How do my plugs look

My carbs were very dirty on my'84 XS400, half of the needle jet holes were plugged, mixture screw o-rings half missing and the wrong main jet. Everything else set to spec to start and other o-rings and gaskets good, also fuel level test good using the external method. I have the mixture screws at 3 turns out.

These are brand new after a 15 minute drive at speeds up to 100kph

 

They look like they just came out of the box!

THAT ... is WAY too LEAN.
Or. ... you are pulling a fast one.

If those are plugs that are in an XJ-Bike and you have been running around ... you are running way to leann and far too hot.

Unless you make an adjustment ... you are at risk for a major breakdown!

 

Rick is right. I posted same question few days ago with a picture of my plugs compare them with what others had to say..so you know whats the right colour. Mine were new plugs (MaximX 750)too and checked after 30 min ride. here is the link..
http://www.xjbikes.com/Forums/viewtopic/t=21134.html
In your case you can defnitely turn 1/4 turn counterclockwise and see how the plug turns out after a ride.

 

That's what mine look like too.....majorly (c)lean.

 

Those plugs were from driving but if I let it idle I get some light browning on the insulator. Tomorrow I'll give the mixture screw more out and I think I'll probably need to go down one clip on the needle.

 

And we have a winner..... drum roll please.... throttle plate shaft seals. Time to order some new ones. I took carb cleaner and shot directly at the seals and RPM's dropped on each side.

 

good you found the problem, although it's not an easy fix.
while you have the carbs apart, might as well go through them and spend a few extra hours doing the job right.
Dunno how many miles are on the bike or it's history, but an ounce of prevention is worth a pound of cure

 

This bike only has 9000miles on it so its worth putting the extra effort in to it to make her run right.

 

Shooting Carb Cleaner on Throttle Seals wouldn't make RPM's drop.
If they were leaking ... the Engine would speed-up.

Let's check em.
Smear some synthetic waterproof grease on the Carb Throttle Rod Pivots.
"Seal the seals'
See what happens.

With 9000 Miles on the Bike its POSSIBLE you have a Factory EPA set-up Bike.
Deliberately Lean.
I'd "Experiment" and add a Half-Turn Out on the Pilots
Get-of the Lean

 

I don't think I have ever seen an engine speed up from carb cleaner, mostly they stumble and die. My rigth carb is not to bad but the left side I have the pilot out to 5 turns and it still won't put color on the plug or change the rpm. The right side it at 3 turns out and looking good on the plug.

I'll try the greese trick but I am not sure I'll be able to get at the inner seal.

 

So the greese thing didn't help so I am guessing I'll need to pull the carb back apart to see what going on. One thing I noticed is the left side that's lean it is smoking while idling, not sure what's that from. It's not oil but doesn't look black or smell from unburnt gas. The motor is air cooled so it's not coolant.

 

Determine if running that lean has caused damage.
Do a Compression Check
You might have damaged Rings or Piston Skirts.

 

Did the compression check, right cylinder is 165psi and left is 157psi. I order new butteryfly seals which will be here on Monday.

 

I'm a little perplexed about this situation.

I don't think that this EXTREME Lean Condition would be caused by Leaking Throttle Shaft Seals.
The working close tolerances of the Throttle Shaft and Bore aren't going to allow that much AIR to enter the Engine.

There isn't even a sign that those Plugs were in the Engine for more than a Minute or so.

Before I would remove the Carbs and dismantle them to replace the Throttle Shaft Seals ...
I would "Experiment" and use RTV to SEAL the Back of the Intake Manifold to the Cylinder Head.

IF ... ⬅ Big IF

If the Manifolds Securing Cap Screws are NOT seized ... I would remove the Manifolds and apply Sealant to the backs of the Manifolds.

If the Cap Screws are seized ... tuck a bead of RTV all the way around to Back-edge of the Manifold.

You are on a Mission to Seal a MAJOR LEAK.
Not a little stream
Niagra Falls.

That much Air IS NOT going to get in from the Throttle Shaft unless the Throtle Shaft is missing.

 

I am going to keep looking for the leak but a for the back of the monifolds I ran a bead of threebond on them before mounting them back to cylinders head a few weeks back. I try the propane test this time around the carbs.

I have been doing some ready online over the past few days and these BS34 that yamaha put on the '80 - '84 400 Maxim are emission carbs setup for extreme lean running, it is possible this is normal for this perticular model? The XS650 of the same year range is also included in this extreme lean running conditions.

 

Yes. But, you have to understand LEAN.

Running a Mixture lean to prevent excessive emissions is a carefully monitored set-up.
The Mixture is set to Burn >Quickly and efficiently< and then, Air introduced to the Exhaust > after the Power Stroke <.
This was a requirement on so-called: California Models

Your LEAN Condition goes BEYOND a SAFE Lean Mixture.

Those Plugs tell us that the Mixture is so Lean that it is FLASH BULB Lean.
The Mixture is explosive rather than Power Generating.
The Mixture you have generates too much HEAT.
The Combustion consumes every molecule of Fuel.

The Temperature generated by that Lean of a Mixture is beyond what the component parts can withstand.
If you run that lean something bad is going to happen.

 

I will temper what Rick said with a bit more about emissions and mixture:

Most emissions concerns are based on what an engine does at idle. This is probably based on a number of factors, including the amount of time that vehicles spend idling in big cities and the relatively high cost of testing emissions under load on a dyno.

This was, back when, a good thing for manufacturers, because it's quite safe to run lean at idle. At idle, and other times when load is light, like when decellerating, the temperatures in the cylinders are too low to damage anything - so, once all of the fuel is burned up, what's left is just hot air that gets blown out the exhaust.

However, when under load, combustion chamber temperatures are much higher... high enough that, if the mixture is too lean, other things in the cylinder will burn, like the aluminum of the piston and head.

Now, a couple of things to keep in mind from this:

1. Carburetors are dumb mechanical devices. As such it's difficult to design them in such a way that they will be lean at low load and idle, but correctly rich under high load. In fuel injected engines it's much easier to have the air fuel mixture follow the load of the engine. As such, carbureted engines normally need to be a bit rich at idle as a safety margin so they don't get too lean at other points in the power band.

2. Unless you're doing plug chops or checking colortune or AFR on a dyno, your plug checks are mainly showing you what the idle mixture is like. It's still possible to be rich at idle and lean at WOT, or vice versa. That's why there are some folks on this board that have actually installed wideband oxygen sensors in their XJ's. The WBO2 will tell you what your AFR is while you're riding around, and then you can see whether other carb changes (main jet, needle height, etc) are needed to keep the mixture where it needs to be under load.

3. On the other other hand. If you're at or near sea level, are running stock (jets, exhaust, air filter, etc), and are getting a light tan to paper bag color at idle on clean and in good condition carbs, then then the rest of the power range is probably OK as well. (Because the factory would have done the wideband tuning work for you as part of their design of the bike.) If any of the above are not true, that's where things get complicated.

By the way, I'm currently working on my second bike, which has BS34SS's. I'm not at sea level (6000 ft or so), have a 4-1 exhaust, and the jets have been significantly messed with. I don't yet have a WBO2, but, depending on what I find after getting this bike back together, I may well buy one... or make this a second fuel injection project.

Cheers,
Paul

 

As I have said so many times before, ...
These Engines run great lean.
The acceleration of a Lean Mixture is an amazing joy to behold.
The experience is addictive.
It wants you to tune the Engine to the razors edge of danger.

Lean gets you to the next traffic light before everybody else.
Lean makes it sound like you are driving a F/1 Racer.
Fun. Fun. Fun.
Living on the edge of fine-tuning.

Step over the edge and you got trouble.
The kind of trouble that will ruin the Engine and leave you flat.
Too Lean.
Too lean, too hot, too long and everything goes swirling down the drain.

That's why the photos of your Plugs scare me.
I think you're over the edge.
More Fuel or Less Air.
Make an adjustment.

 

I hear what your saying.

I am going to put the seals in tonight since the carbs are already apart and ready for them. I have probed around looking for a leak of air and the only thing I found was the seals on the shaft leaking somewhat, it's worth the $10 for seals and screws to change them now.

I got this bike from an uncle in August and must have put about 1800km on it before I decided to clean the carbs since the choke was starting to have a tough time in the colder days now. I never looked at the plugs until I through new ones in after the carb clean. Even that night after the cleaning I got no pinging no strange noises and it seem quiter.

very odd stuff but hopefully I'll have an update late tonight or tomorrow.

 

Wel i'll tell you this Alex, i have to deliberately make my 400 eat the gas to get colour. I mean i have to be 5 turns out and one clip position richer on the needle.

I get colour on the plugs, but it runs like absolute crap. I've been through my carbs so many times i've lost count. No blockages anywhere, and propane test revels no leaks.

I'm curious as to what number your jet needles are. Mine aren't stock and wondered if that would be part of the problem. What i have are Y84Z.

Let me know what you have in your carbs Alex.

 

My needles are 4HZ21

The only manual I have for my bike is the '82 Seca 400, it list the needle for that motor at 4HZ20. I am guessing mine is probably good for my bike as I think the power nicreased in the motor in '84.

You probably have the wrong needles then judging by the number you have.

 

Well after fixing a few things I beleive I have foundthe problem, left cylinder piston rings. I changed the butterfly seals which were missing pieces and rock hard wit new ones, this got back a lot of color on the plugs to a nice tan color.

The left cylinder is still off a bit but with further checks the compression hot n the left is 20psi lower than the right.

right cylindr 165psi cold - 158psi hot
left cylinder 157psi cold - 128 hot

I squirted a bit of oil in the left and compression wet up to 151psi hot which confirms rings.

I guess this winters project will be pulling the motor out and giving it a refresh of new rings and a general check of everything else in side.

 

I wouldn't jump to that conclusion quite yet. One interesting thing is that your compression goes down with heat, it should go up. One thing that might account for this is if your valve clearance is too tight. As the valves and shims heat up, they will expand, and too small clearance becomes none at all and the valves will hang a bit open.

Despite the potential evidence from the "oil test" I'd first verify that clearance is correct.

My .02 anyway.

Paul

 

These are my numbers for valve clearance,

left exhst 0.007
left intk 0.006

right exhst 0.006
right intk 0.004

So my valves are in spec, is there anything else that might cause lower compression when hot?

I am going to go redo my compression check cold just to be sure, come to think of it I used my old tester for the cold numbers and my new tester for the hot numbers.

 

Now, I'm more guessing... but I'd still say "not rings".

Maybe a bad head gasket, incorrectly torqued head nuts, or a warped head. Maybe, also, a bent valve. If a valve's slightly bent, the part of the valve head that's closer to the seat may hold the valve further open as it expands when hot than it does when cold.

 

But if a valve was stuck open squirting oil in would not seal this and make compression go up, so when my numbers went up doesn't that rule out valves and head gasket since the oil I put in would never reach that high to seal?

 

Ok re-did the cold and hot test with the new tester, my numbers are better.

left cold 141psi hot 149psi
right cold 143pi hot 152psi

I guess my old tester is not working so hot anymore. I doubled check the new tester on my RZ's motor to be sure and and the numbers match what my buddy gave me after a rebuild last month.

Maybe then with the carbs being very dirty and the dry rotted butterfly valv seals it ok now. I am going to buy new plugs tomorrow and go for a nice little drive and check the plugs.

 

Your Compression is good to excellent.
Looks like you need to do the Carbs and leaks.

 

Well, this seems to have come down to a measurement error, so further discussion is purely academic, but...

In my recent engine work, where I did in fact have bent intake valves, the oil still helped. This, along with some derogatory comments someone else I know made about it, makes me wonder how useful the "oil test" really is. I would kind of expect the oil to get get somewhat vaporized in the cylinder and thereby still have an effect on narrow gaps where air would squeeze out if not blocked by a thin film of oil.

For comparison, my worst cylinder, the one with a pretty badly bent intake valve, read 10 psi "dry" and about 50 after adding oil. After replacing the valve (and not doing anything to rings/cylinder/piston), I get about 120 psi there.

Anyway, glad to hear that things checked out well on the retest.

Cheers,
Paul

 

You put Oil in the Hole to determine the likely cause of LOW Compression Numbers.

Low - Dry. Is it Rings or Valves?

Wet - Improvement = Ring related problem
Wet - No Improvement -- Indicates Valves might be involved too.

 

Rick, again, this is experience I'm talking from and again I get the impression you didn't read my post before responding.

My experience: Before work - compression on #3 = 10 PSI. With oil, 50 PSI. Your theory says that means ring problems.

Next step I did was to pull the cams and run compressed air into the spark plug holes. I could hear and smell air coming out of #3 through its carburetor.

Pulled the head and found minor bending on intake valves 1, 2, and 4, and major bending on 3. Replaced all intake valves. Cylinders still showed original crosshatch very nicely and no scoring. Engine only had 6400 miles on it, so I didn't do anything to rings, cylinders, etc.

Put it back together and read 105 PSI cold and dry and 120 PSI warm. This is at somewhat over 6000 feet elevation.

So, while theory would say that a 40PSI improvement in compression by adding the oil indicates a ring problem, my experience says that, in my case, the oil test was, at the least, misleading.

Paul

 

Well, ...
I didn't invent the test.
The Book I go by was written in March, ... back in 1975.

I was pretty sure I had it right.
But, you know me. Check it out.
I checked.

The Ruling on the field stands.
Sustained Low Compression during the Wet Test indicates Rings.

There's a Heading entitled:
Sticking Valves

A Sticking Valve is indicated if a Compression reading fails to:
a) "Climb a little bit with each stroke before indicating peak."
b) "Remains the same during the first several strokes before beginning to climb with visible pressure leaking-down."

Head Gasket

Readings on adjacent cylinders 20 psi lower than the rest indicates Head Gasket failure.

 

Huh?

Before you said:

Wet - Improvement = Ring related problem
Wet - No Improvement -- Indicates Valves might be involved too.

Now you're saying:

Sustained Low Compression during the Wet Test indicates Rings.


Doesn't "Sustained Low Compression" mean, no improvement? Aren't your two statements then contradictory anyway?

Although, that second interpretation does not match what I had been taught. I had always heard the first interpretation. My point on this thread, though, is that, regardless of what the books or old mechanics say, my experiences did not match the "Wet - Improvement = Ring related problem" adage.

I don't make any money either way. Just wanted to let people know what I had found in case it would save some of them from doing unneccesary ring jobs.

Paul

 

Here's what the Book says:

Ordinarily, valves don't all wear-out or burn away uniformly so that uneven compression is generally a sign Valve problems.

However, valves can be differentiated from rings by squirting about a tablespoon of oil into the cylinder, ... cranking the the engine to distribute the oil and then repeating the test. If the Readings show a considerable increase, the rings are at fault. If the Readings remain about the same, the valves are at fault.

 

I'm not arguing with your book. It says what it says. My Clymer manual says that too (of course, it also says that the wear limit on the pistons is .81mm LARGER than the initial bore diameter, and gets the cam installation details very wrong... but those are other stories.)

What I'm telling you is what I found. You keep referring to your book and saying you got it right. Congratulations. However, if I'd followed the advice that you just posted, I'd still have bent valves, and I would have nice new rings, and maybe pistons, that I didn't need. Part of what I dealt with when working on this engine was work done by a previous mechanic who may well have followed that book. He pulled the whole thing apart, swapped in a new head gasket, and apparently didn't notice the bent valves at all.

I would imagine this oil test isn't completely useless. It must work in some, maybe even most, cases, or it wouldn't be so popular. I doubt however, that my situation was the only case in history when it was wrong and misleading.

 

Neither wrong nor misleading.

The Bent Valve would affect how the Compression Gauge read the Hole.

Initially, the test would show some sign of inadequate pressure.
The Hole would lose Compression and there'd be the indication of pressure loss between strokes.

What is it?
Wet it and see, ...
The Gauge would Pump-up more efficiently BUT Still bleed-down slowly indicating a Valve issue.

But like our English Language's Rules of Grammar.
There are Rules.
Exceptions to the Rules.
Exceptions to the Exceptions.

 

Now you've entirely lost me. My gauge doesn't bleed down. Like most compression gauges, it has a check valve to maintain peak readings.

A leak down test, rather than a compression test with a compression gauge, would test for "bleed down." Is that what you're talking about?