Topic: Help reading THESE plugs...

[timdhawk]

left to right, 1-4.

[eldar]

2 is ok 1,3, & 4 are rich. I would say that 2 is even SLIGHTLY rich but then for a 78 it would be.

[TwoTired]

How long have these been run and at what throttle setting?  Did the engine get to operating temp?

2 has the right center insulator color.  But, I'm concerned that the base ring has no deposits.  Either very low miles or a bit lean in that cylinder.

All the dark center insulators are far too rich, very cold combustion temps.

#4 looks damp. Is that oil?

I'd like to see the electrode strap from reverse angle.  But, that can wait until you get all the cylinders firing evenly.  I expect you have carb issues.  Or, filter and exhaust changes from stock.

Cheers,

[timdhawk]

How long have these been run and at what throttle setting?  Did the engine get to operating temp?

i was the one having issues after the carb rebuild. finaly got it to run without choke. the plugs are new, other than trying to get it to run. drove it today for about 10 min after carb syncing. idles fine, mild "sputtering" with low throttle, sounds and feels right in mid range, sputters at WOT.

All the dark center insulators are far too rich, very cold combustion temps.

all mixture screws are out 1 1/2 turns (maybe 1 3/4).

#4 looks damp. Is that oil?

i thought that as well. its possible, it certainly blew white smoke when i got it to fire up and stay running

 I expect you have carb issues.  Or, filter and exhaust changes from stock.

Yes, but getting better each time. and yes, i have pods and a F model 4 into 1... soon to be a MAC 4-1.

[eldar]

Now what bike do you have? We need to know that part too.

[TwoTired]

The question you have to ask is, why haven't they all got the same deposit pattern, particularly after a carb sync.  The fact that you don't, means you still have some repair work to do rather than simple adjustments.

If the cylinders all have the same compression, and are fed the same air/fuel mixture,and get proper spark, then they should operate at the same temp and power output.

Pods are individual filters that >CAN< have differing restrictions.  Check to see they are equally clean and free flowing.
I'd do a compression test, if I had confidence the carb clean.  Make sure the valves are adjusted, too.


If the compression is equal, the filters equal, and the vacuum is equal on all intake runners, you have something in the carbs that that isn't.

Cheers,

[timdhawk]

Now what bike do you have? We need to know that part too.

Damn it, i always forget that part....

78 cb750k

[eldar]

OK now we can get somewhere.
All are too rich for the lean nature of the 78. 2 is close and for now, it is the target the rest need to hit. 1 & 3 look like they just need some adjustment, 4 does look wet. IS it? If so, is it oil or gas? It CAN be either.   

Maybe you can clean the plugs and run for a few miles without the pods. I did that and that is how I found the filter I had was too restrictive.

Since I have not followed much, what have you done for tuning since you got the bike?

[timdhawk]

Maybe you can clean the plugs and run for a few miles without the pods. I did that and that is how I found the filter I had was too restrictive.

Since I have not followed much, what have you done for tuning since you got the bike?

i'll do a compression check and then run it without the filters. they are brand new.

What i've done so far:
complete carb rebuild with new main and slow jets. carbs are very clean. Mains are 118, the rest are stock. carbs are sync'ed. idle @ 1000-ish. new plugs and wires.
new dyna coils and accel ignition unit.
valve clearances checked.
i have a crappy F model 4-1 header with a muffler tip??? on the end. But i have a new MAC 4-1 waiting for new gaskets to go on.

[timdhawk]

i did a quick cold compression test (didn't have time to ride, plugs already out) #1 is 112, #2 is 120, #3 is 120, 4 is 122.

full throttle, choke full open (pulled up).

what are good numbers for the 78? I used an automotive comp. gauge and read a post by two tired that said the auto ones can eroniuosly lower the readings.

[eurban]

If you pull the choke knob up on the 77/78s it closes the choke plates and blocks most of the air flow into the cylinders.  This is not what you want to do for a compression test.  Is that what you did?

[timdhawk]

If you pull the choke knob up on the 77/78s it closes the choke plates and blocks most of the air flow into the cylinders.  This is not what you want to do for a compression test.  Is that what you did?

Oh #$%*!!!! Duh.....yea, thats what i did in my haste. I'll do it again tomorrow. thanks for the 'upside head slap"!   

[eldar]

Yeah the engine should be warm. A cold engine will give lower readings as metal expands when warm. A 100 foot steel rod can expand by a foot when heated up a certain amount. Just an example.