Intermitant miss???

[Lucky]

ok, so i've developed an intermitant miss. here's what's up:
83 carbs. mac exhaust, 'new' wires & caps, plugs etc:

symptoms:
it i cup my hand behind the front or rear pipe i can make the exhaust louder as the sound bounces off my hand, giving me a very clear sound from each cyl...
--the front cyl has a nice clear 'Bap-Bap-Bap-Bap'
--the rear cyl sounds more like: 'Bap-bump-Bap-bump-Bap-bump-bap-bump'

it sounds like the rear cyl  is missing on every other power stroke.

I have:
--swapped TCI's
--continuity tested the pick-ups per leathers site (& called Leather)
--checked spark, it looks consistant, but i'm not sure if i'm seeing a spark every time or every other time, just too hard to tell, & i haven't compaired it to the ft cyl's spark yet.
--clamped off vacuume supply to the petcock, fuel pump & accel pump control valve (it's an 83 thang) thinking that if one of those diaphrams split it might produce an intermitant fuel 'pulse'
Valves were adjusted last year.

What else am i missing?

i had a clogged fuel filter problem earlier this season & have since POR'ed the tank & changed the filter, i'm thinking i might have crap in the rear pilot..??

any ideas?

[Night Vision]

umm, this probably won't help much,,,

practice what you preach... clean dem carbs  >:(

sorry.

When I thought I finished and was really close to having the carbs dialed in.... I still had a....

bap-bap-bap-bap-bap-BURP-bap-bap-bap-bap-bap-BURP

a pop, burb or skip about every tenth stroke. but definately rythmic

I ended up turning the idle screw up to about 3k where I could definatley hear it, and just turned the pilot screws in or out until it went away. Cleared up my stumble at 4250 too.

Now, why did I blow my main fuse last night 4 houses down the street from home? The backfire (simultaneous with the sudden death) scared the crap out the kiddies playing basketball.

"mister... why aren't you riding your bike?....
"well, I thought I'd take her out for a walk"  ;D

[Superfly]

How old are the plugs/wires/caps?
Have you drained the float bowls yet, to see if there was anything noticable in there?

[Lucky]

the caps/wires/plugs are all pretty much in their infancy,
i did drain the bowls & got no dirt or water.
(i've also noticed my FI 3.8 caravan will give a slight shudder sometimes at a stop that started about the same time as they started adding ehtanol.. perhaps the stations didn't clean their tanks properly as required before switching over...?)

I also forgot to mention that i also clmped off the YICS hose to no effect.

i'm leaning towards NightVisions theroy of dirt in the carbs, but what i cannot explane is why it is a semi-regular 'cut-out'. 

i also preach that Vision symptoms are often multifold, but i'm not finding anything that i can confirm as a diagnosis...I feel like 'House' trying to diagnose a patient...

[Lucky]

the backfire was probably a result of blowing the fuse, the engine is still turning, pumping fuel, the question is why did it ignite after the fuse blew? hotspot in the cyl somewhere? (hot valve, carbon?)

the question is then, why did the fuse blow?  if it's random & doesn't blow for a long time, carry a spare & hope you get lucky finding the short (but look along the battery/start circuits)
if it blows right away when you replace it, start unpluging things one by one untill it stops blowing (a generic turn signal modual & 12v buzzer hooked up to the fuse leads in place of the fuse will save you the cost of the fuses), when the buzzing stops, you've found the short. if you unplug everythig & still have a short, it's in the wiring harness.
--Lucky

[Brian Moffet]

"Don't do anything."

"But he'll die!"

"And when that starts happening, we'll get some more information".

[dj]

That sounds like a quote from a "House" script.  ;)

[Night Vision]

Lucky, didn't mean to change thread subject. Replaced fuse and started right up, got some spares and going to see how many miles per fuse I'm getting  ;).

bad gas is a possibilty, maybe you got some "Bock Gas" from the bottom of the tank. ( I swear Genesee's Bock Beer came out in the spring, right after they cleaned the kettles  ;D )

[tailwheel]

I just got done watching House also. I Tivo it and wait until it is half way through and then start watching so I can cut out the commercials. Now that the season is over I can get to some projects before my other favorite show Deadwood starts.

Lucky, i feel that if every other Ignition is missed on one cyllinder it is a mechanical issue with the ignition system. I am new to this type of ignition system and most of my experience is with the high technology of Magnetos LOL  :P but I find that if it is consistant and rythmic that it has something to do with a part that rotates that tells the ignition to fire.

Dave

[QBS]

Tail.....when the carbs are just a little out of adjustment, Vs' can have an irregular lope that sometimes reminds me of a pre fuel injected Harly or my old BMW R60/5.  Doesn't hurt anything and goes away off idle.  However, When a V is tuned right on the $, the idle is perfectly regualr and steady.  Almost to the point of having no or a very boring character.  Cheers.

[Lucky]

Tail, it's rythmic, but not that rythmic.. if it was mechanical, it would tend to be very rythmic...usually (i'm not assuming anything on this bike, lol) and the spark appears constant.

QBS, i played with the pilot adjustments, & synqed it 2 weeks go. I suppose it's possable that for whatever reason the synq didn't set right..

i'm just going to have to spend some quiet time with it & figure it out, lol yeah, quiet time, like i have any.. :o

[Walt_M.]

This might be a good time to run a compression check, might be a leaky valve/seat.

[Lucky]

Bite your tounge! I Never ride my bike hard!  ;)

[Night Vision]

totally agree with QBS on the lope. He explained exactly what I was (burp) trying to say
... cheers....  ;)

[Lucky]

yea, i agree i think it's time to pull the carbs.  maybe i'll drop a can of Berrymans in there first & see what happens.  that's the advice i'd give to someone else...

[Tdub]

Possibly a "cross read" with the pick ups????

[Lucky]

shouldn't be, i'd think that would affect both cyls.
Tdub, youget my voice mail?