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72 CL350 Burnt cracked Valve!!

Mattstar

Member
Joined
Nov 29, 2022
Total Posts
28
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Location
clovis, california, usa
good times,, had poor compression on the left, hoping it was stuck ring,, oh no! burnt and broken Exhaust valve? explains the small bits of metal I found when I dropped the oil! ).
need some tools and advise? what tools do I need to do this trick? should I replace all the vales while im in it? any and all input respectfully requested Gentlemen .
never replaced a valve before! sounds like fun! )

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That's not a cracked valve, it is a burnt valve for sure. This is a great example of a bike that was neglected, valves not adjusted in a timely manner and that exhaust valve adjustment got tight (lost valve lash clearance) holding it just slightly open allowing hot exhaust gases to force their way out while acting like a cutting torch resulting in what you see. You should be glad you had to take it apart from the looks of the mass amount of sealer used on the head gasket and I'm sure in other places as well. Almost looks like old school Permatex. And the metal you saw in the oil didn't come from that burnt valve, that went out the exhaust. The shiny stuff in the oil may well be typical wear but you'll learn more when the rest of the engine is apart. And WE will if you post plenty of pictures.

You'll need a valve spring compressor to get the valves out of the head, then you should take the head to a machinist who knows how to work on bike heads and have it inspected (valves, valve seats and guides) and see what he says about the condition of everything. You might be able to make that judgment yourself if the valve seat looks anything like the valve does and if so, you might be in the market for a good used head.
 
That's not a cracked valve, it is a burnt valve for sure. This is a great example of a bike that was neglected, valves not adjusted in a timely manner and that exhaust valve adjustment got tight (lost valve lash clearance) holding it just slightly open allowing hot exhaust gases to force their way out while acting like a cutting torch resulting in what you see. You should be glad you had to take it apart from the looks of the mass amount of sealer used on the head gasket and I'm sure in other places as well. Almost looks like old school Permatex. And the metal you saw in the oil didn't come from that burnt valve, that went out the exhaust. The shiny stuff in the oil may well be typical wear but you'll learn more when the rest of the engine is apart. And WE will if you post plenty of pictures.

You'll need a valve spring compressor to get the valves out of the head, then you should take the head to a machinist who knows how to work on bike heads and have it inspected (valves, valve seats and guides) and see what he says about the condition of everything. You might be able to make that judgment yourself if the valve seat looks anything like the valve does and if so, you might be in the market for a good used head.

Appreciate it! I see the idea here,, valve lash not correct, cutting torch acton! and yea makes sense the pieces went out the exhaust ). the jugs look pretty good, I had it running, lower end seems to be fine, went through all the gears and no lower end rod play. looks like ill need to find a valve spring compressor and get the valves out and take closer look to see what else needs doing. and yes, that head did NOT want to come off, somebody been in there lord only knows when!
 
Aye carumba, or Aaaargh matey !
..recently, I read here at VHT and saw that both AncientDad (Tom :) and LongDistanceRiderJim hired and recommended Schumann in Portland Oregon if you can't find a motorcycle-specializing machinist nearby to you. I got excited at the thought of Titanium valves for either of my Customs whenever, if ever, the time comes for valve replacement. I also know that CMS stocks some aftermarket Japanese-made ones that will also be considered at that time...

..praying with you that all you'll need is a new-valve or valves and everything else will remain re-usable !
 
Aye carumba, or Aaaargh matey !
..recently, I read here at VHT and saw AncientDad (Tom :) recommend Schumann in Oregon or Washington somewhere if you can't find a motorcycle-specializing machinist nearby to you. I got excited at the thought of Titanium valves for either of my Customs whenever, if ever, the time comes for valve replacement. I also know that CMS stocks some aftermarket Japanese-made ones that will also be considered at that time...

..praying with you that all you'll need is a new-valve or valves and everything else will remain re-usable !

yea looking at prices for replacement valve is could almost buy a complete used head for the same price? thoughts?
 
Looks to be heli coils in the spark plug threads .... I much prefer a solid insert for spark plug threads.

My experience is that the intake valves will be no good .... the sealing surface gets dished and they can not be ground.

I have found that the springs from multiple heads are needed to find an in spec set .... that's for the large outer ones, inner springs are never in spec and getting a used set even close to spec is tough.

I have had a head ruined by a shop using modern cutters and figuring these old seats are as hard as modern ones .... seems my message didn't get relayed from the front of the shop to the back.
 
Hmm

Used heads will more than likely have similar issues ..... I have a box of them ...


ey Boomer, thank you for your reply, and I do think that there has been some Helio coil inserts, put in this old head, and from reading your post, it kind of sounds like I may be up the creek without a paddle here, if machine shops can’t fix it, and my valve seats are shot. I’d be really interested in seeing what it might take to have you let go of one of your old heads that’s in better condition than mine?
 
ey Boomer, thank you for your reply, and I do think that there has been some Helio coil inserts, put in this old head, and from reading your post, it kind of sounds like I may be up the creek without a paddle here, if machine shops can’t fix it, and my valve seats are shot. I’d be really interested in seeing what it might take to have you let go of one of your old heads that’s in better condition than mine?

Might send him a PM, it would get a faster response
 
Actually your head looks worse than it is. Yes, there are Heli Coils in the plug thread, easily remedied with Time Serts. The valves will all need replacement since they can't be ground. The only real question mark I have on the head is the burnt valve seat, it may need replacement. Good news is the valves appear to have never been ground by a PO because they all stand proud on the seats, when they are flush with the seats is where problems arise from being ground too much.
Here's the info for Chris https://www.ebay.com/itm/233096185034?hash=item36459d84ca:g:fc4AAMXQDnpTZHPx
https://www.facebook.com/people/Schumann-Motor-Works/100054197273586/
 
thanx

Actually your head looks worse than it is. Yes, there are Heli Coils in the plug thread, easily remedied with Time Serts. The valves will all need replacement since they can't be ground. The only real question mark I have on the head is the burnt valve seat, it may need replacement. Good news is the valves appear to have never been ground by a PO because they all stand proud on the seats, when they are flush with the seats is where problems arise from being ground too much.
Here's the info for Chris https://www.ebay.com/itm/233096185034?hash=item36459d84ca:g:fc4AAMXQDnpTZHPx
https://www.facebook.com/people/Schumann-Motor-Works/100054197273586/
funny thing is even in the heads poor condition I had it running and she moved long better than you might think. and the right cylinder had good compression! appreciate the link though.,, might be an option
 
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