Calling all Guru's....

[CarolynS]

Okay, cleaned the gas out of the tank, checked the plugs, and fired it. It seems like it's got no compression. It turns over fine, but there's no bumping and with a spark plug removed, no wind. Nothing coming from the exhaust either.
Question is: How does the starter connect to the engine? It's almost like it's not connected, or can all the pistons stop moving at once for some reason? It's not making any horrible banging and crashing inside the engine. It's quiet.
Any suggestions where to start?

[dogyear58]

Weard????

You can hear engin spin over or just starter???

[skids]

The starter clutch is not enganing, i'll bet. Have a garage? Take a space heater and set it to heat the crank case to warm the engine oil. That should help if that is the problem (starter clutch not engaging because oil is too thick).

[prometheus578]

Ok...
I trust that you understand the difference between a starter spinning... and a starter spinning the engine.
we shall assume the starter not only is spinning, but is spinning the engine, as well.
Now then... why no compression?
As you have the spark plugs out... take a flash light and look into the plug hole of #1 Cylinder. Hit the start button a few times. You should see the piston rise and fall. (use eye protection... so I don't get in trouble, etc)
Ok.. the pistons are moving.
If the pistons are moving and you have no compression, then you have a valve issue.
Do you have an air compressor in your garage?
You could do a leak down test. (Would take too long to type out the instructions, but there was a thread on this a few weeks ago. Search for "leak down", "tire valve", etc)
Anyway.. next would be to remove the tank, remove the ballst resister(left side, on the tank... one phillips screw) with this stuff gone, you can take the valve cover off.
Check your valve clearances.
As the valves wear, they move up into the head, reducing the clearance. If the clearance gets to zero or less, this will leave the valves open when they're supposed to be closed, hence, no compression.
Now.. do you mean absolutely NO compression? Zero, or just real low?
Is your battery still strong enough... after all your cranking, to spin the engine fast enough to get a good reading on the gauge?
Check the valve clearances and write back

[randy]

Carolyn,

Starter clutch is probably stuck. This is the '80? Do you have a kicker? I don't remember. Try turning over with the kicker if you have one. I had an '81 with that starter problem (no kicker) and I freed the clutch by spinning the motor backwards a few revolutions. If you want to try doing it this way, you must do this with the key OFF:


Install the battery backwards, jump the solenoid screws with an old screwdriver. Re-install the battery the right way, then jump again. If it worked, you'll hear the engine turn and get wind out of the plug hole.

If it din't work, engine disassembly is the only way to replace the starter clutch. Sorry.

[CarolynS]

He's going to run back outside and check it. I'm on my work computer here and he's with the bike.

[prometheus578]

...get wind out of the plug hole.

MY EX used to yell at me for that.

[CarolynS]

The pistons are moving. We have the fuel tank off-want it cleaned out-he used ether. It popped and everything seems to be moving. No expensive noises, or crashing. I'm going to put a little fuel in my other tank and hook everything back up and try to run it.
I'll keep you posted.

[CarolynS]

Update...

Okay, with the fresh gas it backfired out of the exhaust twice on either side, but it's also backfiring out of the airfilter. We figured we'd better check the air filter to make sure we had no "squatters"(mice), and when we took it off it was full of gas, obviously from trying to get it to run.
So, we have fire, we have compression-that leaves either completey gummed up carbs or a timing issue, or both. I still think the valves could use an adjustment and he said that he noticed somewhere in our research, that there's a timing chain that is supposed to be adjusted every 3K miles. The bike has 49K on it. What if it's been 20K since that and the valves were done? That would contribute to some of it, I'm sure.
I'm planning on trying to bring it home tomorrow, and I think the first thing to do is to remove the carbs and get them clean. Once we know they are functioning properly, it should be easier to diagnose the problem.
I'm sure alot of you have faced this same problem trying to resurrect an old XS that you picked up cheap because the PO didn't want to spend the $/or didn't know enough to remove the carbs and clean them, adjust them.
If that is what the problem is-Boy! Did I make a killing getting this bike for $400!!!!
I almost feel guilty.......yeah, right!

[mitch]

Carbs

Clean the carbs 77 times then you will be good to go
Doug

[TopCatGr58]

Hey Carolyn,

Yes, sounds like the CARBS need severe cleaning, the floats are sticking or the float needles are gummed up and not closing, so the fuel is flooding the carbs and flowing into the airbox. IT's very common for it to also flow INTO The engine and past the piston rings and contaminate the OIL! SO...be sure to check to make sure you haven't gotten or already have gas in the oil!

Please be sure to read the tech tips on cleaning the carbs. There are several pitfalls that can occur if you try to rush the process, like breaking the float posts, stripping or mangling the pilot screw tips, the pilot jet slotted heads, etc.! There are differences between the early78-79 carbs and the 80-81 with some bastardized ones from the 80 series where Yamaha was mix/matching parts until they used up the old parts, and then got them all converted to the newer style!

Also, there is a small jet in the FLOAT BOWL itself that can't be removed, but easily gums up, and will prevent the CHOKE, fuel enrichener circuit from working properly and prevent fuel flow for starting!

There have been posts about how to recondition the float needles/seats depending on whether it has the solid metal or the viton rubber tipped ones. There is an O-ring under the float needle SEAT IF your carbs have the press in seats that are secured with the flange and offset screw vs. just the whole seat screwing in, and these O-rings can also dry/shrink, and cause flooding!

Also, don't SOAK the carbs in a bucket of cleaner, the butterfly shaft seals will get destroyed and give you severe vacuum leaks!

So...you don't want to RUSH the carb work, take your time, do it thoroughly, and carefully, and you might get lucky and only have to clean them ONCE instead of the usual "triple clean" that is so often quoted on here for NEWBIES!!!
T.C.

[CarolynS]

Carbs or Valves?

I was talking to my stepdad on Saturday-lots of years with Japanese bikes-and he said that the problem is valves not seating properly. The kid I bought it from said it needed top-end work. Where he got that diagnosis from, I don't know. He wasn't too familiar with the bike. Who knows how long it sat before he got it, or why it sat in the first place. With the condition of the machine, someone really took good care of it.
I realize that the carbs will need cleaning anyway, but I was wondering if I should be prepared for an extreme expense to follow the cleaning.
Is it possible that all the valves go bad at the same time? Wouldn't the engine actually start and run badly? It won't start, just pop once or twice-if that.
I'm not going to attempt the carb cleaning myself. I looked it up in Tech-Yikes!! I'm taking them to the mechanic to do. If valves could be a possibility, I may just take the whole bike over there so that he can work it all out for me.
Let me know what you think.
I'm really hoping you tell me that it's just carbs!

[81xsproject]

If the mech wants more than $375 for EVERYTHING, let me know. I have a set of '78's that are bolt on go for this price; ultrasonic cleaned, upgraded viton float valves, tops and bowls polished, on bike tested, and tuned. I don't recommend mix and matching 70's and 80's carbs/bikes. The difference in the cams/valves makes a big difference. And in my testing, I have found that especially during start up, the 70's carbs are way rich on 80's bikes. Once the bike is warm and off the starter circuit, they are fine but still not as nice as my 81 carbs.

[CarolynS]

Cool! This is an 80 xs11G. That answered one other question I had. I won't bother trying to use my 79's on there.
Now is $375 for the carbs or for the valve job?

[Flatlander]

Hey CarloynS,
Carb cleaning is a good idea, but at this time do a compression test. I just had something like this happen to me. And if your PO new something about the head it leads me to believe that they may have had the head off? And in reassembly something might be off with the cam timing. Just a possibility. The compression should be 142 psi with a maximum difference of 14 psi between cylinders. My suggestion is also to stop trying to start it until you know more. Good luck.