intermitant miss -- nearly solved!

[YellowJacket!]

ahhh grasshopper,,,, welcome to the world of different altitude!!
1. your bike is set up to run it's best at or near sea level.

2. you are no longer at or near sea level

3. your bike may be in need of a change i had to make, just in reverse!

  i moved from high altitude to lower, and ended up running way too rich- you went from low to high, and may now be too lean,   i rejetted, based on dyno readings during a bike week, and run great-- hate to say it, may be time to rethink your jetting, maybe try stock jets and see where you go.

  i know is a lot of work,,  but then , the dragon is so close, and the bike does love to roll in front,,,,,,

Shouldn't be much of a difference here as we are only 900 to 1200 feet above SL.

David

[Phatjap]

Thought I'd just update.

just replaced the offending spark plug and OMG, what a difference! Not a single stutter anywhere along the rev range! Thats with leaving the carbs where I had previously messed about them in no particular place.

Just goes to show how critical the plug is....I'd say change them anyway, for what its worth and what they are worth.

Feels like a new bike!

[hfarley]

Hey Lucky!
Not to change the subject here but what exactly is " arc trail from the coil..." You know as I read what people have suggested to help you I learn at the same time. But I am not quite sure what that term is that you used. Could you explain it to a constantly learning wrencher like me? Thanks!
-Heather

[Lucky]

Heather,
by 'arc trail from the coil' i mean that when there is a constant spark jumping from place to place, it leaves a burn mark.  when high tension (meaning voltage/amperage) ignition components age, they can crack (plug wires, etc) allowing the spark to jump to ground.  any components in an ignition system that produce & carry spark to the cylinder are refered to as "secondary" the part of the system that is regular 12V is known as "primary"



diagnostic update

I made a pony tank & hooked it up. i pulled the lowers, tank & airbox.

i inspected the coils, wires, caps & pulled the plugs everything looked fine.  i checked the connectors for the coils, still clean & shiney & the light coating of grease was still good.  no arcing seen in the dark....

i'm no closer than i was before, except that i have verified that the ft cyl will act up as well, although not nearly as often....

AAARGH!

[Night Vision]

here's something that doesn't get mentioned often... but how about checking your timing?...

might end up on the eliminated list... but seems like a quick and easy check on the TCI

[Lucky]

tomorrow i'm going to throw on my oter set of carbs. untested, & not recently dipped, but as long as i can get them running it might the carbs if it doesn't miss.  also, my intakes look pretty ratty so i might coat them with liquid electrical tape.

i forgot to mention yesterday i also loosened the screws on the choke adjusters so i could operate them indepentantly, & got very different reactions moving the ft & rear ones..  one thing i've allways noticed, I've mentioned that they are allways either 'on' or 'off'  i might try tapering an extra set slightly, or something & see if it makes any difference...

--Lucky

[JakeC]

Well, unless you can determine it is the carbs, I would say it sounds like the fuel pump or regulator.  The odd thing is, it sounds almost exactly like what I am dealing with right now, except that mine does it while I am driving.  I had the bike tuned just about perfect.  I went cruising with a buddy of mine for a couple hours and it ran flawlessly.  Got on the freeway to drive home, and I noticed a slight miss at around 70 mph.  It has progressively gotten worse and worse.  Now, if I drive at 5000 rpm's or more for more than about 10 seconds, it will start to misfire.  I'm not talking about a stumble here, either.  Definitely a misfire that has slowly gotten worse.  I have eliminated almost everything,  checked wires and plug ends, replaced sparkplugs,  filled tank and ran it on prime with gas cap off, checked voltage (14-14.4), pulled carbs apart again (they were spotless, even jet on bottom), replaced all fuel and vacuum lines, replaced fuel filter, plugged yics lines, well, you get the idea.  Anyway, I also pulled apart the fuel pump and the regulator.  Everything looked fine except that the rubber stopper in the regulator (which isn't included in the rebuild kit) looked a little mishappen, which is what I think may be my problem.  I don't think it is allowing enough pressure to build in the fuel system to keep my bowls full.  I am only sharing all this because I know that at least for myself it helps to see what someone else has done.  This thread has been very helpful for me at least.  My solution, I have an electric fuel pump ordered, and all the plumbing sitting here waiting.  It's an '82, so I will add a return line, but I think it should work.  Hope you get it figured out!!

Jake

[Lucky]

Ok, i think i got it!!!!

I started by testing the coils & pick ups per the book.  the pick-ups passed aces, the coils & wires however, showed 14.9 Ohms when they should have been 7.something.,

I gave Tdub a call, to ask him if he thought that could cause my symptoms, & we came up with a couple of more tests to do. (pickup continuity, etc)

the coils themselves, without wires & caps, etc came out at 8.2. the coils & wires should have been almost nothing (the wires were.2, & the caps were .5 ohms, which is correct)

i swapped out the rear plug because i was getting good spark at the cap, but the cyl felt like it wasn't firing, no change...

In one last desperate attempt at eliminating the carbs, i swaped out mine with the ones from Leather, straight out of the box, uncleaned & untested.  i made sure the hoses were good & gave it a try, it didn't catch right away, & after fiddling with the pilots & synq a bit, i got it to idle.

And it idled SMOOTHLY!!!.  NO MISS!!!

i synqed them & put the Irradium plug back in (no change) & it started, ran & blipped well, although i don't think the accelerator pumps are firing, i think i just need to clean them up..  i have new diaphrams in a box if i need them, but it's probably a bit of sludge in there too.

a quick blast around the block proved the accel pumps weren't firing, otherwise i'd take it to work tomorrow..out of time today to mess with it, oh well,

but AT LEAST THAT DAMM MISS IS CURED!!

carbs, carbs, it's allways carbs!!!  i'll have to tear into this one to see what's screwed up on them, but no rush for now...

Hot Damm!

--Lucky

[Tdub]

Glad you got it done Lucky!! I would have lost the bet cause I was sure it was ignition related. Tdub

[Lucky]

I think it was that stupid accelerator pump control valve.  i rebuilt it last year with parts from the Keyster kit, & the almost clear 'valve' gasket had kind of disintergrated when i took it apart tonight. i'm going to look at the controll valve & see if i can disable it on the 'new' carbs.

Egg and bacon
Egg, sausage and bacon
Egg and carbs
Egg, bacon and carbs
Egg, bacon, sausage and carbs
Carbs, bacon, sausage and carbs
Carbs, egg, carbs, carbs, bacon and carbs
Carbs, sausage, carbs, carbs, carbs, bacon, carbs, tomato and carbs
Carbs, carbs, carbs, egg, and carbs
Carbs, carbs, carbs, carbs, carbs, carbs, baked beans, carbs, carbs, carbs and carbs
Lobster thermidor aux crevettes with a Mornay sauce served in the Provençale manner with shallots and aubergines, garnished with truffle paté, brandy and with a fried egg on top and carbs


--Lucky

[YellowJacket!]

Good!  Now we can go for a ride together.  ;D

David

[Night Vision]

what's that... the Atkins diet? very very high in carbs  :D

speaking of carbs... I attacked the carbs on my brother's bike after post op.... both bikes ran great Sunday (what a beautiful day to ride, mid 70's... ample sunshine... nice and cool...)

either we got some magic gas... or those carbs are tweaked! both bikes got right around 55 mpg during a "very spirited" ride along some awesome twisties and hills, very little flats....

ok, I didn't believe the 55 mpg.... so I just did a mapquest and traced the route we rode and it matched for 2 miles

88 miles - 1.6 gal....

[Willie]

That's a play on the Monty Python Spam bit.  Very appropriate!  I was chuckling as I was reciting the lines (substituting carbs for spam).