Smoking bike observation

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JoeR
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Smoking bike observation

Post by JoeR »

Every time I read a complaint about a 2 stroke bike that smokes, even when jetted correctly I always want to reply "It's a 2 stroke! It is a total-loss oiling system! Want it to stop smoking? Stop putting oil in the gas!"

A couple of things stop me from doing that.
1) Very often, the further you open your mouth, the further your foot goes in. You think you're smart...and then find out that it's not the case.
2) I really hate it when guys run their mouth on discussion boards. They are usually total pussies when you are face to face with them, but have all kinds of mouth when they are hiding behind a computer screen. I don't want to act like that guy.

anyway...I rarely ride at full throttle, but today I was running a 2 lane road of crushed stone when returning to my pickup. For about 2 solid minutes I was at full throttle in top gear. I looped around to the back of my truck and drove up the ramp into the bed. While idling in the bed, my bike was smoking out the tailpipe like it ws on fire! It was amazing! There was a bunch of fat guys on quads sitting there looking at me like I was an eco-terrorist. I ran it at high idle for about a minute before it returned to it's normal haze. I bet that all the smoke was because a lot of the oil that had built up in the pipe was now vaporizing or burning.
Maybe that's what's happening to others. Oil builds up in the pipe, and when you hammer it, it burns off. When it burns off, it makes much more smoke than you would see on a normal basis.


Whether that's what's happening to other people or not, I'm glad I didn't open my big mouth, or I would have put my foot in it again.

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Post by fuzzy »

Yes, I think that's at least a great contributor to 'spooge,' and not being able to get rid of it. You have probably mentioned a good way to help keep it clean. The problem will be lessened by those who run good clean jeting, but there is always going to be some accumulation, and it will add up over time. If you dyno a 1yr old pipe, and a brand new pipe there will be a difference, and this is due to build up (this is expecially noticable in smaller motors due to smaller pipes, etc...). The karts I run are a good example of this. I've seen guys w/ xyz pipe shaking their head when they can't catch the other guy running the same pipe...Next thing, when all else fails, a new xyz pipe is purchased, and BAM here come the checkers. Of course these things run a 12:1 castor mix and really make a mess when their not at full song. Then at full song the cup o spooge in the pipe gets burned off leaving a hardened residue that builds up over time. No way to get it out without cutting the pipe open (on these). An acid-flush might be a good trick...Especially on a bike pipe.
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Post by canyncarvr »

It should'a been smelling real good about then, too! A bit hot perhaps? :wink:

There is generally less complaint of smoke than there is drips/spoo/goo. My bikes (2-smokes) have run with powder dry exhaust tips and no drips nowhere..and they haven't. Never had one that didn't ever smoke. I would've been real worried about that.

A btw...your icon being a sled..consider that the operation of a sled/bike are not the same. Aren't sleds closer to fuzzy's depiction of carts than to bikes? My bike is rarely at WOT.

And when it is (like the five mile or so asphalt run to the lunch stop in Prospect), I'm one'a those eco-terrorists in action!!

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Post by fuzzy »

what oil are you running by chance?

Yeah, the karts single speed, high stahl drivetrain is very similar to a sleds, but without the variable clutch which helps A LOT. In the dirt oval karts that I run most pipes/porting make power from 10k-15k...Clutch lockup at 10k. They also run crappy 'pumper' carbs with twist low/high adjustment that can be made on the fly, but it's very tricky. Most, including myself keep the WOT tune in the carb, and just do the right things to keep it cleaned out during cautions, etc. It drools like crazy when off the pipe. The sled is similar, but generally a much more doscile tune(WAY less RPM, WAY broader pipe/ports). Sleds have the advantage of running the same type carbs we do, and can cleanly tune for the load over the whole range. Anyway, you shouldn't really be experiencing this w/ the KDX, but I can see it happening and I'm sure my pipe has a couple shots of oil in it. The KDX will also notoriusely run with very fat jetting without any real performance issues...IE unless you've experienced a truely tuned setup you won't even notice. Sure yout jetting's as good as it could be?
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Post by JoeR »

I run Amsoil interceptor at 40:1. Once I ran the Yamaha stuff, but only because I had half a quart sitting around.
My jetting is 155Main/42Pilot i think. Right now it is fat enough on the pilot that it 4 strokes when it's hot out. Runs nice and crisp at 40F and if I run it coler than that I put the stock main jet back in or just keep it off full throttle. Last year I had stock jetting in it for most of the year.

BTW, I've never had spooge. Never had a drop of anything liquid out the tailpipe....but it was smoking like a brush fire, and the pipe was really baking the mud that was on it. You could smell it cooking. I want to give it another try, but I'm on the road again...Memphis and St. Louis this week, and I'll be back on Friday. I've been wanting to try a 38 pilot for the hot weather. It would be an interesting test. See if it smokes after not running so fat for so far.
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Post by Indawoods »

Your main is what you should be looking at. 155 is at the top of the range on acceptable rich jetting.... especially for hot weather.
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Post by KarlP »

My bike will do the same.
I seldom run WOT, but when I do run down a dirt road or such for a couple of minutes it will smoke like a bandit. First time I saw that (NOT on a KDX, by the way) I was sure I'd blown something up. I figure I'm running the pipe and silencer up to temperatures it doesn't see in my normal riding, therefore lots of condensed oil is gonna come out.

I bet if I ran like that all the time it wouldn't smoke no more!

I don't worry about it.
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Post by canyncarvr »

fuzzy wrote:what oil are you running by chance?
You talkin' to me?

Interceptor. An outfit called 'Amsoil' makes it.

:wink:


After a high-speed run as mentioned..you know it's hot when the glas pipe guard is stinkin'!

I don't worry (much) 'bout mine, neither. I've tried to recall the exact point at which it started doing it (I'm talking drool..not smoke), but simply don't remember. All things considered, I wouldn't take back a change that's been done..so, that one of them, or combination of a number of them, make spoo isn't a big deal. The bike runs good! ..and that suits me fine.

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Post by JoeR »

>|<>QBB<
Indawoods wrote:Your main is what you should be looking at. 155 is at the top of the range on acceptable rich jetting.... especially for hot weather.
I called the local dealer today and he had both a 152 main jet and a 38 Pilot. So I got them and put them in, set the needle to the center clip position and took it for a spin. It has a significant amount of additional power on the main jet. I was definitely impressed. If I'm chugging along and grab a handful of throttle it bogs, but that's to be expected. I need to drop the needle one clip becasuse it's still a little fat at part throttle, but I broke the needle clip when I tried to tighten it a little. I hope I can find one tomorrow.

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Post by Indawoods »

38 is a little lean for my liking....
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Post by canyncarvr »

Those clips are metric. Don't try to force in a 'regular' (US) clip.

You can file a US clip a bit thinner if you have to.

BTW..ALways carry extra clips with you..for when what happened happens out in 'da woods someplace.

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Post by fuzzy »

Inda is right, and that's most likely where your bog is coming from. Part-throttle lean-bog. To prove this see if it get's better w/ the air screw turned in more. This will also help get you aquainted to tuning the A/S on a regular basis which is a necessity. Fatten the pilot, and go lower on the main more than likely at least one more jet in the NY summer...DO a WOT plug chop on the main to get it right. Search for that term on here. Long/short try a 40/150, and buy a 148 too(for summer).
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