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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Regrinding valves
Post Info TOPIC: Regrinding valves
TTRfan


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Regrinding valves
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I have run out of good s/h exhaust valves. I have half a dozen that are pitted to one degree or another that I am not prepared to use.

New valves are relatively expensive which makes me wonder about re-facing the valves I have.

It is possible to buy kits to do this on eBay but only for older "soft" valves and not for modern ones.

Anyone tried this and can say how it went and how much per valve please?

Brian

 



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masterbill


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RE: Anyone have personal experience of having exhaust valves reground please?
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Hello Brian

I would try www.ocservice.co.uk
01962 855969
email - john@ocservice.co.uk.

I can vouch for the quality of work.

Cheers bill

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Keith89


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I have never done ttr valves but have done 100s of valves out of Diesel engines at work as we have the tooling to do so I've never had any issues

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TTRfan


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Regrinding valves
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Thanks for the replies guys. As it turned out, I have a friend who can regrind valves biggrin

It isn't his business so some improvisation was needed. He did them on a centreless grinder that had an optical wheel dressing fitted to accurately form the grinding wheel. I don't understand any of that but it has worked wink

The photo below is from the workshop manual and shows the grinding angle to be 45 degrees and the minimum thickness after grinding:

Valve specification 2.jpg

This is what the valves looked like before I posted them off - I had de-carboned them as best I could:

Valves reground 4.jpg

 

I sent off seven but two were slightly bent so will be binned. That showed up on the grinder - I hadn't been aware of it and there were no obvious signs when I stripped the valves out of the head.

These two valves are typical of the 5 valves that came back:

Valves reground 1.jpg

 

The pitting was quite bad on this one and it wouldn't all grind out without the valve going below minimum thickness. However, it may lap in and give a good seal if the valve seat meets on the valve where there isn't a pit otherwise it's another for the bin biggrin

Valves reground 2.jpg

 

A photo of three of them from above:

Valves reground 3.jpg

 

Apparently the valves themselves are unusual. They are made by friction welding two different materials together and this can be seen with a magnet as the valve head is a nickel alloy and is non magnetic whereas the shaft is a chrome alloy which is magnetic confuse

I am getting "mate's rates" so can't say how much it would cost to have them done commercially but I am guessing that it will be cheaper than new. The difference will determine whether it is worth the extra hassle! 

I hope that helps someone wink

Brian

 



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TTRfan


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I am in the process of refurbishing a couple of cylinder heads to go in Steve's shop and one had some slight pitting on the valve seats plus I had a few valves that also had slight pitting.

Bearing in mind that Steve sends parts all over the world it is especially important that any used parts are as near 100% as possible so I took them to a local engineer who has re-cut the valve seats and reground the valves. 

£48 for 10 valves and re-cutting the 4 seats PLUS he lapped in the valves for me. Not bad I reckon.

I was impressed to see that he had done the lapping "by the book" as there were still traces of mechanic's blue on the valves and head biggrin

This is what the manual says to do:

Valve lapping check.jpg

This is what the head and valves came back like - I am well pleased wink

20161110_224749.jpg



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TTRfan


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Just adjusted the valve clearances and had to go down on each shim by about 20 to allow for the fact that the seat re-cutting and valve grinding allow the valves to sit up farther in the head. Worth remembering if you get this sort of work done yourself wink

Brian



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ttr steve


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Ace stuff Bri smile Proper belt and braces smile



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