ATK Rotax 250

[moono]

I just purchased a 96 atk 250lq. I tore down the top end to freshen it up and noticed the two exhaust ports that bypass the powervalve have either been plugged or still have casting material plugging them. The bike seems to be really sluggish on the bottom end. Would opening these up make it better or worse?

 

[DEANSFASTWAY]

probably worse on bottom .probably would build more top .Are you sure the P/V was working correctly and not opening too early .

 

[moono]

I have played with adjusting spring tension a little bit but couldnt really tell a difference

 

[DEANSFASTWAY]

Maybe you should take it apart and inspect it .

 

[KTM-Lew]

These had pretty lousey low-end power....pluging the sub-exhaust ports makes the power-valve more effective. Remove the wire bail that holds the cover on the valve and see if the valve moves freely by hand. The whole assembly can be removed and cleaned by removing the 2 bolts that are under the cover. They are known for getting carboned up and sticking.

The stock carb was very difficult to jet, I would scrounge up a Keihen off a Jap 250....something with-out any electrical junk...97-98 model KX was great.
The V-Force reed for a KTM fits and is a big help.....12 oz of flywheel weight is also. Milling the head is next. Try www.atkusa.com and check the tech-tips section for more. You can call them, they are very helpfull.

 

[moono]

The valve was cleaned when I did top end and it moves freely. Carb has mikuni pro-needle kit in it. It seems to be jetted pretty close. Who makes a flywheel weight kit?

 

[KTM-Lew]

On my 99 model I sent a flywheel, had a spare engine, to Steahly. Now that I've thought about it, they put 14oz on it. At the time I thought that would be TOO much but it made the bike much easier to ride and to start in awkward situations. Still had plenty of hit but didn't stall and idled much better too. The cost was a little high but worth it. $130 I wish I had done it when I first got the bike.

The rotax has right-hand threads in the flywheel puller hole, thats where the quick attach one's go, and they don't have that type (right-hand thread)available. They (Steahly)put a weight on your flywheel and machine it to suit.

 

[DEANSFASTWAY]

Doesnt that bike already have a counterbalancer spinning around ? We were giving some more timing advance for a bit more bottom help and dropping the head a like 10 thou. Then we had to use good fuel but they ripped. The stock fickstarter was a weak point ,spindly little thing.Only thing I couldnt understand was why did they build a bike with some of the best components in the world and spec out such a puny little kickstarter. They were good bikes but not really too popularin the East but I heard there are a lot of them in the midwest . I think theyre made in Utah.

 

[moono]

Yes it is counterbalanced. As for the kickstarter its on the left and my left leg isnt strong enough to break anything. I was told the head was already milled down but who knows for shure. Would be nice to know how thick a stock one is.

 

[KTM-Lew]

Eric Gorr has a port job that will turn it into a tractor if you don't need alot of top-end. He's cheap too!!

The stock flywheel on these is really light. I was pretty surprised that the 14oz I put on wasn't too much but it still had a pretty good hit when it came on the pipe. They most certianly aren't slow....just unrefined.