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

5twins.....yea, I think I found the problem. :laugh:

I've already cleaned up the head and valves (should have checked the intakes before I went to the trouble of cleaning them :( ) and I know it's hard to believe but the seats look fine and I feel pretty sure they will lap in (as long as I don't do your air leak test :) )

I'm going into the parts bike's engine tonight to see if I can use it's intake valves. Shouldn't take as long this time around now that I've already done it once.

I'm not going to get to the cylinders tonight....but will report back when I do.

Hard to believe the bike ran at all. I wish I had checked compression with my gauge FIRST thing......I'm not used to working on twins. With a single....everything is so simple....no need to balance with another cylinder.

Good thing is this time, I'll know what kind of compression it has......BEFORE the engine goes back in the frame.

I can't wait to hear that beautiful exhaust note again.:bike:

Gordon in NC

Headless 1975 XS650B
and a few jealous BSA unit singles

PS, 5twins....if I think about it I'll snap a pic of that left side (?) exhaust seat tonight now that's it's cleaned up (but not lapped yet)
 
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Well, I guess one small ray of sunshine here is that if you do happen to need to buy valves, intakes are cheaper than exhausts. But be aware that Yamaha changed the collet design sometime in '73. Your '75 should have the newer style with the rounded keeper groove. If you're shopping eBay, many of the older style valves will come up, which you don't want.

ValveStem-Collet.jpg
 
Gordon, those pictures are nasty indeed. Yes, lapping valve seats is for minor clean-up, but yours appear to need machining.

This is a classic example of why 40 year old engines need to come apart for maintenance.

What was it that peanuts said, oh here I found it............ "imo were ill advised to unnecessarily strip your engine"

I guess peanut has to eat some humble pie.
 
Oh, he'll never admit he was wrong, lol. He knows what he knows and there's no convincing him otherwise.

One of the worst motors I ever took apart was one that had sat and was stuck, was freed up without a teardown, and put back in service. It was terribly worn inside because of that. Pistons, rings, valve guides, valve seats, all were pretty beat up. But that's what happens when you pump a bunch of rust and carbon particles through your motor. Stuff wears out, and prematurely. This motor was to the point that it wouldn't go more than 10 to 20 miles before oil fouling the plugs out.
 
Not big on defending Peanut here, but he has a point. Zero compression is a lot more than badly leaking valves and/or almost nothing for rings. I've seen some seriously burnt stuff still pump up enough compression to fire up.
 
Gordon in nc said:
...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...
Click to expand...

Let's see. A lot of carbon buildup, bent valves, slightly mushroomed valve stem tips?

This is sounding like a 17,000 mile engine.

Maybe some more detective work needed.

I smell funny business. We've had "new bike" customers that would disconnect speedo cables, ride numerous cross-countries, reconnect cable, then try to trade-in a low mileage used for new.

Anyways, it was always prudent to re-ring if doing valves, and valve job if re-ringing...
 
weaselbeak said:
Not big on defending Peanut here, but he has a point. Zero compression is a lot more than badly leaking valves and/or almost nothing for rings. I've seen some seriously burnt stuff still pump up enough compression to fire up.
Click to expand...

I'm not sure why peanut is obsessed with finding the exact definitive cause of a "no start" on a 40 year old engine, that sat for 30 years. This is not a crime scene, and no one is going to falsely go to jail, if the root cause cannot be found.

Its now a moot point.Gordon did some measurements, and the results told him to begin a top end re-build. End of the "no start" mystery.:)
 
Look fellows.....this is wearing me out more than all those rusted bolts I undid tonight....it's not much fun anymore.

I have 20+ BSA unit single engines here in the shop and I have taken ALL of them apart...I've seen all kinds of stuff inside them. What I'm seeing wasn't bad at all in my world. I'm not a mechanic...never have been and never will be....I'm just a hobbist...that's all.

What you saw in the photo's cleaned up good enough for me and that's all that counts....right???? I'm not working on one of your bikes.

Weasel wrote: "I've seen some seriously burnt stuff still pump up enough compression to fire up."

None of the valves were burnt......IMO there is a BIG difference here. Take the inlet valve and burn a #2 pencil sized hole in it....that's some seriously burnt stuff.....BUT 90% of the valve is still sealed. Take a chunk of trash the same size as a #2 pencil and stick it under the valve and how much of the valve is sealed? ALL my valves had something under them holding them open. If you could have stood there and watched me pour gas into the head and watched it drain out a fast as it went in...you would know we're not taking about peanut's "tiny" holes.

At this point....I don't give a rats rear end how many miles the engine has on it. I have no way of knowing. I'll fix it. I'll ask questions when I can't find the answers on my own.

I'm pretty sure I bent the valves.

I want to thank you all again for the help.......Gordon
 
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Gordon in nc said:
Nope.....valve stem tips show little wear as do the rockers and cam.
Click to expand...

Great, good to know. Just got a little concerned. Some folks tap out mushroomed heads not realizing what it does to the guides.


Gordon in nc said:
... I'm still having computer server problems...
Click to expand...

I wonder if we have the same service.


Out here, they use something involving tin cans and barbed-wire...
 
TwoManyXS1Bs said:
Great, good to know. Just got a little concerned. Some folks tap out mushroomed heads not realizing what it does to the guides.
I wonder if we have the same service. Out here, they use something involving tin cans and barbed-wire...
Click to expand...

TwoMany.....:laugh: thanks for the laugh my new friend....I needed it. I'm feeling better about the world today and will keep moving forward.

I did have to "tap" both intake valves to loosen them.......but they were NOT driven through the guides :yikes: It was more like they were stuck to that goo that was in their seats. With the springs off, they just sat there on their own....a little nudge with my finger didn't move them. So I used my SMALL hammer (I have LOTS of hammers...a must with BSA ownership) and just barley tapped them ONCE each and they dislodged and then passed through the guide (with a rotating pull) with ease. I know better than to drive a stem through a guide. :thumbsup:

I'll be after those intake valves in the parts bike tonight.....and that will probably take most of my free time. But when I get a chance I'll snap a photo of the ends of the valve stems, cam lobes, rockers and if I can figure out how.....the cam chain tensioner's surface......all those tell a part of the story.

I still have to pull the cylinders.....no way I would NOT do that. Measured ring gap should also add a peice to the puzzle.

Thank you for staying positive......friendly.....and not insulting....:laugh: are you always like that...or are you hitting on me?????:yikes: :laugh: :laugh: :laugh:

Hope you have a GREAT day....your sure made mine a little better......Gordon

1975 XS650B headless in NC
1975 XS650B rust bucket parts bike
and a few jealous BSA unit singles
 
Gordon in nc said:
Beautiful motorcycle and a beast in it's day. Never could get to where I liked the mufflers....I have a set hanging in the shop and from time to time I have to wonder what the heck BSA was thinking. - - -
Click to expand...

Hi Gordon,
OMG it came stock like that?
That photo is the first time I've ever seen that particular muffler.
What card-carrying genius thought that a Bifurcated Buck Rogers Blowjob muffler was a good idea?
WTF was he smoking?
 
Hey, Fred. That pic wasn't really an accurate pic of mine, found a better one, and updated that post.

Mine had the single muffler.

I believe that dual muffler thing came out just after BSA was absorbed into the Britbike conglomeration around 1973-4? I believe it was something the Triumph boys cooked-up.

Of course, Gordon probably knows a lot more about that...
 
Fellows....I'm "pretty sure" that muffler was stock on all the BSA B50MXs 71-73. Triumph just continued it in 74. I have a running B50 special (no way near stock set up) and a couple of B50 projects but I'm really not up on the history of the OIFs.

You REALLY don't want to get me started :laugh:

I finished stripping down the parts bike.....into parts. I'm saving more than I thought at first....even if they are a bit rough.

One of the things I LOVE about these XSs are the fact that they are still afordable. A few years back I could pick up a BSA unit single roller for a couple hundred dollars....or less. I remember when I first started using ebay....15 years now?....there were less than a hundred BSA auctions going on at a time...and most of the time less than 50. Today there are thousands and that same $200 roller is now $1000.

I'LL get into that parts engine tonight and see if I can use it's valves.....but I'm guessing no. I need to take a photo of the rats nest in one of the exhaust ports.....that little sucker made it up all the way through the stock muffler and head pipe. :laugh:

I 've pulled two XS engines out now.....I was worried it'd be a pain but that wasn't the case (pun intended) BUT.......getting a rear wheel off for the first time (and a gummed up one at that) was a PIA!!!! worst job on the XS for me yet. Not sure if I was doing something in the wrong order or not....but man that was a drag. I am a bit spoiled...BSA's Quick Disconnect hub was one of their BEST ideas. OH......and getting the battery tray/tool box out turned out to be no fun either.....it finally came out after a LOT of twisting and turning......sure glad I don't have to put it back in any time soon. :laugh:

Looking forward to some shop time tonight and since payday is tomorrow......I can finally make a parts order....which means I need to pull the cylinders off tonight too.

Gordon in NC

1975 XS650B headless in NC
1975 XS650B nothing but a pile of parts now and one exhaust port rats nest
and a few jealous BSA unit singles
 
Just a quick update,

Finally got around to taking the inlet valves out of the parts XS and they are in good shape so I'll be able to use them to replace the two bent ones. Yea, I spun them BEFORE I cleaned them this time around.

I'll get the time tonight (life got in the way)to get the cylinders off and the pistons out so I can clean them up to see what I have. Already talked to the machine shop to find out how busy they are. This is going to take a week or so.....so I can slow down a little.

I'll lap the valves in this weekend and share some photos of the results.

Thanks again for all the help.

Gordon in NC chomping at the bit to get this XS back on the road.

1975 XS650B headless in NC
1975 XS650B parts only
and a few jealous BSA unit singles
 
Another quick update.....you'll probably not be bothered by me for a bit while I wait for parts. Hopefully next time you hear from me it'll be when the bike is back on the road. :bike: unless I run into a snag when putting it back together.

I pulled the cylinders off and then the pistons. Everything looks and measures good. :thumbsup: De-glaze, new rings, seals, orings, gaskets, replace bent valves and button it up......oh and new points, condensor, coils, and HT wires w/caps

In the meantime I'll lap in the valves and clean up all the sealing surfaces......:) This time I'll leak test from the port in.....each lapped valve at a time to be sure they are sealing. Guess if I get caught up I can go ahead and de-glaze the cylinders and be ready when the rings get here.

I took a bunch of photos but I'm still having server problems....so you'll not have to drag yourself through those just yet.

Gordon in NC chomping at the bit to get this XS back on the road.

1975 XS650B headless in NC
1975 XS650B parts only
and a few jealous BSA unit singles
 
Hey, Go Go Gordon!

Not sure if you're already aware of this, but these engines have been developing a history of warped head-to-cylinder surfaces. Something to check. Member Funky has some posts in this thread with good pics of the leakage that can occur in the camchain tunnel area between the cylinders:

http://www.xs650.com/forum/showthread.php?t=40573

More info can be found in the "Leakless XS Assembly" thread by Grizld1:

http://xs650temp.proboards.com/thread/327

And, some more good tips from RetiredGentleman in these threads:

http://www.xs650.com/forum/showthread.php?t=7500
http://www.xs650.com/forum/showthread.php?t=13212
 
As you've probably noticed, the ports on these are pretty rough from the factory .....

IntPortBefore4.jpg


Since you have some time waiting for parts, you might want to have at them with a Dremel and smooth them out a bit. Nothing drastic, just smooth out the lumps and bumps.
 

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