I have an 88 sportster in my collection that has a 1200 kit. My buddy was riding it and it started bogging down really bad. We nursed it back to my house and I pulled the filter off to find it blowing crank case ventillation out. Now, I figure this is a piston ring issue as I also pulled the front cylinder spark plug wire and nothing dramatically changed with the idle. When I pulled the rear it completely died out, thus leading me to believe it is the front cylinder.

Now I would like to change the rings (piston if need be) out by myself with the help of a friend who works on cars. I do minor wrenching on bikes and anything up to but NOT including engine rebuilds/transmission rebuilds on cars. I would like to know where I should start with parts and what key measurements I will need to provide to get the parts I must have to get the job done. This is within my capabilities I believe and am not afraid to give it a shot. Any and all suggestions and tips are welcome and hopefully this topic can help someone in the future as well.

On another note, does anyone happen to know the cylinder size of the 1200 kit? Would it in fact be the same as the stock 1200? Also, where is a good parts source?

The bike in question, again, is a 1988 XLH883H with a 1200 kit already on it from the previous owner. Thanks in advance.

Dan

 

Pull the pistons off the rods, and take those, and your cylinders to your local competent machine shop(or send them to us) to measure piston/wall specs, and address as needed so you can enjoy your motorcycle.
Scott

 

a STD 1200 bore is 3.500",you should do a compression test,if a compression tester isnt avaliable,put your thumb over the plug hole and crank with the starter,compression should plow your thumb off

 

I would really like to give this measuring and re-ringing a try on my own. I do have a Clymers book to use as a guidline but unfortunately it doesn't get too much into measuring and parts to grab based on the measurements extracted. What tools will I be needing and what measurements should I be jotting down?

 

I do have a compression tester. I figured I got what I needed by the spark plug wire experiment but I will do the test anyways. 3.5, is that the size honer I will need?

 

Do your self a favor and by a factory manual. Any other manual only gives enough to get you in trouble. Do you try a new plug to see what happens? All so recommend doing a leak down and compression test before you do anything. Good Luck

 

You'll need a dial bore guage and fixturing to set that.
You'll need to know what the manufacturers piston to wall clearence specs are.
If not then you'll need to bore/hone to the next oversize.
Scott

 

Okay, started dismantling the rocker cover and got to the heads. Bolt number 3 in tightening order was not even finger tight. It was turnable with almost no force. This wouldn't explain the crank case pressure venting out so I am going to keep going and remove the cylinder head to see what I can see.

 

Got the jug off. Piston rings surprisingly look good. They are shiny and practically new looking as they only have a couple thousand miles on them. A carbon layer but no scratches, gouges or otherwise anything worth noting for the piston itself. Valves look smooth and in tact. I will try and do a test on the cylinder head itself by filling it with gasoline upside down and leaving it for a couple hours to see if anything dripped on the rag/papertowel that I will put underneath it. Any input or anything else I should look for/test while I have the jug off it?

Would that loose headbolt have anything to do with the excessive crank case ventilation through the air filter backing plate and the motor bogging down? Could this have been the issue all along?

I took some pictures also and can take more. If you would like me to post them let me know.

 

There is no opinion or observation out there for my situation? I'm just borrowing your time for my education and I appreciate it. If there is anything to comment or note about my situation I am open ears.