Spark plugs: owned! Help!

[treble]

Hey guys, I'm having some problems with my DT 125R from 2003.

The spark plugs blow after 10 ish miles, and come out looking black and charcoal-ish. Could this possibly be because of a mixture too rich in oil? The guy i bought it off said he adjusted the oil pump thingy because he was scared of seizing it....

Taking it to the mechanic on monday, but can I get some opinions off you guys first? Much appreciated! thanks!

[Minty]

Too much oil and I would expect to be, well, oily. Have a search for plug colours. There are charts floating around you can compare to.
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My fingers smell of your mum.

[Trixie]

Check out the Haynes Manual, as it will have a page with photos you can compare your plug colour too.

Not a great expert, but from what you've described it sounds like you're running rich.
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Dead nobodies in company cars...

[Spoonman]

yup - way-hay too much oil

don't know what those pumps look like as i took it out of my old DT and just premixed my petrol but there's probably an adjustment screw on it somewhere that just need a wee twist in the right direction.

[the grim reaper]

If it's coating a plug in ten miles, it would have to be running richer than creosote.

I'd go for massive over oiling, which can actually cause your bike to run lean as there isn't enough fuel mixed with the air. I'd get that pump adjusted immediately.

Cheers

Grim
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Adverts don't always work: Remember that advert, where the army are running across the desert and they have a wounded man on a stretcher. They get to a ravine, the bridge is down and a caption pops up that says, 'What are you thinking?'. I don't know about you but I was thinking, 'Christ, I'm glad I'm not in the f***ing army'.

[treble]

Well, it seems the problem has gotten worse over the last few days. The first plug lasted like 2 months, then it blew and this last one lasted a week max.

Thing is, I don't really want to adjust the pump in case I take away too much oil from the mix, you know? seized engine is the last thing I want... I´ll do some more research guys, thanks.

[shaun_04]

You won't take too much oil away from the mix - trust yourself.
And you will probably get robbed by a mechanic.

[Spoonman]

just notch it back in steps.

to get a range, see what it takes to set the adjustment to minimum from where it is.

given your current mix state i'd say you could very safely go half that and probably still be a little over the mark but at least it'll give you a start and a reference.

the plugs should be a biscuit brown to light grey sort of colour ideally.

dark grey == rich (the darker it is, the worse the problem)

white == lean (the cylinder will be running hotter so it scorches the plug; again, the whiter it is, the more lean you're running.)

wet (and black) == over oiling (and again, the wetter, the worse) this is where your problem is and the plug will be black in this case due to the amount of oil being burned with the petrol.

dial it back a bit and ride for about 20 mins, then check the plugs again. no need to overtune the oil mix, just do enough to get it working right for now.

[treble]

Thanks everyone, spoonman especially. I just went out and bought 2 plugs incase something goes pear shaped, and when I get home I'll try and find the widget that adjusts the oil pump. Let you know how it goes in a couple of hours!

[Pete.]

From memory, when you look at the oil pump cable quadrant (where the cable connects to the oil pump), you'll see there's a line on it that should line up with a mark on the pump body when you wind the throttle fully open. Adjust the pump so that this happens.

I would say that if you are over-oiling that much, you'd have a cloud of smoke wiping-out the road behind you. I think you have the fuel mixture wrong personally, perhaps the carburettor float has a tiny hole in it and fuel has got inside making the fuel level too high in the carb.

[Finglonga]

If the plug is fouling your not buying a new plug every time are you?

You can clean them with a wire brush, it will save you a small fortune!

Oh and.......

https://www.racesell.com/ReverseRacing/images/plug_condition.jpg
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Andy Sez....
F.Y.Y.F.F.

[treble]

Jesus, it looks like I'll have 3 plugs left over in case anything happens then! LOL!

Strange that, because I'm not trailing excessive amounts of smoke. The plugs are carbon fouled BTW, this whole thing seems to be not adding up though.

I'll go see what I can do about the pump now, but I think from what Geri said about the smoke thing that the problem goes deeper than this! And adjusting a pump I can do, but screwing around with the carbs is really jumping in the deep end for me.
Cheers guys, be back in a while.


EDIT: what do you guys make of this?

Soft, black, sooty, dry-looking deposits indicate a rich air fuel mixture, weak ignition or wrong heat range spark plug (too cold). These carbon-based deposits are conductive, much like oil fouling, and will allow the voltage coming out of the center electrode of the spark plug to track down the core nose rather than jumping the gap. This will result in an engine misfire and further aggravate the carbon fouled condition. Check for correct plug heat range. On fuel injected engines, check for sticking injectors, malfunctioning cold start valves and/or circuits. Also check for correct fuel pressure specifications. On computer controlled vehicles, the "limp home" computer mode will always result in a rich condition. Therefore, it is imperative that you check the operation and condition of the on-board computer system. On carbureted vehicles, check choke and choke pulloff, high float level, and needle and seat condition. On all engines, severe vacuum leaks can decrease manifold vacuum, resulting in a rich condition. Weak and/or damaged secondary ignition systems will fail to spark across the gap lowering combustion chamber temperatures and promoting carbon deposits. This condition could also result from continuous low speed driving or poor cylinder compression.

[element]

DT's are known to run rich. The plug on my 04 DT when I got it was carbon fouled too (Had only done 4k miles. I belive its the original plug). The choke lever was up though and slightly stiff so its possible the last owner ran it with the choke left on? Ive not checked the new plug since I put it in 1k miles ago.

https://www.apbe19.dsl.pipex.com/dt/plug%20when%20bought.jpg
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04' DT125RE (run-a-bout) // 89' DT125R (rebuilt + supermoto conversion)
SPARES FOR SALE. 2RK TZR // 82 DR125 // DT125R/E .... PM ME...

[treble]

Update: went down and changed the plug, tried to find the pump regulation majig but to no avail... I did bring pics though! There were some possibly adjustable bits, but I didn't do anything just in case. HAve a gander:

https://i53.photobucket.com/albums/g71/lluis01/bikebig.jpg
DT porn gasp!

https://i53.photobucket.com/albums/g71/lluis01/plug.jpg
This is how the most recent fouled plug came out. The very first one was carbon fouled, at least as bad as that one, element (bout 800 miles done on it) but this one seems more oily to me. Also, I just ran the bike with a brand new plug for about 10 minutes, then took it out and it was black and oily. Thing is, the bike sounded like it was running lean... really sharp, dry sound. Surely if there's too much fuel it should sound like it? WTF is going on? The plot thickens!

https://i53.photobucket.com/albums/g71/lluis01/whatdoesthisdo.jpg
This is a pic of the bike's innards. The circle on the right is where the oil tube goes into the... uh... silver thing, and the circled thing on the left it some kind of widget I was too scared to mess around with. Where the hell is the pump adjustamajog?

Anyone got any ideas? And yeah, I know my mechanical vocabulary could be better.. but you know what I mean. ~Most of the time, hopefully.

[treble]

Nobody? All I need to know is what knob to turn guys... please?

[element]

3rd pic first red ring. Thats where you put the gearbox oil in.

On the 3rd pic though you can see the plate with the 4 screws. You need to take that plate off. You can see where the cable goes in that pulls the pulley for the pump. Theres an adjuster there Just do it a bit at a time and do a plug chop

https://www.apbe19.dsl.pipex.com/dt/whatdoesthisdo.jpg

from the service manual (04 dt mind but its still the same I belive)

https://www.apbe19.dsl.pipex.com/dt/autolube.jpg

Just remember, a little bit of knowledge can be dangerous
____________________
04' DT125RE (run-a-bout) // 89' DT125R (rebuilt + supermoto conversion)
SPARES FOR SALE. 2RK TZR // 82 DR125 // DT125R/E .... PM ME...

[treble]

thanks thanks thanks!! I'm gonna take it to the mechanic anyway to see wtf is going on, because the problem seems to be more than the whole oil thing or it would have been happening to the previous owner too, right? I'll just take it in for a proper tune-up.

For now though, I´ll be trying this fix. Let you know how it goes tonight!

[Finglonga]

Just a thought...If you are riding very gently ie: not reving the engine up much, then the plugs will foul as the engines are built to be for want of a better word 'used'. Giving the bike a good blowout ever now and again is a must with a 2 stroke, as if the plugs are that bad then the exhaust must bu realy full of shit.

https://img.photobucket.com/albums/v112/finglonga/Finglonga%20Inc/ne_nau.gif
____________________
Andy Sez....
F.Y.Y.F.F.

[treble]

hey, maybe that's part of the problem as well... What a joy to have a bike you HAVE to rag the pants off to keep in in working condition!! I'll be sure to be less gentle with it in the future.

I'll probably have to start a new thread when I want to do a blowout and clean the exhaust if it involves taking stuff apart, but that'll be a whole different story. Cheers

[Finglonga]

I had a KMX years ago, i bought it from new and running it in there was oil coming from the tailpipe, it was that bad.

Gave it a good thrash after it was run in and for the first few miles it would stutter and struggle but slowly it came right and eventually blew all the oil from the pipe.
____________________
Andy Sez....
F.Y.Y.F.F.

[Zimbo]

It may just be me, but that plug you've posted the picture of doesn't actually look excessively fouled to me, in fact it looks near normal.

[treble]

yeah, that's because it is about a week after I started the bike for the last time - it hasn't been started since, and that is the plug that fouled it. it worked fine with a brand new plug, but combine a bad picture with a dried out plug and, you know...

[Spoonman]

dude, there's nothing wrong with that plug but i think finglonga has it sussed for you.

you will be delighted to hear that you absolutly *MUST* rev the nutts of a 2T for it to run properly! - go mad!



if you want the simplified engineering blurb keep reading, otherwise stop now!



**************
2T == 2 stroke:

stroke 1: upward stroke

above the piston:
piston rises above the intake and exhaust ports, sealing the chamber and begins to compress the air fuel mix

below the piston:
air and fuel are drawn into the bottom of the chamber


stroke 2: downward stroke

-the spark ignites the fuel and the piston begins to travel downwards compressing the mix below it.
-about half way down, the exhaust port is exposed and the exhaust gasses begin to escape
-about 5-6mm later, the intake port is exposed and the compressed mix below the piston is forced up into the combustion chamber

the cycle repeats.


now, revs and the exhaust pipe.

you will notice that your exhast pipe has a large bulge in the middle and a very small exit at the tail. there's a reason for this.

if you read the blurb above again, you'll notice that both the exhaust and intake ports are open at the same time - so, what stops the fuel mix running straight out the exhaust??....

back pressure!

that bulge in the exhaust is known as the power pipe and is the most important part of the motor as far as power generation is concerned.

as the piston travels back up and low revs, there is very little gas in the exhaust pipe so you will loose some of the mix straight out the exhuast port - this results in lower compresion and a slower, colder fuel burn --> not all the oil is burned off cleanly --> fouled plugs.

at higher revs, (6K and above) the backpressure from the gas in the power pipe prevents the mix from escaping out the exhaust port --> more air and fuel in the chamber - this means higher compression due to increased volume and more power due to increased fuel in the burn.

it also means a hotter, faster, cleaner burn --> no fouling.

now this doesn't mean you have to run her at the redline all the time, but it doesn mean you have to rev the motor plenty - especially when taking off.

the DT125 is well capable of flipping itself entirely on takeoff in first when you drop the clutch in the powerband (area of the revs where the most power is produced) so get used to taking off at higher revs and using the clutch to feed in the power.

i used to regularly powerslide my old unit (with knobblies) on the dirt when i was a kid - they're a fantastic machine and far more capable that they are given credit for!

[Spoonman]

[Pete.]

Long-term gentle running could have your exhaust port carbon-fouled to the point of strangulation and that might be causing your plug fouling too. One of my first bikes was a DT50MX. It would barely crack 20mph when I got it. I pulled off the exhaust and found that the exhaust port was fouled with a build-up of carbon so bad there was only a hole big enough to poke a biro though. I cleaned this out and the bike was back to full 32mph glory