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1978 gs1000 - Mikuni VM26ss

  • Thread starter Thread starter kdubskii
  • Start date Start date
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kdubskii

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I recently purchased a 1978 gs1000 for $300 as a restoration project. I'm 20 and have no prior motorcycle let alone carburetor experience. This is exactly where the trouble starts because I cleaned the carbs without touching the pilot screw and got the bike running. Although it didnt run good, it idled only on choke at around 3k rpm. This is when I began to research and fiddle with the pilot screw. I got a hold of the original owners manual where it specifies the pilot screw is "pre-set (DO NOT DISTURB)" so I used google. I read somewhere 3 turns out, so I turned all 4 pilot screws to the left as snug as they went and turned them out 3 times so theyre even. Now the bike wont start. How badly did I mess up? How can I figure out factory settings for the pilot screw? Please help me out!! :confused:
 
The screws used to be capped. This was to prevent adjusting them. However, they really needed to be adjusted (usually turned counter-clockwise).
If you did not remove them when you cleaned the carbs, then you did not do it properly and there may be some tiny passages that need to be cleaned.
 
I was thinking that maybe the fuel was dirty because I didnt clean the gas tank before I poured gas in? But the motorcycle started up until the 2nd time where I took the carbs off the bike and turned the pilot screw all the way counter clockwise and 3 turns each clockwise. I'm convinced I ruined the pilot screw settings.
 
kdubskii said:
I was thinking that maybe the fuel was dirty because I didnt clean the gas tank before I poured gas in? But the motorcycle started up until the 2nd time where I took the carbs off the bike and turned the pilot screw all the way counter clockwise and 3 turns each clockwise. I'm convinced I ruined the pilot screw settings.
Click to expand...

That the bike started up is a testament to its engineering, as you're turning the screws the wrong way

Mechanics lesson #1 - righty tighty, lefty loosey

You need to get a workshop manual, free advise, and tutorials here

http://www.thegsresources.com/_forum/showthread.php?t=196338


More reading, less messing with things for the time being

Be sure and read the Top Ten Newbie Mistakes and go from there
 
kdubskii said:
so I turned all 4 pilot screws to the left as snug as they went and turned them out 3 times so theyre even.
Click to expand...
You may have broken the tips off of the pilot screws. Take the carbs completely apart, clean them and make sure tips are nice ans pointy.
 
Float hts must be correct also.

Pilot ( bottom ) screws at 3/4 to 7/8 out. I have not found any problems with my 1000s at 3/4 out.

Mixture ( side screws ) at 2 out from bottom and fine tune them from there.

This is what I have found to be the tried and true settings..thus far.

And as Dale said, completely disassemble them, dip them properly for 24 hrs. Take the basket out of the dip and 2 bodies can be done at the same time. Same 24 hrs for all the jets and other metal bits. Poke all the holes with a fine wire and VERY AGRESSIVELY spray lots of carb spray and air thru all passages and jets holes.

Pay attention that you get the little one on the very tips of the pilot jets too. I pluck wires from a wood handled wire brush as my poking wire. Some have used bread tie wire as well.

Get all new orings from cycleorings.com ( VM KIT ) and newm intake manifold orings. Replace the Phillips head screws on the intake manifolds with stainless allen heads..youll be glad you did later.
 
rustybronco said:
You may have broken the tips off of the pilot screws. Take the carbs completely apart, clean them and make sure tips are nice ans pointy.
Click to expand...

This, those screw tips break off VERY easily if they are bottomed out. Usually they get stuck in the holes and block fuel flow completely.

Pull them out and look, if they are broken off you have work to do.......
 
If they bare broke..look in the hole with a flashlight and youll see the brass shining in the port. There are tutorials and pcitures of how to remove broken tips on the MEGA WELCOME.
 
Thank you for the helpful replies! I really appreciate the link to the mega welcome I can already see the benefit of reading the great stuff on there! I will check the screws tomorrow for breaking. Quick question though, I don't quite understand what this "1 out" "2 out" measurement of pilot screws means. Is there any threads that can explain this better? Thanks again fellas!
 
The VM carbs have 2 pilot screws

The pilot fuel is under the front of the carb. This is the one that's capped at the factory. You turn it clockwise carefully until it seats. then turn it counterclockwise (out) 5/8-3/4 turn for a stock intake and exhaust

The pilot air is on the side of the carb. Same technique, turn out 1 1/2 to start

You need to remove all the pilot screws and all the other parts and clean the carbs per the VM tutorial on the BC site

Post up a picture of your fuel screws so we can tell you if they're broken.

Also, go up to the User CP at upper left and fill out a location and your bike info so we don't have to guess in future posts. This will make it easier to get you the correct answers, like what to use for carb dip if you live outside the US
 
Big T said:
You turn it clockwise carefully until it seats.
Click to expand...

This is the problem. By the time you can feel the screw seat, the tips may already be stuck, then they break off when you go to screw them out. They are MUCH easier to break than the Mixture screws on CV carbs. I don't do this anymore, have broken too many and ruined too many carbs. I take the carbs off, look in front of the the bore, you can see the screw tip stick up into the tiny port. Another tiny turn in and that's it. Any farther, or going until you can feel it bottom risks breaking the tip.

Then turn the screw out whatever amount you want, 5/8 or 3/4 turn or whatever.
 
What we mean by bottom on the pilot screwws ( bottom ones) is that you gently turn them in until they stop going in...period. DO NOT force them further or tighten them down. Thats how you snap off the tips.

Then you make a mark on the rim of the hole in line with the slot as a "witness mark" so you can have a reference as to what a half turn..a 1/4 turn..etc etc is at.

There will already be marks there from the factory, but use YOUR new marks as the indexes. Follow me?

The mixture screws ( on the side ) dont have tips and are blunt ended. you do the same with them but its not a sin to be snug at the bottom. Snug, but not tightened down tight either. Use some common sense with them and youll be ok.
 
Everyone is very helpful and I'd like to thank everyone for the great advise. Last question before I go back and apply the knowledge. Since the bike came with carbs disassembled, and pilot fuel screw's out, how far do I turn them in after I clean and replace them?
 
Any time you do work on the carbs and remove the pilot or mixture screws you start from grond zero.

In your case, since you state they were not in when you got them, the same rules apply.

Seat them all the way in gently and back them out the stated amount. I have had 4 1000s and 3 other GSs and I have found that the IDEAL setting for the bottom pilot jets is at 7/8 out from bottom.

Side mixture screws are at 2 out and younuse the side screws to fine tune each cylinder and leave the bottom ones alone.

If you do this as I say, your bike will start and run pretty close to right. You will then Vacuum sync the carbs and then you will fine tune with the side mixture screws.
 
Be sure you use the right springs on then too. The short ones go on the bottom pilot screws and the long ones go on the side mixture screws.
 
One other thing...bench sync them before you put them on the bike and when you set up the big idle knob in the center of the rack, watch the end of the rod. When the end comes into contact with then throttle liinkage, go in 2 full turns.

NOTE.....his is a basic default spot and the bike will most likely be idling up around 1500 or so..no biggy. Just turn the knob out to lower the RPMs back down.
 
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