Broken valve

[SteveP]

Hi all
I've been working through the masses of amazing information contained within this site. I haven't so far needed to start any post because I've always found what I needed by searching old threads on this site.
I purchased a non running import into the UK around nine months ago. It's a 1974 TX650A that seemed to have bounced down the road, and was then left in a barn for twenty years. It's got 20000 miles on the clock, which seems to be genuine. It was sold with the engine seized.
I'm happy rebuilding engines. I'm just struggling with what is normal for an XS650.
I had assumed that the engine was seized because the rings had stuck to the piston bores. When I lifted the head I found parts of one exhaust valve on top of the wrecked piston. And the other exhaust valve stuck open.
The valve seat seems to have taken a bit of a battering.
The rocker arm faces don't seem bad, but the tappit adjuster screw ends look Damaged.
I'm not sure if the valve adjustment or possibly the ignition timing was set wrong, or the advance mechanism was jammed.
Has anyone any ideas what could have caused this?
Has anyone any advice on what I should be replacing? Possibly exhaust valves and springs. Tappit adjuster screws.
I don't think that I can get away with lapping the valve. Can I get the seat recut, or will this mess up the geometry? Should I try to get a new valve seat? This was common enough with triumphs and Nortons when unleaded fuel was introduced. Should I just source another head?

 

[jpdevol]

The valve seats can normally be cut (to cure various maladies) with no issues. The damage to the valve seat in the pic may be too deep (can't tell from pic) to correct and still have proper height of the valve. If so, the head would need replaced.

I suspect the cause of all that damage is the valve stuck in the guide and then, of course, hit the piston.

The above contingency aside, it appears you need to replace about all the wear parts; the rockers are badly worn and I imagine their shafts are too. I'd also replace the valve guides, new valves, springs etc.

 

[SteveP]

The valve seats can normally be cut (to cure various maladies) with no issues. The damage to the valve seat in the pic may be too deep (can't tell from pic) to correct and still have proper height of the valve. If so, the head would need replaced.

I suspect the cause of all that damage is the valve stuck in the guide and then, of course, hit the piston.

The above contingency aside, it appears you need to replace about all the wear parts; the rockers are badly worn and I imagine their shafts are too. I'd also replace the valve guides, new valves, springs etc.

Possibly a new head then? The guides don't feel to have much play in them.
I wasn't sure if the rocker arm faces were ok, or if they should be polished.
I did get the old seats machined out and new ones fitted and machined on a commando. I just wasn't sure if it was possible with an XS.
I can't seem to find any valve springs for sale in the UK???

 

[halfmile]

Complete heads are dirt cheap. I`d replace the whole thing.

 

[SteveP]

Complete heads are dirt cheap. I`d replace the whole thing.

I'm heading for eBay. Hopefully any XS head will fit.
Though they aren't as common in the UK

 

[gggGary]

While there are many possibles, the #1 for bent/broken valves is someone not spending enough time on a wake up and starting an engine with rust on the valve stems. At least one valve is always open on an XS motor. I go plugs out, rustbuster in plug holes and liberally inside the valve covers/head, kick say 100 times. Then oil everything, another 100 kicks. THEN see if she'll start.
Running a motor with the oil badly diluted by gasoline from stuck float valves is hard on em too.
One i bought from a guy that said it just quit running...........

 

[Jim]

I'm heading for eBay. Hopefully any XS head will fit.
Though they aren't as common in the UK

Be sure and get the head and rocker box cover as a set with matching numbers. They're line bored as a set. Chances of a new head matching your rocker box are prolly less than 50%.

 

[SteveP]

I'm struggling to work out what has happened to this poor bike.
It's thrown a chain at some point and cracked the crank case. Bounced down the road, bending and braking quite a few bits. Then seized the engine. Then been abandoned for twenty years.

Did it all happen in one day?
That's one well mashed piston. I haven't even looked into the carbs yet.
That's certainly good information about buying the cover to mach
Just looked on UK eBay. £200 to £400 for just the head. No guarantee that they are in any better condition than the one I've already got, that matches the head.
May look into costs for repairing

 

[Jim]

Here's one in the US that looks pretty good from the pics. Sez it ships worldwide. You could inquire about shipping cost.


https://www.ebay.com/itm/2922023395...G/qOUG7nOiqzpsw0=|tkp:Bk9SR_6h6JCLYg#shpCntId

 

[SteveP]

Thanks for that but they're asking $168.
It's not a bike that made it to the UK in big numbers. Spares aren't cheap here

 

[SteveP]

Sorry. that's just for shipping

 

[jpdevol]

Here's one in the US that looks pretty good from the pics. Sez it ships worldwide. You could inquire about shipping cost.


https://www.ebay.com/itm/292202339534?hash=item44089ddcce:g:XEsAAOSwqeZZd6G3&amdata=enc:AQAIAAAA0LgoFOpfTzJC/rv1DIcMTx3FBt+uVdpcHyTUENTC5Z33GdVt5H3zPCktN2zSQ5k1/zFaB0U/+NuVRBsSp49YIYGzTmBQtZKkqS1/F2wlmAGhp/F0LXRz9swxwAHTfIwJWz2WlJBTGErf+7p3gxe8XDk5mYCiq87dVpTwspTst91+yrQJ4hgpic4HcVE90YVMIONlXbxk6ILNTslQT1cELywPDdm01WI1m1JZVlh/I+hQtGcs71GrNZg9hh8IarNHb6nD1WtG/qOUG7nOiqzpsw0=|tkp:Bk9SR_6h6JCLYg#shpCntId

Thanks for that but they're asking $168.
It's not a bike that made it to the UK in big numbers. Spares aren't cheap here

That's an exceptionally good looking assembly - as such things go - and likely a bargain vs repairing what you have (if repairable)....just sayin'

 

[SteveP]

I've noticed that. Just a bit reluctant to give up on the head that goes with the bike. And having to justify £225 to the wife

 

[Jim]

That item has a "Make Offer" button. Make a wild ass offer and see what happens.

 

[Jim]

If you do, in the notes add that you're in the UK. Gimmie a break.

 

[SteveP]

I haven't decided against that one. I'll phone around for some repair quotes before I decide
Thanks

 

[Jan_P]

I Broke a chain once and got a hole in the block
I can se a crack on the topside # 8 I would look inside close to the sealing

I used to buy parts from Breakers in UK when you were in EU Normal pricing but good quality parts
If you wait and look on e-bay something will come up

Halfmile can be right in post # 4

I would be nervous about if there is a hole in the Block can be bought but adds to the cost and work needed
The crack can have other reasons lifting there or so

Alternator rotor Resistance ? or $ 100 more

 

[SteveP]

I think you are right.
This isn't going to be quick. I need to totally strip the engine. Then assess what has happened, and what is required.
I'll keep looking on eBay, and talking to people.

 

[WideAWAKE]

I've noticed that. Just a bit reluctant to give up on the head that goes with the bike. And having to justify £225 to the wife

With a motor that looks like yours, your gonna have to figure out how to justify a lot more than 225 to your wife.

 

[SteveP]

---

My last project was a BSA C11. Spent loads on bike with a top speed of 40mph. Lost lot's of money when I sold it. My wife creates a spreadsheet for every bike I build . She mentions the BSA every time I try to spend on the XS
Just another question.
My cam chain and guides look to be in pretty good condition.
Would it be advisable to leave fifty year old parts in the engine? Are the rubber faces of the guides likely to start falling apart as soon as the engine is started. Bearing in mind they were only thirty years old the last time the engine ran.
I've been reading posts that seem to imply the modern parts aren't always as good as the original ones.
Should I leave well alone, or is this just a false economy.
I'm just looking for opinions
Thanks for all the other help. It's appreciated.