Low secondary resistance on coils

[Anonymous]

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!

[KEITH KRAUSE]

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.

[Anonymous]

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

[KEITH KRAUSE]

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

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.

[Anonymous]

Hey Keith (and all),

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

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.

[Anonymous]

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.

[KEITH KRAUSE]

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.

[Anonymous]

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

[KEITH KRAUSE]

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.

[Anonymous]

Ok... So I figured out that jets are pretty common, cheap and that most stores carry them... who knew?

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!!!!!!

[KEITH KRAUSE]

There can be overlap between jetting circuits, but when starting out, don't worry about that. Help yourself by marking your throttle housing and grip. This will eliminate guessing and give you the most accurate info. Just test for the main at full throttle. Test the jet needle at 1/3. Test the pilot circuit at minimal throttle opening, 4th gear at about 35 mph, level/uphill.
I'm assuming the leaness you just mentioned about the pilots was at the correct throttle position? You didn't mention how/where you set the side air screws??? These MUST be adjusted for highest rpm, but not beyond that. If you did adjust them and its still lean...
Since the 15 pilots with pilot screw adjustments didn't help, I would try 17.5's. Normally, the 17.5's work fine. If you try the 20's, who knows? But they aren't normally needed.
Just leave the jet needles at position 5 and test, since you have them there. Always best to start possibly rich and work your way back.
Your re-jet will be more difficult without a vacuum synch.
Don't take this the wrong way, but since you're acting on my advice, please read all the info. Like you said, you just noticed my pilot jet info. This makes me wonder if you also removed the two floatbowl vent lines, etc, etc. Re-jetting can be difficult enough without the mis-communications. I'll assume you did something as I suggested and then not understand whats going on if you report negative results.

[Anonymous]

Thanks Keith... I actually wasn't planning to buy the jets, but I was driving near my local bike shop and decide to check while I was in the neighbourhood. I'll see if I can pick up some 17.5 jets also.

I've been following your suggestions, I try to let you know about everything that I tried (or don't). Please forgive me!

I know exactly what you mean too... I used to work in tech support in the mid-nineties when the internet was just starting! Try teaching grandma how to use a mouse and click on a "window"! Or try troubleshooting someone's PPP settings!!

Ok... enough jokes here

The carb vents are open & I bench sync'ed according to your instructions. The leaness that I noticed was only from idling for a few minutes. I figure if I couldn't get any color idling, I should take it for a spin. I'm a worry wart.

I also wasn't able to hear much difference when changing the air-screw setting. I left them around 1 1/2 turns out.

[KEITH KRAUSE]

OK. Running the bike only a few minutes isn't a good test of the pilot circuit. You have to ride around a few miles, or more is better, to get a read. Run errands or test while going to work or something like that. A steady 35 mph or close in taller gears (4th/5th) on level/uphill roads will give you the best idea of how the pilot circuit is working. You want the throttle at minimal openings. One problem here is you haven't vacuum synched the carbs. Its hard to know what the cylinders are saying if you have uneven plug reads. You don't really know which cylinder/read to use as a "base".
The pilot circuit can take awhile to fine tune and thats after you've made the right pilot jet choice. Theres a lot of tinkering available between the pilot fuel screws and the side air screws. Keep records of adjustments and the results. Besides plug color, you need to pay attention to performance, such as idle quality, warm ups, any spitting out the carbs, how it re-starts when hot, etc.

[Anonymous]

Ok... gotcha.

I will run the bike with the 125 mains tonight and see what I get. I will leave the #15 pilot jet and put the screw at 2 turns out.

Also, could you give me any pointers on setting the air screw? Like I mentioned before, moving it around doesn't seem to affect the RPMs. My idle is set at ~1100rpm.

Thank you.

[Anonymous]

Ok... nevermind the airscrew setting. I was just really far from the "sweet spot" that the revs would never climb.

I took it for a spin (before setting the airscrews) and I was running rich but I think it's partially due to the air screws being too far in.

I ran out of daylight so I will try again tomorrow. I also installed the #125 mains and set the pilots screws to 1 1/2 turns out. I'm keeping the #15 pilot for now.

Many thanks again, Keith. I think I'm almost there!