Author Topic: oil on #2 spark plug..... Why? (Read 4469 times)

Flying J · « **on:** August 11, 2008, 10:07:00 PM »

When i went on a long ride my budy says that somtimes at high rpms my bike blows some blue smoke. I was trying to adjust my pilot skrews today so i pulled my plugs and put in new ones to get an idea if i was running rich or lean. This is what i found. It looks like oil on the #2 but i guess the rest are fine. What do you think?

rhos1355 · « **Reply #1 on:** August 12, 2008, 04:13:03 AM »

I can't really see from the pics if that black stuff is dry carbon or wet oil. But from the blue smoke symptom you describe it sounds like piston ring trouble in that cylinder. Anyone else agree?

Sporkfly · « **Reply #2 on:** August 12, 2008, 06:16:49 AM »

Valve seal perhaps?

Do a dry and a wet compression test as it might not be rings. Could be, but also might not be. This is assuming you have access to a compression tester. If you don't already have one buy one, they're inexpensive and invaluable for diagnosing things like this.

goon 1492 · « **Reply #3 on:** August 12, 2008, 06:39:59 AM »

valve seals usually rear their ugly head when the motor is cold on car engines (I'm not sure if that pertains to these heads), they will smoke until the motor warms up causing the valve seal/guide to expand enough to seal and stop smoking, a bad ring on the other hand will smoke all the time... also are those little specs of stuff on that #2 plug they almost look like metal..... #1 plug looks prime, #3&4 look kinda lean...

Sporkfly · « **Reply #4 on:** August 12, 2008, 06:51:10 AM »

Quote from: goon 1492 on August 12, 2008, 06:39:59 AM

valve seals usually rear their ugly head when the motor is cold on car engines (I'm not sure if that pertains to these heads), they will smoke until the motor warms up causing the valve seal/guide to expand enough to seal and stop smoking, a bad ring on the other hand will smoke all the time... also are those little specs of stuff on that #2 plug they almost look like metal..... #1 plug looks prime, #3&4 look kinda lean...

I also see a fuzz on #2, maybe he has a kitten in his engine?

Yeah, looks a bit speckled. Maybe just from getting it from point A to point B. Anyway, compression test might reveal a bit regardless.

Flying J · « **Reply #5 on:** August 14, 2008, 10:13:45 AM »

Well its not a kitten. I did a comression test and here are the results:
#1 135

#2 70

#3 100

#4 80

Thats bad right?

TwoTired · « **Reply #6 on:** August 14, 2008, 10:25:09 AM »

Not much to smile about there.
This was a dry/cold test?
Put 5-10 drops of motor oil in each cylinder and try again. If the numbers then all come up even, you have ring issues. If the numbers hardly change, then it's likely valve issues.

The 77-78 F model 750s often suffered from excessive and early valve guide wear. They had higher lift cam, domed pistons, and a valve geometry that made the guides wear faster. Also, the valve stems and adjusters went bad, too.

Once the valve guides wear, the valve to head seal wears too, and the valves leak compression. The valve seals can't compensate for the excessive valve guide wear, leak oil and it goes down the valve stem into combustion chamber, or the exhaust port.

Cheers,

upperlake04 · « **Reply #7 on:** August 14, 2008, 10:26:10 AM »

I think the specs for your bike call for 140-170psi with all cylinders within 15psi of this range and of each other. Sorry.

goon 1492 · « **Reply #8 on:** August 14, 2008, 10:29:29 AM »

you might do a search for compression test and see what the average is, if not someone will chime in and tell their results, I know the 70 and 80 are not too good its still better than 40 or less, I think I remember something about 110-130 psi norm. and 130 being the sweet spot.

TwoTired · « **Reply #9 on:** August 14, 2008, 10:38:56 AM »

Quote from: upperlake04 on August 14, 2008, 10:26:10 AM

I think the specs for your bike call for 140-170psi with all cylinders within 15psi of this range and of each other. Sorry.

The specs are for results using the Honda Specified test gauge, which adds very low volume to the combustion chamber. Commonly available testers have a big hose that nearly doubles the combustion chamber volume. You won't get book values for the non-Honda tester.

Still, 70 and 80 are worrisome. But, it is more important that they all be within 10% of each other.

Cheers,

Edit values not valves

upperlake04 · « **Reply #10 on:** August 14, 2008, 10:47:43 AM »

Good point TT. After a top end rebuild which should have put everything to spec, a non-Honda tester showed only 130-136psi across the 4 on the 78F, probably because of cold test with the longer hose. Engine runs powerfully and smoothly but I have nothing to quantitatively compare it to.

Flying J · « **Reply #11 on:** August 14, 2008, 10:54:25 AM »

TT you bring more bad news with the whole 10% thing. Well i dropped some oil in and got this:
#1 160-190
#2 90
#3 100
#4 90
the compresion tester im using has an alomost 3 foot hose.

So im not so bad that im going to rebuild right now but what am i looking at to rebuild?
how much if i build it?(my first time)
and how much if i pay to have it built?
TT you have any spare time to make a liitl cash?

Sporkfly · « **Reply #12 on:** August 14, 2008, 11:03:14 AM »

Yeah, I was going to say earlier that they should be within 10% of each other. You're definitely way off, and you've basically shown it's probably the rings. If this is an F model you might have a problem with valve guides as well, if it is and even if it's a K how many miles are on the engine? Top end rebuild is what you're looking at regardless. If you can access the tools to do so it's something you'll be capable of I'm sure. It will save you some cash and give you a reason to love that bike even more.

TwoTired · « **Reply #13 on:** August 14, 2008, 11:20:51 AM »

Since oil is not compressible and it displaces the air that is, it is normal for all the numbers to come up a little with the wet test.

Since it didn't bring them even, it is safe to assume valve problems, since the oil should seal leaky rings.

How much? ...$$$

Do it yourself? Maybe $300-$400 if you scrimp and get real lucky. The valve seats and face need machining at a machine shop... if you can reuse the valves. Honestly, I would expect $500-$1000 in parts.
Labor is about what parts cost are.

Seems like most people shop for a K7 or K8 engine, to either swap in entirely, or use the barrels pistons head, etc from the K engine.

Sorry, I can't do this job. Doctor says I have Bursitis in the hip. I'm lucky to get out of bed these days. Sitting in a chair is painful. Walking/standing is something to reminisce about. I just hope I don't have anymore emergency room visits.

You might ask Scondon. If he doesn't chime in, PM him. He has built these, and needs funding for his own hot rods. He's in Oakland.

Cheers,

Ecosse · « **Reply #14 on:** August 14, 2008, 11:42:07 AM »

I'm following the thread... any time TT chimes in it's worth a read.

Sorry for the apparently bad news ff, personally I'd rather put the money and effort in one of these machines then most daily driver (cars) I've owned.

I know you're not looking for pity TT but I just wanna say sorry to hear of the hip issue. My best wishes of a recovery!

Flying J · « **Reply #15 on:** August 14, 2008, 05:07:50 PM »

It seems to be running good enough for now. How many more miles can i expect out of it? The speedometer is just over 15000. At any point will it become unsafe to ride, IE catastrophic failure?

TwoTired · « **Reply #16 on:** August 14, 2008, 06:07:39 PM »

What are your plans?
Replace the whole motor or repair it?
The damage gets worse with use. At some point parts have to be replaced instead of repaired. The valves may now be salvageable. But, eventually, with enough damage, they all need replacing. $50 each, I think. (MReick would know better.) Same with the lash adjusters. The longer it is run, the less will be salvageable/repairable, including the valve seats in the head, I imagine.

Your power is already down from what it should be. At some point it won't make enough compression to fire at idle on some cylinders and the oil smoke will get progressively worse and start fouling spark plugs. I can't predict when that will happen. I just know that it will.

Cheers,

Flying J · « **Reply #17 on:** August 14, 2008, 06:29:17 PM »

Well it looks like the best thing to do is start looking for a k head, cylinders and pistons for my future rebuild this winter. will i be able to use my rocker arms and cam or do i need that off a K also? So this engine got 15000 and needs work. How many miles should i expect from a k top end after the rebuild? And last will i still be able to use the same carbs?

goon 1492 · « **Reply #18 on:** August 15, 2008, 06:44:40 AM »

did you get all those 15,000 all on your own? The P.O. and the milage and care he/she took of it has alot to say, regular maintence goes along way, these bikes are pretty reliable if you take care of them, so if you rebuild and reset the clock so to say, if you take good care of it it will return the favor and give you many more miles of smiles.

TwoTired · « **Reply #19 on:** August 15, 2008, 08:32:40 AM »

I did a search for past posts about the the 750 F2/F3 top end.

http://forums.sohc4.net/index.php?topic=17673.0
http://forums.sohc4.net/index.php?topic=8610.0
http://forums.sohc4.net/index.php?topic=38162.0
http://forums.sohc4.net/index.php?topic=16793.0
http://forums.sohc4.net/index.php?topic=7594.0
http://forums.sohc4.net/index.php?topic=3378.0
http://forums.sohc4.net/index.php?topic=8688.0
http://forums.sohc4.net/index.php?topic=20316.0
http://forums.sohc4.net/index.php?topic=28040.0

From what I understand, the 750 lower end is good for 100,000 miles plus, assuming reasonable routine maintenance.
A K or F0-F1 top end is good for 75,000 miles plus.
An F2-F3 top end is good for 6,000-20,000 miles if it has the early soft valve guides.
I don't know how long an F2-F3 top end will last with replacement hardened valve guides. But, I wouldn't expect 75,000 miles.

I think the cam from the F2-F3 can be used on the K engine, but not the rockers.

This is from research NOT experience!

Cheers,

Tower · « **Reply #20 on:** August 15, 2008, 09:36:49 AM »

TT, Bursitis as you know is an inflammation. I treated and cured mine with spices - Turmeric mostly, low dose aspirin, Black cherries, and vitamin E. I.e. Lots of curried foods, cherry juice, and 200mg of Vit E and 80mg of aspirin daily. Important not to irritate the joint, so lots of rest also. Took about 3 weeks. That was two years ago. Hasn't reoccurred.

If you don't cure it immediately, good chance it becomes chronic.

Edit: sorry for the hijack

rhos1355 · « **Reply #21 on:** August 15, 2008, 01:29:24 PM »

Quote from: Tower on August 15, 2008, 09:36:49 AM

TT, Bursitis as you know is an inflammation. I treated and cured mine with spices - Turmeric mostly, low dose aspirin, Black cherries, and vitamin E. I.e. Lots of curried foods, cherry juice, and 200mg of Vit E and 80mg of aspirin daily. Important not to irritate the joint, so lots of rest also. Took about 3 weeks. That was two years ago. Hasn't reoccurred.

If you don't cure it immediately, good chance it becomes chronic.

Edit: sorry for the hijack

Che? Where did this one spring from?
Sorry mate but we're talking heads and rings here!

TwoTired · « **Reply #22 on:** August 15, 2008, 01:37:11 PM »

Quote from: rhos1355 on August 15, 2008, 01:29:24 PM

Che? Where did this one spring from?
Sorry mate but we're talking heads and rings here!

My fault I guess, See reply #13 in this thread.

BTW, I do appreciate the comments by Ecosse AND Tower. Pity I'm allergic to Asprin, though.

Cheers,

rhos1355 · « **Reply #23 on:** August 15, 2008, 01:47:06 PM »

Oh yeah, missed that one.

upperlake04 · « **Reply #24 on:** August 15, 2008, 02:01:29 PM »

I now have a reason to excuse your occasional crankiness TT

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Author Topic: oil on #2 spark plug..... Why? (Read 4469 times)

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