HELP!!! ENGINE CLANKING NOISE!!

It depends on the condition of the cylinders.

Simply put, cylinders need to be round and straight; if they need boring then you will need oversized pistons and rings.

If the cylinders are true enough and clean enough that simply honing is all that would be required, AND the piston-to-cylinder clearances are still within spec (based on bore gauge measurements of the cylinders) then the answer is yes IF the pistons are still in good shape. I've done more than one British twin that fell in this category with no bad results. It's simply a matter of measuring; you're either in spec or you're not (excluding actual damage.)

Your service manual lists bore size, wear limit, cylinder taper limit and cylinder out-of-round limit as well as piston clearances including ring end gap and side clearance limits. The measurements you take in the motor compared to the specs are what answers the question.

 

I have always been taught that if your going to tear apart a motor like that, you might as well rebuild it and rebuild it right with no shortcuts.

 

I wasn't advocating shortcuts by any stretch. You only cut metal when necessary, but you DO cut when it's called for.

 

I wasnt arguing against you, I am just implying that if he was to take the motor apart to replace the rings, he might as well do a lot more while he has the opportunity.

 

Seems like there is someone missing from all the posts. 86maximusXJ700. I offered to post his pics for him the other day have not heard back from him yet. Leave Bill alone (tears rolling down my face)

 

http://jamiedubs.com/f***flickr/data/meme-prints/web/leave-britney-alone-02.jpg

 

Now that is funny. LOL

 

If the specs are there, it seems like a ring job would be pretty simple.

 

Sorry I couldn't get back sooner. Still don't know how to resize pics. cylinder walls are fine. Valve appears to be fine. Only visible damage is top of piston and combustion chamber.

 

Use this to resize those pics... post them quickly... we would love to see them.
http://www.picresize.com/

 

I ride across town to work everyday and depend on this bike. I would like to take this oppurtunity to rebuild the motor properly, but I'm broke. I'm looking for the cheapest way to get it running reliably. I looked online at the gasket prices and those alone are more than I expected-- $90 for the head gasket.

 

read back through your post here... we have questions.

if you had the time you could probably pick up a whole bike for that price but you don't...

Did you put it back together?

 

I dont think hes online Bill

 

It's still apart. Still can't resize pics

 

Think I finally can post the pics

 

Finally

 

Looks pretty nasty. If you really dont want to mess with it, I see XJ motors sell pretty cheap usually.

 

Other than the gouges on the top of the piston and comustion chamber, is there any other damage that I should check for? Could this have affected the lower end?

 

what is your budget like?

 

budget is exremely limited

 

I'll check back tomorrow. I really appreciate any advice.

 

poor some liquid in the damaged head see if valves leak.

 

did you figure out where screw came from yet

 

any gouges in cylinder wall

 

That'll buff out.

Since the head is off, take it to a machine shop and they can vacuum test it in 2 minutes for free.

The big questions are -
(From Waldo) "any gouges in cylinder wall ?"

(from me) did the piston's top land collapse, trapping the ring, causing the ring to no longer work, and imminent failure.
You would need to remove the piston for inspection.

 

Poor some oil in that too compare it to another cylinder

 

You may be in luck. Depending on where you live and how you could get it. Bluemonster has a XJ700N motor to sell in the for sale forum. He is in Canada. But if you could not get the whole engine from him maybe just the top half would do. Pistons, Cylinders and Head.

The crown of the piston is damaged and I personaly would replace it. The head you could smoothe out with a die grinder and sandpaper roll. Be carefull not to remove too much material as it would change to cc of that chamber too much. (cc the head is how many cc's of liquid fill the combustion chamber) If you have a machine shop near by you could get an estimate of how much it would cost to check the valves and clean up that chamber.

Sorry you are on a tight budget but as luck always has it, this kind of stuff never happens when your wallet is full.

MN

 

It's hard to tell from the pics, is there ANY damage to the cylinder wall or just the top of the piston and the head?

TIME's questions and advice are spot on; the piston will at the very least require inspection, possibly replacement. How does the top of that piston look, flatness-wise, compared to the others?

And last but not least, somebody already asked: did you figure out where the screw came from? Do you have it?

 

Just remembered a machinists' trick - -

get the piston to the bottom of the bore
drag a penny around any vertical scratches. If the penny catches, you've got a gouge. You could live with a couple very minor gouges, I guess, but ideally, it should pass this test. You can ignore any flaws in the first 1/4 inch, as they are above the first ring.

The only way I can think of to check to see if the top ring is "pinched" as I described above,(without removal for inspection), would be to carefully look at it while you rock the piston. But bike tolerances are really tight. You would be comparing the look and feel to the other pistons. If this piston does not rock as much, the ring could be caught.

So - if you pass the free vacuum test, and the penny test, and the rocking test, you could re-assemble with Indian Head Shellac for $2.00, assuming you didn't destroy the head gasket. (this advise given because you're on a tight budget).

 

Good news fellas, I dunno if I'll get in trouble for saying this haha but, I found a full service manual online on one of those file sharing websites. All XJ models and years were there actually. All 222 pages, pictures and all on PDF. This'll help with the rebuild for sure haha. Anyway just wanted to share this little bit of good news. I'll include details on the current damage later when I have time, thanks all.

 

I hope this works out for you. Let us know what happens.

 

The cylinder wall is undisturbed. When I have more time (probably Friday night) I will check the things that have been advised here. Between work and school it's hard to find the time. My dad let me barrow his '81 virago 750 for the meantime so I got some wheels for the time being. If the gasket is torn in a couple places can i use the varnish and salvage the gasket?

 

Nope.
Don't be silly.

You just dodged a bullet.
Don't set yourself in the crosshairs again.

Get a Gasket.

 

Think about getting a engine gasket set if you can. While you have the head off, replace the valve guide seals and all the other gaskets. The gaskets aro old and brittle, don't try to reuse them. Thats just asking for oil leaks.

 

any idea how much a complete gasket set will run?

 

Does anyone know if a 82 750 head gasket would work

 

Nope, two TOTALLY different motors.

1986 xj700
1982 xj750

 

It's my understanding that the 700 was made by reducing the bore of the 750. If that's true, then a 750 head gasket would be a few MM larger (at the piston bore) than needed, leaving a gap that would eventually fill with carbon.

Other than this, is there a reason it wouldn't work ??

 

one gasket is for a water cooled bike ???

 

I don't see the water passage holes . . .

 

I thought this was a 1986 xj 700.

When I looked up this year it just shows water cooled bikes. Hmm.

 

No, mine is aircooled, the XJ700XN, commonly called the "Maxim X" is the watercooled version, while mine is just the normal XJ700N.

 

http://cgi.ebay.com/ebaymotors/NOS-Yama ... 1180wt_941


found a gasket

 

To save some dough for a guy, ...

I have traced and Cut-out many a Base Gasket.

Some High Quality Gasket Paper
Plastic Push Pins
A piece of Pine Shelf Stock
X-Acto Kniife
Sharp Utility Scissors
Single Hole Punch
Double-ended Sharpie / Reg and Fine Line
Drawing Compass
Finger & Thumb of old Leather Glove.
Masking Tape

(Tape the Glove Fingers on so the Razor won't get-cha)

 

Well, I ordered a gasket earlier this morning, was about $50... will this do?

http://cgi.ebay.com/ebaymotors/ws/eBayI ... 2000wt_939

 

Is it me or does this one look like its for the watercooled version.

 

Bill was right. Those are water passages. Gasket arrived and although they advertised xj700 it is for a water cooled version. Is it possible to use a sheet of gasket material and make my own head gasket?

 

Ok, we have a problem. So, since the gasket I ordered was the wrong one, I went ahead and salvaged the old gasket and started putting the top end back together. All was going well until I tried putting the cams on, they are binding on the valves. When I turn the crankshaft, I can see that the lobes of the cams are binding against the valves, so the crankshaft abruptly stops. Any ideas as to why this is happening?

 

Sounds like you don't have the cam timing right. Be very carefull you'll bend the valves and you'll be right back to where you started.

MN

 

yeah, i would get a new head gasket...imho yer askin' for trouble using the old head gasket....
just my .02