How much smoke does a 2 stroke smoke?


20 replies to this topic
  • Dante04SRT

Posted August 08, 2009 - 08:22 AM

#1

Just rebuilt the entire motor on my 98 RM250 and am curious just how much everyone else's 2 stroke smokes? I realize there are a lot of factors, namely premix ratios, but what is the norm?

I'm running 32:1 and mine seems to smoke constantly. I mean, its not a plume or anything, but its noticeable, whereas before it wasn't as constant - It'd smoke at startup and for a minute, but it didn't seem to leave a faint smoky trail behind me when riding. I did switch premix oil though - Went from the crappy WalMart "Autotech" (hey, its all I could get on Sunday here and yes, on the OLD motor) 2 cycle oil to Motul 510 (which is supposed to be a less-smoky oil). Power seems to be great on mine, and I'll do a compression test tomorrow.

Just wonderin' what everyone elses experiences are.

  • crider400

Posted August 08, 2009 - 08:28 AM

#2

32:1 is fine, i run 36:1, my bike smokes a lot when i first start it to warm up, then after a min or 2, it goes away.

  • moto_xmayhem21

Posted August 08, 2009 - 09:18 AM

#3

Once you break in that new engine you can give it a re-jet:thumbsup Theres always smoke but as your bike warms up (when jetted corectly) the smoke should be there yet faint.

  • killerdwarf77

Posted August 08, 2009 - 01:30 PM

#4

I used Motul 800 because it was given to me. It seemed to smoke quite a bit more at 40/1 than Dominator does.It even left ny fender oily. I bet 510 is even worse. Especially at 32-1.

  • rpt50

Posted August 08, 2009 - 02:32 PM

#5

It will smoke a good bit when cold. At 32:1 you should only see a little smoke when the bike is hot and running hard. If you are leaving a plume like a mosquito fogger, then you probably have a crank seal leaking, a seriously over-oiled airfilter, or some major jetting issues.

  • Ebs

Posted August 08, 2009 - 02:37 PM

#6

They don't call 'em 2 smokes for nothin'.

  • Dante04SRT

Posted August 08, 2009 - 02:47 PM

#7

I fired it up again today and the smoking is getting better. When we reassembled, I used OEM everything, ALL new seals and gaskets, so I doubt its trans oil.

Plus, I'm running ATF in my trans and something tells me it'd smell vastly different than the 2 cycle smell the exhaust has now. :thumbsup:

  • Ebs

Posted August 08, 2009 - 02:50 PM

#8

If you're a freak about making sure its not sucking trans fluid just measure how much drains out when you do your fluid changes.

  • killerdwarf77

Posted August 08, 2009 - 03:18 PM

#9

If you're a freak about making sure its not sucking trans fluid just measure how much drains out when you do your fluid changes.

I have read about this enough, and now it's time to ask. How the heck is that going to prove anything with any accuracy???

  • Ebs

Posted August 08, 2009 - 03:22 PM

#10

Well if you fill up with 750mL and only drain 500mL and you don't have any external leaks and you've been suspecting an internal leak it would provide some sound evidence to support that.

  • killerdwarf77

Posted August 08, 2009 - 03:27 PM

#11

Sure, if that is what happens, then yes it may. Anyone else care to explain how that oil difference theory works?

  • shrubitup

Posted August 08, 2009 - 03:46 PM

#12

You simply need less Motul to lubricate your motor than the SuperTech oil used earlier. I'd run it at 40:1 and see if it improves. If no MX racing maybe even 50:1 if you aren't on the main jet too much.

  • KTMrideR146

Posted August 09, 2009 - 09:35 AM

#13

get a jet kit for it. they arent to expensive. u probably have the carburator set up to rich. If ur spark plug has a lot of carbon on it, then u definatly are running it to rich.

  • 18 Layers

Posted August 09, 2009 - 11:24 AM

#14

If it is constantly smoking, you probably need some smaller jets for your carb. Easy enough job :thumbsup:

Seriously, mine was smoking like a b*tch, wouldn't idle (yes, it's not really supposed to blah blah). I could oil my plug in about 20 mins... Oh, and it would rev, but something wasn't quite right....

Anyway, with a set of smaller jets, all is good :worthy: It now idles (I only found out, after I stopped, in neutral - it normally died, today, it didn't!), doesn't smoke nearly as bad - and it was BAAAAD - runs better than ever, and almost zero spooge.

And I run at 38:1 - 40:1-ish.

Oh, and yeah, this is my first post! Hello!

:ride:

  • moto_xmayhem21

Posted August 09, 2009 - 03:09 PM

#15

If it is constantly smoking, you probably need some smaller jets for your carb. Easy enough job :thumbsup:

Seriously, mine was smoking like a b*tch, wouldn't idle (yes, it's not really supposed to blah blah). I could oil my plug in about 20 mins... Oh, and it would rev, but something wasn't quite right....

Anyway, with a set of smaller jets, all is good :worthy: It now idles (I only found out, after I stopped, in neutral - it normally died, today, it didn't!), doesn't smoke nearly as bad - and it was BAAAAD - runs better than ever, and almost zero spooge.

And I run at 38:1 - 40:1-ish.

Oh, and yeah, this is my first post! Hello!

:ride:


Hey now Buddy, you don't have to lie to kick it! Says right there this is your second post! Haha j/k...
Anyway, I say re-jet once broken in! Don't mess with your premix ratio to fix it, that won't work~

  • cammeddr-z

Posted August 09, 2009 - 04:02 PM

#16

how much smoke does a 2smoke smoke if a 2smoke does smoke smoke?

  • Dante04SRT

Posted August 09, 2009 - 04:56 PM

#17

how much smoke does a 2smoke smoke if a 2smoke does smoke smoke?


I was waiting for that - Surprised no one got that before you.

  • zig06

Posted August 09, 2009 - 05:02 PM

#18

I use PJ1 Silverfire Smokeless 2-Stroke pre-mix oil at 40:1. And my bike really does not smoke at all, it's almost like (dare I say it...) a 4 stroke.

Posted Image

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  • shrubitup

Posted August 09, 2009 - 06:28 PM

#19

how much smoke does a 2smoke smoke if a 2smoke does smoke smoke?

:thumbsup:

  • Chickenhauler

Posted August 09, 2009 - 06:39 PM

#20

I have read about this enough, and now it's time to ask. How the heck is that going to prove anything with any accuracy???


Sure, if that is what happens, then yes it may. Anyone else care to explain how that oil difference theory works?


Being that the transmission is not in contact with the combustion area (under the piston and rings) and if you have no external leaks, in theory, a trans that you put 750cc into should drain out 750cc of oil.

Now, there will be minute losses here and there (breather boiloff, getting dumped over, small "weeps"), but it should be minimal.

If the crank seal is bad, the suction of the engine sucking the fuel/air/oil mix through the bottom end and up to the top end can and will suck oil from the transmission past the seal and into the combustion chamber, burning the oil, causing excessive smoke.



As for "too much smoke".....I've always followed the rule that if a smoker isn't smoking, then something isn't right. My bikes puff a thin cloud when they're all warmed up and hot, maybe the equivalent of a cigarette sitting in an ashtray? Very little smoke, but enough to see if you're looking for it.




 
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