new 100$ 1980 cr250r with issues, hesitating on take off.

I just acquired this bike and was told it ran great for 2 weeks and then would only start-then die. I though his gas was ok, so i started with cleaning the carb. I adjusted the float to stock height 19mm, it was at 23mm. The jet was on the second clip down from tge top and all jets etc were stock.

The only way the bike would start is if the air screw was almost all the way out, and it didnt need any choke to start it cold. Plus the plugs would come out wet. It wouldnt rev, only run for a few seconds. So i then double checked the fuel and I could see little tiny water droplets in it. So i made new gas-cleaned the carb and gas tank. The bike now idled and could rev!!

So i took it for a test drive and the bike had tons of power below 1/4 throttle. The bike would scream with power as soon as you barely touch the throttle . But there was no power past 1/4 throttle.

I remembered the air screw being almost all the way turned out, so i did the factory 1.5 turns out. It started cold with no choke on the first kick. The idle was crazy high so i unscrewed the idle screw(not the air screw) until idle was lower. I took it for a test drive and the the bike now has power past 1/4 throttle. But, its now has a bad hesitation from 0 to 1/4 throttle.

So, i figured that my idle might be too low and that might be causing the hesitation. I raised it but stil l have it. Sometimes it if i pull back the throttle then it will takea second to slowly ramp up the power, sometimes it will sound like a rev limiter until past 1/4 throttle and then takes off.

I had read that if the bike will start cold without choke then the pilot circuit is too rich. Also, i had read that if its sputtering then the main is too rich. Remember, the bike had great take off power with the air screw almost out but no top end. Now with the air screw 1.5 turns out it seems the bike takes a bit before it wants to really take off.

I also forgot to ask,, how high/fast do is set the idle? I have been listening to youtube videos of a 80' cr250r idling but cannot really discern it.

Thanks so much,


Edited by mescalinedream

Go down a size on your pilot it sounds, if it's sputtering And hesitating down low you're likely getting too much fuel. Once you've dropped a size on the pilot it sounds like it should be okay.

And idle isn't really super important, just put it where your comfortable

Congratulations on the bike Doug! you made a good deal.


As Zotis suggested, I would go down a size on the pilot.


Idle speed....maybe 5-6 pulses a second? It set mine to slow and steady, if you get that.


I read that the jets/needle are stock. Make double sure the previous owner didn't put some weird sizes in, or they are varnished on the insides.


Also, if you really want to do some testing, read the "pressure testing a 2 stroke" pinned thread at the top of this forum. Just to be sure you have no big air leaks.


Have fun!

Sounds like you need the factory jetting specs for it, instead of the guess and check. A manual would be a good start! Good luck. 

Thanks for all of the replies, it helps out so much!

I forgot to put the jet onto clip #3 but that didnt change much, i had it on the 2nd down. I think that this k&n filter is shot. Its just nasty and I spotted some holes in it. I will run the bike with a clean filter and see if that leans it out a bit. Oh, when I took the filter off, there was gas puddlng up in the back of the carb. A little fuel was in the filter too.

What would cause fuel to do that? I need to mention that I turned the airscrew almost 4 turns but dont think I let the bike warm up enough. I have only done short 8 minute rides since I live in a modular home park. Very hard to tune with short rides, and a clogged air filter! The air filter has got to be making it run rich but it seems fine everywhere else.

The main issue is as soon as the throttle is opened, the engine sound doesnt want to catch. The rpms keep skipping.but then it will take off like mad. Revving at a stop sounds great! If a new air filter doesnt help, then I will purchase a smaller pilot.

Thank you!

Classic sign your reeds are not sealing properly. The fuel mix is coming back through the carb and picking up even more fuel (why it is rich). That is also why fuel is in the airboot and on the filter.


Good idea on getting a new air filter. That is a priority.

Edited by RBI

If the fuel is on the filter, it is probably washing filter oil back into the mix which can't help your tuning either. I'd look for some reeds.

This is a little what it sounds like when taking off, although mine revs a bit higher. The weird thing is that it revs perfectly fine while not in gear. It only does that spitting while in gear. I dont understand why it revs fine,but when taking off it doesnt.

In the video when the guy starts it up and everytime it revs it bumbles. It sounds like it revs fine right after he starts it but he isnt moving the throttle. Its the other guys bike that revs fine and sounds like mine. Mine has perfect revs while sitting but when in gear, it only bumbles a tiny bit and then screams like a perfectly running bike.

The fuel was puddled at the air jet which is #19 on the page.

As of now I am patiently waiting for my new 2 stage uni air filter to come in the mail. In the meantime I decided to check the packing in the muffler. It was nasty! Black oily burnt mess and along one side it had burnt a trail 3/4 down about an inch deep. I am going to put some wraps of house insulation in there.

I think that I might have an issue with the intake/reed boot. I think that my intake isnt stock. I have 2 hose clamps and what seems to be a pipe welded onto the original mounting plate. I thought it was the stock intake with a newer radiator hose section that connects to the carb. The stock intake would have an angled rubber boot that is a 1 piece molded part. With the way this pipe and hose is connected to the carb , i would think it would angle the carb differently. So maybe i need to adjust the floats different then stock?

I can buy a new intake for 50$ but i will wait on that until I see if the new air filter changes the way the bike runs. I decided to clean my carb again and was glad that I did. The fuel line had dry rotted on the inside and dropped chunks of rubber in the carb. Maybe that why it was running so badly when opening the throttle. I hope its not the reeds! Kind of expensive.

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