bugger - what to check first??

[SiP]

how long should plugs last? these are only about 500km old.
Secondly - no problem I'll go get some but what could cause that fouling? I'm thinking carbs but they were set up for me so thought they'd be good.

[ClarkGriswald]

If you never foul a plug it can go for years and years, eventually the electrodes start to round off and disappear but most people never have em that long.

But now I'm talking lawn mower or something that performance isnt a big issue..
I think a set of plugs each spring isnt out of the question, plus you save your last year set for spares.

Quick idea, make sure your spark plug wires are ok and not arcing out on the frame someplace. That could probly cause some erratic running/poor spark. You would hear it clicking..

Heat is the enemy of everything so if it was real hot last time ya rode it, mabye something started to let go. Or condensation in gas tank? Rode hard put away wet? Just guessing now. hehe

Mabye its foundering did ya check its feet? JK

[boyat68]

SiP:

I went through three sets until I resolved the problem of my leaking /sticking floats. I found a couple of non performing plugs in the sets. Now that the bike is running well, it is a bit on the lean side as the color of the plugs are not quite slightly brown. I would think that you have something similar to too much available fuel coloring your plugs black. It could possibly mean that you have sticking floats also.

As far as how long plugs should last depends on the carbs as those plugs will not perform well after being coated with carbon no matter how well they are cleaned. If your carbs perform well, then the plugs should last a long long time just like auto plugs do now that electronic iginition systems do not eat plug tips like the old breaker systems.

[egsols]

90 psi does sound low, when you retest it, it also helps if the bike is warm and make sure you have the throttle wide open. Mine was 120 cold, across the board and averaged 160 after warmed up and wide open throttle.

Oh, yeah, how old was the fuel three weeks ago?

[ruffrider]

compression check tips from Prom

Here's some tips for compression check that Prometheus sent me:
Ok, here we go...
Now, I'm not saying anything, but...
Let's go over doing a compression check.
1. Engine should be warm.
2. Pull all sparkplugs (I said all)
What we're trying to find out is the compression... (the "unloaded" compression) of a cylinder. All plugs must be out, or the cylinder you're testing... will be fighting the compression strokes of the other cylinders.
Having all the plugs out... is a good idea as then the engine won't start! It's also a good idea to have the plug caps away from the plughole when cranking. It's always fun to have a hot jet of ignited fuel shoot out of the spark plug hole.
3. Make sure the battery has a good charge. As the battery wears down... by the time you get to checking the last cylinder.. you'll note that the compression reading are getting lower, too.
4. When cranking, hold the throttle WIDE OPEN so the cylinder can take in the maximum amount of air for a good reading.
Ok, engine warm, all plugs out, good battery, throttle wide open. That's it.
Crank each cylinder till the reading doesn't go any higher.
Now then, standard compression is 142lbs. There should be no more than a 10% deviation between cylinders. That means, if your highest reading is 142 lbs, your lowest shouldn't be lower than about 128 lbs.
See what the readings are again.
Rings can get gummed up from sitting, hence low compression. (as shown by the higher readings once you added a little oil(About a tablespoon's worth is all that's needed)
As you haven't mentioned this engine blowing smoke out the exhaust.. I can imagine that the rings are good.(I can also imagine that it did blow smoke out the exhaust after you put the oil in the cylinder... which can be expected)
As for the coils and changing the plug gap... I don't recall that.
I'd stick to the standard gap of .028-.031 for now. (And get NGK BP-6ES plugs. Yes, there is a difference, and I'm not partial to Champion plugs)
When one widens the plug gap, it changes the ignition timing a little. The coils take a little longer to fire, as they must build up a stronger spark to bridge the wider gap. Small matter, but let's not go changing too many things at once...can complicate things and make finding the main problem more difficult.
Ok... new compression check... new plugs... write back with the results.

[rickmc2000]

Bugger - what to check first

Sounds like the old broken pick-up coil wire trick. When you rev the engine, the vacuum advance puts a strain on the pick-up coil leads and often they break. When this happens, the bike will idle but goes crazy when you accelerate cause the advance strains the wires. Easy to check and fix. Let me know if you need more info.

[SiP]

OK - I'm a happy camper 'cos it was just the plugs after all.
Still raises an issue or two with me though.
1. How long should a set of plugs last. My car ones have about 115,000Kms on them, the XS ones had about 250Kms! What is causing them to crap out?
2. Why are they gunged up like that? (See pics in previous reply). Is it 'cos I'm running rich or should I be looking at something else?

At least I'm good to go for now - 'til I need another set of plugs anyway

[rickmc2000]

Fowled Plugs could be:
Oil from rings, valve guides, Any Blue Smoke?
Bad Gas
Driving too slow Does it puff black smoke when you accelerate?
Fuel mix too rich
plug gap wrong
timing
ignition

Are all plugs the same?

[SiP]

I do get a bit of smoke when i rev her up in the garage - out on the road I don't know
Gas was premium and about 20 minutes old.
Timing etc... I am going to say is OK as it runs well now.
I have some different jets that I should get round to fitting on the advice of someone else on this forum, he also cleaned and rebuilt the carbs so I don't think I have sticking float problems.

I'll do the floats and then play with her some more - I'm right in saying the mixture adjustment is just a screw right?

[DiverRay]

Try dropping from premium to regular gas. These bikes WILL run on regular, and they WILL NOT carbon up as fast. You can go to mid grade if you hear any pinging as you give it full throttle.
I ONLY run regular, and it's the "BAD" California gas. I don't have any problem, and plugs last about 10K to 15K.

[SiP]

New jets are in and she's running sweet

Will now check the gas mileage and plug condition.