Almost there! Going to be riding this weekend!

[Skyboy8950]

So, just as an update:

Just put all the carbs back together after rebuild and fixing all the floats. The floats were all measured to the wrong spot on the float, so the bike was running rich on all 4.

Just ordered 4 shims. 4 valves were off by .1-.15 which I think was extreme. All of them, too, had to be reduced in size because there was NO gap at all.

I think that by the time I get this bad boy running, it will run so much better than it is was, and it was running pretty well sans the rough start. What do you think?

Anyone around in Portland, Or this weekend that wants to go for a ride?

 

[Guest]

Just ordered 4 shims. 4 valves were off by .1-.15 which I think was extreme. All of them, too, had to be reduced in size because there was NO gap at all.

are you saying you had to go 2 or 3 sizes down in shim thickness on those 4 valves?

that would not happen by itself (through neglect only) but would mean that someone put the wrong shims in to start with

if thats the case you should definitely notice the difference in how it runs since those measurements would suggest that the valves stayed slightly open all the time

 

[Skyboy8950]

yea, the other ones were right at .04 gap. i did have to go down 2-3 sizes each. Someone who cracked this thing open before clearly didn't know what they were doing... Glad I checked.

 

[Guest]

yea, the other ones were right at .04 gap. i did have to go down 2-3 sizes each. Someone who cracked this thing open before clearly didn't know what they were doing... Glad I checked.

maybe they wanted to see how long it takes to burn a valve

 

[TheCafeKid]

are you saying you had to go 2 or 3 sizes down in shim thickness on those 4 valves?

that would not happen by itself (through neglect only) but would mean that someone put the wrong shims in to start with

if thats the case you should definitely notice the difference in how it runs since those measurements would suggest that the valves stayed slightly open all the time

Im going to have to disagree with you a bit on this one Psy. Over the winter, i bought a GS750 8V motor for my cafe project. The reason i bought it was that it was relatively cheap, only had 22K on it, and was in MUCH better cosmetic condition than the one in my bike (which had been apparently dropped a time or two, and had broken fins and some stuff going on, but otherwise ran pretty good) When i recieve the motor, i decided that the first thing to do was to check the valve clearances. I found that, in order to get the INTAKE side into spec, there were a couple that needed to be dropped as many as four shim sizes. I did so, and after getting them into spec, i then started to worry that they had infact been burned. So, i then decided to educate myself on top end repair/refurbish. After pulling the top end and examining it, i found that the valves werent burned at all. I cleaned them up, cleaned the piston crowns, and checked the rings, which were in spec. I didnt hone the bores, as at the time i didnt realize how important this was. But, at any rate, i put it all back together, and recently fired her up. She smoked a bit for a few minutes, but i havent seen a spec of blue smoke out of her since.

My point here is that indeed it would seem thru neglect, at least the INTAKE side could be that far out of spec and not burn. After all, those valves arent getting nearly as hot as the exhaust side, seeing as how they are being cooled when they open by clean cool air and gasoline rushing in. At that point of neglect however, I DO think the motor ceased to run correctly, obviously, if it ran at all, which likely saved any further damage to it. What would happen as those valves at that point likely never closed is that the bike would be constantly drawing in fuel on every stroke. More than it could burn. This would cause HEAVY carbon build up, and in a way, serve to protect the valves from burning even further. However eventually, the bike probably never started again, since the valves were always open. Just some 330 AM hypothosising

 

[Guest]

not disputing your findings tck

not disputing your findings tck

my point wasnt so much about how long it might take to burn a valve but the following:

valve clerance is a measurement of the gap between the valve stem top (the shim on top of the bucket on top of the valve stem) and the cam journal
that clerance gets smaller as the valve beds into the valve seat
technically, the valve is going to go "up" into the valve seat only as long as there is some clerance (space) for it to do so
at the point where there is no more any clearance to the cam journal i cant see how the valve can keep bedding in further into the valve seat

 

[TheCafeKid]

my point wasnt so much about how long it might take to burn a valve but the following:

valve clerance is a measurement of the gap between the valve stem top (the shim on top of the bucket on top of the valve stem) and the cam journal
that clerance gets smaller as the valve beds into the valve seat
technically, the valve is going to go "up" into the valve seat only as long as there is some clerance (space) for it to do so
at the point where there is no more any clearance to the cam journal i cant see how the valve can keep bedding in further into the valve seat

Hrmm. I saw the wear a bit differently. My understanding is that once the clearance is below the tollerance specified by the manufacturer, the valve would not close, as there was no more room for it to come back to the seat because the cam lobe was constantly putting pressure on it. Maybe we are saying the same thing, maybe i am incorrect. *Shrugs* But, i have to point out that the motor had, as far as i can tell, NEVER had a valve adjustment done, or at least not in recent years. Most of the shims i pulled out of it were 2.8s and 2.75s. The smallest was a 2.70. So it had likely been a GOOD number of miles since its last valve adjustment. And I ended up going from a 2.8 to a 2.55 on one of them.

And to answer another of your questions or points. The valves dont bed further into the seat. They eventually tulip. From my understanding THIS is what causes the tightening of the valve clearances. Again, i could be wrong.

I have often wondered, what happens when you run out of adjustment. This is when i was told that tuliping is what most causes the decrease in clearance, and when you run out of adjustment, new valves are the next step. I have never known anyone who's GS has gotten that far. So i dunno for sure...lol

 

[Guest]

My understanding is that once the clearance is below the tollerance specified by the manufacturer, the valve would not close, as there was no more room for it to come back to the seat because the cam lobe was constantly putting pressure on it.

yup, i agree!
especially as the parts get hot, that clearance (below the tolerance of 0.03mm) disapears altogether, and the seating of the valve is not as good as when there's at least min clearance
but my point was... that at this stage you're looking at placing a new shim of only one size thinner (0.05mm) to bring things back into spec (ok, maybe TWO sizes difference at max)
but i dont see what needs to happen so that the clearance that is no longer there shrinks even further...

i'm not saying i'm like 100% sure here, just cant see the logic of how this would happen - except maybe through the valve and the valve seat slowly burning (excessively wearing) in their contact area

 

[TheCafeKid]

yup, i agree!
especially as the parts get hot, that clearance (below the tolerance of 0.03mm) disapears altogether, and the seating of the valve is not as good as when there's at least min clearance
but my point was... that at this stage you're looking at placing a new shim of only one size thinner (0.05mm) to bring things back into spec (ok, maybe TWO sizes difference at max)
but i dont see what needs to happen so that the clearance that is no longer there shrinks even further...

i'm not saying i'm like 100% sure here, just cant see the logic of how this would happen - except maybe through the valve and the valve seat slowly burning (excessively wearing) in their contact area

Ohhhh. Yes I am not sure what would cause that either, except for maybe what you suggest. I was actually quite amazed that it took that many drops in size to get it into spec. and then, as i said, a bit scared that they were cooked gooses. Thus i ripped it apart. Another worry, and possible problem that could explain this, is that carbon build up would begin to form on the back side of the valve, holding it open further, and causing such an instance. That could be bad, as, unless you had cleaned it off, it i suppose could be possible for it to suddenly let go, and then your shims would be WELL loose, and you might be headed for serious damage if that were to happen at high RPMs. Floating a shim and its disasterous outcome are not something that i would ever like to see happen. At least to MY bike...lol

 

[Guest]

Another worry, and possible problem that could explain this, is that carbon build up would begin to form on the back side of the valve, holding it open further, and causing such an instance.

good point here!

btw, you doin' a night shift or something, being up at this hour?

 

[TheCafeKid]

good point here!

btw, you doin' a night shift or something, being up at this hour?

Well, i didnt get home till bout 130 or so our time. its 445 now, so im starting to wind down and think about bed. My sleep schedule is wacked out, because i work one day say 5pm to 2am, and the next i might be in at 8am to 5pm. Nothing set. No rhyme or reason. and it changes every week. Needless to say, i suffer from long bouts of insomnia. And im not the type that can come home from work and go straight to bed, no matter what time i have to get up. I have to wind down first. So my body is tuned to this. I average about 3-5 hours of sleep a night, and that usually does me pretty good. Tho now and then, it catches up with me, and on my day off i might sleep till noon. This is pretty rare, however, i notice that i do it more frequently the older i get. *sigh*

 

[Guest]

oh, i see
well, then, have a good rest, sir

 

[aruyle79]

see, im at work now, lol.