Compression tester adapters?

[luckynumber0]

Hey all,

New member here. Howdy.

I'm looking at an '80 XS on Saturday and I'm bringing my tool kit. I've just purchased a compression tester online, but while I wait for it to arrive I was curious about whether or not I need a specific adapter for the test. My money's tied up with this potential purchase and I kind of did an impulse buy on a cheap Equus getup from Amazon that has 12, 14, and 18mm adapters that come with it and I'm presuming the standard lead on it (unadapted) is 10mm.

My question is which size I'll need and if I need - and which kind - of adapter to get for testing out the bike's compression.

Thanks in advance!

 

[ANLAF]

Welcome Luckynumber0, and good luck with the potential purchase.

Bear in mind that you are looking at an engine that's over thirty years old. It is very likely to need an overhaul. Mine is running, but age has caught up and needs replacement valve guide seals, so that means I must dive into the top end. While I am there I will be doing the gaskets, valves (cleaning), checking the cam chain and piston rings. I expect some replacement.

You should expect to have to get in there anyway.

Anlaf

 

[retroLS1]

You won't need any additional adapters. I can't remember if it's 14mm or 18mm but I have a tester that has both of those and it worked on mine no problem. Looks like you will be covered with the one you bought.

 

[gggGary]

I think that's the one I have had for years, works fine after I disassembled and lubed all the fittings and schroeder valves. Only adapter I needed was the tiny one for chainsaws NAPA had it in stock.
Don't be surprised if the compression shows bad if it's been sitting. Doesn't always mean disaster and it can be a good bargaining tool. a wet oily plug might tell you more than the compression test.

 

[XSLeo]

Most compression testers have a 3/8 reach 14 mm end. That's because most cars had short reach plugs.
They added the adapters to fit other engines with aluminum heads, the 3/4 inch rfeach plugs. They also make adapters to fit smaller plugs like used on Honda's And harley's, they use the 12 mm plugs.
Some of the olders cars used the 18 mm plugs.
Leo

 

[luckynumber0]

This is all good stuff fellas, very helpful! But now it's got me a bit stumped...

If I should expect poor compression (because this is indeed a barn find), then what else can I check to see if I should buy it or run away?

I know that question is well covered in the Tech section, but after reading that and thinking I had a good strategy for how I'm gonna go over this bike on Saturday...I'm not so sure now!

 

[retroLS1]

If it has a title, she's already leaps ahead of a lot out there that don't come with one.

 

[luckynumber0]

@retroLS1

No such luck...It's 900$ though, which is more or less 900$ cheaper than almost all of the XS's I've seen on craigslist around LA - even with missing carbs, tanks, and forks! A bunch of those even don't have titles. Also, it's not been modified already, which is good because who wants someone else's bob? I want to start stock.

Here's the craigslist post.

I ran the VIN with AAA here in CA and again with the Nevada databases (it's about 3 hours outside of Las Vegas - we're meeting halfway). It's not stolen and they said it doesn't look like it's in the system. Someone on here made a pretty thorough post about how they went about getting their title and while it is a bit of a headache, as long as it's not impossible or incredibly expensive I don't really mind the hassle. I'm a newb so feel free to call me out if I'm wrong!

My concern is finding out if I'm gonna hit a big, expensive wall with a super busted engine.

Let me know what you think.

 

[gggGary]

What miles are showing on the Odo? if it's 25K or less you should be good. He's right though if it kicks over and bonus has "some compression" on both sides they'll usually run and that's pretty much what you can tell with a barn find. High desert bikes often (usually?) have no useable rubber parts, the heat and dry destroys them.
Bring jumpers, car NOT running, if the headlight lights after you kick it over (doesn't need to start) it has a working charging system. I strongly suggest not trying to huff some ether in it and try to start it. check for spark maybe.