Need jetting help please for GS1000 1979

[srsupertrap]

+1: Nice bike Nitro. You have a lot of unique features on your GS1000 such as AN fitting & line to the oil filler cap and what's the shiney cannister on the left hand side below the seat? Marzocchi Strada shocks that look brand new, newly painted white wheels, gold hardware, rearsets, Telefix brace, a braced swingarm from I have no clue. It looks like someone painted that fairing & fender a different color though.

How's is it running now

[nitrogs]

Thank you hp1000s and srsupertrap for the comments. Thought I would take the carbs back off to recheck the pilot fuel screws. So I set them at 1 and quarter turns out, and then set the pilot air screws by the highest rpm method. Then bugger me it started raining, before my test ride, didn't fancy hours of polishing. Managed to get a quick blast just before work, does pull a bit harder from low revs and strong in high revs. But only managed a couple miles before the heavens opened again. I whipped a couple of the plugs out still look rich. But need to give it a few more miles and a plug chop to accurately gauge the pilot circuit. Perhaps I may need to turn the pilot fuel screws into just 1 turn out.

[Zooks]

Nice bike nitrogs. Is that a GSX/R headlight set up? Got any pics from the front?

I have a JPS Norton twin light fairing that I've contemplated putting on my 750.

[nitrogs]

Hi Zooks,

No my friend, it is Eddie Lawson Superbike Fairing Kit purchased many years ago. Would like some advice on how to do plug chops specificallly which gear and at what throttle positions to test the various circuits please.

[hampshirehog]

Plug chops: For the pilot circuit just let the bike tickover for a few minutes, switch off and check the plug colour.

For the needle circuit find a long straight, go as slow as you can in top gear then open the throttle halfway (put a mark on your twistgrip to make sure). Run for as long as you can then hit the kill switch before moving the throttle. Check plug colour.

Mains circuit - find a longer straight, preferably uphill, open the throttle wide open and repeat as above. Remember the speed limit......

You can try the 'other method' if you invest in a Colourtune - Halfords do the kit at a not too rip off price.

[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.