blue smoke

[Tibo]

Hey Guys,

So I'm getting some blue smoke out the tail pipes of my 80sg it seems to be on acceleration, and this morning I come to realize that Its only runnug on 3 cylinders. I'm going to do a compression test after work tonight, but I think I already know what it going to say. So myh question to you guys is if the cylinder walls don't look to bad should I just hone them and put in a new set of rings, or should I go for the big bore kit? and what else should I be doing to her while I have her appart?

The worst part is I was all set for a nice 3 day long spring ride this weekend have the hotel rooms booked and everything and know it's too late to cancel the reservations. Looks like I'm going for spring drive instead.

any advice you can give is appreciated.

[randy]

Blue smoke on DEcelleration is probably rings, on accelleration is more likely valve stem oil seals. You think maybe you lost the one cyclinder because of an oil-fouled plug?

If the compression test shows good, it's just valve stem seals. If it shows bad, squirt a little oil in each cylinder and re-test. If the compression values come up, the rings are gone. If the values don't change, the valves seats are leaking.

As for the hone and re-ring, hard to tell, you'd have to measure the bores to see if they're in spec.

[Tibo]

oil fouled plug

Thanks for the info Randy I'll keep that in mind tonight while I do the Compression test.

As for the plugs I just put brand new ones in and #4s still down. Funny thing, the one I pulled out of #4 looked the best out of all of them a nice tan color.

[TopCatGr58]

Okay Tibo,

Pull the cap off of #4, and inspect the wire for corrosion between cap and wire. If present, snip off 1/4" or so of wire, and brush/squirt clean the inside of the cap connector. Also, while cap is off, take an Ohmeter to it, should be ~5k or less. IF way more, then resistor and contacts inside cap may be damaged, corroded beyond repair, although you can unscrew the cap from inside the spark plug hole, and remove resistor, clean contact surfaces, recheck resistance of resistor, again if >5K, then get a new cap!

Are the pipes warm/hot on all four, or is #4 cold? You can also swap #1 and #4 and see if 4 warms up, or stays cold, or if 1 goes cold or stays warm?

If 4 stays cold after swap, then ruled out electrical, and your carb may need cleaning? IF it gets warm, then carb is supplying fuel, and electrical problem with ignition coil/wire/cap, even bad plug, have been known to be bad out of the box!

Good Luck Troubleshooting!
T.C.

[Tibo]

ignition testing

Ok,

All the pipes but #4 are hot, I used my ignition tester at work at found that I'm getting between 12 to 14KV at all the plugs, I snipped a bit off of the cable and put a new boot on #4 just to be safe. I pulled the plug out and turned the bike over with the boot on it and the plug resting against the side of the engine there is strong spark.

I also did a compression test and got 140/145/145/125. So then I wet tested #4 and it shot way up, so the rings are a little worn, but it should still fire shouldn't it?

As far as I can tell that just leaves the carbs right??? I guess I'll pull them again and give them another good cleaning.

[HobbyMan]

125 is really low. I think I get around 150(not sure) but it is constant all the way around. If It was lower I could say for sure that is why it is not firing.

[Tibo]

Revved up bike to 3500RPM, cylinder 4 started firing properly. Pulled carbs and found that the pilot jet on #4 was plugged. The pilot jet is soaking in PJ1. I'm confident that will take care of the dead cylinder.

I'm still concerned about the BLUE SMOKE though. I guess I'll have to either hone or bore out the cylinders and do a ring job.

Does anyone know of an oil additive that actually works that I can try in the mean time?

[pggg]

Well if the pilot jet was plugged, the air holes that is, then the bike'd be running way rich on that cylinder, not firing consistently, basically one cylinder down, and blowing smoke with a vengeance.

[oseaghdha]

125 is just about 15% down. It should still fire and run at that. Since the plug was not old fouled, and you have sparks, sounds like the carb is a problem area.

There are no miracle cures I know of, but if it was me I would try to keep it going till the off season.

If its not laying down a big mosquito killer cloud, run it while you collect all the stuff for a big bore.

[skids]

Re: ignition testing

The compression is good enough to run that bike. In fact, if it isn-t using a lot of oil, she is good enough for at least the summer.

Originally posted by Tibo
Ok,
I also did a compression test and got 140/145/145/125. So then I wet tested #4 and it shot way up, so the rings are a little worn, but it should still fire shouldn't it?

[Tibo]

Thanks guys,

I'm putting her back together this morning, hopefully cleaning out that pilot jet did the trick.

[Dennyz]

It is possible the smoke will reduce when #4 starts firing. A dead cylinder can cause some interesting things to happen.

Normally, combustion pushes the piston down. The pressure pushes against the valve seals. A dead cylinder is pulled down by the crank. The vacumm pulls on the valve seals.

My 'F' has over 130K (hard) miles on it. She puffs some smoke when she fires up. My last compression test, I got between 125 and 135. Yea, she doesn't have the snap she once had and she uses some oil. And Yes!, I would like to freshen her up with a big-bore kit ($$ flow problem).

However, she still runs and I wouldn't hesitate to take her on a 3K mile ride in a second.

Get #4 firing, carry extra oil and ride her. This is not the time of year to be taking you ride down.

[mro]

compression

Standard...142 psi
Minimum.....128 psi
Maximum....156 psi

should be checked with engine warm, throttle wide open

cylinder bore 71.5mm
wear limit......71.6mm

If still in spec, and cylinder not out a round,
hone and a set rings should do it.
(if going that far would do all 4 cylinders and lap valves.

Gasket set comes with valve seals too.



mro
btw, if smoken not bad and runs on all 4, would just ride it....
Hopefully a ring is not broken and just resting in it's grouve.