Valve Adjustment?

XLFREAK · #1 11th October 2006

For the most part my 75 has been good to me over the summer and into the fall. The one thing that I dont understand is why I would need to readjust the valves on the fron jug every 1000 miles or so...............sometimes less? I just had it in the shop not long ago for an idle problem that turned out to be a tight exhaust valve along with a timing issue. Over this past weekend I took a little trip and noticed a sound change in my exhaust...............then the idle thing started again, not as bad but I could tell something was up. I checked compression and the rear jug was at 120................the front was at 30. Readjusted the valves and once again all is well. Why wont the adjustment hold? Im getting pretty fast at doing this now!!!

BobboJama · #2 11th October 2006

If the exhaust valve keeps getting tight, you are probably eroding the valve seat. Are you using a lead subsitute additive in you gas??

XLFREAK · #3 11th October 2006

I do use a lead substitute on every fill up. I had the heads reworked this past winter and all should be well. When I readjusted the valves a couple days ago both intake and exhaust were tight.....Im not real sure whats going on.

IronMick · #4 11th October 2006

This is a serious situation. You should not ride it until you know what is going on. Here is my experience with the same symptoms:

When i rebuilt my top end i made two big errors. First, the replacement gearcase gasket was not the correct one. There are at least 3 different ones; they are different around the oil passage hole at mid top of the gasket. The one i installed had the hole too big; the hole hung down over the edge of the case; the result was that not enough oil went thru the passage and up thru the oil lines to the top end; some oil just went back down into the gearcase. You must ensure that the gasket seals all around the oil hole, not just at the top outside erdge.

Second, i did not realize that a PO had replaced the flywheel. So the timing marks were not correct for my year of bike. I followed "the book" to determine which marks to use. Big bad mistake! Set the front cylinder at TDC precisely and stick your finger in the spark plug hole to be certain. Then check the TDC mark in the timing hole. Use this mark with your dial back timing light. With a regular timing light find the advance timing mark about 40` before the TDC mark and use it.

Mine was doing the exact same thing. Regardless of how i adjusted the pushrods they got tighter. I could tell because it would not idle properly, and by the exhaust note. What you hear is the fuel exploding in the cylinder with the exhaust valve not fully closed because the pushrod is too tight.

CommandoRoadster · #5 12th October 2006

This may seem simple, but are you getting the locknuts on your pushrods tight? If so, then almost certainly your valves/seats are eroding.When you did your top end,were the valves and seats replaced,or just reground? It has been my experience that you can get away with running old pre-unleaded valves/seats almost indefinately,but when they are reground,the hammer-hardened surface(from running)is removed, and they burn almost immediatly.
Try doing a dry/wet compression test.That might tell you if your valves are burnt. A Sportster, with its long stroke, will still run pretty strong with sub par compression. By the way, any lead substitute that comes in a plastic bottle is worthless.
Whatever it takes,don't give up on an Ironhead!

XLFREAK · #6 12th October 2006

Thanks for the input guys. Im going to hope that Im not getting the locknuts tight. I had the rebuild done at a respectable shop here in my area. The valves were replaced. They went thru the engine top and bottom with a fine tooth comb. Im going over to the shop in the morning to talk with the owner and get his idea on what may be happening. I only have around 1800 miles on the rebuild. Knock on wood...........today it ran stronger than ever. I really hope that this is something simple!

XLFREAK · #7 12th October 2006

One more question...............if my valve seats are at question, wouldnt it be effecting both heads? The problem Im having is only with the front head. Also.........commando which lead substitute do you use? Thanks for the help guys!

IronMick · #8 12th October 2006

Quote:

Originally Posted by Thermodude

... Im going to hope that Im not getting the locknuts tight ... today it ran stronger than ever. I really hope that this is something simple!

It is most unlikely that the locknuts are not tight enough. They only need about 10 ft lbs. If you tighten them more you will only break them.

It will run strong after an adjustment. Do not let that make you think the problem has just gone away.

If, as you said, you adjust them and then they get tighter and this happens time after time then there is a problem. IMO you will have to take it down to find out what it is. Do the wet and dry compression tests and a cylinder leakdown test first.

There is nothing to be gained by hoping there is no real problem and continuing to ride. It will only get worse.

IronMick · #9 12th October 2006

Check the oil line to the front cylinder. It may be blocked.

The oil line can be removed without removing any other parts, except obvious stuff that is in the way. Use two wrenches, one to hold the upper nut at the top [or the lower one at the bottom] in place, the second wrench to loosen the adjacent nut. The oil line itself can then be slipped down then removed angled up.

There is a rubber washer at each end. If either is incorrectly installed it can block the oil flow. Then you would have the symptoms that you do have.