My dad has a 94 classic that blew the oil dipstick out three times in one day and after that he said it seemed to lose some power. We thought it might have a cracked piston so we tore it down today and could find nothing wrong. Does anyone have any idea as to what would cause the dipstick to blow out or anything to check while we have it tore down.

 

poss. oil line blockage-----does it get real hot? does it run fine no spittering, stall out?

 

My thinking was bad rings and blowby,or a vent hose plugged or off.

 

Was anything changed lately? or did it just happen all of a sudden. Therecan be some pressure on the oil tank I found when the dip stick gets a bit worn and doesn't seal well it can pop out. Breather line blockage could do it was there any air coming out of the breather hose? This can happen when you mix up the return hose and the breather hose at the oil tank as if the tank breather hose is under oil it can cause problems. Was the oil tank over full? If a cam was changed and the breather timing off this would cause it. Then the normal stuff broken rings hole in a piston. Usually with broken rings it will smoke and lose power. Besides losing power did anything else happen like noise from the engine blowing smoke etc?

 

it had no other symptoms other than the dipstick blowing out and the bike losing some power, nothing had been changed recently the cam had been changed but it was fine for 10 - 12000 mile after that nothing else had been done during that time other than oil changes. We thought it might be a broken ring or hole in the piston so we tore it down and have found nothing so far, we have the jugs up off of it and checked the cam breather to make sure there was no teeth stripped off of it. I guess we will tear it own down and then rebuild it.Any more help or things to look for is appreciated thanks.

 

So now that you have it apart, what are the plans, it would be a shame to not discover why it was doing this. A leak down test would have been a good thing to do while it was still together as it would have shown if there were problems with the pistons. A head gasket leaking into the oil drain back hole in the barells could have also given you some extra crankcase pressure. Just in case you don't know you can make up a fitting to go into the spark plug hole so that you can put air pressure on it then with a valve and a guage you can see if it will hold pressure (leak down) you can also hear where the air is leaking from. During your rebuild I would buy the reed valve that replaces the timed breather from S&S it works much better.

 

You should also look the oil bag over,blow out all the lines,something is not letting the pressure balance.

 

we will check all oil lines and passages, put new pistons and rings have it bored out and reassemble it we have a few more things to take apart and look at then looks like we start back together with it and i'll look into the reed valve instead of the timed breather as I didnt know about it.

 

Has this bike been sitting for the winter? Is this an initial start up? If it is check the breather bolts to the heads I've seen bee's plug these holes

 

this was an issue that happened during the middle of the riding season and only occured under hard acceleration so we are thinking it might be the rings we are going to have the cylinder checked and probably bored out when we go with new pistons