Im fixing up a 2007 LTZ-50 for a friend so our kids can enjoy it at the camp and having all kinds of trouble. He tried messing with it and got frustrated and then put the three rubber hoses on wrong, fuel, vent, and vacuum line. Got that straight, soaked carb for hours then blew with air and blew through all passages with carb cleaner spray. Since fuel lines were reversed the fuel filled up the airbox and completely screwed up the air filter so new one is in the mail. Heres the problem. I can get the bike to start with the pull start on the first try, but the engine will now surge up and down up and down until finally killing after about 2-3 mins. I cleaned the carb atleast 35 times by now and even triple checking that everything was as it should be. I replaced the o rings for the air screw and idle. I some how got lucky yesterday and had it idling perfect and let the kids ride it around the yard for a minute. Go outside today and put it back together and let the kids try it again and when my son gave it throttle it would die out so he would have to barely touch the throttle. I pulled it back to the patio and put it on the stand and now its surging again I sprayed the carb with carb cleaner on the outside of the carb and no rpm changes at all. I can not for the life of me find the stock settings for the carb air screw and idle screw. I used my calipers and adjusted the float height according to the service manual. Im losing my mind with this thing.

So right now it starts first pull then will sit there and idle up and down. Any suggestions.

 

May be the crank seals leaking

 

I didn't have the battery in, I read a few threads of people saying this happened in the higher rpm range but didn't effect the idle too. I put the battery in and it ran fine, bike is slow as poo but I think that's normal. I then removed the battery and it started to surge again. I'm out of town so when I get home I'll check it again with and without the battery just for a price of mind and will update here.