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Discussion Starter #1 (Edited)
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So here’s the head before cleaning, in quite a sorry state:



And after:



Now obviously that is not good! But, given that a new head is very unlikely to be found, I am wondering how long it will last like this. From the first picture, and my own inspection, the carbon covering the actual crack had no mark or crack itself, meaning the crack is “static”.

Now, I know there will be some who will say don’t use it like this, but surely there is a chance the old bike will just plod on for a while yet, seeing that it has obviously run for quite some time in this state to get the build up of carbon over the crack??

What ya reckon?

Steve
 

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I'm no XL expert, but how can you be so sure that you won't find a replacement? Or another engine waiting to be bought...

As for running it, yes, you may be able to run it for a while, i'm sure, but is it worth the risk? I don't know how the engine will pop when it does, but it'll probably happen when you're riding and who needs that, especially if you know the risk is much greater?

During an overtaking, mid corner etc...there's never a good time, but some times are notably worse...

Loosing power and seizing the back wheel mid corner aside, there is also the risk of explosive failure. Unlikely, but who knows, but as someone who often sits almost directly above an engine, I would not relish the thought of a piece of cam shaft blowing my proverbials off, mid corner or otherwise...

So, is it worth the risk? Can't you get it welded, then machined back?
 

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When it fails it will prob loosen the valve seat so you'll end up with a bent valve, damaged head and possible guide and piston.
This is a common prob for all the rfvc engines so they're getting harder to get hold of secondhand.
My Dominator head is not to far off that and I've chosen to keep it in use.
Just a waiting game now.
I thought about welding but you'll have to get the seat out, welded up, refaced and re-assembled, all done professionally. Gonna cost a fare bit.
 

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When it fails it will prob loosen the valve seat so you'll end up with a bent valve, damaged head and possible guide and piston.
I've always been lucky so far... I've had several valve seats come loose and never had anything else broken, except for a bent valve. So, never anything serious.

I've also never had any engine seizing of the kind that causes one to fall over or have an accident. Mostly, valve play will start changing quickly and randomly as a sign that one of the valve seats has come loose.

I'd keep it as it is for now. It may very well be years before the valve seat comes loose. And yes, it's hard to get good cylinder heads second hand. Almost all of them are cracked. :(
 

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take it to somwhere that does rebores and presure checks and so on and they will weld that and smooth it back off no problem lyndale engines in peterborough did a few for me
 

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google zoom factory,they did mine=£240 inc 2x ex valve seats,welding and skim.they are located near warwick
 

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Discussion Starter #7
OK, lots of good comments thanks. Now, here is the problem: I am out of work and cannot afford several hundred pounds to get it repaired properly.

IF it could be satisfactorily repaired with a simple run of weld and a smooth off for, say, 50 quid then I would do that.

Otherwise I have two options, 1/ break the bike and make a bit of money, or 2/ use it as it is, and if it grenades then break the remains and still get my money back!

Hope this makes sense, given my circumstances?

Steve
 

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3/ Use it as it is, and if/when the valve seat comes out, have it fixed. That's what I'd do.

In the meantime, keep an eye open for used parts. You might get lucky.
 
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