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Must know 2 stroke tips/facts

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I've been in the dirtbike world forever but recently my cousin gave me his 97 cr250r. Ive never had a 2 stroke before only a four stroke. So does anybody have any tips or facts from maintenance to riding or tuning. I've dialed in my four stroke but that was easy. 2 strokes seem more complicated.

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2 stroke more complicated? oil in the gas...ride it...

I jetted my 97' when I got it in 00' and has been the same since.

my 97' has NEVER let me down! been a great bike!

keep an eye on the muffler, lower subframe mount, and kickstarter bolts mine like to come loose....

as far as riding it...it's all about throttle control!

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Two strokes have narrow powerbands...power like a light switch...on/off. Just keep it up in the revs,work the clutch(two stroke clutches can handle abuse) mix the gas and rip!

You'll find two strokes are waayy easier to rebuild as well, very little moving parts to deal with.

One last piece of advice is to never hold it wot for more than 10 seconds, feather the throttle every once in a while...it isn't very pretty when it sticks the piston in 5th gear and the back tire locks up.

Good luck and have fun!

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This winter I'm planning on a fresh piston and then I'll check out the crank. Im basically restoring it with all oem parts. Coming of a four stroke I'm not used to all the vibrations. Might change the triple trees or something

Does anybody have a link to an owners manual?

Edited by rayztruckz307

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One last piece of advice is to never hold it wot for more than 10 seconds, feather the throttle every once in a while...it isn't very pretty when it sticks the piston in 5th gear and the back tire locks up.

? why I do this all the time

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To get rid of vibrations, try the Fasst Flex-bars. I rode mine again yesterday and they are great.

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I've been in the dirtbike world forever but recently my cousin gave me his 97 cr250r. Ive never had a 2 stroke before only a four stroke. So does anybody have any tips or facts from maintenance to riding or tuning. I've dialed in my four stroke but that was easy. 2 strokes seem more complicated.

Owned a 97 when they first came out. It's the first gen. aluminum frame design 97-99 yrs. The frame was was rigid & stiff I had FC revalve & respring the suspension it made a difference. You can also run rubber mounted triple clamps & different bars as mentioned. The motor is good stock. I'd check the bolt chain adjusters they have a tendency to corode & seize in the swing arm. Check the topend & bottom replace if needed (cheap insurance).

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? why I do this all the time

@ high rpms the oil in the fuel just blows by the piston and crank bearings without providing adequate lubrication...I've never peronally done it because I don't hold it on but a couple of my buddies have...one of them had to get their face reconstructed because he did it on pavement, locked up and tossed him..not a pretty sight what so ever. I'm sure you can get away with it more often then not but why risk it. You can still hit top speed just not quite as fast...jmo

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@ high rpms the oil in the fuel just blows by the piston and crank bearings without providing adequate lubrication...I've never peronally done it because I don't hold it on but a couple of my buddies have...one of them had to get their face reconstructed because he did it on pavement, locked up and tossed him..not a pretty sight what so ever. I'm sure you can get away with it more often then not but why risk it. You can still hit top speed just not quite as fast...jmo

this is untrue, learn how to jet or maintain your bike properly, cant say what your friend did for sure

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this is untrue, learn how to jet or maintain your bike properly, cant say what your friend did for sure

This is correct. If your running lean at WOT shit will happen. Put in a bigger main jet if its too lean. I used to run my 2 stroke watercraft engine at WOT all the time and never had a failure due to being too lean on the main jet.

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http://www.thumpertalk.com/forum/archive/index.php/t-286565.html

Seems like there's people on both sides of the fence here. All I know is Ive seen my fair share of bikes seizing being run wot forever.

Besides, bikes are normally incredibly rich from the factory...I have my 125 leaned down.

390 main, 32.5 pilot, dropped the needle with the air screw out 1 3/4 turns. Much better throttle response and no more fouling plugs. So bottom line, unless your running in the desert or top speed running, your gonna want a crisp bike and it's gonna have to be leaner than stock.

One more to the OP I almost forgot...when running wot don't let the throttle just snap shut...cuts off all lubrication to the engine since the oil is in the gas..add screaming high rpm into the mix and say hello to some motorwork

Edited by cr125Rooster

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If you run good premix at the proper ratio, and your jetting is correct, your engine will have a coat of oil on the inside of it all the time.

You can run it hard, but it is always safe to vary the throttle / rpm's.

I like to let it climb on the pipe, then back off, then hit the pipe again.

I don't like to just run it WOT for long periods of time.

I dune with my bike, so when you shoot up a dune, you are on the pipe WOT.

Then you hit the top, and coast down the backside, then you hit the power and gas it up the next dune. Rinse, cycle, repeat.

On, off, on, off, on, off.... welcome to dune riding.

MX is the same way. You gas it on the jumps, the straights, and coming out of the turns. You let off going into the turns. You are always working the throttle. 2-strokes like that. It's what they were made for.

:smirk:

( You wanna cruise around? Get a 4-stroke! )

:bonk:

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f 4 strokes, they suck at that too

I would rather have an rd400 on the street than a 4 stroke

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http://www.thumpertalk.com/forum/archive/index.php/t-286565.html

Seems like there's people on both sides of the fence here. All I know is Ive seen my fair share of bikes seizing being run wot forever.

Besides, bikes are normally incredibly rich from the factory...I have my 125 leaned down.

390 main, 32.5 pilot, dropped the needle with the air screw out 1 3/4 turns. Much better throttle response and no more fouling plugs. So bottom line, unless your running in the desert or top speed running, your gonna want a crisp bike and it's gonna have to be leaner than stock.

One more to the OP I almost forgot...when running wot don't let the throttle just snap shut...cuts off all lubrication to the engine since the oil is in the gas..add screaming high rpm into the mix and say hello to some motorwork

The only time anything like that happens is when someone doesn't know how to jet a bike and mix their gas at the proper ratio.

Please stop posting incorrect information for convincable minds to soak up and repeat this nonsense.

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If you run good premix at the proper ratio, and your jetting is correct, your engine will have a coat of oil on the inside of it all the time.

You can run it hard, but it is always safe to vary the throttle / rpm's.

I like to let it climb on the pipe, then back off, then hit the pipe again.

I don't like to just run it WOT for long periods of time.

I dune with my bike, so when you shoot up a dune, you are on the pipe WOT.

Then you hit the top, and coast down the backside, then you hit the power and gas it up the next dune. Rinse, cycle, repeat.

On, off, on, off, on, off.... welcome to dune riding.

MX is the same way. You gas it on the jumps, the straights, and coming out of the turns. You let off going into the turns. You are always working the throttle. 2-strokes like that. It's what they were made for.

:smirk:

( You wanna cruise around? Get a 4-stroke! )

:bonk:

I'll leave the 4 strokes for the quads thanks...2 smokes rule:ride:

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The only time anything like that happens is when someone doesn't know how to jet a bike and mix their gas at the proper ratio.

Please stop posting incorrect information for convincable minds to soak up and repeat this nonsense.

Sorry...guess my experiences are less important than your experiences:worthy:. I was taught not to hold wot for more than ten seconds in top gear without varying it every once in a while...I've seen bikes running 40:1 mix on 91/103mix octane lock solid..more than once and seen a couple buddies get pretty banged up. You also seem to forget that most bikes, CRs in particular are pig rich in the low and mid from the factory, so they get jetted down to make the bike crisper feeling and get it to stop fouling plugs like it's nobody's business.

Logic says if it's leaned out low, it's gonna get leaner and leaner as the rpms climb. It's not EFI when you can change the fuel curve and keep it safe.

So for the common man who isn't a hardcore racer, with a jetted down bike, should not hold it wot for too long...all there is too it.:bonk:

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Sorry...guess my experiences are less important than your experiences:worthy:. I was taught not to hold wot for more than ten seconds in top gear without varying it every once in a while...I've seen bikes running 40:1 mix on 91/103mix octane lock solid..more than once and seen a couple buddies get pretty banged up. You also seem to forget that most bikes, CRs in particular are pig rich in the low and mid from the factory, so they get jetted down to make the bike crisper feeling and get it to stop fouling plugs like it's nobody's business.

Logic says if it's leaned out low, it's gonna get leaner and leaner as the rpms climb. It's not EFI when you can change the fuel curve and keep it safe.

So for the common man who isn't a hardcore racer, with a jetted down bike, should not hold it wot for too long...all there is too it.:bonk:

Ever heard of an outboard motor? Moto GP? Sand Dunes? A two stroke in those environment see extremely long durations of wide open throttle.

I'm not here to change your mind, I just don't want the next poor kid to come in, read your post and repeat these mindless statements.

Spend a few mintues researching what premix does, how to determine premix amounts (32:1 etc) and then adjust your jetting around that. Simply dropping your jet sizes from factory and running 40:1-50:1 is asking for trouble in my book. But since I've done my research and tuning, I would glady hold my bike wide open for minutes (and have, ever hear of a sand track).

Read this thread, it'll do you some good.

http://www.thumpertalk.com/forum/showthread.php?t=1030096&highlight=

And as far as your experiences being less worthy than mine, I would say engineering school gave me an ability to think critically on this issue.

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Exactly...23:1 by by any low to mid range power, more plugs. You have the motor set up for wot runs, as with anything. I'm saying that Joe blow from pleasant hill road buys a 2 smoke to run on the track maybe once every couple weekends and off tracks it the rest of the time will want to vary the throttle every once in a while. I run 32:1 in my bike, vary the throttle and have yet to melt it down. Haven't fouled a plug nor do I have that god awful mid range bog I used to with the thing jetted down.

Put 23:1 in a stock jetted 02 CR125 and go run it in the woods.I'm not saying that 2 smokes can handle wot, just the average set up of something like a 125 bike, your not going to want to do it. You get what I'm saying now?:bonk:

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