Cylinder pressure - 130PSI

[vonny232]

Hi Folks,

I had my bike serviced yesterday (Oil, fluid, filters, repair rear brake etc) and i asked him to perform a pressure test on the cylinders as well since It seems to be burning too much oil.

Anyway, the pressure test came up as 130PSI per cylinder. The mechanic said he had spoke to a friend and they thought it was fine, and was surprised how consistent the pressure was between cylinders.

The manual says all 4 cylinders need to be above 156PSI else the engine needs to overhauled.

The mechanic thinks its Ok, and a better quality of Oil (Motul 5100 10w40) should reduce any Oil reduction.

I dont know whether he put Oil in the cylinder to differentiate between Valves and Rings because to his mind the pressure was ok anyway.

Not sure what I should do. I certainly dont want (and cannot afford) an engine overhaul this riding season (i.e. the upcoming summer months) but would consider it as a winter project if it was absolutely necessary.

Thoughts?

[Andre]

One of the first things I did when I bought my 14 was a compression test - just to have a baseline. Result: 152 psi on all cylinders

That was done with an el-cheapo tester My better tester's adapter did not fit. I made it fit with a file and retested: 181 psi

The thing is that none of the 2 testers were CALIBRATED! For a calibrated tester you have to pay lots.

When deciding to overhaul the engine make sure a calibrated tester has been used!!!

Also the engine has to be at operating temp and the throttle has to be fully open.

To pinpoint the possible cause you need to do a compression leak down test. Putting oil in the cylinder is not the way to do it even though it's done quite often.

[vonny232]

Yeah someone else said it might be a poorly calibrated gauge, and that the consistency between the cylinders was actually good news.

I dont want to piss off the bike mechanic just yet by quoting the service manual (hes popular in the area amongst bikers), so I might just take his advice and monitor the oil level over the next month or two and see if it goes down.

Performance seems fine. Will do 150mph with a fair wind

[KiwiCol]

If she's hitting those sorts of speeds, there's nowt much wrong with it.  If an engine overhaul were required, there'd be huge plumes of smoke behind you at those speeds.   

As for the oil - hell, each to their own on that score, heard lots of bad reviews on Motul 5100 & others are happy with it?    Just bang in some semi syn 10/40.

[T 24]

The engine seems to be OK with those speeds!
Maybe it was tested with closed throttle??
Engine must be warm and the throttle must be open, like Andre mentioned.
My last test two years ago was 184 to 187 psi (uncalibrated gauge)

And about those oils: In my own "tests" Motul 5100 is the worst oil I've ever used, it just don't wash enough, dirt will stay in engine.
15W40 mineral based diesel engine oils will work better in Suzuki engine and clutch.
Diesel oils tested 150 000 km(GS 1000 G)+ 60 000 km(14), and 15 000 km with turbo engine ( 41 000 km total with turbo).

[Hooli]

To pinpoint the possible cause you need to do a compression leak down test. Putting oil in the cylinder is not the way to do it even though it's done quite often.

The idea of a 'wet test' is the oil seals the rings better, so if the cylinder is still down on pressure it's more likely to be a valve issue.


As to the OP's results, if they are all the same I'd say you're safe. It'd never be all four cylinders that died together without mega mileage. As a reference, mine has done nearly 130k (miles) and doesn't use a drop of oil.

[Andre]

Hooli, the idea of the "wet test" is clear to me - it's a poor man's test

A leak down test will give you a lot more info that is important when considering an overhaul.

[KiwiCol]

Poor man with a Jag?   Just sayin.  Perhaps a better choice of description of the oil test would've been better?

[vonny232]

Ok, Cheers folks for the replies.

Funny about the Oil, as people have strong contradictory views. My bike mechanic swears by the Motul.

As for the pressure test. He mentioned a low and high rev test but I didnt drill down and ask him specifics, ill ask him next time I see him.

Ill just keep an eye on things, and see how the Oil level is in a month or twos time.

If his readings are correct, what would cause the PSI to fall to 130 on ALL 4 cylinders so consistently? As opposed to a single cylinder drastically lower than the other three?

[Andre]

Funny about the Oil, as people have strong contradictory views. My bike mechanic swears by the Motul.

Same as religion.
However, there are objective differences. As oil consumption goes, I think that an oil with a high NOACK (evaporation test) may make a difference. I have seen oils from 5% to 15% on the NOACK. Theoretically 285 ml evaporation with 5% NOACK and 855 ml with 15% NOACK of the 5.7 liters in our 14. I think that the difference can be seen in real life.

If his readings are correct, what would cause the PSI to fall to 130 on ALL 4 cylinders so consistently? As opposed to a single cylinder drastically lower than the other three?

Even low PSI on all cylinders point toby high mileage  Low compression on a single cylinder points to damage.

[vonny232]

Cheers, yeah I was thinking evenly low pressure though the mileage is just 26,000 (and that seems legit as I have the MOT history).

So, which Semi Sythetic has the lowest (best?) NOACK?

[grog]

Andre, sure would be full with 5.7 litres.

[T 24]

@vonny232
Religion or not,
And with those miles, you can try some higly washing oil before that Motul or what ever oil,
to clean your engine(piston rings) from soot etc.

[Mick_J]

If all the cylindres are reading the same pressure and the bike will still do 150mph and there are not plumes of smoke billowing out the back I would just ride it and worry less.

[grog]

Vonny, no expert but from your description  seems gummed up rings to me. Low cylinder pressure and oil use points that way. Me, just me, in same situation would try a high detergent oil. As said above. Mobil Delvac is clutch friendly, high detergent. Have used before for a clean out. Give it a 1000k run, see if it helps. I once tried the Motul bike oil, wasnt at all impressed, clunky gear change and expensive.