GS850 camshaft advice needed

[uteman]

I am an old guy trying my best to help out a friend.
My expertise is in heavy equipment not motorcycles.
Even then 77 years are taking their toll!
This 850 has been converted to cafe racer and looks great but running leaves something to be desired.
Owner went for cheap air pods that look great but are they?
Ebay item:54mm Air Filter Cleaner for Suzuki GS650 GS750 GS850 GS1000 GS1150 GS1100 (Firebird - moto) brand
That's one issue.

The bottom end of the engine is sound having been rebuilt.
When he had the head "done up" it was not in great condition and the recon shop did advise that the exhaust valves are now close to min thickness but not mushrooming (I have the head off again)
They are still above to .5mm min thickness.

Valve springs are all within height guidance figures as per shop manual.
He did get a carb jetting kit from USA and has played around with that but it just did not run right.
New coils fitted.
Number 3 cylinder was not performing well and when I removed the plug lead from that cylinder it makes only "some" difference whereas removal of others will stall the engine.
Compression at cranking speed was
Cyl 1: 110 PSI
Cyl 2: 100 PSI
Cyl 3: 105 PSI
Cyl 4: 110 PSI

With a few revs on the engine (around 3 to 4 thousand) the exhaust was giving sounds akin to a fluttering valve and that led me to head removal after checking all clearances once again.
The torque on head bolts was less that I would have expected and there were signs of gasket leakage around number 3.
I decided to check all cam lobe heights.

Inlet should be: 1.4299 to 1.4315 with a service limit of 1.4181 inches
What I found:
number 1.: 1.4165"
number 2: 1.4195"
number 3: 1.4025"
number 4: 1.4160"

Exhaust should be: 1.4083 to 1.4098 with a service limit of 1.3965"
What I found:
number 1: 1.4095"
number 2: 1.3955"
number 3: 1.3950"
number 4: 1.3965

It is clear that this engine could do with some better camshafts.
To the experts out there: What effect do you believe that badly worn lobe on number 3 inlet would be giving?

Now there are plenty of camshafts advertised on Ebay but does anyone have a set with on spec measurements both on lobes and journals?
If so will you sell and ship to the land down under?
It would be so easy to buy a set that are just as bad or worse and I do want to travel that road.

Thinking about this engine a bit more:
For an engine that has new piston rings etc it seems to breathe quite a bit from crankcase vent hose that would normally run to the air cleaner.
I have an 850 of my own that I rebuilt but i used different piston rings to this guy.
So. I start to think of deeper issues.
I will compare compression readings with mine tomorrow. (night time here in Melbourne)

Thanks to all who took the trouble to read and did not laugh:
It's still ok if you did!

[fastbysuzuki]

There's quite a lot of old guys here including myself age is of no matter.
It is well documented about putting pods on especially cheap ones Here
Setting up carburettors for pods is not much fun unless you like constantly taking the carbs off and on perhaps a Dynojet kit may be the best route.
As for no 3 the wear on the camshaft will be restricting the fuel/air mixture into the cylinder due to the valve opening time and dwell being deminished.
As you say replacement cams are in order.
The compression readings are not great either considering new piston rings I assume the cylinders had a light hone?
you say it breathes quite a lot via the crankcase breather (sounds like the compression escaping past the rings) even if the rings are not yet bedded in I would expect higher readings than you have assuming the valve clearances are ok
You are opening the throttle wide open with a warm engine when taking these readings?
Compression readings when new are around 170 psi.

[2BRacing]

Unfortunately I cannot help out with camshafts, except to say that worn inlet number 3 probably results in lean condition in that cylinder due to small lift/short duration caused by the worn lobe.

My thoughts on rings / compression are as follows:

For a rebuilt motor, the compression readings are low (I assume that the engine was warm and the throttle held fully open while taking the compression measurements?). This indicates that the engine has not been run in properly yet, or run in incorrectly, resulting in poor piston ring sealing.

You do not say which year model the bike is. Early models with VM carbs had the fuel petcock vacuum from carb 3, while later models with CV carbs have the vacuum from carb 2. Leaking fuel petcocks result in excess fuel to one of those cylinders, and can result in rapid bore wear from washing away the oil film.

So it depends on how many miles the engine has done since rebuild, and how it was run in.

Others with more engine rebuilding experience than me would be able to give you better guidance on the way forward.

Good luck!

[uteman]

Camshafts & Compression readings

There's quite a lot of old guys here including myself age is of no matter.
It is well documented about putting pods on especially cheap ones Here
Setting up carburettors for pods is not much fun unless you like constantly taking the carbs off and on perhaps a Dynojet kit may be the best route.
As for no 3 the wear on the camshaft will be restricting the fuel/air mixture into the cylinder due to the valve opening time and dwell being deminished.
As you say replacement cams are in order.
The compression readings are not great either considering new piston rings I assume the cylinders had a light hone?
you say it breathes quite a lot via the crankcase breather (sounds like the compression escaping past the rings) even if the rings are not yet bedded in I would expect higher readings than you have assuming the valve clearances are ok
You are opening the throttle wide open with a warm engine when taking these readings?
Compression readings when new are around 170 psi.

I got to thinking about those compression readings which I also agree are low.
I could attribute part to Chinese gauge that I have but do also suspect more serious issues. Throttle was wide open when readings taken and engine warm when readings taken,
In regard to the breather emitting more than expected I just recalled that the owner purchased ring set at around 50 Aussie Dollars on EBAY.
I would not use those when I rebuilt my GS850 around the same time and it runs beautifully with rings 4 times the price from IMD Pistons in UK.
Now that the cylinder head is removed it will be easy enough to replace piston rings
Yes the bores did get a light hone.
I think that is a must whilst at this stage.
One gets what one pays for when it comes to piston rings and I reiterate that I was not impressed with the cheep ones.

The bike has never been on a run since any engine work as it has never run good enough to do so.
My standard 850 which I rebuilt from one end to the other ran perfectly from the moment it started up and has probably now done around 200 km or 120 miles and sits in my garage looking very nice indeed.

The bike having issues is a 1982 model which of course has the later carbs.

I hope someone on forum has some cams so will place an advert.

My strong thanks to you both.

[fastbysuzuki]

I would not use those when I rebuilt my GS850 around the same time and it runs beautifully with rings 4 times the price from IMD Pistons in UK.

I used the rings from IMD 4000 miles ago runs really sweet.

[uteman]

Just an update for those who responded.
I have been gifted a good pair of camshafts so can start to move forward.
There are good people out there!

[bwringer]

Compression readings when new are around 170 psi.

Even on a fresh example, I don't think 850 compression readings are anywhere near that high.

What's in the manual as a theoretical maximum?

[zbodan]

Clymer states in Table 10 on page 49,

GS850G: Standard - 128-171 psi, Service Limit - 100 psi.