Help request - How to Read a Spark Plug

[yukonerdave]

Hey guys

Been a while since I've been active on the forum - I moved and have been busy with other stuff, but I still check up on what's going on once in a while. Anyway, my bike started running like sh*t a week or two ago and I could use some advice. I'm actually looking into what it would take to fly Sean up to Vancouver, Canada to see what he can do (and to fix everything I've undoubtedly messed up over the years!). If that's not gonna end up working, I suppose I'll see what I can do on my own.

Symptoms: bike's been running rich for some time but I've been trying to pretend not to notice. It's enough that after I park in the garage and close the door, I can smell a sort of gasoline-y smell throughout the basement. I also occasionally got a loud backfire right when turning the key on (before touching the starter). Despite that it's been running strong up until a week ago. All of a sudden it started to bog down and feel really sluggish. I have poor throttle response. I don't ride anymore because its bad enough now that I have trouble making it up a hill. It seems to idle fine, at least at half-choke.

I had my carbs cleaned by someone on the forum here (I'm sorry I forgot your name - Fargo maybe?) with an ultrasonic unit about 1000 miles ago. At that time I installed new air/fuel mixture screws. I fiddled a little with them to eliminate some decel popping, and seemed to get it in a good place. Now, however, I tried doing the shotgun procedure and something seems wrong. I was able to get all four screws out with compressed air, but I never did see the springs or o-rings. I tried some carb cleaner without getting them out. When I screwed them back in and tried to reset them to the right place, it seems to me that when I screw in the ones from cylinders 3 and 4 all the way, the engine stumbles, but I don't seem to get any reaction from screwing in #'s 1 and 2 all the way. Also, the screw from #1 didn't seem to thread in as far as the others before stopping. I dunno.

One more thing that probably matters. Early this year I laid the bike down when I jumped off it to help a buddy. It was on a slight decline and rolled off the kickstand. It was only on its side for maybe 30 seconds and I didn't think anything of it at the time, but when I opened it up this week I noticed that the airbox had a considerable amount of oil in it, and the air filter was wet and dirty from oil. I'm assuming that engine oil came up from the cylinders and through the carbs when the bike was down. Aren't piston rings supposed to keep oil below the pistons? Is something like that a normal thing to look for if your bike every goes down?

Finally, I've been told that if you know what to look for you can tell a lot about the health of an engine from the condition of the spark plugs. My plugs are 2 seasons old. Problem is, I don't know how to read them. I'm attaching some pictures, which may or may not have enough detail for any of you to give advice on, but I can't get a good focused shot any closer up with my camera. You'll notice that #4 is filthy right up to the nut, perhaps because some oil leaked out? Also, #1 looks pretty black and wet at the tip, while the others are dry and kinda light brown. The threads on all four are pretty dirty.

Any specific advice about what to look at, given my symptoms, would be very appreciated. Also, if anyone wants to offer some general advice about what to look for when inspecting plugs, maybe a short "How-To" writeup would be useful to others (come to think of it, I haven't even searched for such a thing yet - it's probably already on there!).

LAST THING (I promise!). I recently moved to Vancouver Canada and would love to hook up with anyone for a ride. I've already met Steve from south of Seattle (fantastic gentleman who let me borrow some space in his garage when I had to leave my bike in the States for a bit). You'll have to give me some time to get my Mistress back in top condition again, of course, but there is still plenty of season left this year.

Thanks,
Yukoner

 

[KJShover]

If I remember right, there is a spring, washer and a rubber o-ring behind the a/f screw (I may have my carbs mixed up). What I've found, on motorcycles, is exhaust leakage is almost always the cause for a deceleration pop through the pipes. There might be a leak or a crack in the pipes somewhere.

As far as the plugs, its tough cause of their age. Ideal would be a plug chop on a fresh set of plugs. But looking at the base ring on all of them, a slight rich condition going on.

The porcelain, again looking past the deposits, don't look bad. However, I can't get an up close look at it. Take a magnifying glass and check of specks of silver or any dark spots, you may have some detonation issues.

Looking past the deposits on the ground strap, your in the right heat range. So your good on that unk:

If you turn in your a/f screws and the engine doesn't respond, it's very possible there is some blockage somewhere, or a float issue. It is also possible that when it tipped, some tank crud could have been jarred loose and made it's way in the carbs.

 

[tugla]

well im not far from van, about 2 hr plane ride hahahah but ya maybe a full go through the carbs would help, checking float levels and such.....making sure all the parts are there for the a/f screws..... if it was running good before and now just started should be able to bring her back to life like she was....

 

[naughtyG]

Defo get new plugs - it's worth it. Then look at them after doing a few hundred miles.

Black and sooty like you posted = well rich
Whitish and dry = well lean
Light tan (brown) is what you're looking for.

A/F screws definitely have a spring and a metal washer, can't remember an o-ring but there may be one too. If they're not coming out you most defo need to take a good look with a bright light and maybe a pick - make sure they're not stuck in there!
If they're missing, get some new ones from Sean. Bike won't run right without them, so that could be your prob.

It's normal for oil to go all over the place when you lay down the bike, especially if it's hot as the oil is then very fluid. A good cleanup will sort it out. It is possible you got some in the carbs but unlikely - from the crankcase breather it should only go in the airbox then drip back into the crankcase.

Hope this helps, and good to hear from ya Yukoner!!

 

[MaxMidnight]

Quite a few issues there...where to start?

When trying to identify and fix an issue always start with checking the basics.

You mention the state of the air-box and air filter. You are correct in thinking that piston rings normally keep the oil where it should be. However, the designers do make the assumption that the motor will be running in a reasonably upright position and not on its side!
This can allow the oil to come up through the breather system and cause the mess that you found.
Another way of achieving the same effect is to over-fill the sump.

The oil will also cause any debris pulled in to the air-box to stick to it. The end result is that it will flow less air than Yameringha intended inducing a rich mixture.

Start by replacing the air filter and see how the bike runs - it may be that simple.

Next check the float heights which if set incorrectly can cause richness. Adjust if required.

Also make sure that you have a full compliment of parts in your carb assembly - there should be a spring, washer and O ring behind each idle mixture screw. Use the exploded parts fische diagram for reference.
At this stage don't worry too much about #1 & 2 cylinders not responding to the idle mixture screws - whilst it will have an effect on the running it shouldn't give the extreme condition the relate.

The clolour of the plugs indicates what was happening in the combustion space when the motor was turned off. It won't show you what is happening at (say) 4K if you stop and let the motor idle before turning off. Mr Shover mentioned doing a plug chop - have a look here.

Whist I can see that your plugs are black I can't make out if they are sooty (indicating an over rich mixture) or oily (indicating you are burning oil). If the latter this could be due to the spill you had. It's unusual for all four plugs to be oiled up unless the motor has suffered severe neglect or has done very high mileage.

To surmise - start by changing the air filter and plugs and see how it runs.

 

[06VMAXIMUS]

Welcome back Yukoner! As stated above, the plugs look oily and over rich to me. Tipping the bike over would saturate the filter with oil, and make it run rich. Any oil that made its way past the filter could cause the plugs to foul. I would change the air filter and spark plugs for sure, and also find out whats going on with the mixture screw assemblies. They should have the screw, a spring, a washer, then the o-ring. As far as backfiring when turning the key on with out starting.....never heard of that happening before, unless you could somehow have a spark happening in a cylinder that has some fuel vapor left in it? Let us know how you make out.

 

[yukonerdave]

Wow thanks a lot for the feedback - knew I could count on you guys. I'll have some time tonight and tomorrow to spend on it so I'll keep ya posted on how it goes. Should have thought about that crankcase breather hose - of course that's where the air box oil would have come from. I'm running a K&N filter. Think I can clean it sufficiently, or would it be best to just replace it?

 

[tugla]

no if its a k&n just clean it and re-oil it put it back.and to get a good plug read you should do a wide open cut test.....get to that once you got the bike up and running decently.

 

[cgswss]

Clean the filter, and replace the plugs before you do anything else.

 

[RaWarrior]

The backfire when initially turning the key on indicates there is raw fuel sitting in the cylinders. This bike has a somewhat more primitive ignition, and shortly after energizing it, it fires all four plugs simultaneously if it doesn't detect any pulses from the pickup coil. This one spark is to discharge the system, since if it was left charged and not firing for a long time it would heat up and potentially damage the ignition.

Due to that, I'm thinking you may have a leaky needle/seat, resulting in a too-high float level. This would make the bike run rich, and can also explain the backfire when you turn the key on.

Tipping the bike over shouldn't matter. Mine tipped over to no ill effects afterward. Not saying it couldn't but not very likely.

Your plugs look pretty rich. Plug chopping can give you a little insight, but is an annoying practice for street vehicles. To get an accurate "chop", you need to drive in the suspect RPM zone exclusively for a couple minutes, then pull in the clutch and kill the engine simultaneously. Any idling or decel can "ruin" the plug's appearance. Remove the plug to check.

It's more of a tuning tip for 2 stroke dirt bikes and such(where removing and installing the singlular plug takes a few seconds, and there's no traffic to worry about), but the principle does apply. Bit more of a hassle with 4 recessed plugs on the side of the road.

I'd start by replacing or cleaning the air filter, though I suspect you'll have to tear into the carbs again to get this sorted. Something went awry in there.

 

[yukonerdave]

Pulled the carbs and two of the A/F screws had the little needle at the end broken right off. The hole they sit in looks clear but do I need to worry about those needles still being in the carb body somewhere? I used compressed air to clear of the PAJ1 and PAJ2 holes but didn't notice those needle ends. I don't think I would have noticed, though - they are pretty small and my lighting wasn't great. In addition, it looks like my floats are all over the place. I'll set them properly and get new AF screws. Anything else to look at while the carbs are apart?

 

[sdt354]

I'd try to locate the needle tips, or at least make sure the circuit is clear-compressed air blown down one of the orifices on top of the carb (pj1 if I remember) will be a help.
. I'd go through the carbs and install new plugs. I'm in the habit of doing a compression test anytime I have an issue, just to eliminate a possible problem. A compression gauge, volt meter and spark checker are close by when working on a bike.
Steve-o

 

[mr.maxx]

the tip and the center of the plug should be free of carbon. looks like you have 2 cyl runnin rich. 1&3.....the other 2 are prolly fine.

 

[tugla]

id set the floats dry and then double check wet prior to putting it on the bike or back together the rack. save you from redoing it again.check the rubber plugs on the jet block if the need replacing and the gaskets. basically your into a carb rebuild, might as well since your there.

 

[yukonerdave]

I have a left over flat washer from the carb assembly. I noticed it on my work bench before I really touched anything so I really don't know where it came from. Any guesses?

 

[06VMAXIMUS]

Looks like a washer from the choke linkage to me.

 

[one2dmax]

Possible choke as noted. Also the only other thing that takes a larger washer like that is the seat for the spring on the needles.

 

[yukonerdave]

Alright I'm back up and running. I don't think I have the pilot screws zeroed in just right yet, and I may also have an exhaust leak, because I'm getting some decel popping. It would be worth it to me to ensure that the pilot screws are where they need to be. Am I right in thinking this can be done with an air sniffer? Does that take a lot of messing around, or can a reliable shop do it in a reasonable amount of time?

One more question. My Vboost isn't cycling properly when I turn the key. The motor will turn and pull the cable up, opening the valves, but then it stays there and won't retract. I can hear the motor stopping and see the tension relax a little on the wire, but it doesn't close on its own. For now I forced it closed and disconnected the round plug, but I'd sure like to have it operating normally (whats a max with no boost, right?).

Sean - still trying to figure out how I can get you here. Be in touch soon

 

[naughtyG]

Hey Dave,

the vboost controller box (under left scoop) is usually the culprit. It's worth opening it up and refreshing the soldering (if you're handy with an iron) or get another box from Kyle or Sean and that should sort it out.

The A/F screws most usually set to 2.5 turns out as a start point and then tweak by 1/4 to 1/2 turn and ride to see if you notice a difference. I assume you've sync'd your carbs, right?
A sniffer is the way to tune the A/F properly, but it's best done on a dyno as you can then see the A/F ratio across the rev range, telling you where adjustment is needed (A/F screws, needles, jets etc). Of course dyno runs aren't cheap..