83 ATC 250R rattle HELP!

[Hammer_head94]

Hey guys first time posting on the website so take it easy on me. Ok so to the point I bought a 1983 ATC 250r off of Craigslist for $400.00 and its my first two-stroke three-wheeler. When it's idling there's a rattle/knock noise i cant figure out coming from around the stator cover area. But since I've never owned an R i cant tell if its normal. I've watch every 250r video on youtube trying to hear and some sound like it and some don't. I've read it could be counter balance or piston slap. Maybe a little help or ideas before I tear it down? I have a link to a video i have of it and you can hear it. Cold start thus the smoke I hadn't started it in a few days. :)
Just let me know what you guys think.
http://www.youtube.com/watch?v=2Q5aLOpt7N4

[shortline10]

Sounds like either a lower rod bearing or piston slap . Need to remove the top end and inspect .

[Buck Snort]

I agree with atc300r. I have had 4 old 2 stroke dirtbikes and the one old Yamaha had a loud rattle from day 1. Rode for 2 years and then sold it to a friend and he simply rode the hell out of it.

[JasonB]

totally normal from my own experience. my 84 sounded just like that with the stock 250 top end and both 300cc top ends we stuck on it as well. We ran an 89 rod in the 300 kits so it did have a 'rebuilt' crank in it as well and it still sounded all rattly like that. always felt like it was about to explode lol

[Hammer_head94]

Thanks guys. I appreciate the replies. Good to know. I guess I'll run it and if something happens to blow then ill fix it. ;) I had some other people tell me it sounded normal also but wanted to hear it from the pro's.

[shortline10]

I've rebuilt a ton of these fooler motors over the years and the last 10 seconds of your video it sounds excessively loud to me . Does the noise get worse under a load ?




Thanks guys. I appreciate the replies. Good to know. I guess I'll run it and if something happens to blow then ill fix it. ;) I had some other people tell me it sounded normal also but wanted to hear it from the pro's.

[Hammer_head94]

no i cant here it above an idle but could be just drowing it out with the exhaust im not sure. But the bike has awesome power and runs like an airfooler should in my books. Then again I'm a newb But i have another question. So today i went riding all day and as i was riding i missed second gear and put it into neutral and hit the gas so of course it just revved up and started dieseling. I had to shut the fuel off to keep it from blowing up. is it running to lean?? The carb is stock jet sizes and the needle clip in in the middle. im running a stock head pipe and a dg silencer. what would cause that? :wondering

[Bren_downe]

The death rev is a sign your too lean. I'm not sure where Orovill CA is but you need to jet up in cold weather. Other than that you may have developed an air leak. Check you intake boot, they're known trouble spots.

[HondaRidr]

With it idling in neutral, try pulling in the clutch and see if the sound goes away some. The clutch is very loud in the foolers. Its just the way they are designed. I thought it was a top end noise at first too but never had an issue. They are just noisy engines haha

[airbats801]

Thats normal noise. I have a NOS 81 250r motor on my 81 racer and it sounds the same right from day 1. The 300r kits realy rattle louder than the stock 250 topend.

I always wondered about my 81 250r, it always made some bad sounding noises I associate with a 4 stroke, but I have never had a single problem,. I just figured it is like that. My 83 on the other hand doesnt make those funny noises

[JasonB]

if it started revving up like that on its own and then went away after you restarted it than you probably have a clogged pilot jet. pull the carb off and clean out the pilot and main jets with some carb/choke cleaner. I had my atc500R do this a couple times last summer when i first started riding it and nothing is more terrifying than hearing a motor that big start dieseling lmao. I had debris in my tank i didnt know about that kept clogging my pilot jet just enough to lean it out and make the bike go ballistic

if the bike has constant issues with running lean like that and its not the carb than you have an air leak. google 'how to build a leak tester 2 stroke' and make one, cheap simple and will let you chase down any leaks you have that are creating jetting issues. if you run these air foolers too lean you will burn up top ends QUICK, i killed 3 on my 84 like that. I had a 210 main jet in my 39pwk carb on the last 300 top end it still burned up from an air leak i didnt realize i had

[Hammer_head94]

Ok ill do that. Ill find out one way or another. I checked the spark plug i had been running all day and it was kinda greyish black color,I thought it would be whitish. So I'm going to to a plug chop and start there then clean the carb and do a leak down test. One question tho if it was like a head gasket or crank seal or something down that line wouldn't the problem be less intermittent? The only time it would do that if i missed a gear and got neutral and the rpms would shoot up and then start dieseling.

[JasonB]

ya it would be a general air leak and hard to track down if it was a crank seal or base gasket. if the bike revs up and hang for a few seconds like that when you just stab the throttle i think that means you have a lean pilot jet (idle circuit) or you need to move the clip on your needle. Typically the needle clip should be around the middle ring on the needle and people just jet around that. The plug should be the color of a brown paper bag. Whatever color it is after you run it all day wont tell you anything, plug chops are the way to go. I would recommend pulling the bowl off the carb and seeing what jets are in it and determine what carb you have and other mods are done to that R. Try throwing a bigger size pilot jet in there and see if it still does the high rev thing you described. might just be lean on the idle circuit. Also I dont know alot about carbs and 2 strokes, just enough to be dangerous lol

[Hammer_head94]

Ok so i might have figured out the issue. When i was cleaning the carb i noticed the mixture/airscrew was about three and a half turns out maybe even four.
If I'm not mistaken turning the air screw out leans it out and turning it in richens it up. I believe. So could that have been the issue? Because on the top end and WOT it had crazy power through all gears and so i believe the other jets are ok. Bare with me hear im a newb at all this. Also the slow jet (pilot jet) is a 50 and the main jet is a 130 and is a Keihin 30mm carb. So the carb and jets are all stock.

[barnett468]

...1983 ATC 250r... When it's idling there's a rattle/knock noise i cant figure out coming from around the stator cover area. I've read it could be counter balance or piston slap.I listened to it 6 times and all i heard was what sounded like a little piston slap for 2 seconds at 23 seconds onto the video likely because idle was getting to low and maybe 1 knock at 30 seconds. Are either of these the sounds you are referring to? Doesn't sound unusual to me but the video was short.





Cold start thus the smoke I hadn't started it in a few days.Does it stop completely after a while or does it still smoke a lot?

Might be a rich mix of oil with gas or a bad right side crank seal.





...on the top end and WOT it had crazy power through all gears...

...as i was riding i missed second gear and put it into neutral and hit the gas so of course it just revved up and started dieseling. I had to shut the fuel off to keep it from blowing up. The only time it would do that if i missed a gear and got neutral and the rpms would shoot up and then start dieseling.

The carb is stock jet sizes and the needle clip in in the middle. ...the slow jet (pilot jet) is a 50 and the main jet is a 130 and is a Keihin 30mm carb.

...i noticed the mixture/airscrew was about three and a half turns out maybe even four. could that have been the issue?

...The carb is stock jet sizes and the needle clip in in the middle. im running a stock head pipe and a dg silencer.

I checked the spark plug i had been running all day and it was kinda greyish black color,I thought it would be whitish. So I'm going to to a plug chop...

...is it running to lean??

Did it diesel with the ignition off?

What is your spark plug number?

What octane gas are you using?

Did you ever notice it pinging or rattling when rolling on the throttle from any speed?i

What brand of 2 stroke oil are you using?


Your plug color suggests to me your jetting might be close but a photo would help. I prefer them to be tan as opposed to gray.

Your dieseling suggests to me that you might have had pre ignition occurring. if so, in general it means your bike was running hot. This can be caused by several different factors.





Cold start thus the smoke I hadn't started it in a few days.Does it stop completely after a while or does it still smoke a lot?

Might be a rich mix of oil with gas or a bad right side crank seal.





if it was like a head gasket or crank seal or something down that line wouldn't the problem be less intermittent?Often but not always.

[briano]

^^^^^ pay no attention to the post above. He tries to over complicate things, do your plug chops and jet accordingly.

[Hammer_head94]

Hey guys thanks a lot for all the helpful posts I really appreciate it. And thank god for 3WW! ;)