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Low secondary resistance on coils

  • Thread starter Thread starter Anonymous
  • Start date Start date
I don't think the coils are the problem at all. You're not that much off the readings you are supposed to get. If you decide to replace them jusst go with GSXR, Bandit, or Kat coils off Ebay. The newer the better.

Keep working the carb settings. As Keith suggested, make sure the spacers are stacked right on the needles.
 
23k doesn't seem bad though for secondary resistance... GS1000 bikes use anything from 11k - 35k depending on the model of the bike so to me it doesn't seem like a short if they are reading 23k.
 
Ok... back on carb track. :oops:

I've taken them apart and compared some things with my spare carb set. My spare set indeed has the little plastic spacers. I'll be moving those over.

1st) my current set has the needle one notch from the bottom. Should I leave it here and just use the spacers properly? This should raise it a tad, right?

2nd) When comparing the needles with my spares, it looks like my current needles are pretty fat. The markings are 5F21. My spares say 5DL36. Should I swap or keep the larger ones?

3rd) My current pilots are 27.5s. My spares have 15s in them. Should I stay with 27.5s?

Ok, enough questions for now! :lol:

Thanks again!
 
Keith Krause would be your best bet with your questions on jetting. Just be aware the jet needles and needle jets have to be compatible.
 
First of all, I have to say your carbs may have been jetted by a fool.
They were missing the jet needle plastic spacers.
A 27.5 pilot jet would fuel the Queen Mary. The 107.5 mains you have are very lean for your mods. As for your jet needles, I believe you should have the 5DL36 for the '77. What bothers me about all this is I have to wonder what else may be changed incorrectly?? The needle jets may be wrong. The float levels screwed up, though that is fixable. You could see differences in the pilot fuel screw design. There could be even more "changes". It seems your spares have all the correct stock parts and may be the wiser choice? I can't say without seeing the two carb banks, but I wonder if you should transfer all the new o-rings to the spares? I just don't trust what other things may have been done to these carbs. If you must stick with these carbs, I suggest using the needle jets from the spares too. Also, double check that the pilot fuel screws are the sharp tipped design and the tips are all in good condition. Check throttle slides, side air screws, etc. Check for any other missing parts.
Reading back, you said you would check/adjust valve clearances. Just be aware this should be done, along with correct ignition timing and point dwell setting/advancer action check and side air screw "highest rpm setting", BEFORE the vacuum synch, which also must be done to get accurate performance/plug tests.
As for your latest jetting questions, I would try the stock 5DL36 needles in the highest position. So put the e-clip in the bottom groove. Be sure the stock plastic spacers are replaced as I said earlier. If you had K&N's, this needle set up would probably still be too lean, but I think it will work with your Emgo's. If still lean, jet kit time. If the Emgo's run even richer than I think, then we'll lower the needle some. Depends on the performance/plug reads you get.
Your 15 pilot jets should be given a chance to work with the help of pilot fuel screw (underneath) adjustments. Start testing them at 1 1/2 turns out or close to that. If you can't get the mixture correct by the time these screws are 3 turns out, then go with a 17.5 pilot jet.
As for the main jet choice, I'm guessing 125's. That's only a guess of course. Jetting can take a few tries. I'm actually a big jet kit fan instead of trying the stock needle and buying seperate jets. But with the Emgo's you have a better chance of making the stock needle work.
 
A 27.5 pilot jet would fuel the Queen Mary.
Click to expand...

:lol: Hahah... I figured that a 83% increase on the pilot seemed odd when compared to a 7.5% on the mains!

With regards to the spacers on the needle (plus the round plate & spring)... it looks like they were only introduced in 78! Perharps after some problems??

Take a look at this fiche from 77:
http://tinyurl.com/7b7uv

And now from 78:
http://tinyurl.com/c6npk

Strange... anyhow...

I will give your suggestions a try this week. Hopefully tonight. Should I be able to continue using the 107.5 jets with their "pipes" (what are those thing called??)

I'll try sticking with my current carbs as I put a lot of effort into cleaning them . If this still doesn't work, these new carbs will be my winter project ;) The float levels in my current set were reset by myself to 26mm using new valves and seats.

I've checked the tips and they are good in the current and new sets.

I do have spot-on timing right now, done with a timing light. I also tried the "highest-rpm" air-screw setting, but it would never modify the RPM when I turned it.

Thanks so much Keith for your assistance so far. Your commitment to the GS community is to be commended! 8)
 
I'm not sure what you mean by "pipes" regarding the main jets, but the 107.5 mains are way too small for your mods.
As for trying to set the side air screws, they won't respond normally with those huge pilot jets in there.
As for those two carb parts pics, they both say 77-79. I don't know what to say about them. I haven't worked on the VM carbs with no spacers/plate/spring, etc. I can tell you that if earlier carbs came without the plastic spacers and spring and brass plate, those jet needles would wear very quickly from vibration. The plastic spacers stop metal to metal contact and the plate and spring keep the needle under a light tension so it doesn't shake and rotate around.
The earlier design is inferior and I would use the newer carbs. I can't be absolutely certain if you can swap the plastic spacers onto the earlier jet needle without causing an unknown jetting problem. I'm just saying there could be differences and I would be cautious.
I'm not sure what your plan is but I think I wouldn't transfer just the plastic spacers over...I would transfer the entire throttle arm/thin brass plate/spacers/spring/jet needle/slide over as a unit. To go further, I'd clean up and rebuild the spare carbs and use them. But I know you've decided against that. I just hope this "problem" doesn't create a jetting headache. It's hard for me to say anything 100% without being able to check and compare every part.
 
Agreed on the slides and needles, the earlier ones are not compatible with the springs and plates, so I will have to transfer the whole assembly over.

I'm hesistant to use/clean the new carbs because they are extremely nasty. It looks like molasses in there... Plus, I really can't stand that carb dip biohazard anymore. I just dipped a carb last weekend and the stench lingers for a week at least.

The plan right now is to:
  • Replace all of my jets with the #15s.
    Replace the slides, needles and linkages from spares
    Move the needles to the bottom clip
    Install plastic spacers (large bit on top)
    Double check float height a confirm "floatiness" of said floats (swap from spares if required)
    Set pilot screw to 1 1/2 turns out
I'll let you know how it goes.

Thanks again!
 
OK. Hope the slide assemblies work correctly in the other carbs.
I feel funny making suggestions when I can't see the parts myself. All I can say is that I'd look hard at all the parts being swapped. The length of the slides, etc. I guess you know what I mean. So easy to not notice something. If at all possible, I'd use the better slide assemblies though.
Be sure to keep the 5DL36 jet needles with the needle jets they are designed to move through. Very important.
Also, set the side air screws to 1 3/4 turns out for starters.
Don't forget the mains.
You'll also need to bench synch the slides. I'm not sure if you know how?
I made a detailed post on how to at Hoomgars topic about re-jetting his GS1000/bad fuel economy? The only difference in procedure is your 750 carbs I believe should be synched starting with the #3 carb. I'm too stupid to know how to provide the link, but you can search if you need it or someone here may help? If it's easy, I'd like to know how to do that by the way. :oops:
After the bench synch, which is really done to make the vacuum tool synch quicker/easier, you'll need to get the carbs vacuum tool synched. It's easy to learn and a Motion Pro tool is about $40. The Morgan Carb tool is more money, but easier to use because it doesn't get condensation gaps mixed with the mercury (a problem for some). Some people live with their bench synch but I don't recommend doing so. The tool and its effects on tuning are more than worth the money and time taken to learn how.
 
Found it! No, I didn't know how to do this so I will give it a shot. I love learning this stuff.

Here's the link in case you need it in the future:
http://www.thegsresources.com/_forum/viewtopic.php?t=34488&start=30#332826

I don't have a sync tool, but I will probably get the Motion Pro at some point. We'll see how well it runs with the bench sync, maybe it can last till the spring.

I tried using the 5DL36 needle on my existing jets and it seems to run through it smoothly. What should I be looking for in terms of imcompatibilities?

Cheers!
 
As for the synch quality, it's very difficult to bench synch the slides as perfect as you can with the tool. You may feel the imbalance in performance and this just adds to tuning difficulty. You also can't read your plugs accurately because you have no idea which cylinder(s) read to trust. If you have uneven plug reads, such as 1/2 darker than 3 and 3 darker than 4, how do you know what to use as a base for re-jetting??
If nothing else, have a mechanic you trust vacuum synch the carbs, but be aware if you have to change the jet needle position in the VM carbs, you must re-synch the slides every time.
As for the jet needle and the needle jet, they come "matched" from the factory. You already said the jet needles look different. There's a good chance the needle jets are different too. Many times the number isn't stamped into the needle jet and you can't just look into them and say they "look" the same. If you use the 5DL36 needles with the "other" needle jets, you may have jetting problems that can't be worked out. If indeed the needle jets are a different size, you WILL have problems, big problems. Please use the 5DL36's needle jets too.
 
Ok, just so I'm clear on this, the needle jet is the entire main jet assembly or the small screw-in jet bit?

Thanks once again
 
fatpat said:
Ok, just so I'm clear on this, the needle jet is the entire main jet assembly or the small screw-in jet bit?

Thanks once again
Click to expand...
The main jet screws into the "bottom" of the needle jet, or as some call it, the emulsion tube or bleed pipe. It's long. It has an o-ring on it.
 
Hey Keith (and all),

I'm sure you are dying to know how things are progressing! :lol:

Well, I decided to bite the bullet and use (and clean) the newer carbs.

After looking more closely at the newer carbs, it's obvious that they carb bodies are slightly different. It looks like there are more internal passage on the sides around the air jets. I was also told by a knowledgeable friend that the slides usually wear to the carb bores, so swapping them around to different bodies might cause problems.

I will be changing the jet to the #107.5s. I will also be placing the needle on the lowest clip setting.
 
Oh also forgot to mention... the same friend recommended I use Yamaha Combustion Chamber Cleaner to clean the jets.

I just tried soaking all of the brass components in the mixture overnight and I have to say the transformation is amazing.

The brass comes out looking SHHIIIINY... Kind of like when C3P0 was all cleaned up at the end of StarWars.

I picked some up at a local Yamaha dealer for $5 a can... not bad.
 
Sorry to answer this so late. Not sure where you're at with it.
Any differences in the two carb sets (besides the slide assemblies) was what I was afraid of. If identical, except for the better designed throttle slides on the newer carbs, I would go with the newer slides installed in the older carbs (since you had them all set up/cleaned) or just clean up the newer ones and use them. But with the differences you now mention, you can't swap slides. So you would either have to use the older carbs complete, or the newer carbs complete and hope there's no unseen changes made to the newer carbs that would cause carburetion problems. I think your decision to use the newer carbs will work. Your friend is right about how the slides can wear to each carb. I have successfully swapped slides around with no problems, but vacuum problems can happen. Since you're using the newer carbs complete, you don't need to worry about that.
Reading back, your plugs were black and sooty you said. You also said the original carbs had the jet needles in the 4th position. The needles come from the factory in the 3rd position, so raising them just one position shouldn't be the cause of those black plugs. I'm sure the black plugs were the result of those 27.5 pilot jets. It still would depend on exactly what throttle positions gave what reads.
Anyway, with your mods, try the 15 pilot jets and see if richer pilot fuel screw adjustments will work for the pilot circuit.
Because the Emgo's don't flow as well, theres some chance the jet needles may work in position 4, but I'd guess position 5 or position 5 with a jetting spacer above the e-clip (same as position "4 1/2") would be more likely to work.
And once again, you said you want to try the 107.5 mains? They won't work! Stock is 102.5. I have to believe you need something closer to 120's to 125's. Going up one full size to 107.5 is simply too lean. Trust me on this. :)
Mark your throttle housing and grip. Test the jet needle performance at solid 1/3 throttle. Test mains wide open.
 
Thanks Keith,

I went with the 107.5 because they are the biggest I have. I assumed that would have a higher chance of making it work "reasonably" well. I have the needle on the lowest clip.

I'm keeping my eye out for a DynoJet kit, but I can't find anything for the 77-79 GS750.

That same friend is offering me a GS750/850 motor (Wiseco 850cc pistons, trued crank, valve job, shaved head) with CV carbs in exchange for some other work, so I don't want to spend to much on this current setup. I was just hoping for a couple of weeks of riding this year.

Thanks again, I'll let you know how it goes!
Patrick
 
Well, regarding just the main circuit performance, the bike will run but the top end will suffer. Going up one full size just isn't nearly enough for your mods. I understand why you're using the 107.5's, but at least you know what to expect.
 
Ok... So I figured out that jets are pretty common, cheap and that most stores carry them... who knew? :oops:

I tried to run the bike on the new carbs with the #15 pilot and it was WAAAAAY lean on idle... the plugs looked brand newm even with 2 1/4 turns out on the pilot screw.

So...

I picked up some #125 mains, and I'm waiting on some #20 pilots. I hope that works. I just noticed, now, that you had recommended I use #17.5 pilots in an earlier post. Did I go too large?

Also, should I then reset the needles to 4th position? I have it in the bottom clip (position 5, I think). I'm not sure what the effect the pilot and main will have on the needle position.

Thanks!!!!!! :D
 
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