Need jetting help please for GS1000 1979

[nitrogs]

At last managed to get out on GS1000 in the sun prior to work today. Did 2 plug chops, one at a 1/3 to 1/2 throttle for 3.5 miles and one at minimal throttle opening for 4 miles. Plug reads on each circuit look rich particularly on minimal throttle opening, will post the pics of plug colours tonight for you guys for some advice.

 

[nitrogs]

Right guys,

Here we go, the results of the plug chops.

Firstly these are the results for the 1/4 to 1/3 plug chop after 3.5 miles, cylinder 1 first to cylinder 4 last

What do you think guys?

 

[nitrogs]

This is the plug chop after 4 miles of minimal throttle

What do you think guys, what is my next move?

 

[49er]

Hey Nitro, those plugs aren't pretty. For some reason you're closer to the correct mixtures on the first pot than any of the others, on both the pilot and needle chops. You haven't over oiled some of those pods, have you?

Have you done a compression check on your engine? That's one more tool you have to help make tuning easier. You said that you have reset your valve clearances, so any wild variations in compression numbers will indicate poor cylinder sealing/ring wear.

If compressions are even, it's time you pulled the carbs and eliminated a few guestimates :-\\\

The needle positions need to be checked as do their numbers. Pilot jet #s need confirming and the float needle valves and float levels re-checked as well. Once these checks have confirmed all are correct, then you will be in a better position to make some further tuning judgements.

 

[KEITH KRAUSE]

Very sooty for sure. Not sure why #1 is different.
Be positive all other tuning is correct. Valve clearances, timing, spark quality/voltage, clean carbs, float levels very close to .94/.95", properly oiled filters...
Have you actually checked the advance timing? How's the spark look at each cylinder (with a fresh plug)? What plugs are those? I recommend NGK B8ES only. What about float levels, etc?
What's the weather like there normally? I've heard about England but want to hear it from you (humidity/temps...) Jetting that works for most bikes here would tend to be rich in your climate.
If solid 1/3 to 1/2 throttle position makes the plugs that sooty and it IS jetting related, then place the jet needle e-clip in the 3rd position from the top, re-synch the slides and test.
As mentioned earlier, is there a chance your carbs are 28mm?? If they are, the jetting will have to be altered to what works, providing the kit will work in your case. Find out so we're not spinning our wheels.
I'm still concerned about the #1 plug being different too.
Please answer all questions so we know what's been done and what parts we're working with.

 

[nitrogs]

Thank you for your replies, here are some answers just so we know the starting point. The pods are new and I have fitted them straight from the packaging (done about 100 miles). All the valve clearances have been checked but I will do another compression check and feedback the numbers. I have used the stage 3 dynojet kit with the 138 Main jet with the e clip on the 4th groove and utilised the stock pilot jets (15). The pilot fuel screws are set one and a quarter turns out and air screws set to highest rpm. I will recheck the float levels but they were okay. Carbs are fully cleaned. Have checked the timing and advance and all is okay. Just fittted a brand new heavy duty battery and plug sparks look good. Keith will purchase a set BP8ES plugs and fit, at moment was fitted with the highly acclaimed splitfire plugs which alledgedly give a more efficient burn + extra power. As regards the carbs does it tell me anywhere the size i.e if they are 26's or 28's, as far as I know they are the standard 1979 GS1000E carbs. Keith the temperatures at the moment here are between 15 and 22 degrees centigrade and shortly we shall be in the 19 to 24 range. Humidity is approximately 76%.

Thank you guys for sticking with me it is greatly appreciated. I am determined to get this sorted.

 

[nitrogs]

Tried measuring my compressions with my Gunson Gauge but even that does not want to work, pressure builds up as you crank then instantly drops. It is supposed to hold the pressure then release on a flick switch, it is just one of those days. Anyway decided to take off the carbs again and check the pilot screws have now adjusted to only 1 turn out. Also decided to check the needles and they are all on the 4th groove down from the top. Have to go to work again now, but will move the e clip to the 3rd position from top, then bench synch, vac synch and set up pilot air screws. Is there anything else I should check first?

 

[hampshirehog]

When you've got the carbs off, measure the internal bore - engine side. If it's a UK bike I bet it'll be 28.9mm +/-.1mm. If they are they're VM28SS.

If they're under 27mm they're VM26SS (I forget the exact measurements).

Also have a look to see if there are any tiny marks punched into the carbs - these were put in at the factory to line the pilot and fuels screws up and they're always a good starting point.

Your Splitfires should be fine but worth trying the 'proper' plugs first - you can always swap back easily enough later.

I liked your humidity figures. Keith, one thing's for sure in the good ol' UK, it'll be way different tomorrow

 

[nitrogs]

Many thanks hampshirehog, I will measure the carbs when I leave work to find out what I have. It sure is confusing the model codes and specs for the UK motors compared to the US.

 

[KEITH KRAUSE]

Yes, let us know the carb size. Many differences from 26 to 28. Do they have an accelerator pump? I couldn't even guess from the pics of your bike. Even if they are 28's (and they probably are) we may still find the jetting that works. The bike sounds like it runs fine while on the mains so that's encouraging.
As long as you're sure the other tuning is correct we can focus on the jetting. I really don't know much about those plugs you're using but I would run the factory plugs - NGK B8ES. No "P" in there. Set gap to approx' .028". If you have a good bluish spark with a fresh/clean plug then we should be good.
I still wonder about #1 read looking so different. Could be so many things that could be beyond basic tuning checks. Since that plug appeared to be getting more air (or less fuel) in the mixture as compared to the other carbs, double check the carbs while you have them removed for jet needle adjustments. Make sure all the air jets are clear (filter side). If any doubt or you don't KNOW the history of your carbs, compare the pilot jets size and length and the number of holes in them. Be sure all air screws are identical. Make sure the thicker plastic spacer for the jet needle is above the e-clip and the thinner is underneath...things like that.
Be SURE the choke circuit is completely closing when the choke is off. Some people install the little choke lifters (that slip over the shaft) upside-down and this can result in the plungers not sealing well. The small "bump" on the lifter should be facing downward as per the factory. Observe the choke action closely. The plungers should seat completely while still having just a bit of slack in the cable or thumb lever. Though the choke circuit is designed to be largely bypassed when the throttle is opened, there can still be some effect on jetting if you have a sealing problem.
I hope moving the e-clip 1 position leaner will work. Those plugs were very sooty and part of thinks they were richer than 1 position off. But 1 position is a significant change and there's a good chance it will work. Be careful when bench synching and that will make the final vacuum tool synch easier. Don't over-tighten the holder nuts for the slide adjuster screws. 3.5 ft/lb is factory. Double check your adjustments to be sure by slowly throttling it. After synching, re-check the side air screws for highest idle. Be sure to use 1,000 rpm's as base setting or it can be more difficult to hear subtle differences.
The bike should need choke if starting stone cold.
Once fully warmed up, let the bike idle for several seconds at 1,000 rpm's. Now blip the throttle once (a 1/4 turn is good). No puff of dark exhaust should come out. If it does show dark exhaust, blip again but at a minimal throttle opening closer to 1/8 turn. If still dark is observed, close the fuel screws underneath a 1/4 turn. This of course assumes the side air screws are correctly tuned. You might want to check a couple of plugs to see what they're saying.
If they look OK, mark your throttle/grip and go test the jet needles.

 

[nitrogs]

Thank you Keith, excellent advice as usual. There is no accelerator pump my friend, will measure the carbs tonight Keith and report. Got a good bluish spark and my new B8ES plugs are in the post, while they arrive I shall use my old but good condition B8ES plugs set to .028. Good strong bluish spark (just got brand new Dyna Ignition and Dyna Coils fitted. One thing that I have noticed Keith when observing the protrusion of the pilot fuel screws in the carbs when looking from the engine end is that when all the screws are lightly seated the number 1 cylinder screw seems to protrude slightly more then the other screws when they are seated. All the screws are the same length and tip condition is good on all. Have checked the needle clips and all were in the same 4th groove from top thick washer above, thin washer under. Going to move upto the 3rd groove Keith. Will double check the choke lifters to make doubly sure of the seating. Got a day off tomorrow Keith so hopefully will get all done.

 

[srsupertrap]

Nitrog,

While you are investigating how about verify the size of the Throttle Valve Slide cutaways (1.5 , 2.0's ?) size. When you move the e-clip postion you will see that number embossed on top of the throttle valve slides ( I probably didn't have to say that ). I bring this up because when I moved to Colorado from sealevel my GS1085 with VM29's S/B with the pilot jet at 15 & K&N's etc was running very very rich on the Pilot & Needle circuit. No amount of air screw adjustment helped. The pictures of your spark plug chops looked exactly like my plugs before I figured out the 1.5 slides were too rich at an altitude of 5000 feet. I had to bump the Throttle Valve slides to 2.0 and that cured the low end rich rich condition. Now granted you are at sea level but who knows what the P.O's did.

According to the US factory manual GS1000 VM26 have 1.5 T/V slides. I looked under the GS1000S section thinking they were VM28's equipped but it also states that S model had VM26 with 1.5 T/V slides. I think is a misprint error.

 

[nitrogs]

I will definately check those slides srsupertrap and report back, thanks my friend.

 

[nitrogs]

Burning the midnight oil here in the UK, to try and get things sorted. Just to let you know I have measured the carbs and they are 28's. The number on the slides is 1.5. Hitting the sack now for a early rise tomorrow to sort the carb work, speak tomorrow gents

 

[hampshirehog]

Your slides are the standard ones for 28s and you should be ok with them (as you're not up near the moon like srsupertrap!)

 

[KEITH KRAUSE]

As you can see, lots of help here if you need it.
Hopefully you won't need to adjust the needles again since they are the most work and require a re-synch. Solid 1/3 to 1/2 throttle tests will tell.
The stock pilot circuit should be able to be adjusted. Since these are 28's I hope the cut-aways will work in transitioning to the DJ needles. Testing will tell. Hang in there. Jetting is fun (keep telling yourself that).

How many hours ahead of the US is England? About 12?

 

[nitrogs]

Thanks for the inspiration Keith, we are approximately 8 hours in front of you my friend. I really appreciate all the help the guys on the forum are giving me. I am afaid the GS is near on a forgotten machine in the UK. In particular where I live there are no motorcycle shops to mention and just plastic rockets roaming the streets. So it is a maintain yourself approach, hence why this GSR forum is a life saver. Most the parts for my GS I obtain from the good old US.

 

[KEITH KRAUSE]

Believe me, the "maintain yourself approach" is often much better than the alternatives: giving it to a mechanic who isn't trained on older bikes, or, let the bike die from neglect.

 

[nitrogs]

Weather absolutely miserable today plenty of rain. Stripped down the carbs and thoroughly checked all passages, jets and floats. Setup pilot fuel screws to 1 turn out. Moved the e-clip on the needles to position 3. Bench syncing done and bank of carbs fitted, air screws set to highest rpm followed by vac synch. Just need the rain to stop so I can plug chop tomorrow to see if the changes have been successful, cross fingers!!. Hampshirehog was sure right about the changing weather

 

[srsupertrap]

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