Sooty Plugs

Well folks eventually i got my scoot on the road for the first time today after 2 years( thanks for all help), just done 6 miles local . havnt been on a scoot in 20 years - clutch takes a bit of getting used to and the ride was bouncy, dodgy with no little/no front brake but great fun.

motor did miss twice or 3 times more in second and third gear, i think i havnt dialled the high speed needle in properly yet. im running OEM plugs no 3's and when i pulled them they are black and sooty(dry). i done the leak test before(twice) and tried the condenser,points,& coil &all were Ok so im hoping its just running rich.

i havent tried to adjust the high speed needle while driving it but i guess its the next step, when i advance half way and blip the throttle while stationery she is popping in the end of the exhaust - that would indicate rich wouldnt it?

appreciate any advice

regards
Steve

Popping in exhaust usually means a leak at the pipe to barrel joint.

Wilko,
ive the pipe to barrels sealed with red silicon so id say i can rule out that one.

[Pa]

Is the float sticking a bit ?

great to hear your on the road steve, happy blattings, jib

Pa its a possibility and one i need to investigate fully, swapped the old logged float for a rubber ducky awhile back and thought i checked it wasnt hanging on the bowl and was correct distance from top,but could be hanging on the centre nozzle chamber maybe!
Does the bowl spring keep the nozzle firmly at the top of the shaft into the venturi or does the nozzle actually move up and down in the shaft during operation? my nozzle fitted firmly enough from memory, if it has to move up and down inside the shaft mine might not be doing that- is that another possibility or is the nozzle always in the same position?

JIB thanks - good to see it goes - heres hoping i stay vertical

regards

Steve

Steve!

The spring should hold the nozzle firmly against the venturi.

If the nozzle spigot and/or the venturi hole are worn from rattling about, performance and tuning are compromised.
If the venturi is loose in the bore, it will rattle upon the spigot as well, and any daylight around it adds another performance and tuning compromise.

If your low-speed needle is dialed in fairly well when warm, then find a safe straight-a-way where you can cruise at a steady speed above thirty mph (48 kph). Turn the high-speed knob in leaner a few clicks at a time, waiting several seconds each time for the circuits to equilibrate.

When the exhaust note goes tinny, or the motor begins to falter, back the needle out in the same fashion, counting the clicks until you find the limit on the rich side. Then turn the needle back in half the number of clicks.

At this point it is usually best to pull over and re-adjust the low-speed. The circuits over-lap, and the low-speed actually controls air at higher RPM. So tuning is a matter of tweaking the needles alternately for a finer and finer adjustment. Your return trip on the straight-away should require just a couple of clicks to find the high-speed sweet spot.

If accelleration problems persist, then inspect for the problems mentioned earlier, as well as borewear from the throttledisc, etc.

Good luck!

....Cotten

Thanks for the reply Cotten,
The nozzle is NOS and is firmly against the venturi and it doesnt rattle- i was just concerned that the nozzle might need to move in operation. (least i can rule that one out)

The venturi is firm with no daylight. Low speed needle(OEM) seems to be dialling in fine and high speed is a NOS one backed out 1/2 to one turn which seemed to be the optimum in stationery postion. unfortunately it is the high speed needle with the screwdriver slot so i cant count the clicks, but i can still try and diall it in on a straight road.

i know its only something small causing the plugs to soot but its elusive.

what sort of float do you have steve?

Steve!

The military needle was designed to be left fully closed, to allow all control through the fixed jet.

So, if you intend to use the military needle for adjustment like a "civvy", the fixed jet is best removed and plugged, to put control back within the needle taper's range of sensitivity.

Please remember that the highspeed needle will have little effect until the machine is operating over 30 mph.

Larry Elias of The Netherlands produced adjustable HS needles with knobs that look like the cap over the military needle. They are available through most vintage H-D vendors.

Good luck!

...Cotten

Thanks Cotten,
i wasnt aware of the removing and plugging of the fixed jet and the Larry Elias needle - i must arm myself with one of those and plug that jet.

tool her for another burn today and screwed in the high speed needle all the way and readjusted the low speed.Had her at 40 and she was happy out with the odd miss and pulls away fine on a hill with the advance/retard on.She was sometimes unresponsive /missing when taking off both before and after the low speed was adjusted.

Heres a photo of the plugs - the porcelain centre and metal electrode are not sooty just the threads and bottom of the plug are - am i reading this correctly - i presume the bottom of the plug should be more of a light brown/tan colour.



JIB im using the rubber ducky float as it was the same weight as the original . i heard there were a few problems with the brass ones.

That is about what my plugs look like.

I don't think that the metal is going to get hot like the insulator. And will always have a bit of soot on them.

I have Cottens DuraFloat in the M88, float level set to specs. Brass floats, DON"T .. and will give ya nothing but heartache, and issues that can be solved with just changing the float.

PEEK seals (also from Cotten).

Try riding more with steady speeds and let everything settle down before adjusting the carb anymore.

Na,,,, no kickback from Cotten

George,

PS, make sure that all your electrical connections and grounds are clean and tight...And do a double check on the exaust system. My WLA had issues, till I found the rear cylinders pipe had a small leak...I silver soldered every joint & seam on the repo muffler, every part on it was loose. All tight now.

thanks George,
its comforting to know the plugs dont seem too bad after all.

i did read in a few of the forums about the peak seals but assumed (wrongly) they were only used on Knuckleheads

i guess i will have a better stab at the carb diall in when the driving becomes less eratic

i read one of your old threads George where you had a similar problem with plugs and I thought i might have a bad connection at my timer to coil cable, i replaced it and it made no difference .(needed to be replaced anyway).

i do have a pinhole in my pipe at the first welded joint from the front pipe of the engine. (havnt located it yet).

regards
Steve

Steve,

I should also mention... my plugs.

They both look like the one in the photograph at the the top.

Both insulators are a tan brown color, and they both have the dusty (not oily) soot on the bottom of the threads.

I use MMO in the fuel tank as well, and that will cause some of the soot buildup on them.

Get the PEEK seals for your manifold.

And make, if you don't have one a tool to pressure test the system.

George

as a general comment on plugs, the area around the bottom of the threads will often be cooler than the centre electrode due to conduction of heat through the threads into the metal of the head. I normally reckon that if the centre electrode is a clean dry tan colour, whatever deposit on the outer circle is dry and the throttle response is ok, then the mixture is as good as you will get.

the inlet manifold will cause more problems than everything else combined. If this isn't fully airtight, it just has to be so +1 for the best seals you can find for this area.

+1 for the seal on the numerous joints on the exhaust. I also use a flexible sealant for all such joints, especially the port/header pipe joint ( ie between the cast surface of the barrel and the steel pipe )

+1, also, for the variable quality of internal and external welds on after-market silencers