Suzuki GS 750 - Won't start and other problems

[Hariii]

58 minutes ago, Swiss Toni said:

As they say, 'A picture tells a thousand words'! Video's even better! Either the shaft's bent, or corroded at its contact points with the cases or, the hole in the casing is deformed, as 1460 says. Have you tried rolling it on your flat surface? Looking at your video, the shaft is definately the problem!

I did and i couldn't see any bent with the naked eye. It seems perfectly straight...

[bob654]

Mine was a lot easier to move than that. If I lifted mine it would fall when let go.

When you see the pawl spring size, a stiffness like that would be all it would take to stop it doing its job. I think thats your problem.

Edited June 8, 2020 by bob654

[Hariii]

39 minutes ago, bob654 said:

Mine was a lot easier to move than that. If I lifted mine it would fall when let go.

When you see the pawl spring size, a stiffness like that would be all it would take to stop it doing its job. I think thats your problem.

Guess we have figured out why the shifting isn't working as it should. When i remove the clutch cover, the shaft moves/turns easily without any resistance. If i put the cover back, it gets a little bit more difficult, but still better than in the video. Now, if i tighten up the bolts (especially the lower ones) it gets worse.

My conclusion: Either the shaft is bent and i can't see it, or the is a problem with the cover? Guess its just a few mm that are giving me the headache of a lifetime

[Blubber]

Just tuned... that shaft looks weird to me. I would expect it to be cylindrical al the way.

This one has a weird asymetric wear / step in it. 

 

Not an expert.. just an observation

[Hariii]

Seems to be normal with the GS 750 as you can see here: https://www.cmsnl.com/suzuki-gs750ec-1977-b-usa-e03_model34282/partslist/BLCK0040.html#.Xt5qv54za8o

 

Nevertheless, in order to exclude the shaft i ordererd one from cmsnl. It's impossible to get a new one, as they are no longer beeing fabricated. What a surprise. I also thought about filing the hole in the clutch cover to make it just a little bit wider. But somehow i'm really uncertain if that would be a good idea. 

[Swiss Toni]

@Hariii Have a look at the outer cover. Is the hole ok, and is it square to the shaft, ie 90%? If the bike's been dropped, the cover may be slightly distorted where the shaft exits. Shaft moves fine without it, binds when it's fitted! Knock the shaft back a couple inches towards the clutch side. Fit the cover. Now, get someone to gently tap the shaft back in, while you're watching it approach. If it hits the side of the hole first, (which it seems to do in your video) then finds its way in, instead of coming straight through, and you're positive the shaft's straight ... then the cover's the problem. When you say the shaft binds worse when you tighten the cover ... it's the cover (as long as you're sure the shaft's straight)!

Edited June 8, 2020 by Swiss Toni

[Hariii]

@Swiss Tonithe hole is ok and i there were no signs of any damage on the cover. Guess the alternator cover protected it. As already mentioned, i orderd a new shaft just to be safe and because i don't think that the cover is really the problem too be honest. 

Short info: I tried out the shifting with the bolts of the sprocket cover loosend up and it felt way better than before. Not perfect, but i think i'm getting closer.

Edited June 9, 2020 by Hariii

[Swiss Toni]

Well. I hope the new shaft solves the problem! Bit on the pricy side but, needs must!

Edited June 9, 2020 by Swiss Toni

[Hariii]

I pray to the motorcycles gods that it will solve the problem. Today i tried shifting without the sprocket cover on and it did work quite well. Now i also know how smootly the shaft should be able to move.  The only thing left is to figure out, why it's not working with the cover and how to solve it.

[Swiss Toni]

The shaft has to be bent then! Works ok (ish) with no cover. Slightly worse with the cover fitted. Worse again with it bolted up! The shaft is bent! You're pulling it out of line with the cover, and more so by bolting it up! Sheet of plate glass works wonders! 

[Hariii]

I searched the whold god damn house and couldn't find any glass of plate or an old mirror. Other than a bent shaft, i found another possible reason for my problem. https://www.cmsnl.com/suzuki-gs750ec-1977-b-usa-e03_model34282/partslist/BLCK0013.html#.Xt57kp4za8o . Number 15, out of the 6 spacers 4 are missing. Maybe this could result in a slightly disortion of the cover when tighten up the bolts? 

[Swiss Toni]

They're not spacers ... they're dowels! They ensure the cover will fit precisely! Without the dowels, the cover can move very slightly. Enough maybe to nip the shaft.

[Hariii]

Today i received the missing parts i ordered a while ago in order solve the mystery of the gear shifting problem. I replaced the shaft, the spring and put in the missing dowels (or spacers). 

Then i put everything back together, filled in some 10W 40 Oil, startet her up, did a short run (still not registered yet) and hell yeah, the shifting works just fine and without anymore problems. 

Don't know what solved the problem in the end, the shaft or missing dowels, but well i don't really care. 

So here is the simple solution for my problem which took me weeks to figure out. All thanks to you and your guidance!

 

Therefore, thank you guys!! 

[Captain Chaos]

Result! 

[bob654]

Good news, next job then.

[Hariii]

Thanks guys. My next and hopefully last big challenge are the carbs i guess in order to make her run better? She starts immediatly with the choke on. Engine cracks up, then goes down to 1000 - 2000 revs. At this moment, it's possible to drive for a few minutes but not really smooth. There is misfiring and throttle response is sometimes lagging. 

If i slowly remove the choke (about half a turn), the engine cracks up til it gets better. At this point she runs better (maybe best), but far from beeing perfect. If i remove the choke, the engine goes out. 

Also, if the engine is running and turn the keys to "OFF", nothing happens. Cause of this, i have to turn off the engine either by removing the choke or by the killswitch.

 

Any ideas what i should do or try? Would like to register her the next month in order to visit a professional mechanic. But for this, she needs to run way better then now. 

 

Here is a vid:

 

Edited June 19, 2020 by Hariii

[Gixer1460]

I'd say you've a wiring issue to sort out as having a 'seemingly' permanent live electrical system isn't cool and quite dangerous! And as with most 'old bikes', the carbs need stripping and cleaning thoroughly - not a bit of carb / brake cleaner - if you have or know someone with an ultrasonic cleaner, use it for a few cycles with whatever strong solvent / cleaner you can find.

[bob654]

Check ignition ground is clean fixed and working.

 

http://gsarchive.bwringer.com/bikecliff/images/vm_carb_rebuild.pdf

Edited June 19, 2020 by bob654

[Hariii]

I didn't clean the carbs by just using some regular carb cleaner of a can. Well, not the third time At the third time, i completly dismantled the carbs and put them in a special ERC cleaner over the night. Greg or Nanno as he is known here gave me this tip and it worked wonders.

 

The electrical problem is annoying and i hope i will find the issue in the following weeks. I mean, i should find the problem if i follow the cables of the ignition, don't i?

 

Short Edit:

Screwed in the air pilots a 1/4 turn and adjusted the idle srew. Now the bike drives way better. As it's quite early in the morning here in Austria, i took a little drive on the street (lucky me there were no police present) and it felt just awesome. 100km/h were no problem and they bike accerlerated quite smooth. Can't wait to get the carb snyc perfectly. 

 

Edited June 20, 2020 by Hariii
Spelling errors

[Hariii]

Not sure if anyone is still interested but here is a little update. 

I was able to detect the electrical issue after some testing. Turned out that i made mistake with the wiring of the "new" regulator from a Kawa GPZ 500 S. 

As you probably all know, this is the original wiring of the GS:

And this is the one of the GPZ

 

Now i did the wiring like this: 3x yellow - alternator, white/red -> plus, black -> ground and brown -> orange (ignition plus?). Now the bike turns off as it should, although i'm not sure if brown is really connected correct. Well, time will tell. 

 

Cheers

[Captain Chaos]

if it charges the battery when running and does not drain it when off, it should be ok.

[BigT]

As to your carbs, did you ever follow the link I sent you?

What are your settings?

Main jet

Pilot jet

Fuel screw

air screw

Needle clip position

 

What pods are you running? Do they block the pilot air holes?

[Hariii]

I adjusted the setting of  thecarbs just like in the link describtion you had sent me. I use the original jets and air filter box and the carbs are running really nice at the moment, even without any synchronistation so far.

Would love to change the air filter box to simple pods though, but it seems to be a rather difficult task unfortunately.

16 hours ago, Captain Chaos said:

if it charges the battery when running and does not drain it when off, it should be ok.

Well i hope that it charges the batterie while running. To make sure it won't drain the batterie, i installed a simple battery disconnecter switch. Takes 5 seconds now to simply disconnect the circuit after a ride

Edited June 25, 2020 by Hariii

[Swiss Toni]

Stick with the standard airbox.