Need jetting help please for GS1000 1979

[KEITH KRAUSE]

Dave,

While waiting for the rain to subside, you may want to review the VM Carb rebuild Pdf, specifically Page 3 which shows the internal components of a typical VM series carb. Does your pilot jet, fuel & air screws match the components shown in attached Pdf? I am still wondering why your spark plugs are black when you performed plug chops on the pilot circuit with stock GS1000 pilot jets (size 15) installed. This in light that you have a 1085 kit installed. Turning in the fuel screw a 1/4 and raising the needle one clip will sure lean it out but I am not convinced your spark plugs will suddenly turn light brown from pitch black unless those spitfire plugs are problematic.

But I could be wrong.

http://www.thegsresources.com/files/vm_carb_rebuild.pdf

All good info. How black they were concerned me too but the change I recommended is what I'd try myself. I can only assume the correct parts are in there and go by what he says is checked/done.
With a stock pilot and "ballpark" screw adjustments it makes me wonder too. The fact that these are 28's is what's different.
Nitro, what did you set the floats at? Do the 26's and 28's run the same float levels or?

 

[nitrogs]

Well here we go eventually the rain subsided and managed to get the plug chops. Certainly a difference. Here is the first chop at a solid 1/3 to 1/2 throttle in the order cylinder 1 to 4

What do you reckon chaps, for sure the headers are blueing

 

[nitrogs]

Here are the results of the plug chop at minimal throttle 20 to 30 mph for 3 miles

Plug chops Minimal throttle 20 to 30 mph. Still awaiting my B8ES spark plugs gents but good strong blue spark on all four.

What do you reckon?

 

[49er]

Nitro, much better looking colour on the needles, maybe a little on the lean side. That's about the colour I run. #2 though looks like it might be burning some oil.

Your pilots are still too rich though. How far out are the pilot air screws set at? If more than 2.5 turns off the seat, you may need to set the mixture screws into 3/4. How much oil are you using? It's hard to tell from the pics if some of the black might be oil, especially at lower rpms, with less heat at the plugs.
It should be pulling well in the midrange now!

 

[nitrogs]

Hi 49er, oil consumption is minimal my friend. The fuel screws are set just under 1 turn out. Mid range is alot better.

 

[srsupertrap]

I am with 49er, its still too rich. Turn those pilot fuel screws in another quarter turn to 3/4 from seated and rechop when the B8ES spark plugs arrive. Next, I would fine tune using the air screws.

 

[hampshirehog]

Looks like you're on the home straight! I'd like to see a bit more brown on your mid range though - maybe it's the camera and light? It looks pretty close though. If you think they are too lean (you'll be seeing the plugs for real) the next step would be to revert to your original needles, not the Dyno ones, and start with the clip one notch off the bottom.

For your pilot circuit you can just let the bike tickover (as long as the motor doesn't get too hot) on the centerstand and plug chop from there. No 3 looks a bit weak to me. (This is where a Colourtune really comes in to its own).

 

[49er]

Hi 49er, oil consumption is minimal my friend. The fuel screws are set just under 1 turn out. Mid range is alot better.

Have you ever had the fuel screws removed to visually compare the length and angle of their tapers? I seem to recall in an earlier thread that you commented that one of the air screws was sitting higher in the carb body than the other three, when set at the same setting. That indicates that it is probably from a different set. I'm wondering if you have some mis-matched fuel screws causing the same problem.

 

[nitrogs]

Hi there, I did take out all of the fuel screws and compare their lengths and they are all identical. I will do as you say a move to 3/4 on the fuel screws and see how they look. I will also try another 1/4 to 1/2 throttle chop. Thank you for all the help guys

 

[KEITH KRAUSE]

As always, plug pics are hard to really see. As you can see, one position leaner is significant.
For those jet needle reads, if you have a moderately gray or light tan on the insulator then it's probably good as long as you think the performance is good and you have no "lean" issues. From your previous pics of your bike, I saw some bluing already on the header. Even with todays generally thinner finishes on headers you may get some initial bluing even with good jetting. Excessive bluing or purple isn't good though. Once the jetting appears good, rub out the blue with Blue-Away or Blue-Job or similar and then you should get no more than additional "golding" after that. If it blues up again, I'd take that sign as too lean.
The one problem I saw was at #2, being possibly oil? Sure looks shiny like oil. You have to tell us what those reads look like in person. If you think they're too lean then position "3 1/2" should work. That would mean placing the e-clip in position 4 from the top and placing a jetting spacer directly on top the clip. How is the performance? Any issues?
As for the pilot circuit, you can see how things rapidly change. Older bikes can be harder to synch also due to older parts and simply their design. The pilot fuel and air screws are sensitive to changes and you may have to tinker here and there to get the plugs reading good and reasonably uniform. You did say it's hard for you to tell much difference when adjusting the side air screws for best idle. I've never had much problems with it unless something wasn't right. But if YOU can't hear much difference then you have no choice but to make minor adjustments that make sense, just as you would the pilot fuel screws. 1 3/4 out is a very common final setting. I don't like simply suggesting a "set" adjustment though. As with the fuel screws, you can tinker from a range of 1 1/4 to 2 turns and you should be good somewhere in that range.
You don't have to make perfectly uniform adjustments with the fuel screws. If you think one cylinder looks good but another/others dark, then lean out the dark cylinder(s) only. #1 and #4 looked richer than #2 and #3. Maybe 1/4 turn in on the richer ones only and re-test? If you had to actually close a screw to get a good read that would suggest something else is wrong. Don't worry about final differences of 1/4 to 1/2 turn.
Another thing that can effect reads is how you vacuum synched. I prefer to synch at approx' 3,000 rpm or a tad higher. The vacuum levels can jump around too much to bother setting them at factory idle. The difficulty varies with the bike. My point is that these are older carbs and they may show characteristics that you wish they didn't. The vacuum levels may not rise and fall perfectly like you'd like them too. Each cylinders vacuum read can change compared to each other as you lightly throttle it up or down. How you choose to synch and how close you get the levels can result in moderately different plug reads. What rpm did you synch at?

 

[nitrogs]

I am at work at present, I will try another plug chop and supply a description as well as pics of the plugs I understand how hard it is to judge pictures. I have a feeling due to excessive header blueing & a bit of purple and the plug reads being very marginal that I need to move out to position 3 1/2. I see what you mean Keith, the pic of #2 is decieving it is the light (no signs of oil). I must admit there doesn't seem to be any performance issues (no surging or popping etc). I have found now Keith after all the cleaning etc the air screws now do raise the rpm when moved accordingly and have set to highest revs. I will move the fuel screws #1 and #4 in a touch and leave #2 and #3 which look reasonable. Once all the adjustments have been made I will re synch at 3000rpm previously synched at 2500rpm.

 

[nitrogs]

Just checking when moving up half a position on the needle do you just leave out the thin washer and put the thick washer directly on top of the e clip, thank you in advance

 

[srsupertrap]

Dave,

I am reluctant to answer so have a look at this thread . . . perhaps Keith explanation #3 will help. There is no mention of removing the thin washer in question when adjusting the needle to the 3 1/2 or 4 1/2 position etc . http://www.thegsresources.com/_forum/showthread.php?t=119189&highlight=dyno+jet

2) While you are at may we suggest performing the Coil relay modification, this is a easy modification that maximizes the performance of your coils resulting in smoother idling etc. Just keep a spare relay with the bike there has been cases of relay failures.

 

[KEITH KRAUSE]

Just checking when moving up half a position on the needle do you just leave out the thin washer and put the thick washer directly on top of the e clip, thank you in advance

Always replace the factory plastic spacers in factory order.
In your case, place the e-clip in position 4 from the top and place the jetting spacer directly on top the e-clip. The thicker spacer (actually a "ring") goes on top the jetting spacer and the thinner spacer goes under the e-clip.

 

[nitrogs]

Got that Keith thank you. I have tweaked the two rich pilot circuit cylinders and tweaked the air screws to highest revs and have re synched at 3400 rpm and got all the vacuums to the samel level. Done another test and the engine has strong pickup and strong top end. Tested the needle circuit at between 1/3 and 1/2 throttle and all plugs read very similar. Just trying to decide in my mind and make a decision if the very light gray plug colour is too lean or okay.

 

[nitrogs]

Dave,

I am reluctant to answer so have a look at this thread . . . perhaps Keith explanation #3 will help. There is no mention of removing the thin washer in question when adjusting the needle to the 3 1/2 or 4 1/2 position etc . http://www.thegsresources.com/_forum/showthread.php?t=119189&highlight=dyno+jet

2) While you are at may we suggest performing the Coil relay modification, this is a easy modification that maximizes the performance of your coils resulting in smoother idling etc. Just keep a spare relay with the bike there has been cases of relay failures.

Just checking what would be the coil relay modification please

 

[49er]

Got that Keith thank you. I have tweaked the two rich pilot circuit cylinders and tweaked the air screws to highest revs and have re synched at 3400 rpm and got all the vacuums to the samel level. Done another test and the engine has strong pickup and strong top end. Tested the needle circuit at between 1/3 and 1/2 throttle and all plugs read very similar. Just trying to decide in my mind and make a decision if the very light gray plug colour is too lean or okay.

The light grey colour of your plugs will be fine. You're not running in a really hot climate, so won't have cooling or detonation issues.
You will have more torque with that AFR, than the tan colour. When you get dangerously lean, the bike will surge under load. That's definately a no no!!
Just my 2 cents worth.

 

[KEITH KRAUSE]

Got that Keith thank you. I have tweaked the two rich pilot circuit cylinders and tweaked the air screws to highest revs and have re synched at 3400 rpm and got all the vacuums to the samel level. Done another test and the engine has strong pickup and strong top end. Tested the needle circuit at between 1/3 and 1/2 throttle and all plugs read very similar. Just trying to decide in my mind and make a decision if the very light gray plug colour is too lean or okay.

On my way to work so just a quick reply.
So this is after adjusting the jet needles to 3 1/2? Wish I could see the plugs in person. I'd still like to see the NGK plugs in there. Maybe another set of pics? Have you tried any plug reads after some "general" riding around? Just putting around/combination of city and some higher speeds.

 

[nitrogs]

Keith, that is with the vacuum synch done at 3500 rpm and the other tweaks mentioned but retaining the e clip at position 3. Still awaiting the B8ES plugs, will do some plug reads after general riding and put up the pics my friend. Thanks Dave

 

[KEITH KRAUSE]

OK. Your reply made me think you had already changed to position 3 1/2 and still saw possibly lean reads. You had me mumbling to myself :lol: since we know position 4 gave rich results.
Your initial synching at 2,500 rpm was fine. I mentioned doing it around 3,000 to 3,500 because I've heard some people synch at normal idle which to me is a waste of effort. I thought you may be synching at idle too. I like the 3-3.5 range because it's close to where you'll spend a lot of time just casually riding. I don't see much reason to synch higher because the bike can get much hotter while synching and if using mercury the mercury can get sucked up too easy.
I have little experience with those split fire plugs but I see no reason to run anything other than the NGK. I suppose if the split fire is the exact same heat range and gap then plug color would stay similar. I still suggest the NGK. As for plug reading and colors, the color can change with a little mileage on the plugs, especially the pilot circuit. I've taken out plugs after many miles and noticed some change after I called the jetting good. Never a big difference but SOME difference. And at higher speeds such as testing the jet needle and main circuits, the lead free gas today burns clean and doesn't leave much plug deposits when the mixture is correct or getting close. Especially with very low miles on the plugs.
We ask for pics but we all know by now how hard it is to judge and give advice based on those pics. It may help to pop all 4 plugs into some cardboard close together and get an all in one shot? The brown cardboard will help minimize under/over exposure and pics out of direct sunlight may work better too?
If anything, I have to say the jet needle reads looked on the lean side. Depending on how you ride, slightly lean can be OK or it can be bad for the motor. Like most of us you get tired of taking things apart but that's how jetting is sometimes. Unless you can see some better plug reads with more testing I'd probably go to 3 1/2 and then you will have tried every workable position. You'll KNOW and be able to decide if position 3 or 3 1/2 is best. I'll add my past experience to say that the leanest position I ever found to work on your model with your mods was position 3 1/2. Dynojet actually suggests a starting/base setting of position 2 which I'll never understand. I like to try to give advice that gets you done as soon as possible so I'm sorry if position 3 doesn't work. Based on my past experience, I thought it seemed lean but in position 4 your plug reads were SOOOO dark I didn't believe just 1/2 position leaner would be enough. I also felt your climate was factoring in more regarding a rich effect. It DOES have a richer effect but maybe not as much as I thought.
But we're almost there. Hang in there.

PS: be sure the factory plastic spacers stay in correct order. In your case, if you decide on position 3 1/2, put the e-clip in groove/position 4 from the top, place the approx' .022" DJ jetting spacer directly on top the clip, place the thicker plastic spacer directly on top the jetting spacer, and install the thinner plastic spacer under the e-clip.