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Need jetting help please for GS1000 1979

  • Thread starter Thread starter nitrogs
  • Start date Start date
N

nitrogs

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Its good to be back! have suffered repeated health problems but now cross fingered have made a full recovery and looking forward to finally sorting my GS1000. I would like to thank Keith Krause for the wealth of information that was supplied prior to my illness for which I am greatly indebted for setting up my Suzuki GS1000 1980 model. I have frantically been trying to find our previous dialogues. My Suzuki GS1000 has a wiseco 1085cc forged aluminium kit fitted, a vance and hines 4 into 1 system, K & N pod filters, a dyna s ignition, dyna coils and a stage 3 dynojet kit. All the valve clearances are set, carb boots replaced, timing set and carbs synced. Currently running standard pilot jets as suggested for the dynojet kit set, pilot screws 1.5 turns out. The bike does not seem to have crisp pickup from low revs (feels fluffy) and the plugs are very sooty (rich), but pulls strong from 5500 to redline the plug chop on top end plugs are good and tan. Presumably it is the richness on low revs that is causing the lack of crispness. What is my best move.

kindest regards
Dave Welton
 
Thank you for responding sorry for the confusion, it is the 1979 VM26 carb model. The needle is on the fourth slot my friend.
 
Dave, are you sure you haven't got VM28s on your bike (29mm diameter on the inlet side)? That would have been UK spec then.

You don't mention the setting on your fuel screws - that could be the source of a rich mixture at the bottom end. If you've got a Colourtune you'll be able to set your idle ciruit in about 5 minutes.
 
Thanks for the replies guys. Hampshirehog maybe that could be the case my friend, the fuel screws are set at 1.5 turns out. Does turning the fuel screws in lean off the mixture. Never tried a colourtune to be honest.
 
Yes, turning in the fuel screws (the ones under the front of the carb) leans out the mixture for low revs.

Since you have all these mods, try setting them at 1 turn out.

What is your air screw set at?
 
Dave,

I agree with Big T you are rather close in getting it dialed in. When you turn in the fuel screws be it 1 1/4 or 1 turns out, readjust your idle speed by adjusting the air screws using the high idle method. I would then recommend installing a relatively clean set of plugs and see how it runs with out ever exceeding 1/8 turn of the throttle (index your throttle grip). This of course will only test the pilot circuit. I would also throw in some small hills in your test ride: if it bogs your jetting is probably still a little rich. Conversely surging suggests it's lean but that not your reported condition. Put a couple of miles on it under 1/8 turn and do a plug chop and tell us what you see.
 
Thank you for the replies, do you chaps have to drop the carbs to adjust the fuel screws or can they be done in situ please. I was fairly sure the air screws were set about 2 turns out. When I did all the synch etc it was very hard to notice a max rev peak when altering the air screws
 
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The fuel screws are the ones underneath at the front of the carb (ie engine side). They are a bit tricky to get at - either a very stumpy screwdriver or a screwdriver bit is the tool. Be real careful winding them in fully - it's only 'lightly seated' - or the tips will snap off. Then wind them out 1 turn. You can either tweak with the airscrews or the fuel screws to get the right mix.

And be doubly careful if your hands aren't made of asbestos - it gets a wee bit hot down there!

A Colourtune is a really good investment - dead easy to use and takes all the guesswork out of the job.
 
Thank you for that, when testing the needle circuit at 1/3 to 1/2 throttle how long do you need to travel at that speed to get an accurate plug reading please.
 
Here are a couple of pictures of my GS1000 that I am trying to sort, just for interest.


c8840b00.jpg



c8940b00.jpg
http://www.minimotos4u.com/c8940b00.jpg
 
nitrogs said:
Thank you for the replies, do you chaps have to drop the carbs to adjust the fuel screws or can they be done in situ please. I was fairly sure the air screws were set about 2 turns out. When I did all the synch etc it was very hard to notice a max rev peak when altering the air screws
Click to expand...

If you don't have a stumpy screwdriver, you can fashion one out of a piece of hacksaw blade. I found that the blade thickness matches the slot size in the fuel screws. Length is quite important. I settled on 1&1/2". Any shorter and its too hard to hold when trying to line up the slots. Any longer and your hands wont clear the crankcase top and associated vent plumbing. I use a mirror to aid finding/aligning the screw slots. It's still a major test of your patience!! :mad:
As a guide, I'm running my fuel screws at 3/4 off the seats for 900cc, 4-1 and a stock airbox. Because you've got pods, I would think that you will end up in the 1-1&1/4 area.
That's a fine looking 1000 you've got there.
 
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Thank you for the advice 49er, it is much appreciated will do the required adjustments and thank you for the compliments on my GS
 
Nice bike, Nitro...interesting front failring; it looks like an Eddie Lawson Kawi hooked-up with a HD Road-Glide
 
+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
 
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.
 
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.
 
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.
 
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......:D

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