gt550, uneven oiling

[smokey]

Hi all,
so the gt550 project really has not got on the road much since getting it together last winter. Was really hoping to use this part time as my commenter bike, ohh well. Seems this bike had every common GT issue manifest its self during the rebuild.

So the latest issues is cylinder 1 is not getting enough 2T oil and cylinder 3 is getting too much oil. Cyl 2 is somewhere between the 2. cly 1 is showing some scuffing when I look in the exhaust port, so this needs to be fixed. The issues seems worst at higher speeds when the engine gets hot. I look at the spark plugs to verify oil, i figure the outer shell should be a tad wet with oil.

My first thought was the brand new crank seals must be leaking and #3 was so wet due to that, so I re-ran leak-down testing on the bottom end, and at 6 psi, the gauge does not move over 5 min... I guess that does not rule out a issue that perhaps the cases / seals leak only when they get hot?

The oil line check valves were replaced with the new ones from the person selling them over in Great Britain on ebay. When we got the bike, it was hydro locked with 2T oil. unfortunately the new valves still leak slowly when sitting. As you can guess, cyl 3 is the worst for this. Before riding, I have been using a vacuum pump to remove any excess 2T oil via the SIRS fitting, I was hoping that would at least get all cyls on the same level before the test rides. It makes no difference.

All i can guess is my oil pump is weak or worn and the far cylinder is getting under oiled since its the hardest to get oil to coupled with oil check valves that seems to be inconsistent.
I don't think the GT oil injector pump is as precises a a diesel injector pump, but on our diesel F250, it had a issues after the engine was hot, it would not start due to the tolerances opening up in the injector pump and not enough fuel getting pumped.

my next step is to switch to a contrasting 2T oil after the engine is hot, then verify that the "length" of the new color oil in the lines is the same for all cylinders.

any words of wisdom?

any sources for the oil pump top gasket ?

thanks!

[tz375]

It's very unusual for an oil pump to wear - unless it is run without oil. The pump is an interesting design in that it only has a couple of pistons - not one for each cylinder, so if it pumps enough for 1 cylinder it will pump the same amount for the others as well.

Top gaskets are not available from Suzuki but Astrax in the UK and GT Reiner in Germany have them for sale.

It is possible that the pump outlet passages are partially blocked or the oil distribution "octopus" may have some sort of restriction. It's also possible that the drillings in the crankcases could be partially blocked.

I would start by removing the oil pump and use a hand oiler to push oil into each leg of the octopus to see that it goes through as easily on all 6 legs. With only 6 legs it's a spider rather than an octopus, but that's not important.

If it's just as easy to squirt oil down all of the lines, it would be worth looking at the pump body next.

[Alan H]

Also remember that SRIS non return valves and 2T oil non return valves are different.
They work the opposite way so if you have the wrong ones anywhere oil doesn't get through.........
SRIs NRVs, oil runs banjo to pipe. 2T NRVs, oil runs pipe to banjo.
So if you fit them in the wrong places, oil can go through into the cranks.
Saying that, oil shouldn't go through the pump when it's not running unless the pump is worn.
Way to check, is take the oil lines off the bike and hang them with pump end up.
Use a syringe to fill the lines and leave overnight to see if any lines leak.
If they do, there's the problem (unless the pump is shagged).
Wrong valves in the SRIS lines just means the oil doesn't get from crankcase to inlet as it can't get through the valve.
Plugs shouldn't show oil.
I guess that you have auto correct enabled as I'm not sure what a 'commenter' bike is!

[smokey]

Yes, auto correct to correct for my horrid spelling.
I meant commuter, last year I put close to 2000 miles on the gt750 riding it back and forth to work, but is a bit too much bike for that, especially with very loud chambers and lots of cops on the roads.

the gt550 is a fun bike, for the few hundred miles I put on it so far I have enjoyed it.

The octopus was already hung up to test for leaking check valves. All the valves were replaced. The person that sold them to me said "will leak until broken in" , a few had slow leaks that apparently never broke in. I'm bit annoyed, but I think they were sold in good faith.

I'm going to try the trick of putting dye in the gear box oil. I got bad suspicion that when the motor gets hot, some how the gear box oil is getting in there. If I didn't already do the crank seals and re-run the leak-down test, there is so much oil in the pipes, excessive smoking at 60 MPH plus and spewing out the ends of the pipes, I'd say crank seals or some how there is a sealing issue for the case half's. however it does not spew out the breather and it passes leak down testing.

this one got me, why I'm asking.

[Alan H]

I'll be very surprised if gearbox oil is getting into the crank at all, only the right side crank can 'touch' gearbox oil unless the cases aren't properly bedded, but then it wouldn't run and the gearbox would pressurise. Hmmm.
It sounds like excess oil is being pumped into the 2T system, I would back it off at the pump lever a tad as the oil nowadays is so much better than 'back then'. Might be an idea to ensure that the valves in the oil tubes are the correct types though. The ball and spring inside can be fitted the wrong way, so the valve allows oil to pass in the wrong direction. You should be able to blow through in one direction by mouth - don't use compressed air or you can push the ball into the spring and it will never seat.
If you lift the pump off the nylon base and get an air bubble in each oil line (with a syringe), then refit the pump and when you run the engine next - on tickover - with the pump arm at max, you should see the bubbles slowly move along the pipes.
I can understand the comment about 'leaks until broken in' as the ball is hard and the seat is soft. One has to fit the other perfectly so as not to leak. It shouldn't need to, but probably will need to, if you know what I mean.
Originally the bikes would have been shipped from Japan dry I should imagine, then a PDI when sold. The new owner would do the breaking in with all the rest.
Lovely bike the 550, just done the second and 1 more to do. The others will be parted out then.

[tz375]

did you take the arm off the oil pump by any chance? It is possible that it is on back to front and the pump would be fully open at low revs and more or less closed when wide open.

[yeadon_m]

Its been my observation that if there genuinely is a different supply rate to any cylinder in a 'triad' of lines (ie a three lines to cylinders, or the three lines to crank bearings) then the *only explanation is that the 'cracking pressure' at the one way valves in the banjos at the motor end of the oil lines are different.
(*agreed, if the oil way inside the cylinder or crankcase is blocked, that would indeed be another reason, but thats easily eliminated by testing - pushing oil in with a syringe).
As Teaser says, there is but one piston in the oil pump per 'triad' and that slug of oil pumped per piston stroke gets split between the lines in a 'triad' evenly if the cracking pressures on each line in the 'triad' is even, and not if not. Imagine the starved cylinder has a banjo whose cracking pressure is a bit higher than those on the other two cylinders. Unless I'm mistaken, then you will also see a bias of oil in favour of the lines with lower cracking pressure.
This can only be fixed by changing the banjos to identify three with similar cracking pressures.
My GT380 is super-even, when hot, light smoke evenly from all pipes. My GT750 has a semi-starved RH cylinder and its baffle is bone dry. But its been fine for 3000miles so its presumably getting enough. One of these days I'll take the lines out and investigate/replace with a spare. My GT550 has a slightly less semi-starved LH cylinder, but I can just see oil mist if I winch the pump right open, so its good enough.
Cheers,
Mike

[smokey]

Just a update ...
So what was going on was the brand new needle valves on the carbs were leaking very slowly. While I was running tests to see oil flow the engine was idling for a while and gas started to flow from the carb overflows. Likly also why it was getting only 20 MPG.
This made those 2 cylenders too rich, so the oil never got burnt off. I thought the plug color and oil wetness was due to too much 2t oil or gear oil... when it was actually due to too much fuel. Also the oil line check valves were a bit stronger on cyl 1, so I swapped out with weaker ones. Not sure that made much difference. .. but took almost 6 psi for them to pop open.
So this proves most Kester carb kits are truly junk and it's good to regularly check plugs.

Now that all the cyl are running more even, it looks like it's a bit lean up top... very little color on plugs. But with modern gas it's so hard to tell A/F ratio by plugs it seems
. That's a good topic for another thread.

Thanks again!

[ConnerVT]

So this proves ALL Kester carb kits are truly junk and it's good to regularly check plugs.

Fixed it for you.

My experience with the float needles from Keyster carbs left my garage smelling of gas, strong enough to make one think it was unsafe to light a cigarette, and to drain over a cup of gasoline from the crankcase of my T500.