Need help reading plugs please

[ontherocks]

Hello all,
I have been tuning my bike by observing the color on my spark plugs, using info from strappe.com and other sites. However, alot of spark plug pics are black and white or the same pics from the 70's with bad detail.
I am posting pics of my plugs and perhaps some of you can give me hand with your observations and expertise.
I have a slight stumble in upper 4th and 5th gears when rolling on the throttle. Drives me crazy. I can back off the throttle just a hair when it happens and it will go away. Or I can power through the stumble and acceleration picks right up after a few seconds.
I just can't seem to tune out this little bit of hesitation.
Here are the specs on what I have:

1.Bike: Bobber with 1975 motor
2.Carbs: 78-79
3.New Accel 140403 coil. 3.3ohms primary. 21k ohm secondary including the 5k caps.
4.Pamco ignition
5.140 main/ 30 pilot.
6.stock exhaust headers cut off right under the m in yamaha on the right side cover. 2 ft of 2 inch pipe welded on with 4 inch baffles. no leaks.
7. Cam chain adjusted to within 1mm in and out when running
8. Valve lash adjusted cold. .002 intake and .004 exhaust per chilton manual.
9. Timing set dead nuts on the timing mark with timing light.
10. Mikes xs performace pod filters.
11. Dead Cylinder method performed seeking highest idle. left mix screw at 2 1/4 turns. right screw at 3 turns.
12. synced using manometer before and after dead cylinder method.

Just trying to give you complete information to go by before diagnosing.
Her are my plug pics for your viewing pleasure.
And yes, ipad2 camera is less than stellar.

 

[ontherocks]

I think fuel color deposit on insulator looks ok.
First two threads have deposits which is good from what I've read. Base ring has nice dry soot all around.
I might be able to retard timing a bit to get the deposits right in the middle of the 90 degree bend on the ground strap.
My mixture ring is right at 4mm. I have read that 2mm is good for non-racing conditions.
These plugs have about 200 miles on them.
I should probably reduce right mix screw to even out color between the two plugs.
Not sure what to do next to get mixture ring reduced and get rid of stumble in higher gears.

 

[5twins]

I think those plugs look too rich. The mixture ring is too high, especially on the right one. You made no mention of your needle setting. You should probably have it leaned a step with 2 up on the mains. Needle position will do a lot for plug color because it controls your midrange and that is where you do the majority of your running. Leaning the needle setting should also help with that stumble.

 

[ontherocks]

Thanks 5twins. My needles were at the 3rd slot. I have dropped the needle one notch as suggested. The stumble is much improved. 2nd and 3rd gear is nice clean power through WOT. 4th gear has just a tiny bit now. 5th gear definitely has less now but lasts 2-3 seconds more than before? I installed new plugs and put about 30 mi today so will post a pic once a cut them open. Ceramic on the plugs is much lighter now as well.

Btw, that circle clip that retains the plastic piece on top of the needles is a pain to get back on. Is their a trick to that?

 

[5twins]

The best tool I've found for that slide e-clip is the long nosed 90° snap ring pliers that MikesXS sells for master cylinder work, part #35-0009. They work perfectly.

I would also reset the valves to .003" intake and .006" exhaust, 2 and 4 is a bit tight. Then revisit mix screw settings now that you've leaned the needles. That 3 turns out on the right carb doesn't sound right. There may be something off in that carb like the float level or an air leak. Mix screw settings should end up pretty closely matched between the 2 carbs.

 

[grizld1]

A few points here, ontherocks. First off, you need to reread the Jennings article. Deposits on the ground strap can be informative on heat range selection, but it's the clean-burn line on the electrode tip that tells you where to set ignition timing. Second, when selecting mains, you can get very little useful information from a plug that's been used in mixed riding. The smoke ring at the insulator base is read to select main jets and yields significant information only from new plugs read after a full-throttle chop following a run of no less than one and preferably two miles with the slides at full lift, which on BS-series vacuum carbs will occur only at rpm's north of about 4500.

You'll get better results from selecting mains by engine function, which will allow you to work at lower speeds with less risk. Try this. Drop your mains three steps. Then ride gently till the engine is at full warm-up, get rolling in 2nd at about 4500 rpm, and quickly roll--don't snap--the throttle wide open. If the engine cuts out or hesitates sharply and recovers when you reduce throttle, increase MJ size by one step and go again. When you find the size that yields no hesitation, go up one step; that's rich enough.

 

[ontherocks]

Thanks for the tips 5twins. I'll perform another dead cylinder method to set the mix screws again . Hopeully I can get them a little closer to each other than before.

Grizld1, i reread the article and understand what he was saying about the electrode tip.However, the electrode on the autolite 63 plugs I use are black from the factory and hard to read. I have since bought a box of NGK BP7ES which are nice and chrome everywhere. Seems like a much nicer plug overall and will be easier to read.

I thought that the timing would be indicated on the ground strap due to this video on youtube.

I have also been using the info further down in this link http://www.rays-shop.com/ (Jan 16 post) for what to look for for average throttle position while riding.
I would like to read plugs using the plug chop method as it is a skill i would like to learn.
I'll also try your method based on engine function as that seems like a really good way to do it too.

Now I need to figure out how to resolder the tip on my broken throttle cable before I can continue testing.

Ill keep updating until i reach conclusion and i get rid of that stutter in higher gears.

 

[ontherocks]

Update:
Ive been experimenting with plug chops and rolling the throttle to WOT to verify main jets.
Always using new plugs for each run.
I've concluded that 140 main jet is right for my bike.

5twins, leaning the needle definitely helped with the stutter in higher gears. Plugs look much better. I performed another dead cylinder and synch and got 2 turns on the left and 2.75 on the right by setting it right before the idle sounded highest.
Here is the pic.

I tried the ngk b7es on the same route. Lots of big hills, curves, and straight runs to give a good mix of riding conditions. My bike does not care for these slightly cooler plugs. Maybe the extras I have will be useful in the summer. I will stick to autolite 63 as they run good, cheap, and easy to pick up at the store. You can see it in the third set of plugs in this pic.

After spraying carb cleaner all around looking for air leaks, my right throttle shaft seal is sucking in air. I dabbed some lucas transmission fix fluid I had laying around hoping it would swell the seal a bit. Then i placed a little three inch piece of fuel hose over it and plugged one end of it. retested for air leak and its gone. Temporary fix until I can replace those seals during the winter.

Performed another dead cylinder and synch with this temporary fix. 2 turns on the left and 2.5 turns on the right. This is as close as I can get it without excessive popping through exhaust on the right. Her is the pic comparing my newest set of plugs(on the right) to the plugs I cut right after leaning the needle(on the left).

Conclusion;
I think I'm pretty happy with the performance now. I have a few one second stumbles in high 4th gear or mid 5th when gunning it up the steepest of hills. Occasional pop on fast deceleration. This is the best my bike has ever run. Hauls some serious ass. I think I need a fork brace now. My OCD will cause me to chase those stumbles though. Will be asking for unifoam filters for Christmas

Can anyone verify the uni foam filters are better?
Anyone use a hoop style fork brace like gordonscott sells and can comment on them?

Thanks for all your help!

 

[5twins]

Yes, the UNIs are better. The carbs on my '78 are jetted exactly like yours now that I have the UNIs. Before, with the K&Ns, I was only able to run a 137.5 main, one size up over stock. Anything more produced stumbles in the upper midrange even with the needles leaned a step. I put the UNIs on and was able to go up to a 140 main with no stumbles. I may even try a 142.5.

 

[ontherocks]

Im looking at uni UP4200 or PK82.
PK82 are nicer looking with the endcaps but has less filter element.
Does length matter on the filters?
The double filter red one are nice too but may have too much filter material?

Also, for those of you with an accel coil, what plug gap are you running at?
I could not find voltage output specs on the accel ultimate coil and have been running the plugs at .030. Think I will try .035 on the next ride.

 

[retiredgentleman]

I have an Accel super coil, and I use 0.035" gap..............works just fine.

 

[5twins]

I think length would matter on the filter. Longer gives you more filter area. I run the UP4200 on my '78 and it seems to work well. If I buy more, I will get the dual layer to try out. If it's too much, you can just take the red outer sleeve off and you're left with the regular plain black pod. Seems worth a try since it's only about a dollar more. I've never tried the short PK82s so I can't comment on them.

A word about oiling these black foam pods. The regular foam filter oil may be too thick and clog them. It's recommended that you use a 50-50 mix of gas and motor oil. I bought a bottle of cheap Walmart brand straight 30 weight to use.

Switching to the UNIs should cure the last of your stumbles.

 

[ontherocks]

RG, thanks for confirming you're plug gap. That really helps me feel better about opening the gap with this coil.

5Twins, I think I will go with the dual layer ones as you suggest and see how they work out. I like the red anyway
And thanks for the tip on oiling them. I was actually going to by the foam oil spray, so thanks for saving me some money.

I will post an update with the results when I get a chance to test them out. I'm trying to hurry before winter sets in.

 

[grizld1]

The red prefilters add very little restriction--unless you get them wet. And right, if you use a spray oil with UNI filters, use the UNI product. K&N and some other filter oils will make a real mess on UNI pods.