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Need jetting help please for GS1000 1979

  • Thread starter Thread starter nitrogs
  • Start date Start date
Many thanks to Keith and the rest of the guys for sticking with us. I truly think we are getting there with your help on the jetting issue. Currently at work at present but took the GS for a 70 mile ride yesterday at all varying speeds and the bike felt strong throughout. I will use the cardboard photo tip Keith to show the plug colours (the bloody post is slow on those B8ES) and upload tomorrow. Thanks again guys.
 
Just too keep you informed guys, it has done nothing but rain for the last four days, so unable to play, looking forward to a dry day.
 
Finally the rain has stopped and I have got a few days off work. Saga of the B8ES plugs goes on, was sent the wrong number. Never mind got out on the road and did 25 miles of generally travelling at a variety of speeds and these are my plug reads including a pic of my exhaust headers to see if this is typical. What are your thoughts guys. Number 1 cylinder is on the right, actually No2 is not quite as dark as it looks.

cba80e00.jpg


cbb80e00.jpg
 
nitrogs said:
Finally the rain has stopped and I have got a few days off work. Saga of the B8ES plugs goes on, was sent the wrong number. Never mind got out on the road and did 25 miles of generally travelling at a variety of speeds and these are my plug reads including a pic of my exhaust headers to see if this is typical. What are your thoughts guys. Number 1 cylinder is on the right, actually No2 is not quite as dark as it looks.

cba80e00.jpg


cbb80e00.jpg
Click to expand...

Dave, it's difficult to tell what's happening when general riding. It depends what throttle position was dominant over the last 2 minute or so of riding.

I have just done a visual comparison between my B8ES plugs and your spitfires, from a few threads back. The spitfires appear to be a lot colder plug. The base ring is thicker, the electodes and ceramics are also larger. But the key clue is that there is no heat discolouration of the first and second threads just off the base ring. By running the wrong heat range (too cold), you are not allowing the mixture to burn off correctly in the idle and part of the needle circuit. It is near impossible to tune acccurately for the idle circuit with colder plugs.

You will always discolour chromed headers, unless you run overly rich, or have a set of OEM double skinned ones. Your headers do show a leaness up top, but too lean?? Get those correct plugs and do the plug chops again.
That darker plug, have you tried changing over plugs, to see if it's a rich pot, or a crook plug? If the plug stays black, it will be the plug at fault.

Enjoy the journey.
Ian
 
Since you showed us plug pics at specific throttle positions I was interested in what, if any, changes would show after general tooling around. The most recent pics would show the mixing of the pilot, cut-away and jet needle circuits. I just wanted to get an idea of what was going on.
I didn't like the idea of using different plugs and know little about the split fires. 49er backs up my concerns about them though. In trying to help you jet over the internet I want to keep things as familiar as I can. Your header suggests you're lean. I've seen much leaner during a re-jet but yours do look on the lean side. And the plug reads still look on the lean side too. Once we get the plugs looking acceptable, I'd clean up the header with a blue away product and they shouldn't blue up anymore. Over time you can get a "haze" of blue re-appearing over the gold but it will be minimal.
What we need to do is get the known correct plugs in there and do some testing again. Do you get any other symptoms of running lean? Any "spitting" out of the carbs which is most noticable at a constant throttle position (usually about 30 to 55 mph)? Any reason to think the motor is running hotter than it should (more external heat or "ticking" of metal parts)? I know you probably haven't paid much attention to fuel mileage but does the mileage seem too high? The typical 1000 I've jetted lost approx' 4 mpg when jetted correctly.
We'll see what the tests say but as I've said before, I haven't jetted a 1000 that ran correctly with the jet needles in the 3rd position but your climate would factor into this to some degree. I still think you'll need to go to position 3 1/2. Testing will tell.
 
Many thanks both Keith and Ian, I really appreciate your input my friends. I have spoke to the spark plug supplier again today and he is rushing through my plugs (B8ES), I totally understand where you are coming from, will put them straight in when they arrive. No real signs of leanness i.e no spitting through the carbs at constant throttle Keith. Not to sure on the mileage to be honest. Will give you an update as soon as the plugs are in. Thanks guys
 
Dave, sure hope things are OK with you.:)
I know you've posted health problems in the past and I just hope you'll be OK.
Maybe you haven't posted because you're out enjoying that professionally jetted bike of yours?!?
Maybe you just need to get off that island and move somewhere with a better climate? Just pulling your chain a bit.:p
Hope all's well.:)
 
Hi Keith,

Sorry I have not been in touch for awhile, been stuck at work nearly every hour of the day. Things have quietened down now. I have eventually get those NGK plugs fitted my friend and done a plug chop today the photos I include. Your right Keith I think she looks to lean on that 3rd groove.

cda80200.jpg
 
nitrogs said:
Hi Keith,

Sorry I have not been in touch for awhile, been stuck at work nearly every hour of the day. Things have quietened down now. I have eventually get those NGK plugs fitted my friend and done a plug chop today the photos I include. Your right Keith I think she looks to lean on that 3rd groove.

cda80200.jpg
Click to expand...

Nice clean plugs now Dave. A touch on the lean side, but not dangerously so. I prefer mine like this. There's no hint of overheating, by the colour of those plug threads. I guess that judgement is subject to how much hard running you've done on those plugs! If very little then the threads won't be telling the true story. Give it a good hard workout, and pull the plugs out and re-check the treads. You should see a dark discolouration of the first 2-3 threads when the heat range is just right.
Great to see you've won the battle, now enjoy the ride.
 
Hi 49er,

The plug condition shown was after 8 to 10 miles, I will try a longer run. Just was thinking they were showing a bit white in colour and didn't want to kane it to hard just in case my friend.
 
nitrogs said:
Hi 49er,

The plug condition shown was after 8 to 10 miles, I will try a longer run. Just was thinking they were showing a bit white in colour and didn't want to kane it to hard just in case my friend.
Click to expand...

Hi Nitrogs,

You just need some trials in the half to full throttle range. Take it to redline and then shut it down to do plug reads, looking at the colour of the porcelains right at their bases and thread heat depths. If the engine starts to surge under hard acceleration, back off.

By the look of those plugs you're slightly lean, but I doubt that you'll experience any surging, or extreme heating.
 
Last edited:
Dave, based on the plug pics and past experience, I'd set the jet needles 1/2 position richer. You already tried position 4 and it was rich. Your current position 3 just looks too lean in my opinion. Nowhere to go but position 3 1/2. I believe it will work well.
Just in case you're not sure, place the e-clip in the 4th position from the top, place the DJ jetting spacer directly on top the e-clip, place the thicker factory plastic spacer over the DJ spacer and the thinner plastic spacer under the e-clip. That's position 3 1/2.
Then you'll have to bench synch again, fully warm her up and vacuum tool synch again. She should run well and the plugs will probably have some graying/light tan on the insulators. The pilot circuit may require some minor pilot fuel screw adjustments and you'll be good.
Glad to hear you were just busy with work. I know too much about that subject.
 
Hi Keith and 49er,

Thank you for the reply my friends. I will have a go this weekend at adjusting to position 31/2. Many thanks
 
Just checking, have taken the slides apart and I only have 2 spacers, the DJ spacer and the thicker factory spacer, do I need to buy the thinner spacers please.

Dave
 
nitrogs said:
Just checking, have taken the slides apart and I only have 2 spacers, the DJ spacer and the thicker factory spacer, do I need to buy the thinner spacers please.

Dave
Click to expand...
The thinner plastic spacer that goes under the e-clip, missing or not, has no effect on mixture. It's there to eliminate metal to metal contact between the jet needle spring and the e-clip. The factory felt the need to use this spacer or they wouldn't have designed it in. Friction between the two parts is one obvious reason. Also, the spring end could possibly "catch" on the e-clip if the spacer isn't used and cause unintended operation or wear?? Without the parts in my hand I'm not sure the spring CAN hang up over the e-clip but it's just a thought.
What happened to the spacers? I can't say how critical it is that they be installed, only that they should be installed. If you can't locate any I guess you can make some or choose to run without them. I'm sure many members here have some laying around. I know I have only one complete set for spares that I have to keep.
 
Hi Keith,

Have completed the 3.5 position mod. I am faced with another problem, I bench synched the carbs, then vacuum synched. The funny thing is I cannot lower the tickover below 2000rpm. The idle adjuster is turned fully out so it looses contact with the throttle cam. I have checked the throttle cables and they are loose any other ideas please.
 
nitrogs said:
Hi Keith,

Have completed the 3.5 position mod. I am faced with another problem, I bench synched the carbs, then vacuum synched. The funny thing is I cannot lower the tickover below 2000rpm. The idle adjuster is turned fully out so it looses contact with the throttle cam. I have checked the throttle cables and they are loose any other ideas please.
Click to expand...
I know exactly what you've done but it's not as easy to explain in type.
You've simply over-adjusted the slide adjuster screws at the top and/or the bench synch wasn't done right to begin things. I've done it myself years ago and was surprised it happened, given how many times I'd done it correctly. You can incorrectly synch or adjust the adjusting screws so the bike will have a high idle even though the idler tip is off the throttle pulley. I'm sure you've noticed that over-adjusting a single slide screw can actually raise the other 3 slides? I've seen this while bench synching. It starts a nasty chain of adjustment that ends up as you've seen.
I always simply started over. This means removing the carbs again. Trying to do it on the bike can give poor results and more frustration.
I'm not sure if I can explain this easily but you have to loosen up the slide adjuster screws and start over. Loosen all the holder nuts for the slide adjuster screws and back off the idle knob so there's plenty of gap between the tip and the throttle pulley. You should be able to loosen all the adjuster screws so they are REASONABLY uniform (how much thread is visible above each holder nut). I've found they don't need to be exact but should be reasonably close to each other. If all 4 are backed off correctly then they will be "relaxed" and none will be actually raising its slide.
Now with all tension removed from the throttle shaft you should be able to start your bench synch over. Be sure all throttle arm to throttle shaft bolts are correctly torqued to approx' 4 ft/lb to begin with too.
Slowly adjust each slide until it barely rests at it's lowest point. Using the slide cut-away "nick" is the best way to do this. When the slide stops lowering, stop turning. Otherwise, you will effect the other 3 slides. Adjust all 4 to a uniform, maximum closed position. Now raise the idle knob enough to allow the bike to start initially. Don't worry about setting it too high, you can adjust it correctly as soon as the bike is running.
Warm up fully and then hook up your vacuum tool. Note the initial vacuum levels. If you did the bench synch carefully, you may be lucky and see only one that's a bit off from the others. You should find them all with adequate vacuum to begin with. It's generally much quicker and easier to adjust the higher level(s) DOWN to match the lower levels. Adjusting "down" also helps you avoid the problem you created.
Don't over tighten the holder nuts for the screws.
By the way, to back up a little, you should also check for the fully OPEN slide position too. I cover this in my VM bench synch post you may be aware of ? I have to leave for a bit but will help you with that if you need it.
 
Hi Keith,

Thank you for those last comments as always you were spot on. I decided to take the carbs off and visually check the slide nicks engine side and was amazed at the difference. So have bench synched again as you have described, fastened the carbs back on the bike and connected up the gauges. Unfortunately it is now 22:00 here and I cannot start the bike (your children asleep next door). I just craftily started the bike on tickover for a few seconds and the idle adjuster now works fine (for peace of mind). Roll on tomorrow!
 
The other thing you could have done is put the shaft that connects the slide arms in back to front (i.e. 180 degrees out). One side has a slight bevel that guides the bolts in, the other side is a just a flat ending thread. I've done this before and baffled myself - and looking at it you'd think it can't possibly make any difference but it can.
 
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