HELP!!! I broke it!!! Won't start. Warning LONG!!!

[retiredgentleman]

Well done Gordon! You'll be glad you opened up the engine. There will be more than a few items that need attention.

Sitting for 30 years is just about the worst thing you can do to these engines. All rubber components such as oil seals, valve stem seals, etc. will need replacing.

 

[Gordon in nc]

Well done Gordon! You'll be glad you opened up the engine. There will be more than a few items that need attention. <snip>

Yes sir, you were right. I have some photos of the inside of the engine but I'm having computer problems right now....maybe tomorrow morning. I will say that I found no damage and I have to believe this bike has only done an easy 7000 miles.

I have the head off and on the bench. I'll do a leak test tomorrow before I take the valves out but right now....I'm thinking a combo of weak springs and cruddy seats.....we'll see tomorrow.

Take care...I'm off to bed.....Gordon

 

[Gordon in nc]

My computers are giving me fits.....this is my third attempt at this reply.

Here's a peek inside the top end.

The scratching you're seeing is my attempt at the "gun brush" cleaning method.

and here's the operating room. I'll get a chance to build a proper engine stand while I'm waiting on parts. This time around I'm taking my time so I will only have to make one order........yea right

I'm off to leak test then pull the valves then we'll have a look at those seats.

Gordon

1975 XS650B.....under the wrench
and a few jealous BSA unit singles

 

[fredintoon]

My computers are giving me fits.....this is my third attempt at this reply.
Here's a peek inside the top end.
The scratching you're seeing is my attempt at the "gun brush" cleaning method.
and here's the operating room. I'll get a chance to build a proper engine stand while I'm waiting on parts. This time around I'm taking my time so I will only have to make one order........yea right

I'm off to leak test then pull the valves then we'll have a look at those seats.

Hi Gordon,
parts in lined boxes, tools in trays, things in tubs under a bench, floor completely free of tripping hazards and left-over stuff from your last project - - -
What kinda neatfreak are you???

 

[angus67]

that's some serious lighting. If the motor keeps being unco-operative, start waterboarding!

 

[TwoManyXS1Bs]

Hey, Gordon. Of all the things to check in that engine, here's an unusual one, cracked valves.
Have a look in here:

http://www.xs650.com/forum/showthread.php?t=39706

 

[5twins]

I'm going to guess you'll find the trouble in the combustion chamber in that 2nd pic. Looks like some rust got in there. The bike probably spent much of it's long down time sitting with one of those valves open.

I'm not sure what method you use for leak testing but I like to fill the combustion chambers with solvent (I use kerosene) and blow compressed air up into the ports against the bottom of the valve heads .....

Leaks will appear as streams of bubbles emanating from around the edges of the valve. I'm sure yours will show more than this .....

 

[TwoManyXS1Bs]

Oh, ho! I love that bubble pic! Great shot 5T...

 

[5twins]

Yes, I've been meaning to get some good pics of the "bubble test". Here's another, of a very slight leak .....

This head I'm working on now was pretty good. Just the one small leak on one of the exhausts (above pic) and one slightly larger leak on one of the intakes (previous post above). Small leaks like this won't show if you just fill the combustion chamber or port with liquid and let it sit. Nothing will leak through. That's why I like this compressed air test better. It will show you the little leaks. Be aware that you must place the blow gun just right or you can actually blow the valve open. Then you'll think you have terrible leaks when in fact you may not. I have a very small portable compressor I like to use for this testing as it doesn't develop much pressure. Blowing the valve open with it isn't much of a problem.

 

[retiredgentleman]

Those bubbles make for a neat picture 5twins

Gordon, your pistons and heads certainly have enough carbon build up to cause problems, but just for comparison have a look at what I found when I did a top end re-build. The head gasket had failed, and oil was being sucked into the cylinders. It looks ugly, but the carbon is easily removed using some paint stripper.

 

[angus67]

5Twins, how many psi do you use?

 

[5twins]

I really can't say. I do it more by "feel", manipulating the position of the blow gun, than by setting a specific pressure on the compressor. Like I said, the little portable unit I use isn't much of a problem as far as too much pressure goes. On my full size compressor, I'll just move the blow gun farther away from the valve if it is blowing it open. You can also pressurize the port more if need be by partially closing off the entrance with your fingers. This isn't difficult to do, just takes a little fooling around to get the "feel" for it. I feel it's worth the effort because the test results are much more definitive that just the "holds liquid" test. You will be able to detect any and all leaks this way, no matter how small.

 

[Gordon in nc]

Well, I'm having computer problems and can't download photos right now, so they will have to wait.

It's a shame beause a couple of them show how BAD my leak test turned out.

Poured the gas in the top......and it poured out the bottom. All four valves were leaking. How in the world did this thing run?????? AND....as far as I'm concerned, it ran well.

I've been making a parts "want" list.....and wish I hadn't spent my play money on that rust bucket roller. Now I'll have to wait until pay day (Thursday) to make an order.

I've got the head and the valves cleaned up and will lap the valves back in this week.

I'll pull the cylinders off after that and check that end of it out too. Looking in from above...both bores are spotless and I can feel no ridge at all at the top....and it never put out one puff of smoke the whole time I had it running.

Photos when I'm able.......Gordon in NC

Oh and Fred......that's what it looks like when I'm taking it apart....you should see it when I'm putting it back together!!!!! Yea....I'm a sick puppy but the rest of my house is a wreck.

 

[Gordon in nc]

These just made it through......my failed leak test.

The gas came out as fast as I poured it in.......

No burnt valves......just really dirty valves and seats on all four....some were worst than others....but they were all leaking.

Gordon

 

[peanut]

Tiny Leaks around the valves and seats is not the cause of your bike not starting !

.! You could have had small holes in your valves and the engine would still have started and run (allbeit badly) .

You haven't found the source of your problem but by the time you rebuild the engine and check everything, the problem you had will probably get sorted and you'll never know what it was .

how did you plug your spark plug holes ? they look open in the picture.

 

[Gordon in nc]

Peanut......there are spark plugs in the head.

TINY holes???????? those are 5twin's photos.

My bike ran for a little....a little over 50 miles total but when it decided to not run.....I could not get ANY reading on my compression gauge. If you spun the engine fast enough (drill on the rotor nut) it'd blow your hair around with air out of the plug holes but there wasn't enough compression to let the bike fire.

The compression had always been weak (but not measured...my fault) but I tried starting it anyway because I had nothing to lose. When it decided to not run anymore...I focused on the last thing I did to the bike...thinking I had done something wrong and assuming the compression was still the same as it was when it was running.

If you could have seen the gas pouring out of the head as fast as I poured it in.....you'd know the bike couldn't have run like that. If my bike would have had thoses tiny holes like are in 5twins photo's....we wouldn't be having this conversation....I'd still be riding.

Peanut......I'm VERY new to XS650s but have been riding and wrenching on motorcycles since I purchased my first motorcycle, a 1965 BSA B40 Enduro Star back in 1968. I ride thousands of miles on my bikes a year. My daily ride is a 1967 BSA B44 Victor Roadster with a Velorex chair attached (sub-frame and set up by me). To date, this 1975 XS650B is the most modern bike I've ever owned. My bikes (all BSAs)go from 1965 to 1972. So...this isn't my first BBQ. even though it's hard to tell at times with some of the lame stuff I pull.

Gordon

 

[peanut]

These just made it through......my failed leak test.

The gas came out as fast as I poured it in.......

No burnt valves......just really dirty valves and seats on all four....some were worst than others....but they were all leaking.

Gordon

these are the pictures that I was referring to . I presume that they are yours ?

The tiny holes I was referring to was the very slight leak that you appear to have around your valves . perhaps I should have used the word 'gap' instead.

The point I was trying to make is that even if you have a huge gap at the edge of your valves and the seats were burnt out it would not stop your engine from starting and running!

All valves leak all of the time . A newly cut and ground valve seat might only last a few hundred miles before it starts leaking. Your engine would have been losing a heck of a lot more compression from your rings than those valves .

Your engine would happilly start and run on as little as 75psi half that of a freshly built engine

Your non starting problem was NOT the result of your valves leaking slightly. I have owned a bike back in the 70's that had 1/4 of an exhaust valve completely burnt away and yet it still started .

Even if you took the piston rings off you'd still get some compression. The reason that you had zero compression in both cylinders could only be due to a faulty compression tester or incorrectly set valves which is what I believe was the problem


Gordon It is clear that although you were unable to find the non start fault and imo were ill advised to unnecessarily strip your engine for a non-start fault you obviously believe that you know exactly what you are doing and what is wrong with your engine so I'll not waste my time further .

 

[Gordon in nc]

Peanut, you said:

"Your engine would happilly start and run on as little as 75psi half that of a freshly built engine"

BUT.....would it run on 0 compression? If I walk across the shop and try my gauge on one of my other bikes (I tired it twice, on different bikes to be sure) and the gauge works as it should....what's so different about the XS?

If you look back through these replies.....you'll see I know where to set the engine when adjusting the valves...with the valve covers off it's easy to watch the intake valve.....you could train a monkey to do it.

You are convinced I set my valves wrong......so be it. Tearing this engine down was not a waste of time.....no matter what. I now know that taking the engine out of the frame is a snap and nothing to worry over and I now have seen how the top end works. I've said this before.....this is my hobby, not my job and if I wanted bikes I didn't have to wrench on....I'd buy new Hondas.

I'll be fine, you'll be fine, the bike will be fine.....and you could be right, so just have some comfort with that.

Gordon

 

[Gordon in nc]

Quick update with photos ( I hope)

I chucked up the valves in my drill press to check them out and BOTH of my intake valves are bent. The both took a "slight" tap to get them started out of the guide but once they moved a bit they fell out.

More later......Gordon

 

[5twins]

Well, I think you've found the problem, lol. Wow, some of those seats are really crusty and bad, especially that last pic. Hand lapping may not be enough for some of those. You may need to get the seats cut. But try the lapping first, can't hurt. I've lapped some pretty bad ones back in, but maybe not that bad. That parts bike just may come in handy sooner than you thought.