Oil change help, '78 GS400

[cyrenus]

Hi all,

I haven't introduced myself yet, but am in the middle of an oil change on a bike I just picked up. I'll make an effort to do a proper intro later. I'm afraid I've been a little spoiled by modern spin-on oil filters, not to mention I don't want to screw something up here. A couple of questions I hope someone with a GS400 will be able to answer.

1.) According to the service info. on Bikecliff for the GS400 there are two oil drain bolts. The photo of the bottom of the crankcase in Bikecliff shows the oil filter cover (with drain bolt and 3 filter cover bolts) and then another round fixture that has less ribbing on it and a drain bolt in the middle. However, on my bike the fixture is smooth and looks more recessed and has a big bolt on the outer perimeter, not the middle. Can anyone confirm that there are two bolts for the GS400? Maybe there are two, but the photo on Bikecliff shows a GS425 crankcase (It does say two bolts for both GS400 and GS425 on Bikecliff)? Here's a photo of what I think must be the other one. You can see the opening for the oil filter behind it, I've already removed all that:




2.) I drained the oil out of the drain bolt on the oil filter cover and the oil sight glass still shows full, so this leads me to believe that there is another drain bolt as not much oil must've drained out. Either that or the oil was so old and dirty it has permanently dirtied up the window. Hopefully I just need to drain the rest of the oil out and the sight glass will show oil level.

Here's a photo of the bike I'm working on. I inherited it from my stepdad and am going to do what I can to get the maintenance up to speed.

 

[cyrenus]

UPDATE: I pretty much answered my own questions. Yes, the bolt in picture is the main drain bolt; makes sense, the other drain bolt must be to just drain excess oil out of the filter cavity before you remove the cover. Duh, right?

Also, I put the bike on the side stand to remove the other drain bolt, and whadya know, the sight glass window showed empty. Duh again. Engine must've been overfilled as the sight glass was completely filled, so good thing I'm getting that dirty, over-filled oil out of there...

 

[chuck hahn]

Always fill and check the oil on the center stand so it gives a proper reading. Fill it to just below the F line, start it and run for about 30 to 45 seconds or so to get the filter full, shut off and wait 2 minutes. Check level and fill as needed.

 

[chuck hahn]

Use Shell Rotella T diesel oil in it. I get mine at Oriellys.

 

[cyrenus]

Chuck, thanks for the input. Yep, I always check the oil on the centerstand on my other bikes. Too late for the Rotella, I had some Honda GN4 10-40 handy so that's what I used.

 

[chuck hahn]

I also make the oil "just touch" the bottom of the F line. That way, when i look at the level I can tell if it has gone up from a possible leaky petcock allowing gas to get into the crank case. This is another achillies heel on the bikes. Leaky petcocks.

Heres how I do a leak test. Get two pop bottles and 2 old pieces of vac line. Set a line into each bottle off each nipple on the petcock. Be sure the petcock is in the ON position and let it sit over night. Check the bottles to see if they have collected any fuel. If no then its a good thing..if there is fuel youve got a problem. And rebuild kits for petcocks are useless..replace the petcock if it leaks.

 

[cyrenus]

I also make the oil "just touch" the bottom of the F line. That way, when i look at the level I can tell if it has gone up from a possible leaky petcock allowing gas to get into the crank case. This is another achillies heel on the bikes. Leaky petcocks.

Heres how I do a leak test. Get two pop bottles and 2 old pieces of vac line. Set a line into each bottle off each nipple on the petcock. Be sure the petcock is in the ON position and let it sit over night. Check the bottles to see if they have collected any fuel. If no then its a good thing..if there is fuel youve got a problem. And rebuild kits for petcocks are useless..replace the petcock if it leaks.

That's a great tip, thanks, I'll try that. I have to admit I'm a little baffled by the petcock -- is there no 'off' position? I figured it must be a vacuum petcock, and wasn't sure what position to leave it in. Bike didn't come with the owner's manual unfortunately.

 

[chuck hahn]

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.

 

[chuck hahn]

And when starting the bike, its choke and hit the button. Hands OFF the throttle. Twisting the throttle will make the bike NOT start while cranking it.

 

[Guest]

And when starting the bike, its choke and hit the button. Hands OFF the throttle. Twisting the throttle will make the bike NOT start while cranking it.

Unless that GS400 is KICKSTART only...

 

[chuck hahn]

Looks like it has a starter cover there to me.

 

[cyrenus]

Thanks for the info on the petcock. Sounds like I should replace it at some point as preventative maintenance, so will plan on doing that come next spring as the bike isn't going to get much use between now and then.

 

[chuck hahn]

Leak test it first..may be just fine. Also, I give all mine a little shot of penetrating oil from time to time on the lever. Keeps it lubed and moving easily. I am just laying out things Ive learned to check and keep an eye on over then years. If I can share my findings its a plus for you as far as getting things checked and making you familiar with the bike and its little quirks.

 

[cyrenus]

Leak test it first..may be just fine. Also, I give all mine a little shot of penetrating oil from time to time on the lever. Keeps it lubed and moving easily. I am just laying out things Ive learned to check and keep an eye on over then years. If I can share my findings its a plus for you as far as getting things checked and making you familiar with the bike and its little quirks.

Chuck, I filled the oil to just below the full line on your suggestion, and will keep an eye on it for a while to make sure the level doesn't increase. I've also noted your advice about hooking up hoses to the carb nipples.

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?

Thanks again for all the advice. I plan on taking good care of the bike as it's such a nice old survivor and deserves some good care.

 

[chuck hahn]

Only other thing I know of is the mesh cover in the oil sump over the oil pick up tube...but you wouldnt drop the oil pan every 6K to check that. Maybe by "strainer" its meaning the filter. May be a British term for filter???

 

[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

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! :nightmare: 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.