Need some advice with my first bike project - Custom 1974 Ironhead Sportster

My own 77XLH never sumped oil but my modern evo XLH did, which did catch me out when I thought "wow I've used a lot of oil!" and filled it up only to loose my filler cap and waterproof my jeans!
 
Oldguy said:
Before you buy any goodies, I suggest you check the compression on each cylinder, just to see if there are any issues.
Like some "ladies" I used to know, they looked ok, but you just didn't know where they'd been --
The engines are not hard to take apart (other than the crank) so check big ends if you take the barrels off.
Generally if oil returns to the tank, you have enough oil pressure ---
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Hi.
As a point of general maintanence on H-D twins, compression test are so easy to do that it's useful to do a cold comp* as well as a hot one.**
Doing both h & c can establish a baseline for wear comparison(s) for F & R cylinders.

* cold, but kicked thru enough to loosen-up & get the oil flowing...
** I'm assuming that all who read here know how to listen at the holes..........
 
Cheers Skip, I don't understand how to listen at the holes, you'll have to explain that one. How does doing a hot compression test help you compare the wear of each cylinder?
 
Sutherland said:
Cheers Skip, I don't understand how to listen at the holes, you'll have to explain that one. How does doing a hot compression test help you compare the wear of each cylinder?
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;) 'listening at the holes', see also, Terms of Endearment".
As briefly as I can make it.....
OK then,..... when you put a bit of air pressure in at the spark plug hole, you can listen at the !. crankcase breather (or timing plug) for air blow past the rings and 2.,listening for air blowing past the valves at the intake and the exhaust ports (or at the silencer if you're not inclined to remove the pipes).
Idealy, and in a newly run-in motor. on a hot comp test, one may expect the readings to be within 1/2 point (or pound) of each other on compression and no leaking of air past the rings or valve seats.
A cold but throughly kicked through motor ( kicked or turned over fast enough to get the oil flowing) will show you differences or an un-balance....
.... say for example's sake, that on a hot check there's no air leaking past anywhere but on a cold check it sounds like a good bit mor air is leaking past some point in one cylinder more than the other..... this might explain un-eveness at startup that goes away once warmed up*.
Compression tests are an excellent diagnostic tool when performed properly. There's a lot of info out there on comp tests.... what they'll do and what they'll don't. Read it up. The knowledge will stand you well.**

Oh! Did I answer your question?

* -vs- chasing your tail over idle/low speed carb settings....... ask me how I know..... no.... don't.....
** if you do go looking for the knowledge, you might give some viewing time to how comp tests are done on small, 4-6 cyl. aircraft engines. There are useful pointers that may help you beyond what a motorcycle vid would show.
 
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