Oil change help, '78 GS400

[clutchthirty]

One other question -- I saw on the Bikecliff service manual that it says to check the oil strainer every 6k miles, but I don't have a clue where it would be. Again, the photos of the bike the manual shows looks different than my GS400. Is it possible my bike doesn't have one because it has the paper filter element

The manual on Basscliff's website is for a GSX400, which is a totally different bike than your GS400. Get an FSM on ebay (they can be had for around $30).

Edit: That's a very pretty bike. So is the 750 you have, I love the 750s with spoke wheels. Hope to have one myself someday.

[jbird7262]

petcock variations

Should be 3 positions..PRI ( prime). ON and RES ( reserve ). When the engine is running, the vacuum line from the crabs to the small nipple suck on a diaphram and open the petcock so fuel will flow. No suction no flow. the normal operating position is ON.

PRIme is use for things like if you tear down the carbs or completely empty the bowls for whatever reason..and to reprime the carbs if its sat for a long time without being run. Gas will evaporate out of the bowls and youll use PRIme for maybe 30 seconds or so to refill the bowls before trying to start the bike. ALWAYS swing it back to the ON position soon as the bike starts. Leaving it on PRI does NOT shut off the fuel even if the bike is not running..thus leaving it there can flood the crank case with gas..bad thing to do.

REServe is self explanatory and this position also works off the vacuum system. long story short..never leave the petcock in any position except ON unless you need to reprime the carbs or use the reserve. Once the situation is cleared. switch back to ON immediately as is possible.

Question... My GS450 has that design of p/c but my GS750E has one that does not have a external lever, just a recesed screw so switching to reserve is kind of futile, I believe it does have the (pri.) option, whats the thoughts on the old school gravity style p/c besides remembering to shut it off? I'm also searching for one that fits a 79 GS550 w/50mm spacing thats proving to be a battle. I can cnc an adapter from aluminum for a honda style to fit the bolt pattern, the battles of keeping the classics alive.

[chuck hahn]

Is it a 80 750 or one from 77 or 78???? 80s had that "F"ed up leverless piece of crap. The petcock still works the same way off of vacuum. But you have to make vacuum to prime it and to keep it open to ride it. So what you do is hit the button for just a few revolutions and wait a good 30 seconds or so and repeat that a few times to get the carbs primed if its been sitting or the bowls are empty like from rebuilding them.

Yes you need to bump it over to get the prime to work where as the lever petcock you can just do it manually.

[cyrenus]

Last night I serviced the air filter -- well what was left of it. I opened the airbox, took out the air filter assembly and the foam just fell apart into a bunch of dried-out crumbs. It may have been the original foam! I happened to have some UNI filter foam handy, so I cut it to size, oiled it with some K&N filter oil and installed it after cleaning up the intake and air box. The UNI foam fit perfectly, so one more maintenance item out of the way. Oh, and forgot to mention have also intstalled new spark plugs. Will most likely need to check the points etc., but I'm going to leave that to a buddy who has a lot more expertise with points and timing.