Intermittent problems are the worst!

[bottobot]

Hi guys,
I'm new around here but I do have some understanding of how to fix bikes. The story I have is a sad one. Sometimes the bike the starts and sometimes it won't budge. It sat for nine months so first things first I charged up the battery and drained the carbs. I then sprayed a serious amount of carb cleaner into each carb and into the fuel intake. Then I let it sit for awhile. That seemed to do the trick as the yesterday the bike was running. Well running rough but oncee the carb cleaner worked its way out and the bike warmed up things seemed fine. Rode if for 1/2 hour and then parked it.

Then last night I tried to take it out and the thing would not start for love nor money. The next step I think is to take the carbs off and check each float bowl manually and see if any of the floats have leaks causing them to sink. My thinking is that if there was any fuel in there when the bike was parked it could have attracted a fair bit of water since it was parked outside over the winter. With a full tank of gas too, not winterized. When I tried to start the bike last night I noticed I had forgotten to turn the petcock off so maybe the floats filled up and bogged the start.

Thats my best guess for now. I am about to go check it out. What do you guys think?

[MisterCinders]

In before, (1) Clean your carbs the right way (dip and strip, poke through all passages, bench synch and vacuum synch); (2) what bike?; (3) adjust your valve clearances; etc.

Also, you might get rid of that old gas and replenish your CLEAN carbs with fresh stuff.

Add your location to your profile, so we can know if you are nearby to other members and gauge what 9 months of winter means for your bike (Florida winter or Alaska winter?).

[bottobot]

Hey there
It's a 1978 GS750 and it's been in Vancouver, BC. Any idea what the valve clearances should be? Are they a shim or are they adjustable? About to do a full carb clean but I can't drain the tank because I'm just out in the parking lot and don't have anywhere to put the fuel. Can't bring a fuel can into my apt and can't leave it outside. Once I have my workshop set up in a couple weeks I can to a vacuum sync test. Last I checked it was set up by a real mechanic before being stored so I would be surprised if the carbs need balancing, but it's best to check everything.

Thanks for the tips.

[BigD_83]

Hey there
It's a 1978 GS750 and it's been in Vancouver, BC. Any idea what the valve clearances should be? Are they a shim or are they adjustable? About to do a full carb clean but I can't drain the tank because I'm just out in the parking lot and don't have anywhere to put the fuel. Can't bring a fuel can into my apt and can't leave it outside. Once I have my workshop set up in a couple weeks I can to a vacuum sync test. Last I checked it was set up by a real mechanic before being stored so I would be surprised if the carbs need balancing, but it's best to check everything.

Thanks for the tips.

Bottobot,

I have a Morgan Carbtune if you need a synch tool.

You have shims. I have a couple of spares if you need one as a place holder for checking your clearances.

[bottobot]

Here's a look at my workshop aka the parking lot behind my apartment.


I noticed that one of the passages is blocked on purpose.
It's the little brass ball on the left side. It's the only carb that has this. Kinda weird.


Then I noticed that the pilot screw(?) is dialed way out on the carb on the left in this photo. Going to have to check the manual for correct settings.


All in all the float bowls and passage looked pretty clean. No noticeable buildup anywhere to be seen on any internals. None of floats had any fuel on the inside that I could detect using a shake and listen test. Not the most scientific but they are plastic and aren't prone to corrosion like other older floats I've seen. The lack of corrosion or varnish anywhere on the carbs leads me to believe the problem is elsewhere.

I put everything back and discovered I was riding the bike yesterday with the choke on the whole time! I tried to start it again but no luck.

Now I think I may have fouled the plugs. The battery is also pretty dead from cranking it over so much so I put it back on the charger. After my back unseizes I will go back out there and pull them out and check them. The plugs are BR8ES ngk's. Should I run something else you think?

[BassCliff]

Hi,

See your "mega-welcome" in your other thread in the "Owners" section. Otherwise, click the link to my website (in my sig) and you will find many answers to many of your questions. Start with the READ ME link. Welcome to the forum.


Thank you for your indulgence,

BassCliff

[bottobot]

Thanks Cliff, I am going through the mountain of info you linked me right now.

[cableguy]

It sounds like your biggest challenge is your workspace! Once you have that set it seems like you're reasonably able to take advice and follow the lead of the many gurus who will stick by you until its running. Good luck and don't forget pictures!

Welcome to the site BTW

[bottobot]

Thanks Cableguy. I am pretty limited by my workspace. My back isn't great due to a few years of working on the sidewalk and without a lift. I've taken whole bikes apart out front of my house or on the side of the road to fix them and my back has paid the price. More than that its just hard to do what you need to sometimes without a drill press, vice or bench grinder.

I love to learn about my bikes and have no problem taking pictures or advice!

Good news is that I have a workspace becoming available in a week or so and I have a proper hydraulic motorcycle lift there. It has electricity and I can build my workbenches and really get to work in a serious way.

[MisterCinders]

Hey there
It's a 1978 GS750 and it's been in Vancouver, BC. Any idea what the valve clearances should be? Are they a shim or are they adjustable? About to do a full carb clean but I can't drain the tank because I'm just out in the parking lot and don't have anywhere to put the fuel. Can't bring a fuel can into my apt and can't leave it outside. Once I have my workshop set up in a couple weeks I can to a vacuum sync test. Last I checked it was set up by a real mechanic before being stored so I would be surprised if the carbs need balancing, but it's best to check everything.

Thanks for the tips.

You won't need to drain the tank to do most of this, except to get rid of the old gas. That may not be necessary.

Your fuel pilot screws should be around 3/4 - 1 turn out from GENTLY seated. Don't bottom those screws out with any force. They are sharp and soft and the tips will break off in the carb body.

If you clean the carbs properly, with a dip and strip, you will have to synch them again once they are back together. You will also need to re-synch them after changing any valve clearances, as that can change the vacuum pull from the engine.

DO you have any mods to the ari or exhaust on that bike? Pods or a 4-1 will require a change to your jetting. If you or a PO changed those, that will alter our advice on carb settings. (Some here will grumble about pods and pipes. Obviously, I like them.

[salty_monk]

You can see he has cheapo pods in the picture above... You'll need some modifications to main jet & pilot screws out 2-2.5 turns from lightly seated as a minimum. You'll also need to lift the needle a bit.
The float setting in the manual is about the only bit you can use once you take the airbox off...

[bottobot]

Yah, I have a 4-1 exhaust and no airbox, just four cone filters you can see in the pics above. I don't know if the previous owner re-jetted to compensate. How hard is it to tell if he went bigger jets? Do I take them out and measure them? A few people have already said I could come by and borrow their sync tools, but I have to get the bike running first. I think I will go to crappy tire and get some new sparks, cuz I have a feeling these ones may be fouled.

[Big T]

The jet sizes are stamped on the jets

If they're Mikuni jets, there will be a small double box stamped on them

[Steve]

Any idea what the valve clearances should be? Are they a shim or are they adjustable?

Valve clearances should be 0.03 - 0.08 mm for intakes and exhausts.

They are shim and they are adjustable, too.

The plugs are BR8ES ngk's. Should I run something else you think?

The stock plugs are B8ES, not BR8ES. If you have resistor caps on the plugs (stock items), you do not need resistor plugs.
However, if you have non-resistor caps, you should have resistor plugs.
Remove one of the plug caps (they unscrew from the end of the wire) and measure its resistance. If it's about 5k ohms, get the B8ES plugs.


[QUOTE=bottobot;1629719 I don't know if the previous owner re-jetted to compensate. How hard is it to tell if he went bigger jets? Do I take them out and measure them? [/QUOTE]
The easiest way is to simply look at them and read the number. HOWEVER, ... some previous owners will drill them out, basically rendering them useless, because you have no idea what size they really are.

.

[bottobot]

Wow! Some awseome info you guys are dropping on me here. I'm going to get proper spark plugs and try the bike again today. Once I'm in my workshop next week I will do all the syncing and a full carb rebuild and valve adjustment and check the jets and everything. Thanks to everyone who has offered tools and help so far. This forum is pretty cool. I'll post an update if it gets started today. The sun came out so I really want to ride!