Compression fitting size?

[Motorbike_Mike]

Last fall I started up my bike (79 XS1100 Special) and it made a loud kind of "pop" sound, almost like a backfire but more metallic sounding... It then ran, but terribly, sounding as if it was only firing on 2 cylinders or way out of time.

I would like to check the compression to start and was wondering what is important when I buy a compression tester? For instance, what threads do I need on the fitting to thread into spark plug holes?

Also if I end up needing engine parts, are they readily available? Or are they hard to find like everything else on this bike?

Thanks in advance.

[bikerphil]

Compression tester fitting would be the same size as the spark plugs, 14MM.

[Gmac]

I have a cheap one somewhere

Before when I was poor and stupid I bought a compression tester that just has a rubber stopper for the plug hole, fit everything, was a bitch to use if I was by myself and couldn't kick or pull. Still, it worked well enough.

Buy a Harbor Freight tool and it will have the fittings you'll need to get accurate data.

[Motorbike_Mike]

Thanks! I will order one today.

[Motorbike_Mike]

Help please?

I can't seem to find any "how to" guides on rebuilding this engine. Can anyone point me the right direction?

The bike only has 21,000 miles on it. Needless to say it has sat most of its life. I will post more info on my problem when I get the tester in the mail. Anyone have any guesses on what might be wrong?

[motoman]

I can't seem to find any "how to" guides on rebuilding this engine. Can anyone point me the right direction?

The bike only has 21,000 miles on it. Needless to say it has sat most of its life. I will post more info on my problem when I get the tester in the mail. Anyone have any guesses on what might be wrong?

Just sitting is its biggest demise. Needs to be ridden a lot and forgo any rebuild. It's hardly even 'broke in' yet.

[motoman]

Last fall I started up my bike (79 XS1100 Special) and it made a loud kind of "pop" sound, almost like a backfire but more metallic sounding... It then ran, but terribly, sounding as if it was only firing on 2 cylinders or way out of time.

I would like to check the compression to start and was wondering what is important when I buy a compression tester? For instance, what threads do I need on the fitting to thread into spark plug holes?

Also if I end up needing engine parts, are they readily available? Or are they hard to find like everything else on this bike?

Thanks in advance.

'checking compression for a start' is not a good option. Electrical plugins behind fuse panel would the better starting place. Oher than that, it just needs to be ridden several hundred mles before getting excited about doing a compression check. Riding it several hundred miles will re-seat the valves in the seats for a good seal. In other words, the running issue or lack of on all cyls. is ignition electrical, not mechanical.

[Motorbike_Mike]

Thanks for the advice. Let me tell you more about the bike.

I bought it 7 years ago from my old boss. It used to be his brothers but had sat in the barn since he passed away. At that time it only had 2,900 miles on it, and I only paid 500 bucks. So i have put around 18k miles on it in the last few years.

I had to do a lot of work to get it running. I had cleaned and adjusted the carb 4 times over the last 7 years and it was finally running great as of two seasons ago. But then last fall it all of the sudden made the "pop" sound and so on.

So I had already been riding it from spring through summer before it happened.

It runs sorta, but there is most definitely what seems to be a serious problem. I don't think it would stay running with a load under its current condition. I haven't tried for fear of doing further damage. I figured I would wait until the compression tester arrives before I turned it over anymore. I ordered it on ebay for $15 today.

I just thought some of you experts might have some insight on what might be going on. I am almost sure there is some internal engine damage, but I am no expert.

Thanks

[motoman]

Thanks for the advice. Let me tell you more about the bike.

I bought it 7 years ago from my old boss. It used to be his brothers but had sat in the barn since he passed away. At that time it only had 2,900 miles on it, and I only paid 500 bucks. So i have put around 18k miles on it in the last few years.

I had to do a lot of work to get it running. I had cleaned and adjusted the carb 4 times over the last 7 years and it was finally running great as of two seasons ago. But then last fall it all of the sudden made the "pop" sound and so on.

So I had already been riding it from spring through summer before it happened.

It runs sorta, but there is most definitely what seems to be a serious problem. I don't think it would stay running with a load under its current condition. I haven't tried for fear of doing further damage. I figured I would wait until the compression tester arrives before I turned it over anymore. I ordered it on ebay for $15 today.

I just thought some of you experts might have some insight on what might be going on. I am almost sure there is some internal engine damage, but I am no expert.

Thanks

Alcohol content in fuel unnecessarly draws extra moisture from sitting. I suggest pulling the carb bank, remove the float bowls and clean the 'science project' from internals of carbs......that means remove all jets, metering rod assembly by removing vacuum diaphrams from topside of carbs, ect.,ect. and spray carb cleaner thru everything.

[Motorbike_Mike]

Thanks. But I have done that 4 times already. I am confident my problem lies elsewhere. It hadn't been sitting before the problem occurred.

[TopCatGr58]

Hey Mike,

Glad to hear that it had been running for several years, and that you're fairly familiar with the carbs. As was stated, the bike is barely broken in with those low miles...these engines are 100+K with just regular maintenance procedures. SO..speaking of maintenance, have you ever checked the valve clearances?

Next, even though it has quite low mileage, the wires in the timing section still age and get brittle, and it's a known weakness for these bikes to have the PickUp Coil wires to fail/break, and that will cause you to loose 2 cylinders, backfires, etc.! The metallic sound may have just been the mufflers vibrating with the pressure wave?? There is a tech tip on both how to find if they are damaged, as well as how to fix them.
http://www.xs11.com/forum/showthread.php?t=543

Also, have you performed the cam chain tensioner adjustment procedure? However, instead of doing this, we really recommend that you get a Automatic Cam Chain adjuster from eBay...see the tech tips for a listing of bike models you get harvest one from for your bike. The OEM tensioner is faulty/weak and can fail, loose tension, which can then allow the chain to skip teeth and throw the valve timing out!

Take a look at this thread...it's a few pages and covers several years, with differing opinions on whether to do the manual Mod vs. the ACCT, (with your low miles, the ACCT would probably be the best and easiest to do) but PLEASE review the thread to understand the steps in removing the OEM unit, taking up the chain slack, and installing the replacement ACCT unit.
http://www.xs11.com/forum/showthread...nute+cam+chain

Here's the ACCT Mod tech tip and parts listing:
http://www.xs11.com/forum/showthread.php?t=35501

Finally, sounds like you don't have a manual, so follow this link to Catatonic Bug's profile:
http://www.xs11.com/forum/member.php?u=13221 Then click on About ME tab, and follow his LINK to his website to download user and service manuals in PDF!

T.C.

[Motorbike_Mike]

Thank you T.C.! Those are great ideas.

I repaired the pickup coil wires 4 years ago, but I will definitely check again.

Checking the timing was going to be my next step after compression testing. I have never adjusted/tightened it. Should I adjust it even if I discover it already shows to be in time?

I am new to troubleshooting this type of problem and am not sure what exactly to look for, or what it means if one or more cylinder shows low/no compression.

Any advice would be appreciated.

[CatatonicBug]

You say you've cleaned the carbs 4 times in the last 7 years? That's hardly enough to rule out a carb problem. If it has sat since last fall, you most definitely need to clean the carbs again. Initial cleaning usually takes 3 times. Any length of time (over a month or two) sitting with fuel in them may also require another cleaning. Carbs are probably the most troublesome part of these bikes, followed closely by electrical issues. Mechanical things seldom happen, and when they do, it's usually easy to diagnose.

I'm not trying to diagnose your popping sound here, but don't think that your carbs are clean just because you cleaned them last year.

[Motorbike_Mike]

I see. I will go back through them If I don't find anything wrong then.

The thing is though, It hadn't sat but a day before it happened. I ran it all season, and finally in the fall the problem occurred. And it wasn't just running, it was running great! (Except for 2nd gear of course... that was already gone when I bought it at 2,900 miles)

I won't write of the carbs though.

Thanks for the advice.

[motoman]

I see. I will go back through them If I don't find anything wrong then.

The thing is though, It hadn't sat but a day before it happened. I ran it all season, and finally in the fall the problem occurred. And it wasn't just running, it was running great! (Except for 2nd gear of course... that was already gone when I bought it at 2,900 miles)

I won't write of the carbs though.

Thanks for the advice.

Well, if it has sat since last fall with the same fuel in the tank, it needs to be drained/emptied and fresh/new fuel put in...... before its run again.