VM26SS carbs GS1000

[simesman]

Having bought a GS1000 recently, I have been restoring it and hoping to get it working nicely this month. It ran really rough when I bought it, but got me home (although only a few miles). After going through it, I found a couple of valve clearances below bottom tolerance, so all shims have been checked/changed. One of the contact breakers was bent as someone had fitted it wrongly, so both were replaced. Still on original coils. I started it up and although it idles nicely, it has very poor pick-up and pops and bangs a bit. So, I took the carbs off and removed the float bowls. Looked fine in there and all jets are clear. Before I took them off the bike, I noticed petrol dripping from around the no.1 front, just below the rubber intake rubber, but the float height looked OK and the needle valve is OK too. Looking at my o-rings on the main and pilot jets, I will change these. Any idea what the size of these are or do I just buy a full rebuild kit?

I will check the float height,  but can I fill the bowls with water to do this off the bike? Can't see why it would have to be petrol. Any other stuff I should be doing whilst the carbs are off?

[simesman]

Also, forgot to mention, the manual states main jet size of 95 but I have 97.5. Have these been fitted by previous owners or is this standard fitment in some markets? My GS came from the USA. Should I leave them as I will be fitting an Exhaust Craft Harris replica with race baffle?

Thanks chaps.

[BigT]

Likely the carb body passages are clogged. It's not just the jets that need to be cleaned

rebuild kits are mostly crap. Get an O ring kit from CycleOrings.com

That's a pilot fuel screw, BTW, not a pilot jet

The 95 mains are standard. You will need to rejet and raise the needle for an exhaust change. How much depends on a number of things, like stock air box, or air pods?

[simesman]

Thanks BigT. I will strip the carbs and blow through all passages with my trusty airline. I will keep the stock air box and filter. I'll leave the 97.5's and see how they work out with the new exhaust (when I get it).

[simesman]

BigT, that Cycleoring site is very interesting. I didn't think to check the o-ring between Head and intake rubber. That could be my main problem as the first one I took out was flat as a pancake. These will be changed for sure. Shame he is in the USA. The Wemoto site lists a few kits, so I will probably order there.

Anyone have ny advice regarding the float height idea of mine, using water and a u-tube? Is it a sane idea?

[Captain Chaos]

9 hours ago, simesman said:

Anyone have ny advice regarding the float height idea of mine, using water and a u-tube? Is it a sane idea?

don't really know how to say it but petol is much more "liquid" than water. You'll get a false reading.

Also the density is different so the float er... floats higher on water than on petrol.

[Gixer1460]

38 minutes ago, Captain Chaos said:

don't really know how to say it but petol is much more "liquid" than water. You'll get a false reading.

Also the density is different so the float er... floats higher on water than on petrol.

The phrase is ' has less surface tension' therefore flows easier / is less 'sticky' Just because things 'look' ok doesn't mean they will be. These valves will probably be getting on for 40 yrs old so generally replacement saves an awful lot of grief long term!

[Captain Chaos]

32 minutes ago, Gixer1460 said:

' has less surface tension' therefore flows easier / is less 'sticky'

that's what i mean, thanks for reminding me

[simesman]

Thanks both, I had a feeling this would be the case. I will use petrol.

I think the needle valves must have been changed as they look good to me. I am guessing the guide to a pooped valve is exaggerated in the manual, as the pictures show a heavily indented cone and mine look great to the naked eye. If you use a magnifier, you can see the faintest ring marking where it has butted on the tapered seat. It also seems to shut off effectively if I blow up the fuel inlet with carbs inverted.

[BigT]

20 hours ago, simesman said:

Thanks BigT. I will strip the carbs and blow through all passages with my trusty airline. I will keep the stock air box and filter. I'll leave the 97.5's and see how they work out with the new exhaust (when I get it).

Blowing air is useless until you either run some carb cleaner thru/dip, boil them in detergent or lemon or ultrasonic then first. Air won't remove any old fuel deposits

You might as well move the needles while they're apart

 

[simesman]

Hmmm, that was going to be my next question regarding needles. I know a previous owner has fitted one size up on mains and all pilot air screws are 3/4 turn out with  between 1.5 and 2 turns out on the mixture screw (the one on the side of the body). I bit the bullet and stripped the carbs completely (man, what a load of parts there are!) and I cleaned the individual bodys to get the big muck off and I will take them to work and sneak them in the ultrasonic bath. All bits (jets, floats etc) are bagged up in numbered bags and I will clean these in the bath too. I will check needle clip position this week.

My question is, how do I set the carbs for my new pipe (Exhaust Craft Harris with race baffle) and no other mods? Keep the 97.5 mains, air screw 3/4 turn out and maybe 1.5 on the mixture? Needle clip height? I can't find any decent set up info for these carbs, everything just says not to touch the preset settings.

[gs7_11]

I've never rejetted GS1000 carbs for any pipe; they are fine on standard. Having 97.5 mains is likely to be better though if anything for a more open pipe.

I've only rejetted for modded/removed airboxes. My advice on that is: don't.

Stock jetting and settings, spotless carbs, balance and off you rattle!

You're confusing float height and float bowl fuel level. You only need a steel rule or calipers to set the float height, as per the manual.

Don't worry about the actual fuel level unless there's an obvious issue. Set the float height and move on.

Edit: I can post a pic of the manual page with the settings if it helps.

Edited July 2, 2019 by gs7_11

[BigT]

There's no single way to tell how to set up your carbs, cause every engine/cylinder/carb/exhaust is a bit different. It will be trial and error once you install the zorst

I suggested raising the needles because a) your off idle response is poor and b) carbs have been messed with. Pull a slide apart and see if there are any changes. Stock, the clip is in the middle of 5 slots. I'm recommending second slot from the bottom to bring more fuel to the off idle mixture. Also, US bikes are set up lean for emissions

The pointy screw in the picture you posted is the pilot FUEL screw. If it's between the slide and the cylinder head, it's fuel.  3/4 out is a good starting point

The less pointy screw on the side is the pilot AIR screw. you are correct in using that one to tweak the idle mixture. 

Be sure to toss the float bowls and the needle jet (that thing in the picture with the main jet attached to it) in the ultrasonic as well.

I'm attaching a chart that shows which carb part does what and when.  Plus, some carbs

[simesman]

Thanks gs7_11. Had pods in the past and I don't get on with them either. Stock airbox for me!

I am happy to set float height with a ruler, I thought I heard from someone on this site not to depend on this setting as actual fuel level will probably not be within limit using this method (although it has always worked for me in the past). I have the proper workshop manual, but thanks for the offer.

BigT -  thanks for the chart and pics. My carbs will look like yours soon. Just bathed the bodies and they look lovely now. Will do all the other parts too, just don't want to mix them all up. I really want to get needle height correct as that looks like a real pain to adjust with carbs on the bike (can you even do it?). Not sure how open the baffle will be on the Exhaust Craft Harris and I know the main jet is one size bigger, so do I raise the needle as you suggest or leave in middle slot as gs7_11 suggests? I know this is an impossible question, just looking for the most likely  answer to save dropping the carbs later. Looking at the chart, it is obvious that clip position has massive effect in the normal running mode.

[simesman]

Lovely fresh body................

[simesman]

Just noticed that pilot jet is 17.5 and standard is 15.  BigT tells me that they are set up lean in the States, so could this be normal for a UK bike?

[gs7_11]

No.

[simesman]

Typical, another unknown. Maybe I ought to reset to standard and go from there. Looking on the bright side, they are all nice and clean after a good soak in the 'bath.

[BigT]

Since you'll be doing trial and error for a bit, just leave your current one size larger jets in and see what results you get

you do have to pull the carbs to adjust the needle

[Kawitim]

Actually you don't have to remove the carbs to do the needles. Take off the tops, pull all the bolts out of the slide lifters and the throttle, remove the rubber plugs and the tab that locates the throttle shaft, and you can slide the throttle shaft to the right to free the left 2 slides, and back through to the left to free the right side 2 slides. Don't push the shaft all the way out of the throttle connection...it's a pain to put it back in without removing the return spring.