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.