1 long story!!!

[79moneypit]

I bought a basketcase 79 gs 1000 3 years ago for $200 and it has challanged me to no end. I am in need of some guidance if possible. Here is what i have got and what is new:

1085 big bore kit with wisecos
open exhaust( 4 into 1 with no muff)
Pod filters
reseated valves and new shims (180 psi in all 4 cylinders)
New stator
Dyna s electronic ignition
All electronics are new aftertrmarket, coils are stock (only thing left original)
new carb kits, running stock 95 mains and 15 pilots

here is my problem:

Bike starts and idles great, throttle response is ok till about 4500-5000 rpm, bike has no power and backfires flames out of the pipe, plugs are completely carbon fouled after 5 minutes of messing around with the bike. I thought with pods and open exhaust I would be lean?? I have monkeyed around with the mixture screw and the other screw on the front of the carb underneath. I have no idea where the settings are supposed to be, evey book I have looked at says these are preset from the factory. I have over $7500 invested in this bike and I spent 3000 last year at a repair shop, mostly in electronics and carb work. I love the bike and am longing to ride it, but my experience is mostly in building 2 stroke snowmobiles. Any help would be greatly appreciated. I will post some pics when I get this thing running. I think this is a great resource for GS owners and have checked many posts and it has helped me a lot on this bike, but I am stumped on this one.

[psyguy]

carbs not my forte, but couple of guesses:
you may be running too rich on idle only if your screws are incorrectly set - hence the fouling of the plugs
but lack of power at higher rpms indicates fuel starvation
with pods and open exhaust i think you definitely have to upsize the main jet from stock size

im sure "chef" will see you right when/if he sees your post

[Nessism]

Jetting is sure to be lean although that may be masked at low speed by the adjustment screws. Set the bottom screw (pilot fuel screw) to one turn from lightly seated. These screws tend to jamb in the carb and for the tips to break off inside so you might want to check these carefully. The upper screw should be set to about 1.5 turns from lightly seated. These are just starting points but should get the bike idling.

For jetting, get a Dynojet Stage 3 kit. https://cart.jetkit.com/p-564-jet-ki...79-gs1000.aspx
At minimum, you will need larger main jets.

If the bike is still fouling plugs after setting the screws appropriately, the problem could be ignition related or the carbs are further messed up and leaking internally.

Hope this helps.

[KEITH KRAUSE]

I bought a basketcase 79 gs 1000 3 years ago for $200 and it has challanged me to no end. I am in need of some guidance if possible. Here is what i have got and what is new:

1085 big bore kit with wisecos
open exhaust( 4 into 1 with no muff)
Pod filters
reseated valves and new shims (180 psi in all 4 cylinders)
New stator
Dyna s electronic ignition
All electronics are new aftertrmarket, coils are stock (only thing left original)
new carb kits, running stock 95 mains and 15 pilots

here is my problem:

Bike starts and idles great, throttle response is ok till about 4500-5000 rpm, bike has no power and backfires flames out of the pipe, plugs are completely carbon fouled after 5 minutes of messing around with the bike. I thought with pods and open exhaust I would be lean?? I have monkeyed around with the mixture screw and the other screw on the front of the carb underneath. I have no idea where the settings are supposed to be, evey book I have looked at says these are preset from the factory. I have over $7500 invested in this bike and I spent 3000 last year at a repair shop, mostly in electronics and carb work. I love the bike and am longing to ride it, but my experience is mostly in building 2 stroke snowmobiles. Any help would be greatly appreciated. I will post some pics when I get this thing running. I think this is a great resource for GS owners and have checked many posts and it has helped me a lot on this bike, but I am stumped on this one.

That's a lot of $ for a bike that still isn't done. I spent 10K on my '79 GS1000E but the bike is family.
If you read any of my posts you'll see that you need to do a complete tune. That means don't skip anything. Electrical, valves, carbs...
Verify good compression first.
Check/adjust the valve clearances between .03 and .08mm.
I suggest an Electrex or similar reg/rec.
Check/clean entire electrical system.
Verify timing of that new S system with a timing gun. Many installers screw up the mounting and the timing ends up way off.
I suggest the green Dyna coils too.
Make sure the petcock is operating right, I suggest a Pingel anyway.
Clean the gas cap venting.
If the pods are K&N, oil them CORRECTLY.
Make sure the header gaskets are good or replace is better.
Replace manifold o-rings/verify the manifolds are good.
Re-install the baffle and re-pack.
Jetting...get a stage 3 DJ kit.
If you want to try jetting with the stock jet needle and separate jets, it may give decent results but never as good as the kit. That said...
Be sure carbs are clean and all inner o-rings replaced with Robert Barrs kit.
Set floats to .94/.95".
Bench synch the carbs well.
I suggest a 130 Mikuni main.
Stock jet needle with the e-clip in the 5th (bottom) position. Make sure the factory plastic spacers on the needle go back in factory order...thicker ring above the clip, thinner spacer under the clip.
17.5 pilot jet. Get the right length PJ.
Initially set the pilot fuel screws underneath to 1 turn out from lightly seated.
Set the side air screws to 1 3/4 turns then adjust using the highest rpm method after start up and fully warm.
REMOVE the 2 floatbowl vent lines and leave the ports open to breath.
Synch the carbs with a vacuum tool.
Test the mains at full throttle, the jet needles at 1/3 to 1/2, and the pilots at minimal throttle. Do what the plugs/performance say to.
The mains should be good the first try. The stock jet needle is many times still too lean for your mods but you can try if you don't want the kit. The cheaper pods "help" the stock needle if that's what you have.
Some fine tuning of the pilot fuel screws is generally needed.
If you do the above and the bike is ready for the re-jet, this should get you close, if not spot on.
If you get the DJ kit, use the 138 main, needle clip in position 4 from the top, stock pilot with simple richer fuel screw adjustments (1 1/2 out initially). Test.

[79moneypit]

Thanks

Thanks keith for the info. Alot of this has been done by a shop last year, but they weren't even close on the jets. I can tell you right now that I am way off, and way disappointed in myself for not starting this project with a running bike. What a nightmare. I am printing your list and going down to start marking off things. Thanks.

That's a lot of $ for a bike that still isn't done. I spent 10K on my '79 GS1000E but the bike is family.
If you read any of my posts you'll see that you need to do a complete tune. That means don't skip anything. Electrical, valves, carbs...
Verify good compression first.
Check/adjust the valve clearances between .03 and .08mm.
I suggest an Electrex or similar reg/rec.
Check/clean entire electrical system.
Verify timing of that new S system with a timing gun. Many installers screw up the mounting and the timing ends up way off.
I suggest the green Dyna coils too.
Make sure the petcock is operating right, I suggest a Pingel anyway.
Clean the gas cap venting.
If the pods are K&N, oil them CORRECTLY.
Make sure the header gaskets are good or replace is better.
Replace manifold o-rings/verify the manifolds are good.
Re-install the baffle and re-pack.
Jetting...get a stage 3 DJ kit.
If you want to try jetting with the stock jet needle and separate jets, it may give decent results but never as good as the kit. That said...
Be sure carbs are clean and all inner o-rings replaced with Robert Barrs kit.
Set floats to .94/.95".
Bench synch the carbs well.
I suggest a 130 Mikuni main.
Stock jet needle with the e-clip in the 5th (bottom) position. Make sure the factory plastic spacers on the needle go back in factory order...thicker ring above the clip, thinner spacer under the clip.
17.5 pilot jet. Get the right length PJ.
Initially set the pilot fuel screws underneath to 1 turn out from lightly seated.
Set the side air screws to 1 3/4 turns then adjust using the highest rpm method after start up and fully warm.
REMOVE the 2 floatbowl vent lines and leave the ports open to breath.
Synch the carbs with a vacuum tool.
Test the mains at full throttle, the jet needles at 1/3 to 1/2, and the pilots at minimal throttle. Do what the plugs/performance say to.
The mains should be good the first try. The stock jet needle is many times still too lean for your mods but you can try if you don't want the kit. The cheaper pods "help" the stock needle if that's what you have.
Some fine tuning of the pilot fuel screws is generally needed.
If you do the above and the bike is ready for the re-jet, this should get you close, if not spot on.
If you get the DJ kit, use the 138 main, needle clip in position 4 from the top, stock pilot with simple richer fuel screw adjustments (1 1/2 out initially). Test.

[79moneypit]

Keith went the cheap way and bought the pilots and mains you suggested: 17.5 and 130's. Ran it today and plugs are white on the ends, rode about 5 miles , 8000rpm max. have the pilot air at 1 3/4 turns and the pilot fuel at 1 turn. Running the cheaper pods, needle in lowest postion. Can I richen up the fuel screws or are they just for the low end? I am running a 4 into 1 exhaust with no baffle (open pipe). any suggestions would be great

[duaneage]

AN open pipe may require more extensive mods to the tuning, are you set on having an unbaffled pipe? Beyond the legal questions (varies state to state) the bike may run a little better with some backpressure to help scavenge the cylinders.

Just a suggestion, don't hurt me.[-o<

[Zooks]

AN open pipe may require more extensive mods to the tuning, are you set on having an unbaffled pipe? Beyond the legal questions (varies state to state) the bike may run a little better with some backpressure to help scavenge the cylinders.

Just a suggestion, don't hurt me.[-o<

Totally agree.


But can I hurt you anyway??

[psyguy]

Keith went the cheap way and bought the pilots and mains you suggested: 17.5 and 130's. Ran it today and plugs are white on the ends, rode about 5 miles , 8000rpm max. have the pilot air at 1 3/4 turns and the pilot fuel at 1 turn. Running the cheaper pods, needle in lowest postion. Can I richen up the fuel screws or are they just for the low end? I am running a 4 into 1 exhaust with no baffle (open pipe). any suggestions would be great

before taking things further i think you need to do a proper "plug chop" - at three different levels of rpms - that should get you an idea on where your pilot and mains and needles are

if you do a search you ought to find a really detailed description of the procedure (i do not dare to try repeat it )

well, i remember the first stage - start with clean plugs, warm up the engine and do a drag style open throtle in all gears (under load), hit the kill switch / close throtle / pull clutch / all at the same time - take the plugs out and take a photo - thats your reading for the main jet
(before doing the above you can ride under high rpms for a minute first - that should clean the spark plugs)

[KEITH KRAUSE]

As others said, you must do proper plug checks and test each jet at the throttle position range it operates at.
Interesting how your stock jetting resulted in black/fouled plugs but the jetting I suggested results in white plugs? Stock jetting with your mods wouldn't cause fouled plugs, quite the opposite. Now if the jetting I suggested resulted in white plugs then it could be (if purely jetting related) that you actually tested within the jet needle range and as I said before, the stock jet needle commonly gives lean results though it's sometimes worth a try. The DJ kit is the way to go. I only mentioned separate jets because I read your post as you're tired of spending money. A 17.5 pilot jet is plenty for your mods. Minimal throttle position tests could result in lean reads but simple richer pilot fuel screw adjustments would be all that's needed for the pilot circuit. No way a 20 jet is needed if the bike is truly tuned correctly.
As for the main, a Mikuni 130 jet is approx' the same size as a DJ 138 and the DJ 138 is what most of us have found to work with the '78/'79 1000. The 138 is in the stage 3 kit. An unbaffled pipe can result in your reads and I did suggest you re-install the baffle and replace packing. If you want, a 135 Mikuni may work but I'd have to see the plugs in person after a full throttle test to determine that.
I suggest the DJ kit. If you follow all that I first posted, this bike should run great. Remember, if you go with the kit, re-install the stock 15 pilot jets as the kit is designed to run with stock pilot jetting.

[Steve]

..., needle in lowest postion.

When you say "needle in lowest position", do you mean the needle is in the lowest position or the clip on the needle is in the lowest position?
With your mods (pods and open pipe, you would want the clip in the lowest position, raising the needle to the highest position.

.

[79moneypit]

Keith I am really leaning toward the dynojet kit, what exactly does it do??? How can it help with tuneability? As you can probably see from my pic on my signature my bike is custom (sorry for chopping up a GS, but it was in really bad shape hence the $200 price tag. I have seen many of these bikes with stock headers and no baffles, just chrome turndown tips. I would be interested in a muffler if it went with my theme. Right now the exhaust comes out under the right foot peg. Any ideas?

[terbang]

With big bore kits you can end up in no-mans land with regard to jetting and with the addition of an open pipe your problem is compounded.
I have found that by just boring the engine, leaving carbs/filters and pipe standard, the engine richens a little. Sounds strange, but the theory is that the larger capacity engine "sucks" or breathes stronger than STD and tends to run rich.
Opening up the pipe leans things off as there is less back pressure in the exhaust and the unburnt fuel (part of the cooling) escapes out the pipe.
Putting pod filters onto the engine also leans it off as you are quite simply allowing more air to freely flow through.

Main jets only affect the engine at full throttle at around 7000+ rpm
The needle clip position will effect the range between 5000-7000 rpm
The pilot jets affect steady operation at around 4000 rpm
The float level affects the engines performance at around 2000-3000 rpm
And the idle screw....Well self explanatory really.

When setting the engine up, start at the top with the mains first, getting the correct settings and work your way down finishing with the idle.

[KEITH KRAUSE]

Keith I am really leaning toward the dynojet kit, what exactly does it do??? How can it help with tuneability?

You're mostly paying for the differently tapered jet needle with greater adjustability.
The stock needle will work with certain mods...sometimes. The stage 3 DJ kit works well with basic quality pipe/K&N pods/with or without a bore kit.