Don't rush prepping race bikes or how to learn to love low oil pressure

[Kyler]

One of the major problems with motors in racing sidecars is oil starvation when the oil sloshes away from the pickup in a turn. Many put baffles in the pan. Some add oil accumulators. It gets even more complicated when you add an external filter and a larger oil cooler. Me, I just run a lot more oil. Normally the pressure is near 60# in the turns (when I remember to look) and 70# in the straights.

I moved my oil filter a few weeks ago and apparently forgot to top off the oil. When I looked in the sight glass Saturday morning, it was over the top of the glass which is normal. Unfortunately that doesn't tell you if you have enough.

The ticking noises from the motor followed by a quick glance at the oil pressure in a turn is a dead giveaway. I shut the motor down before the screeching sound of fusing metal started.

So ... what are the odds this is a quick fix? I'm assuming the bearings are unhappy. I've never split the cases. Are special tools required? Is it a difficult task?

btw, this is my '80 GS750 motor.

I am debating trying to clean up a '82 GS750 motor I was given. I've never started it and it had mud-dobber nests in the exhaust ports. Not sure which motor would be cheaper and faster to get running.

 

[Guest]

There are no special tools and it is actual quite easy to do. Just follow the repair manual. Do you have to stay with a certain year motor or size.

 

[blowerbike]

80-82 750 engines are known for spinning rod bearing and top end oiling problems.
everyone that had been brought to me for a ticking valve(valve adjustments) ended up having a spun bearing.
i would check into the spare engine as under size bearing's and turning or the rod/main journals is not an option on your model.

 

[Kyler]

There are no special tools and it is actual quite easy to do. Just follow the repair manual. Do you have to stay with a certain year motor or size.

1982 and 1100cc is my class max. I may have one bought but not till the end of the year. I want to go to Barber in October and just want a running motor. Would rather dump the funds into the GS1100 (assuming the deal goes through).

 

[Kyler]

80-82 750 engines are known for spinning rod bearing and top end oiling problems.
everyone that had been brought to me for a ticking valve(valve adjustments) ended up having a spun bearing.
i would check into the spare engine as under size bearing's and turning or the rod/main journals is not an option on your model.

thanks. I'm hoping the '82 motor just needs a little TLC. I'll put a bore scope in the cylinders and check for internal debris.

 

[Guest]

Is there a reason you can't use a newer air/oil cooled motor from a GSXR1100 or Bandit 1200. They weight a lot less and have a deeper sump which would help the oil pick up.

 

[posplayr]

I did an 81 750 and I think I was going to swap some bearings between motors. Not sure what a set are going for but since it is a race motor a small investment into new bearing is probably prudent.

you will probably need to start over with your cooling explorations one you go to a roller bearing 1100 so slow plenty of time.

 

[GregT]

If it was me - or a customer of mine - I'd build one good motor out of the two. Cost would be a gasket set....
You've got what should be good pistons and bore on your current motor - and if you're lucky, a good bottom end on the spare. Drop the sump on your current motor and see what is on the pickup. Then do the same on the spare...

Fingers crossed....

 

[Kyler]

Is there a reason you can't use a newer air/oil cooled motor from a GSXR1100 or Bandit 1200. They weight a lot less and have a deeper sump which would help the oil pick up.

yes, my class limits me to 1100cc and a 1982 motor. No water cooled motors allowed in my class.

 

[Kyler]

If it was me - or a customer of mine - I'd build one good motor out of the two. Cost would be a gasket set....
You've got what should be good pistons and bore on your current motor - and if you're lucky, a good bottom end on the spare. Drop the sump on your current motor and see what is on the pickup. Then do the same on the spare...

Fingers crossed....

I'll unload tonight and open the filter to see what debris is in there. I'm praying no metal bits. Right now I need a running motor for the last race. I'm hoping I can salvage the spare. If my 1100 deal falls through, I'm going to rebuild one and hope I do both.

 

[Kyler]

you will probably need to start over with your cooling explorations one you go to a roller bearing 1100 so slow plenty of time.

In regards to the 1100 and roller bearings, it sure will change my cooler approach. From what I've read here, even with a 750 oil pump gear pressures won't be the same. Might need to go to an oil accumulator. Dunno - too much to think about right now. I'm stressing over the last race.

The only good news is my wife will be very happy if I have to cancel the rest of the season :indecisiveness:

 

[Guest]

yes, my class limits me to 1100cc and a 1982 motor. No water cooled motors allowed in my class.

The motors I was referring to are not water cooled motors but they might be to big the GSXR1100 is a 1127 cc motor

 

[Kyler]

The motors I was referring to are not water cooled motors but they might be to big the GSXR1100 is a 1127 cc motor

wasn't the production run 1986?1998? I'm limited to 1982 max.

 

[posplayr]

In regards to the 1100 and roller bearings, it sure will change my cooler approach. From what I've read here, even with a 750 oil pump gear pressures won't be the same. Might need to go to an oil accumulator. Dunno - too much to think about right now. I'm stressing over the last race.

The only good news is my wife will be very happy if I have to cancel the rest of the season :indecisiveness:

I have a 15 psi pressure gauge connected to the rear sensor plate. With 750 gears and top end oiler, I can still peg the 15 psi gauge when reving but it also doesn't take too much to drain the pan. This is with a stock Oil pan.

 

[GregT]

I'll unload tonight and open the filter to see what debris is in there. I'm praying no metal bits. Right now I need a running motor for the last race. I'm hoping I can salvage the spare. If my 1100 deal falls through, I'm going to rebuild one and hope I do both.

You're still going to have to drop the sump on the current motor. Can you do it in the frame ? Most of the swarf won't get past the oil pump pickup screen in the sump so you might not see anything in the remote filter. If there is debris in the remote filter, don't forget to wash out the lines and filter case....

 

[Kyler]

You're still going to have to drop the sump on the current motor. Can you do it in the frame ? Most of the swarf won't get past the oil pump pickup screen in the sump so you might not see anything in the remote filter. If there is debris in the remote filter, don't forget to wash out the lines and filter case....

thanks - good to know. more to come.

 

[Kyler]

I have a 15 psi pressure gauge connected to the rear sensor plate. With 750 gears and top end oiler, I can still peg the 15 psi gauge when reving but it also doesn't take too much to drain the pan. This is with a stock Oil pan.

thanks. I'll add this to my 1100 motor file.

 

[Gammaboy]

I have a 15 psi pressure gauge connected to the rear sensor plate. With 750 gears and top end oiler, I can still peg the 15 psi gauge when reving but it also doesn't take too much to drain the pan. This is with a stock Oil pan.

Can you clarify what you mean by "drain the pan"?
Are you running a stock pickup?
The stock pickups are terrible and will pull air easily because the highest point of the pickup is 1" above the bottom of the sump. Blank the tubes and cut a hole in the bottom of the pickup so it will pull oil from the bottom of the sump like a modern bike (Well, anything post 1983!)...

 

[posplayr]

Can you clarify what you mean by "drain the pan"?
Are you running a stock pickup?
The stock pickups are terrible and will pull air easily because the highest point of the pickup is 1" above the bottom of the sump. Blank the tubes and cut a hole in the bottom of the pickup so it will pull oil from the bottom of the sump like a modern bike (Well, anything post 1983!)...

Based on watching the pressure gauge when reving out the engine (2nd 3rd gear),

The pressure gauge will ramp quickly and peg the gauge at 15 psi, and as I recall it will drop quickly after a few seconds. It comes right back.
All stock 1983 gs1100ED (pan, pickup).
I don't remember pressure dropping to zero but perhaps back down to 10 psi from 15 psi. It is all happening pretty quick and not data logged.
It is possible it is related to a slow shift, it has been awhile. My recollection was I assumed the pickup was running on air for a moment or two.

 

[Gammaboy]

My recollection was I assumed the pickup was running on air for a moment or two.

Well, I guess if it's a stock pickup - that's probably pretty likely combined with the oil surge from acceleration.