How do you warm-up you kdx?

johnkdx220 · Oct 6, 2004

Regularly, I witness guys that start their two stroke engine and immediately rev the engine. The engines misfires constantly and the guys seem to think that its a good excuse to twist the throttle even more. I'm no mechanic but I have a feeling that reving a cold two stroke engine is a bad thing (right?).

What is your warm-up proceedure for your kdx?

Here is my procedure: I let it run idle, choke on for about 30 seconds, then idle for another 2 minutes (I take this time to stretch my aging body.. ). I jump on the bike and will take it slow for a while until the engine responds without misfiring. Yep, there's a lot of blue smoke during the warm-up... I prefer the decarbonise everything when the engine is warmed-up.

rethnal · Oct 6, 2004

Pretty much the same way you do... 'cept I only choke it to get it running and take it off after a few seconds. Then I let it sit and idle while I finish putting on my gear.... usually about 3 to 5 minutes. I walk over and twist it every now and then while idling until I get a good crisp rev on her. Then... I ride it around to finish the warm up until it responds the way it should. Then I rip!

KDX's are very cold blooded in my experience and require a long warmup period. IMO.

dsndblm · Oct 6, 2004

You are right johnkdx220. It is not good to rev a cold 2 stroke or any other engine for that matter. There are more physics going on inside that cold engine as it is warming than I will ever understand :clue:

I saw a guy seize a nearly new KX 250 from doing just what you described.

I start mine, let it run with the choke on for 30 seconds or so, let it idle for another couple of minutes while I am getting my gear on. I am lucky enought to be able to hit the desert from my house, I take it slow down my street, the bike is pretty well warmed up by time I reach the start of my riding spot. The total time is probably 5 minutes.

wibby · Oct 6, 2004

Start with choke, immediately turn off choke, let idle a couple mins, shut off and wait a few minutes for the smokey cloud to dissipate and then ride around staging area til it quits making those terrible burbling noises

css_elfers · Oct 6, 2004

I was told to turn the choke on only to start. Once it starts turn it off then warm it up.

Elf

G. Gearloose · Oct 6, 2004

Choke (ahem, enricher) to start. When revs drop I stab the... uhm, choke for a sec, don't even click it.
Rinse and repeat every 25-35 seconds until it can idle by itself.

Never touch the gas.

crazymike · Oct 6, 2004

Since the weather temperature varies so much here, so does my starting procedures. But I usually choke mine until it idles on it's own (a few seconds) then let it sit while I get my gear on.

On super cold mornings I have to rev it a little just to keep the engine going for the first 30 seconds or so.

johnkdx220 · Oct 6, 2004

For the record, the kdx owner's manual states:

"If the engine is cold, pull the choke nobe...even after the engine starts, keep the choke knobe pulled up. When the engine is thoroughly warmed up, push down the choke knob" (as is you could push it up!)!

Anyways, seems like there is a lot of sensible guys in this forum. I can't help it, every time I witness a dump dump reving the cold engine, I go like :ohmy: :yikes: :|

lankytim · Oct 6, 2004

I agree that there's something wrong with giving a cold engine some stick... but I've got a curious question: what?

Unlike a 4-stroke that's gotta get oil pressure up (hehe - my KDX is the "wet sump" model at the moment, with the jetting outta whack) isn't a 2-stroke already nice and lubed as soon as it's getting fuel mix into the cylinder?

I am guessing that "warming up" means exactly that: warming all parts of the engine up to operating temperature so tolerances are right (closer?) but what is likely to cause a cold seize? Does the piston heat up (expand) quicker than the cylinder does so it gets too big for the bore?

...is there a mechanical thermodynamic engineering authority in the house? I wanna see formulae and calculus and dh/dt graphs, OK? :joke:

bcVulcan · Oct 6, 2004

I don't think the warm up "procedure" is all that important, as long as you DO warm it up. Only a moron would crank it, then rev it to the moon. That's really asking for it.

dsndblm · Oct 6, 2004

lankytim

The Carnot Cycle and The Efficiency Of Engines Theory states:

efficiency = 1 - Tc/Th = 1 - 300 K / 373 K = 0.20

I have no idea what this means as I flunked out of the class about this point. I just keep the book for some odd reason. :aj: :aj: :aj:

lankytim · Oct 7, 2004

Wait a sec... :think: ahhh ok, now it's crystal clear - if you've got a "warmed up" cylinder/engine, it'll absorb less heat (:worship: Newton, Fourier) from the combustion, thus the engine will be more energy efficient and your ride will throw roost further, err, I mean go faster.

Still interested in how a cold engine is damaged by revving it.

JasonWho · Oct 7, 2004

G. Gearloose · Oct 7, 2004

lankytim said:
but what is likely to cause a cold seize? Does the piston heat up (expand) quicker than the cylinder does so it gets too big for the bore?

bingo, especially a liquid cooled engine, there is a lot of thermal mass with the jug and coolant, and very little with the piston.

rethnal · Oct 7, 2004

The warm up procedure in the manual will not work on my KDX anyway.... If I left the choke on until it was warmed up... It would die a several hundred times. :think:

kdx633 · Oct 7, 2004

choke ,start ,choke off,hold SLIGHTLY above until heat is felt in radiators, ride conservativly for a short way.she will let you know when to twist her up.

canyncarvr · Oct 7, 2004

re: Still interested in how a cold engine is damaged by revving it

I don't know if this is a serious question.......

Clearances change considerably from choke cold to operating temp. While an oil film may successfully lubricate a small space it does less well with larger spaces. Imagine how a lot of things that are cold are more subject to cracking, annealing, tearing, breaking, whatever than something that is warm. Same applies to some extent to metal and engine parts.

And no, 2-cycles aren't 'instantly' lubricated either. And if they were, consider the temp differences of the charge, the atomization differences in the fuel (gas-wash is a reason for intake side seizure)..there are plenty of reasons why the instant twist method is just plain stupid.

Some use that 'method' to 'jet' their bikes...or to 'clean it out', too.

More stupidity.

Oh well. 'No one ever went broke underestimating the intelligence of the american people (public?).' -Henry Mencken
(I always thought that came from Samuel Clemens)

...or any other peoples, neither.

Yes, I am an American, too! ;)

rethnal · Oct 7, 2004

Hey CC .... your an American! Or ARE you? :laugh:

G. Gearloose · Oct 7, 2004

"The Americans will always do the right thing..
After they've exhausted all the alternatives"
-Winston Churchill
:think: think about it...

Jason02R · Oct 7, 2004

mine runs very loaded up and will not rev up until its warm, not that I would rev it cold anyway. I pull the choke kick 2-3 times sometimes only once, let it run for maybe 10 secs, then push the choke down and let it idle down for 3-4 mins before ridding. Then I ride it nice and slow gradually faster to clear it out then its readdy to rip

kawrider · Oct 8, 2004

Warm -up

Hey!
I usually pull up the choke and kick start the engine, leave the choke on for a couple of seconds, depending on the age of the gas, temperature, etc. Then, I finish putting on my gear.
The gloves are the last thing to put on, so, right before I do, I feel of the radiators. If I can feel a noticeable amount of heat, I put my gloves on and ride as I please. When the coolant gets hot, That lets you know that the engine is good and warm and ready to ride.
Dave

KDXMAC · Oct 9, 2004

cold starts....ummmmm

Im pretty much the same except that once started- choke off after 4-5sec the engine still idles high and as it warms up the idle gradually lowers to correct idle, this is when I ride off taking it easy no more that 1/2 throttle for a bit, the bike lets you know when its ready, crisper responce. Did you know you can cold sieze even after a long ride, high reving 2-strokes need lots of varied revs when ridden, if you toddle around at very low engine speed for prolonged periods of time and the air temp is cool the head can cool down enough to squeeze the piston. Think about it cool air, cold cooling coolant.......bang! :ugg:

89kdx200rdr · Oct 9, 2004

choke on start then take choke off right away then let idle a couple min then put around in 1 or 2 till the radiators are warm to touch then clear it out

How do you warm-up you kdx?

johnkdx220

rethnal

dsndblm

wibby

Mod Ban

css_elfers

G. Gearloose

Pigment of ur imagination

crazymike

johnkdx220

lankytim

bcVulcan

dsndblm

lankytim

JasonWho

G. Gearloose

Pigment of ur imagination

rethnal

kdx633

canyncarvr

rethnal

G. Gearloose

Pigment of ur imagination

Jason02R

kawrider

KDXMAC

89kdx200rdr

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How do you warm-up you kdx?

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