compression depression

[chopwatchagot]

Starting to feel sick... can't breathe...note to self- when PO says "just needs sticky carb fixed", do a little investigating. Like check the crankcase...is it full of gasoline?...yes? ok, sticking float, not too tough. Starter button missing... hmmm, is there something he doesn't want me to know? Now that the carbs, master cylinders, wheel bearings, steering head bearings, forks, throttle, etc., etc., etc. are all rebuilt/replaced/fixed I guess it would be a good time to check the compression. Since I'm just turning the engine over to circulate some new oil, (will change it again before I actually fire it up), I'll just screw in the compression guage to see what we have. First cylinder 130. Ok, I live at 5200 feet elevetion, it stands to reason that it's a bit lower than the 142 it should have at sea level. next cylinder (#2) Oh oh! only 95. Next one (#3) 95 too! Dang! #4 back to 130. All right what gives. Why are the middle two cylinders way low? Could it have something with the missing oil pipe? Say, why am I missing the oil pipe? AM I missing the oil pipe? Did the '80 not have it? Ok, I'm rambling again. Sorry. If anyone feels like commenting on any of these issues I'll be a very attentive listener.

Dean

need to figure out how to use yhese smiley things!

[GNEPIG]

.. first put some oil into the cylinders that are giving you problems and test again. if your values remain the same then it's your valves- check your valve clearance and make sure you dont have a tight valve or two. if your values get better then it's your rings.
.. if this bike has been sitting for a while, it is common for the compression values to be low for a while after it's been put back into service. if it runs good and doesnt smoke exsesively i would ride it for a month, then test it again. you are testing with the motor at or near operating temperature, right?

[pac00t]

you probably know this, but to get an accurate reading you need to have the engine warmed to operating temp and the throttle held open all the way. Otherwise you'll get lower readings that you should.

[TopCatGr58]

Hey Dean,

As has already been said, aside from retesting with a little squirt of oil into the cylinders, you can't tell too much from a static COLD comp test. Were you using the starter, or just a wrench on the timing cover plate? Also, throttle needs to be Wide Open, unless you have the carbs off! And, yes, ALL XS's had the oil line running up the back of the cylinders!

To use the smileys, you need to have the cursor where you want them to appear, but only the last place you typed, you can't insert them into the middle of text you've already typed just by placing the cursor and then clicking on the smiley, it will only put them at the end of whatever you have typed.

However, once you learn the characters that are used to make the smileys, ie. colon+)= colon+( = colon+small letter o=
colon+capital letter D= semicolon+) = colon+letter p=

Last 5 are words bracketed in colons;
colon+cool+colon=
colon-rolleyes-colon=
: mad : =
: eek :=
: confused :=

You can type these into any place in your message and they will be created once posted!
T.C.

[chopwatchagot]

Hey Gene,
whew! I feel better already! No, the bike was not at operating temperature as it's still not quite back together. I see now that it only makes sense that I would get screwey readings as long as this thing has sat. Of course I didn't explain any of that in my original post. Thanks a million for your in insight!

T.C.
Hey Man, thanks for helping me out. I really appreciate your careful reading and helpful response(s) to my rather verbose inquiries. Sometimes I just can't get right to the point to ask a question and have to type a bit to get it out
Now I need to get back to work on this beast. I'm going to try to fire it up today. My plan is to get it sorted out in the next Month so I can ride it to Lexington,KY. to pick up a truck that I'm buying from my sister. This will be by FAAAAAAAAAAR the longest trip I've ever taken on a bike and although I'm a little concerned
about the weather, I'm going to do it anyway

Dean

[LoHo]

Warm engine and WOT? I guess you learn something everyday. Should the other plugs be pulled? I'd assume that would affect the values, too....

[prometheus578]

All plugs out.

[skids]

...and you might want to vacuum any dirt , sand or other from arounf the plug before you do that. You wouldn't want the engine to suck it in!!!

Originally posted by prometheus578
All plugs out.

[chopwatchagot]

I got the 80G bastard carbs all rebuilt (thanks to the incredible amount of experience and helpfullness of all you guys) and put back on the bike and she fired right up Idled pretty darn good too! However, when I revved it a little it was reluctant to return to idle speed, like the slides weren't coming down fast enough. Are the diaphram springs the only form of throttle return? My Honda 500 four has an external spring to help facilitate throttle return. It seems like this would be helpful on the BIG UNIT (Hey, I just named my bike!) also. Any thoughts on this?

[Ken Talbot]

You still need to do a vacuum sync to get the carbs working properly. That, and setting the pilot screws either with a colortune or 'by ear', should get it acting the way it should.

[chopwatchagot]

Ken,

What exactly is a color tune and where do I get one? I've heard mention of these things in several threads here but I don't know a thing about them.

Dean

[pac00t]

I'm not entirely sure of everything, but I think they're a spark plug with a little window in it, so you can see the color of the flame in the cylinder. Something like white being lean and yellow being rich, a certain color of blue is what you want.

[Ken Talbot]

Here's a link for the colortune