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Discussion Starter #1
first off, how often do you guys change out motor oil? I put Motul 7100 full synthetic in the bike ('86 750, wiseco 771 kit) and not even 2k miles later its no good anymore: shifting is rigid and clanky, clutch slips when shifting under power. keep in mind this is a JASO-MA2 approved oil, 10w-50

I went to bleed my clutch system, thinking there might've been some air in the system preventing the clutch to fully engage (it wasn't, this was happening when I was shifting without clutching) sure enough, though, fluid was all black. it hasn't even been a year since I changed it out. is that normal? all new components and no leaks anywhere. again, how often do y'all change the clutch fluid?

after a long ride last weekend, I noticed my front brakes felt more spongy and less responsive. to brake real hard the lever has to be pulled back to the bars. this is probably due to the original 30-year-old rubber lines that I planned on replacing with stainless units soon anyway, but the fluid was a little dirty, still salvageable. thought maybe there was some air in the system, checked and bled it and no improvement. how often do y'all change brake fluid?
 

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IMMITIGABLY VERBOSE DUDE
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I do oil change with rear tire change interval... about 1,500 miles.

Brakes? Mainly bleed/refresh... full-flush if/as needed, not even annually, and depends on bike.

Steel-braided lines and always maintain the pads... motor is built on all my bikes. I use Mobil I Full-Synthetic 15/50 with no clutch slippage. Filter every other if not every oil change. First flush/fill oil after fresh motor build at about 500 miles after good heat-cycling and break-in.

Just my methods, others will vary.

G/L!

-crisp
 

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Discussion Starter #3
awesome, thanks, I just found it hard to believe that this full synthetic oil is pretty much wasted after about 1700 miles. I know our bikes are tough on any oil thats in the motor, but not THAT tough. It never slipped like its doing now so I suspect the oil is at fault, especially with the way it shifts
 

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IMMITIGABLY VERBOSE DUDE
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My oil comes out "cleanish". The consistency is excellent. If it's "poor" like you describe, there is most likely contamination of some sort.

Find the source.

Blow-by
Raw fuel
Other fluids/chemical compounds
Debris

...something

-crisp
 

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If it's "poor" like you describe, there is most likely contamination of some sort.

Find the source.

Blow-by
Raw fuel
Other fluids/chemical compounds
Debris

...something

-crisp
+1. With that spec oil and at those km's, the oil shouldn't be 'worn out'. If it's black it will contaminated.

Is this the first oil change since you rebuilt your engine?

Clunky gear changes - how's your chain tension? Was your gearbox rebuilt with new bearings, bushes, washers etc. Was the selector mechanism o.k.? Was it yours that had a bent selector shaft? Maybe something else is slightly out of alignment or spec (selector forks?)

Clutch slipping - did you fit new plates during your rebuild? Or did you measure the originals for remaining life? Were the clutch spring free lengths within spec before you fitted them?

I don't think these engines are notorious for destroying oil - especially modern fully synthetic oils. Even during destructive testing I don't think the oil temp exceeded 130deg C
 

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The other OG
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Gixxerider86;8220993 I went to bleed my clutch system said:
there is a bleed back hole in your master cylinder that clogs and stops the clutch from fully engaging -if you open your slave bleeder and it pisses
shut off before fluid stops -tempory fix
 

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Discussion Starter #7
+1. With that spec oil and at those km's, the oil shouldn't be 'worn out'. If it's black it will contaminated.

Is this the first oil change since you rebuilt your engine?

Clunky gear changes - how's your chain tension? Was your gearbox rebuilt with new bearings, bushes, washers etc. Was the selector mechanism o.k.? Was it yours that had a bent selector shaft? Maybe something else is slightly out of alignment or spec (selector forks?)

Clutch slipping - did you fit new plates during your rebuild? Or did you measure the originals for remaining life? Were the clutch spring free lengths within spec before you fitted them?

I don't think these engines are notorious for destroying oil - especially modern fully synthetic oils. Even during destructive testing I don't think the oil temp exceeded 130deg C
Its definitely darker than when it was new, but still can see the color of the oil, it isn't completely black. I ran mineral oil for the first 30 miles or so, changed to fresh mineral oil after about another 100 miles, switched to synthetic blend for the next 600 miles, then I switched to this Motul 7100. It was real nice when poured in, not so much now.

drive chain tension is within spec, a little on the loose side. all new bearings and bushes in the gearbox, washers, dogs, gears, forks, drum, and selector mechanism all looked great and I couldn't measure any significant wear, if any. for the detent arm, is it normal for the wheel to have some side-to-side play? I wanted to upgrade to the factory pro shift kit but its unavailable everywhere

I installed an EBC SRC clutch setup with all new fibers, steel plates, and springs probably not even 1000 miles before I rebuilt the motor. never slipped. I would assume that when bleeding the clutch it would "reset" and there wouldn't be any force still keeping the clutch disengaged. last time I bled the system I took the sprocket cover off and bled the slave cylinder with a C-clamp keeping the piston compressed. maybe I might have to do that again, although maybe it might not be necessary
 

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The other OG
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clutch it would "reset" and there wouldn't be any force still keeping the clutch disengaged

you don't know these bikes -it is their reputation for having master cyl prob
I've been here since '07- 6000 posts
 

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Discussion Starter #9
clutch it would "reset" and there wouldn't be any force still keeping the clutch disengaged

you don't know these bikes -it is their reputation for having master cyl prob
I've been here since '07- 6000 posts
huh? I wasn't questioning anyones credibility or saying that I know something that you don't, heck thats why I posted this thread: to get answers to something I don't know or to something I should be aware of.

I made an assumption that maybe any load that would be keeping the clutch disengaged would be released the second I open the bleed nipple on the slave cylinder, therefore eliminating the necessity to keep the diaphragm "clamped in" when bleeding the system like I did last time

?
 

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The other OG
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I would assume that when bleeding the clutch it would "reset" and there wouldn't be any force still keeping the clutch disengaged. last time I bled the system I took the sprocket cover off and bled the slave cylinder with a C-clamp keeping the piston compressed. maybe I might have to do that again, although maybe it might not be necessary

you assumed but the prob is in the master cylinder




therefore eliminating the necessity to keep the diaphragm "clamped in" when bleeding the system like I did last time



so was there a release opening the bleed nipple on the slave cylinder
 

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Discussion Starter #11
so was there a release opening the bleed nipple on the slave cylinder
when I opened it up fluid did start coming out for a little bit, almost like there was some pressure inside the system. bled all the dirty fluid out with fresh fluid and purged it of air, clutch was still slipping under WOT shifting. master cylinder was cleaned out too. Ill change my oil and report back to see if dirty / contaminated oil was the culprit
 

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The other OG
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I cleaned my master 2 times - went to cable clutch -most people do after frustration
 

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The other OG
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katana have cable clutch - 2nd time I cleaned I was througher -I'm a mechanic by trade
 

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I bought my 85 750 in Jan 1986. It was a daily rider all weather and by about 1992 my hydraulic clutch slave cylinder was leaking. I replaced it with a used slave and it's been good for the past 23 years.

Back then I didn't freshen the fluids that often. I've always been good with my oil but brakes and clutch have gotten pretty murky before getting changed. Now I flush the brake and clutch fluid every year or two and with steel lines there is less chance of trouble.

It seems the slave has some crap in it that contaminated the fluid on my bike. With a new master, new steel lines and fluid, it didn't take long to get murky again. I flushed everything again this year and it's murky again. Brake master is lovely and clean but the clutch gets foggy. My clutch operates perfectly and no leaks but something is contaminating the fluid.

I change engine oil (and filter) every 3,000 - 4,000 Kms and I used Shell Rotella full synthetic. I think it's a 5w-40 oil. It's formulated for diesel engines without detergents and has a good sheering factor. I've been running it for about 8-10 years and the bike appears to like it. It gets dirty but that's to be expected for an in oil clutch engine. My Limited with the Dry clutch has lovely transparent oil but the 85's oil gets murky as soon as you fire it up. Such is life.
 

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Oh another thing to check is your drive chain tension. Too tight or too loose will play hell with shifting. It won't promote clutch slippage or anything but it will make the tranny feel old and clunky.
 

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Discussion Starter #17
I bought my 85 750 in Jan 1986. It was a daily rider all weather and by about 1992 my hydraulic clutch slave cylinder was leaking. I replaced it with a used slave and it's been good for the past 23 years.

Back then I didn't freshen the fluids that often. I've always been good with my oil but brakes and clutch have gotten pretty murky before getting changed. Now I flush the brake and clutch fluid every year or two and with steel lines there is less chance of trouble.

It seems the slave has some crap in it that contaminated the fluid on my bike. With a new master, new steel lines and fluid, it didn't take long to get murky again. I flushed everything again this year and it's murky again. Brake master is lovely and clean but the clutch gets foggy. My clutch operates perfectly and no leaks but something is contaminating the fluid.

I change engine oil (and filter) every 3,000 - 4,000 Kms and I used Shell Rotella full synthetic. I think it's a 5w-40 oil. It's formulated for diesel engines without detergents and has a good sheering factor. I've been running it for about 8-10 years and the bike appears to like it. It gets dirty but that's to be expected for an in oil clutch engine. My Limited with the Dry clutch has lovely transparent oil but the 85's oil gets murky as soon as you fire it up. Such is life.
awesome, this is exactly the kind of input I wanted, thanks! yeah my whole clutch assembly is brand new with a SS line, like you explained the fluid gets murky within a few weeks and theres no leaks or problems with it, still works great
 

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is water getting in your reservoir ?
 

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Not in mine... Brand new Hayabusa master cylinder + new steel hose. It could be that there was moisture in the old line and some of it was still in the clutch cylinder. It may be that I just never managed to get it flushed it through and out of the system.

I'll bet the only way to get it right out would be to rebuild the clutch cylinder and flush the lines out again. I don't know if you can get a rebuild kit for those.
 
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