Low secondary resistance on coils

[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! :wink:

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!! :lol:

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!

 

[Anonymous]

Ok, I'm still running rich (or sooty?)... I can see that the inside the spark-plugs is getting a little tan, but the electrode is black. This was after driving around at low speeds (very small throttle openings) for about 15 minutes.

Here are my settings so far (and a recap)

Pilots: #15
Pilot Screws: 1 1/2 turns out
Air Screws: Set to highest RPM

Needles: Stock, set on lowest clip (#5)

Main Jet: #125

Floats: 26mm
Vents: Clear

Filters: Emgo

What should my next steps be? Lowering the needle a notch? I find that I get a lot of smoke when I blip the throttle in idle.

 

[KEITH KRAUSE]

OK. Sorry for delay, had some server/modem problem.
I'm assuming the "smoke" you mention is dark/heavy exhaust.
Also, so we're on the same page about the plugs, by the "inside" of the plug, I assume you mean the center electrode that's surrounded by the ceramic? The ceramic color is what we're reading. And by the "electrode", I assume you mean the ground electrode, or tip? Plugs are gapped correctly too?
And please record and tell where the side air screws are set. How many turns?
That float level seems lean. Seems something closer to 24mm is right(?)
Anyway, because of the overlap effect between jetting circuits, you need to provide plug reads at full throttle, 1/3 throttle and the minimal throttle positions (as you did). The results will help me to help you.
Part of your dark minimal throttle reads could be effected by the jet needle position, just as needle reads/performance can be effected by the main somewhat. Get reads at a solid 1/3 throttle position. Mark your throttle and grip to be sure. Be sure the bike is completely warmed up/hot. Run a good mile or so, even if you have to momentarily back off a couple times due to conditions. Basically, you want a fair amount of time for the plugs to color up at an exact throttle position, so a steady run of a mile is better than having to break up the run. Same for the main, only at full throttle. "Chop" the bike off and read the plugs. Take a rag and piece of hose that will fit snugly over the hot plugs to help you remove/re-install. Let us know if the needle circuit plug color/performance is acceptable first. I'd like to get the needle circuit right and then see if we can make the stock pilot jet work with screw adjustments. Then we'll do some wide open/roll on tests for the main circuit.
As always, I feel a little funny suggesting high speed testing, not knowing your roads/traffic/skill level. Please be careful. Without a Dyno, this is really the only way to find out how the bike performs.

 

[Anonymous]

Hi Keith, and anyone who reading this, I'm back.

1st, yes, the smoke is heavy black smoke when I "blip" the throttle.

Yes, by the inside, I meant the ceramic portion, but deeper into the plug. Plugs are gapped to 0.028 inches.

The side air screws are at 1 3/4 turns out, except for cylinder 1 which is at 2 turns out.

The float level of 26mm was recommend by Earl at one point and it's in my service manual (25-28mm). I just remembered, though that I have carbs from a 78, now! DOH! The clymer specifies 23-25 mm for the 78-79 series. Back to the garage

Anyhow, I did some testing today with the same settings as above except I moved the pilot screw to 1 1/4.

My 1/4 throttle run showed that I was lean on 2-4, but 1 was a almost perfect (still a little lean).

My 1/3 throttle run showed that I was rich on 2-4 and almost sooty on 1.

My I wasn't able to do a 1/2 throttle run as there was just too much traffic, even in the country roads (it's Thanksgiving in Canada and everyone is travelling).

If I read this correctly (maybe I'm finally figuring this out), I think my pilot curcuit is a little lean, but my needles are maybe too high.

Action plan:
Readjust the floats to 24mm
Raise needles 1 clip
Put back the pilot screw to 1 1/2
Try again!

Does that make sense? I also gather that I also really need a good carb sync, but riding season is quickly ending here, so I think that will have to wait till next spring, if I still have the same motor. I would just like to get it stored and working properly for my enjoyment next year.

 

[KEITH KRAUSE]

OK. I just gotta say that when you get uneven reads across the plugs, you have no idea if or how much of the uneven reads is related to a poor carb synch. Without all the vacuums being verified as close to each other, we're just guessing here. Now if your reads were all basically lean or rich at a certain throttle position, then we could at least blame a certain jetting circuit for those reads, but not with uneven reads. You also don't mention #3 plug reads. The pilot circuit test must be done at mimimum throttle opening, just above idle, slowly cruising, not 1/4 throttle. I've found that testing at minimum and 1/3 effectively separates the two circuits enough and gives you honest reads of what each circuit is doing with the least amount of overlap effect. Testing at 1/4 then 1/3 is too close together. All I can really make of your reads is that the slides are going up a bit more and the mixture appears to be getting richer. Your first reads you stated were at minimum throttle but your latest reads are at 1/4 and then 1/3. The latest reads should also be taken at minimum throttle, then the 1/3 test is OK. I'm guessing that your 1/4 throttle read is being effected a lot by the jet needle, but the 1/4 test doesn't help much on what we need to do with the pilot circuit. Like I said, more separation is needed.
Re-jetting on just a bench synch leaves questions. We can't add any more things to make it more difficult. I also understand about not being able to test the mains safely, which must be done at full throttle by the way, not 1/2.
So I don't know what to recommend because the procedure is being altered on me. I need true minimum and true 1/3 throttle reads/performance notes to make a helpful suggestion.
So the best suggestion I have is based on what you're thinking in your last reply. Yes, the floats should be adjusted to the correct factory levels FIRST.
As for the jet needles, it sounds like they're rich. Since you don't have .023" thick jetting spacers to make a 1/2 position change, then you can put the e-clip in the 4th position (second from the bottom) and test.
Without a true minimum throttle test for a couple miles, I don't know what to say for the pilot fuel screws.
If testing for the main isn't possible now, at least try a roll on test. If the jet needle operates well (this means the plugs/performance are acceptable at 1/3), then you should be able to ride the bike in 5th gear at 55-60 mph and fully open the throttle as you would in a serious passing situation, WITHOUT any bogging/hesitation. The throttle should be rolled on as normal if you know what I mean, quickly, but not "whacked" open which is not normal riding and could momentarily "fool" the carbs and give you a false read. If it bogs with those 125 mains and takes a while to start pulling, then the mains are probably too large. If it pulls well, then the mains are close or may be good. Though this roll on test is not a complete test, it at least means the mains are close pending a top speed run.

 

[Anonymous]

Two words... CARB SYNC :lol: I'm all over the place... Sorry about the lousy testing on my last post. I had the 1/4 test in mind because I was reading the Mikuni VM tuning guide.

I reset the floats to 24mm and moved the needles to position 4.

Ok, again due to traffic constaints (and not having time to travel very far), I could only do 1 mile runs.

Minimum throttle: 1&4: almost good, slightly lean. No brown. 2&3, slightly more lean.

1/3: 1&4, rich, electrode clean, though. 2&3 slightly lean. No brown.

60mph roll on: Good. No noticeable bogging. I think I could go down to a 122.5 though (to make it slightly more crisp).

So, because I'm not sync'ed I can't tell much. It LOOKS like maybe one of my coils is weak, but I can't tell without swapping. I also have some gixxer coils coming in a few days... if next weekend is still decent I will test some more with those.

I also noticed 2 backfires later in my run when I was coming to a stop. I was not engine-braking noticeably.

Thank you very much again, Keith.

 

[KEITH KRAUSE]

If you think you have a weak coil at 2/3, then I'll just wait 'til you replace the coils. However, those reads could very well be attributed to uneven vacuum levels, so you may be doing work for nothing. Without the carbs synched, I just don't know what to say next. Synching is a mandatory part of jetting.
As for the pilot circuit, those reads could be corrected by simple pilot screw adjustments, but like I said, because of no vacuum synch/unknown levels, how can we say if the uneven reads are vacuum or screw related?? We can't. And if you just decide to play with the screws to "even" things out better but the reads are because of the uneven vacuum levels, all you've done is compensate and compensation jetting never works. I hope you're following me on this. The screws and vacuum have to be set at their best settings. You can't combine a lean pilot fuel screw setting with a richer (more vacuum) and expect them to counter each other. The bike won't run right if you try.
As for the jet needle positions, there's simply no way the bike should run well at any leaner position, so I suggest you leave the needles at the 4th position in case you were thinking of leaning them further. The factory needle position is #3. With your mods you would AT LEAST go to #4 position. After a carb synch with a vacuum tool, I would re-test for that circuit.
As for the main, you basically want the main that allows the highest top speed WITHOUT creating any bogging during roll-ons. I would NOT go leaner on the main at this time because you haven't tested correctly/completely for the main yet and without a carb synch you can't blame the main for any "lack of crispness" during a roll-on. Varying a little from bike to bike, there is still some jet needle overlap during these roll-ons. So leave the main also until these carbs get synched properly.
We're kind of at a dead end here. I've always said that the carbs need synching unless you were very lucky and got uniform reads we could adjust. You don't have uniform reads. To allow for your situation we've tried to get around a vacuum synch but it's not working. Though it's possible a weak coil could be part of the problem, I doubt the synch can be put off regardless of what the newer coils do for you.
Anyway, I'll wait to hear from you and I'll try to suggest something to help get you by for a while if you need it.

 

[Anonymous]

Agreed. I can't really tune at this point with these uneven reads.

My next purchase will certainly be a MotionPro or a Carbtune II.

We'll see if the new coils make a difference, but somehow I doubt it.

Thanks for all of your help to this point. You've certainly educated me quite a bit in the ways of carburettor tuning 8)

Cheers!

 

[KEITH KRAUSE]

Just trying to help. Get the carbs synched and we can go from there.