'79 GS550L: airbox removal, and oil change?

[Anonymous]

I may need to remove my airbox to get to the carbs in the next couple of days. I did a search but nothing turned up for this specific question. I expect to get a repair manual in the next few days, I'll order it tomorrow. Can't find it locally.

Also, I've been having problems with the petcock. It was in the PRI position since I bought it last Sunday, and I just found out today that it can NOT be in that position all the time (hadn't even noticed till now). I'm not new to engines, but new to bikes - and this petcock thing wasn't something I knew about. So now, after the air filter got soaked in gas and the plugs turned black, the bike won't start. Only cranks over. (It ran great on the trip home, though - 40+ miles.) I'm replacing the petcock and will put a fresh filter in there tomorrow, but in my research here I realized that I must change the oil as well. How to? I'll probably figure it out tomorrow, but if I know in advance, all the better. Should I replace the filter as well?

TIA

[Anonymous]

Ok, just a little more research found me the answer for the oil change, I think:

drain plug at bottom of engine and tranny
engine and tranny integral, both use the same oil (?? so 20w50 will do it for both? Hmm, cool)
oil filter by the sight glass, can get a new one at NAPA

What about the gear lube? For the middle and rear gearboxes (?). I won't concern myself with that now as the bike is not yet being driven, but I'd like to know for the near future. I hope I can find a manual tomorrow!

Thanks for any help

[SqDancerLynn1]

Chain drive models share common oil supply for trans and engine Only the shafties have a seperate oil supply for the trans

[Anonymous]

Not sure what you mean when you say the oil filter is by the sight glass. On my old '79 550L, the oil filter was on the front of the crankcase, covered by a little circular cap with three acorn nuts holding it on.

You should be able to remove the carbs without removing the airbox completely, but you may have to loosen the airbox off (one screw at the top on the front of the airbox). Just detach all the hoses, cables, etc. from the carbs, loosen the hose clamps on front and rear, and give the carbs a bit of a twist, then slide them out. It's a bit of a pain, but that's the basic idea -- the manual will probably have some good pictures.

Only one kind of oil on the '79 550L -- lubricates everything back to the drive sprocket.

Fill with oil through the capped hole above the sight glass. Check the oil level with the bike on the center stand.

I don't believe my '79 550L had a PRI position on the petcock... Could be wrong, but is everything stock?

Michael

[Anonymous]

Thanks for the replies. I read in another post that oil filter is by the sight glass, but then that might have been a different motor? I know what to look for, though, so I'm sure I'll find it. I just haven't gone out to look at it yet.

As for the petcock, you're right, I'm pretty sure it's not stock. There is only the one marking, PRI, and an arrowhead in the middle. I set it to the arrowhead, or just a little past.
The part is discontinued, apparently. Any ideas? I could install a shutoff valve between it and the carbs so I don't get any fuel flow while it's sitting (which seems to be the problem), unless it really does work at the arrowhead like it's supposed to. I'll go check now.

By the way, if it working properly, and the motor ran fine all the way down to my place, the problem wouldn't be the petcock, then, would it?

As for the carbs, I tried that the other day and had no luck at all. Do you mean the two screws on the top of the airbox, tucked in under the frame and just over the engine? I managed to get a Phillips head in there and loosened them up pretty far, but the carbs just wouldn't twist enough to come out I even had the gas tank off to make everything easier. I want to take them out as I'm pretty sure this whole problem is gonna be the floats on the carbs. I want to pull them out and just rebuild the little suckers.

Thanks!

[Anonymous]

After over an hour of waiting due to crappy service, I finally got an oil filter from NAPA (about 5.77, PN#4931). I got 20w50 Valvoline, though not MC oil.

My filter IS located at the front of the engine, I must have been looking at another motor originally. I haven't changed the oil just yet as I went to disconnect the line from the petcock, whihc has been away from the PRI position since yestereday, and gas just kept dribbling on out. So I guess it's busted.

Would this be a suitable replacement?:

https://www.directparts.com/isroot/dp/SiteImages/cci/12-726.JPG

PETCOCK EARLY HD 3/8" FIT

I'm guessing that it's for a Harley, hence the HD? So it probably wouldn't work. Only other I can find is the Pingel, a little more than I want to spend right now, but if it's the only ticket ...

Or I could install a shutoff valve, but I could not find anything up to the task at the auto parts, or even the brass fitting section at the hardware store. Wouldn't a fuel-disconnect switch for race cars work just as well?

Sorry for all the newbie questions ("Yet another noob asking about petcocks!" lol), I really just want to get my bike running so I can start riding it.

[Anonymous]

As for the petcock, you're right, I'm pretty sure it's not stock. There is only the one marking, PRI, and an arrowhead in the middle.

This is a stock 79 GS550 petcock:



"Pri" is meant to fill the carb bowls. Normally the petcock should be set to "On" or "Res".
There should be a vacuum line, connecting the petcock to carb #3 if you have slide carbs, and carb #2 in case of CV carbs.
The vacuum line shuts off the petcock, when the engine is not running.

[Anonymous]

Thanks for the pic, Harry. Mine is definitely not stock, then. It has PRI to the upper left of the adjusting screw, and the small "bowl" (diaphragm?) is at the bottom on mine, I think.

That little adjusting screw just goes 'round and 'round on it, too. How can it ever be set right, then ...