My 86 250r here lately has been cutting out or missing at 3/4-full throttle. The problem has gradually gotten worse here lately. Heres what I know so far. The motor has trinity port/polish, fmf exhaust, k&n filter, 165 main, 48 slow, dont know need needle position. It could very well just need a top end rebuild. I also have a small exhaust leak around the head pipe. Is there any kind of o-ring or gasket there. I couldnt find one. Any way to check to see if it needs a rebuild? Im pretty new at this, so just looking for some help.

td250r
===========
86 trx250r
97 warrior

 

There is a an o-ring that goes on the exhaust flange, replace that and that should take care of your exhaust leak. The cutting out issue could be a number of things. Lets start with the simple thing first. Have you cleaned your air filter lately? A dirty filter could cause this. Have you tried a new spark plug lately? When an engine starts running funny, the first thing you should check is to make sure the basic things are ok. When you kick start it, does it kick over easier than it used to (less force on kickstart lever)? If so, you are down on compression and would need a top end rebuild (piston, rings, and maybe an overbore, depends on wear on the cylinder). If that all checks out ok, then the problem probably lies in the electronics. If the CDI is bad, there is no way to test it, the only way to figure that out is to put in a different CDI and see what happens.

 

Check the spark plug wire where it fits into the spark plug cap. My R used to have the simular cutting out problem. The wire on mine was stripped out. The spark plug cap has a screw , it screws in to the plug wire coming from the coil.
Mine would slip loose and it would have to jump a spark from the wire to the cap before it ever made it to the spark plug, by the time it got to the plug the spark was to weak to have any power at wide open. It took me forever to find this problem since you dont know the wire is slid back a litte. (it looked fine until I pulled on the cap , it just slipped off)
Just an idea[img]i/expressions/face-icon-small-wink.gif[/img]

 

it can't be the cdi for one if it were the quad would ever even act like it wants to start in the frist place cdi's don't wear they just go out it sounds more like a carb problem to me also check your reeds for anything that doesn't look right like cracks for one but if its the carb it wouldn't be jetting if it ran fine befor and u never touched it sounds like dirt to me clean the wole fuel system its a cheap frist shot at the problem clean the tank lines and carb well clear the passage ways with compressed air good look dude hope this info is useful to you

 

alot of people dont even worry about jetting and run the same all year,if you're one of those people ,just remember its been warming up and that will definitly effect jetting,warm wheather makes my R run fat w/ fall/winter jetting..........L8R

 

Thanks for all the help. Friday I tore the carb down and it was still spotless, jets were fine, cleaned the filter, new spark plug and wire, and still having the same problem. I have had a couple of people look at it and ride it, and the only thing we can think of is it needs a new topend. Ive had it for almost a year now and it hasnt been rebuilt since Ive had it and I dont know about the guy that had it before me. So Im tearing down the topend after I post this message. Well thanks for all the help.

td250r
=========
86 trx250r
97 warrior

 

Now would be a good time to spend a few dollars on a compression tester. Even a $25 cheapie will work OK. Every 2 stroke owner should have one.

 

had the same thign happen to my banshee took me two months to find out what it was but my flywheel was slowly advanceing it self so it got worse and worse till i burned a hole in my new pistons that i put in because i thought maybe i should rebuild the top end so your story sounds dangerously close to mine. so look at that timing

 

Yea I would get a compression tester.

 

Well, I got the R back together a couple of nights ago. New piston bored .50 over. It ran good for awhile, still having a full-throttle problem. It acts like it has no power, you can dump the throttle from a still and the thing wont hardly even take off. It has been running a #9 spark plug, so I tried a #8 and that helped for a little while. It almost acts like its fouling the plug, but it will start right up every time. I dont know what else it could be. Its got the original carb in it still, and I think the floats are not set right because if you leave the gas on, it will just run out the carb vent hoses onto the floor. Any help or suggestions would be greatly appreciated.

td250r