top gear dawdling. You need something like an 1100 with some proper low down torque for that.

Greetings

Richard

[ukjules]

You are right on my riding style ..... on
these old bikes as I think for some mad reason
they will fall to bits if I dont preserve them
buy riding slow...... I cruise about at 6rpm
and have done since my top end work on old engine.

compression:
I agree it doesn't really matter on the new engine.
It clearly is spot on ... and the compression shows that.
I am not concerned at all with that.

it's just that with the same tester I got these mad
results on old engine . a significant difference.
the old engine is now on the bench... ready for me
to do a top end overhaul and might split the cases.
But no hurry now.

I def rode below 7k. the few times I tried to push higher
it didnt.do anything ... no power band. But
it worked and works now. it would go round Europe
tomorrow but just use oil.

It is a disgrace that I cant even remember if I.put in new
pistons rings. I am sure j didnt rebore it.
I think the head was skimmed. I did this not PO
many years ago. I def lapped the valves to learn soming ...
clearances were always spot on. just the appalling
gaskets j used.

I just dont understand the high compression?
it doesnt matter as engine to be stripped but how
can my previous slap dash top end job cause such
fabulous results ? albeit my 180-200psi is out of suzuki
spec as top is 171 they say.
perhaps the high compression is causing the oil leak ?

perhaps I should start being an engine rebuidler
for race bikes !or work for Athena gaskets !

[ukjules]

If anyone does have a old bike with a old
engine and is bored during lockdown do get up,
and do a compression test and show results !

[Nessism]

If anyone does have a old bike with a old
engine and is bored during lockdown do get up,
and do a compression test and show results !

I'm confused as to why it would matter when the engine was built? Bottom line is that a solid GS engine will make about 150 psi. Slightly higher if fresh and typically somewhat lower.