compression comes out of primary chain adjustment bolt when bolt is removed

 

new to the forum. I wrote this message to find out if compression coming out of this bolt hole is normal on the 79 xlh? thanks

 

Is this with engine not running? The answer is that primary oil would leak/drain out but there would be no compression release.

To Confirm our terminology: The primary chain adjustment "bolt" is actually a long set screw that is loosened/tightened with an allen key. It is on the bottom of the primary chain cover, behind the kick stand. It should have a nut [1/2" I think] and a sealing washer [if I remember correctly].

 

I may have described the wrong bolt. I got this bike slightly disassembled and it is not currently running. the bolt i'm referring to may be the primary cover bolt that seems to thread into the inner case just forward of the clutch basket. seems like it may take a nut on the outside of the primary cover. the bolt was out when I got the bike and as I spin the crank with pugs out by turning compensator sprocket pressure comes and low low compression on rear cyl. if I plug the bolt hole compression goes up on rear cylinder.

 

There is a bolt on the left that is removed from the engine to do ignition timing. It is at the base of the two cylinders, just below where they meet. Technically it is a plug, size 5/8-18, part number 720. I do not know the length but it is quite short, less than 3/4". If it is not the original part, and if it is too long, it will contact the flywheel and cause possibly serious damage. The stock part takes a hex bit socket.

Most certainly compressed air will come out here as each piston moves down in its cylinder.

It is a steel part going into aluminum threads, so care must be taken to not strip the threads. You can install it with two or three drops of blue locktite, tighten it to what I refer to as "firm plus a little more, but not much more".

 

Thanks Iron Mick, your information is helpful, but it is in fact the primary stud that I'm dealing with. With it removed pressure comes out of it when turning engine over by hand.

 

I'm not familiar with a '79 motor, but with the motors of the '60s, the primary chain adjusting shoe is bolted to the left case and I believe it's the top larger bolt hole that goes through the case. When removed you can see the left fly wheel. Thus if the primary chain adjustment shoe is removed and you crank the motor over, yes, you will feel and likely hear air escaping from this hole on the down stroke of either piston.

 

You are really going to have to post a picture of what you are talking about. I suspect now that it is the primary chain inspection hole, which has a large cap the same size as the clutch adjustment hole cap. I don't think there should be any compression release from this hole.

Best to acquire both factory manuals ...

99484-85 Factory Service Manual
99451-85A Factory Parts catalog

You need both of these in order to work on the bike and also to know the names of the various parts. Word descriptions are no good. When you go to buy parts whether it is from an HD dealership, eBay, an internet seller or wherever - you must have the correct part number. No one will sell to you on any other basis so you must have the parts catalog which is the only reliable source of these numbers. You cannot do any maintenance without the Service manual in hand.

Put the part numbers for the manuals into the Google and eBay searches, or buy from any indie or HD motorcycle shop. These are your two most important shop tools.