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99 KX 125 high rev at start up

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Bike runs and starts great, it only happens when I cold start with the choke. The bike will rev to the moon if I leave the choke on. If I feather it on and off for the first 30 seconds or so it's fine. Bike idles great, it is only at cold start that this happens, and only with the choke on. Any advice is appreciated...

One thought I had was I drain the float bowl after each ride, am I not giving it enough time to refill before I start, and thusly creating a lean start? Just a guess, but seemed logical...thanks!

The bike does not smoke, and crank has about 20 hrs or so on it. (rebuilt early summer), top end is same vintage.

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Bike runs and starts great, it only happens when I cold start with the choke. The bike will rev to the moon if I leave the choke on. If I feather it on and off for the first 30 seconds or so it's fine. Bike idles great, it is only at cold start that this happens, and only with the choke on. Any advice is appreciated...

One thought I had was I drain the float bowl after each ride, am I not giving it enough time to refill before I start, and thusly creating a lean start? Just a guess, but seemed logical...thanks!

The bike does not smoke, and crank has about 20 hrs or so on it. (rebuilt early summer), top end is same vintage.

the kawasaki choke rev.... normal, search the forum there have been many topics on this. the fix is to just feather the choke, try to keep it from revving to much when cold.

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Thanks, that is the perfect answer. I'll keep my normal starting procedure. I really appreciate it.

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Thanks, that is the perfect answer. I'll keep my normal starting procedure. I really appreciate it.

not a problem

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the old suzuki RM does it as well. its just the thing is really rich from being kicked and not starting and it has all this extra fuel in it, and it just burns it off really quick when it does that. I throttle mine as well. its not necessarily bad because it does have lubrication in it especially if you shit it down right! and start it up right.

I was taught to always rev your two stroke up and then push the kill button as it is winding down at the end of the day. and IF it is a really cold day and its been a while since you started your bike, a good idea is to push the kill button in and kick like 5or6 times and then start it so that way it has lubrication in it when it starts up. these are just tips and tricks though, not to be taken ultra seriously.

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Have to checked your pilot jetting? A really rich pilot will cause this too. Do you even need to use the choke to start from cold?

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Have to checked your pilot jetting? A really rich pilot will cause this too. Do you even need to use the choke to start from cold?
You beat me to it. Screaming revs during cold start-up almost always indicates a too-rich pilot. Because the pilot is so rich, the slide is raised higher than it should be to allow the engine to idle when it's warm. This high slide position combined with the super-rich choke mixture causes the screaming revs.

My KX250 did this with the stock 55 pilot jet. With a leaner pilot I don't have this problem at all.

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:lol:

You beat me to it. Screaming revs during cold start-up almost always indicates a too-rich pilot. Because the pilot is so rich, the slide is raised higher than it should be to allow the engine to idle when it's warm. This high slide position combined with the super-rich choke mixture causes the screaming revs.

My KX250 did this with the stock 55 pilot jet. With a leaner pilot I don't have this problem at all.

Ha, I wonder who it was who passed that knowledge on to me:excuseme:

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My KX250 did this with the stock 55 pilot jet. With a leaner pilot I don't have this problem at all.

I have this exact same issue but it is only the very first start of the day, after that it is fine. Interesting that it is related to the pilot jet as I knew I was mine was too rich but, wow, if you needed to go leaner than the stock 55 in Florida then I really need to go leaner living and riding at 5,000 feet elavation!!!

Good info. :lol:

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I have this exact same issue but it is only the very first start of the day, after that it is fine. Interesting that it is related to the pilot jet as I knew I was mine was too rich but, wow, if you needed to go leaner than the stock 55 in Florida then I really need to go leaner living and riding at 5,000 feet elavation!!!

Good info. :lol:

I need to go leaner in the summer when it's 95 degrees and 95% humidity. Not because of altitude, obviously...:)

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Thanks for the info. I do need to choke, and it is only the first start. Once I run and get it warm, it starts without choke and no high rev.

I will pull the carb, and check it out. Wish me luck as carbs/jetting is surrounded by a shroud of mystery for me.

I will say the feathering the choke for the first 30 seconds or so makes the bike run fine, and it will idle fine without the choke.

I noticed a fluid drip from the expansion chamber/cylinder connection. I knew I had a leak there, seemed to maybe be fuel? I assume this is the rich condition at start up?

I will post findings when I pull the carb, and as a thought it seemed to get worse as the weather cooled. I rode last weekend, 38 degrees and thought the colder weather had some impact?

I have never re-jetted a bike for cooler weather, they always seemed to like it and run great below 50 degrees. I guess the old bikes I used to have maybe weren't as picky? The bike runs really good, what is the larger benefit of re-jetting vs feathering the choke?

Thanks again for the advice.

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rejetting your bike makes it right, if your bike is jetted properly, as in perfectly, it will run, as you can guess, perfectly. Jetting isnt really that hard, it just takes some trial and error, and some learn as you go knowledge

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B4 you pull the carb you may as well try to get a idea how many sizes you need to drop on the pilot. Wind the air screw all the way in and then out 1 turn, warm the bike up. While the bike is running count the amount of turns out on the air screw you get to b4 the idle starts slowing down. If its around 3 you only need to drop one size but if its out past 4-5 you are probably smart to drop 2 sizes. Just for interest, is your idle screw wound way in to get it to idle?

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B4 you pull the carb you may as well try to get a idea how many sizes you need to drop on the pilot. Wind the air screw all the way in and then out 1 turn, warm the bike up. While the bike is running count the amount of turns out on the air screw you get to b4 the idle starts slowing down. If its around 3 you only need to drop one size but if its out past 4-5 you are probably smart to drop 2 sizes. Just for interest, is your idle screw wound way in to get it to idle?

Thanks for the tip, don't know where my air screw is currently, but I will check it out. I will report my findings.

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