Plug chop test pics

I would appreciate any advice I can get from the XJ gurus out there to help get this '82 650 non-yics running smoothly. Here is the situation:

Plug chop procedure used:
1. I used old plugs to warm up the bike.
2. Put the new plugs in.
3. I rode around the block in first gear under load (the bike runs too rough to go faster) for about 2 minutes. 2-5k rpm varying

New plugs after chop. 4 - 3 - 2 -1
4 is clean and bone-white. 1 and 2 are bone-white with a few black flecks. 3 has a black sooty patch on it and the other side is lightly tanned.


Used plugs. Almost new; they have been mostly used at idle & warm-up speeds. Black and sooty.



Problems I've been having:
-Bike will bog with throttle input below 2000rpm, then hang at high rpm.
-Bike won't take a steady idle. It will start idling fine when cold, then gradually struggle and die w/o throttle or lots of choke.
-small popping sounds in the carbs at low rpm. at one point it looked like some fuel vapor was shot vertically out either the enrichment plug, or the mixture screw

Stuff that can be ruled out:
-Valve shims are in-spec and the valves were recently lapped
-Compression is generally OK. Cyl 3 is kind of low at ~100psi, but there hasn't been any smoke coming out the exhaust.
-carbs are super clean and all the jets are in the right places
-carbs pass clunk test. float pistons movement is good
-float level is fine
-oil changed recently - castrol gtx 20w-50. It's at the right level.
-petcock recently rebuilt. no leaks
-carbs synced using paper-clips

The only thing I think it could be is the mix screws. I lost the factory setting, and now I have them all at 3 turns.

 

Ok, when she's cold see if all the pipes get hot at the same time with your hands. Did the bike ever run good when you owned it? In your situation a Colortune would help you immensly. Got a volt meter? Checking the resistance on the ignition system is quick and easy ; )

 

what's the compression on all 4 cylinders. you shouldn't have a variance of more then 10 percent between highest and lowest.

100 lbs compression on #3 is getting pretty weak. specially at your altitude. did youi double check your compression? weak compression usually causes blacker plugs. as your not pulling in enough air to have the proper air/fuel mixture. weak cylinders generally run richer.

your also going to have a hard time syncing the carbs properly. and a whole slew of other problems

your plugs actually look good.

popping in the carbs indicate intake valve not sealing. compressions is leaking through. your valve adjustment might be too tight. cylinder leak down test with the piston at top dead center and valves closed will tell y ou if the intake is leaking.

popping in the exhaust means exhaust valves aren/t seating.

since you've got weak compression in #3 i'm betting that's the carb that is backfiring and popping. and that's the valve that's too tight.

 

Greensboro is at 900 feet- - no need to re-jet.

Set Pilot screws by ear after doing a running sync using a home made water devise. Get some tan color on the plugs.

 

Compression is as follows:

1 - 120
2 - 119
3 - 100
4 - 119

Yep, I know #3 has low compression, but it's definitely the rings, and I DON'T want to resort to new rings. If it were lower than 90, I wouldn't bother, but its still got most of its compression. The valves have been lapped recently and the clearances are in spec.

Any tricks to carb tuning with a low cylinder?

 

You only indicate a "paper-clip" bench sync. Have you done a running vac sync yet?

THAT will be your only hope of "carb tuning with a low cylinder." You've skipped a step if you're doing plug chops

"Float level is fine" checked how?

The issue is really rather straightforward: You have a "soggy" motor, none of the compression readings are all that stellar, and you're sure it's not just valves. OK.

You CAN "tune around" that, to some extent, and get the bike running halfway decent; however, to do so, everything else has to be as right as can be, and then the vac sync will help "bring down" everything so it matches. Get the cylinders matched first THEN go after the mixtures. Otherwise it's not gonna happen.

 

Since my last post I synced w/ a 2-bottle tool. I actually saw a little improvement - now it holds idle below 1200; granted it's a stumbly rough idle. Floats were set w/ calipers and confirmed with a clear plastic tube while the bike was running.

Bike will still die if I turn out the idle screw all the way (close the butterflies). Maybe another bench sync?

 

Vac sync comes after bench sync; floats need to be set with the carbs dead level front to back and side to side so you might still be off a bit there.

Bike WILL die if you completely close the butterflies by turning the idle screw all the way out. Use the idle screw to set the idle, it shouldn't be all the way out.

 

was the engine warm and wide open throttle on that compression check?

 

Referring to the Service Manual, ...
Regarding Compression.

Standard: 158 psi
Minimum: 128 psi

Do another Compression Test.
Fully Charged Battery <---
Wide Open Throttles

Add a Tablespoon of Oil top the Cylinders "Wet Test"

Let's see if you got Ring Trouble or Need a Valve Job.

 

Use ... "PhotoBucket" and resize the Photographs to something other than Drive-In Movie size.

PHOTOBUCKET:

http://photobucket.com/

 

LOL


with compression like that. the bike probably isn't worth messing around with. gonna be tough to keep up on the freeway.

defenitly going to be tough to sync. one weaker cylinder won't be pulling down as much vacuum.

 

The engine was COLD during that compression test - done with wide-open-throttle (well, no throttle, manifolds or exhaust). I'll test it hot soon - maybe I'll get a more favorable reading.

BTW Rick, it is most certainly the pistons. Valves have been lapped, greased, and shim clearance is to spec. What took this bike off the road was gas in the oil caused the rear main seal to start leaking.

In any case, if I can't somehow tweak it back to ridability, I'll be parting it out - really vexing considering this bike consumed my winter.

 

They make all sorts of Parts for rehabbing the Mill back from Ring-induced low compression.
Rings
Oversized rings
Oversized pistons.

 

True, but that would be big undertaking for me, and the only machine shop in the area is really shady.

Frankly, my relationship with my GF has been affected by the amount of time I've been putting into bike repairs, and I want to either get this bike on the road quick or get rid of it.

 

Found time to do a warm compression test. Results are similar with about 20 more PSI across the board:

140, 135, 122, 138

So compression is still mostly good except for that one cylinder. Circumstances still forbid doing any serious work on the bike, so I'm going to try and tune it the way it is - with one low cylinder. Any tips?

 

If #3 plug is blacker than the others It may be the valve spacer/shim thing is a fuzz tight. Ooops! didn't notice that you already made sure the spacers were good.

 

Its not low, the book says they should be within 20 of each other or a certain percentage & it looks like your ok. Just can't remember Exactly but I broke my toe and can't go in the garage for ya, sorry