GS750 oil pressure

[ccroaker]

ok guys heres my first question.... i have a gs750 with an oil pressure gauge on the engine.... at tick over the oil pressure gauge reads zero.  does nt move ... only registers readings when the engine gets revved or when riding.... engine seems fine and no noises or smoke ... is this normal readings..feel free to mock and riddicule my mechanical expertise ... after i get the answer...lol

[Gixer1460]

Depends on the gauge but a 0 reading, hot is not unknown. I think 5-6psi is Suzuki spec @ idle and tops out at about 20psi @ 5,0000 rpm although as a 750 it should have a bit more due to better ratio pump gears.

[Swiss Toni]

Don't worry about what it shows. With it being a roller bearing crank, it's as 1460 says, very low (5-6psi) at idle. I can find exact pressure for you later if you really need to know. Those cranks are almost bullet proof, unless subjected to real abuse. 

[ccroaker]

thanks lads.....no need to go looking for exact pressures swiss toni.....its seems all is normal....thanks again

[Swiss Toni]

Roller cranks need nowhere near the oil pressure of plain bearing cranks. Stop worrying! 

[coombehouse]

Remove gauge & place in dustbin. Problem solved.

[Gixer1460]

9 hours ago, coombehouse said:

Remove gauge & place in dustbin. Problem solved.

Wasteful but effective for a GSX motor.

[Swiss Toni]

Similar problem occurred a few years ago, offshore. Civil pilots (Bristows) had a warning light showing in the cockpit. They tried all ways to find out what was causing it, to no avail. SAS landed on, in their Puma's, for anti-terrorist excercises. Bristows pilots asked them about the light, and if they resolved the problem, what did they do? You all know the answer...they took the bulb out! As far as I know, they never found out the cause of it!

[arnout]

On 14-8-2017 at 1:09 AM, ccroaker said:

.. i have a gs750 with an oil pressure gauge on the engine...

What indeed about the oil pressure warning light? Does it stay on?

If so, ignoring it seems unwise to me.. The crank may need little lubrication -as has been said- but the cams do!

There may be a perfectly good reason for the low oil pressure (if indeed that is the case) like a clogged oil strainer (pull the oil pan and the oil pickup to check) or a worn out oil pump.

The low reading on the aftermarket(?) gauge may also just be the inaccuracy of the gauge itself. Also check the service manual for the actual pressure spec.

On 14-8-2017 at 10:02 AM, Gixer1460 said:

..although as a 750 it should have a bit more due to better ratio pump gears.

Sorry to be the anorak here, but the oil pressures shouldn't be much different between the GS(X)750 and 1100/1000 engines as the different oil pump gear ratios are chosen to compensate for the ratio difference in primary gears. The clutch spins slower on a 750, and so does the oil pump drive gear that is attached to it.

(oilpump reduction ratio 1100&1000: 1.723 (87/49 x 33/34) , oilpump reduction ratio 750: 1.642 (99/46 x 29/38)  Oh well, pretty close..)

[Arttu]

Just to add one more reference point: Factory spec for GSX1100 oil pressure is 0.2-0.4 bar @ 3000 rpm, warm engine.

[Gixer1460]

You are indeed an anorak - but dammit correct as usual! You really do need another hobby! LOL!

[Reinhoud]

I've been busy with the oil pump...

 

The GS has hardly any oil pressure, when the engine is cold you should be able to get about 15psi when you rev it.

When the engine is on temperature your glad when you get 2 psi.

 

I made an oil pump what was 14mm wider as the stock one, and even with that  the pressure hardly got any higher. 

 

 

[jameskat]

GSX750 is a plain bearing engine. Check pressure at 3000rpm like Arttu says.

[ccroaker]

thanks lads.     and it is an after market gauge.... maybe i ll just throw it in the bin as was already suggested...it seems to driving perfect.    so if it aint broke......forget about it....lol

[Sheep]

7 hours ago, jameskat said:

GSX750 is a plain bearing engine. Check pressure at 3000rpm like Arttu says.

I was under the assumption these were roller bearing cranks like their bigger brothers!!

[Swiss Toni]

26 minutes ago, Sheep said:

I was under the assumption these were roller bearing cranks like their bigger brothers!!

So was I! Stop running the motor, and drop the sump. Check the strainer and the oil pump clearances. If all's well there, you're gonna have to dig deeper. 

[arnout]

5 hours ago, Sheep said:

I was under the assumption these were roller bearing cranks like their bigger brothers!!

GS750 - roller bearing crank

GSX750 - plain bearing crank

So quite different engines (and prim. gears 99/46 vs. 93/43), but both sharing same the oil pump gears.

Well-now-that-is-interesting-fun-fact: Prim. gears on the GS750 are straight cut, and were used "in the old days" on GSX1100 drag race engine to replace the stock helical gears when 1100-ratio aftermarket straight cut primary gears weren't available yet.. 

[Gixer1460]

How the poor old GSX750 got dragged into the conversation - it's go nowt to do with the OP.

GS750 primaries were and indeed still are (or replicas) used in drag motors mainly high rpm Prostock units to ease clutch tuning. Graham Dance still uses one of these geared cranks in his SSB probably due to the years of data he's got.