ET: Engine (Twin) Fogging for Mosquitos; Valve Guide Issues and Solutions

ClassicBiker

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If you could sort out an oversize lower guide, I would have thought someone near you could put a bigger thread and make you a special thread ring ?, Just a thought. Cheers Bill.
Bill,
Funny you should write that. I was just seeing what material is used for the valve guides, 630 bronze seems to be it. I'm waffling back and forth with whether to make up the slide in cup device TT suggests or get the threads repaired back to original size, or over size. I was also thinking that if I sent it out for repair I would get no-lead valve seats installed. But the valve seats look reasonable, so I might pass on that. The club does sell over size guides, I have to see if I need them or not, or an over size outside of their range. I see I can easily buy a tap in larger sizes and making a ring is not an issue. I think I talking myself into doing myself.
Stay tuned.
 

Bill Thomas

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Most of us have to send stuff out at some time, But If I can do it, I will have a go.
Last month in the Vintage Club, There was a Bloke who sent a Vin' Cylinder Head away for repair, It was gone for 3 years !!, He had to take Legal advise, To get it back, They told him, If the stuff is away for more than 6 years, It's not yours anymore !!.
He does not say who he sent it to.
I don't think there are many cases like that, But it makes you think.
Cheers Bill.
 

timetraveller

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If you use my modification you do not need a lock ring. You just have to ensure that the new part fits tightly on top of the flange around the guide. It just holds it down.
 

ClassicBiker

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Bill, That was what I was a little afraid of. The head disappearing into big wide world, never to be seen again.

TT, your mod it was I'm going with. Upon closer inspection, where the lock ring would engage the threads of the head has been worn away to such an extent it is nearly the same size as the major diameter where the rocker works. So no chance of going up a thread size. I've been looking at my choices of 7075 and I can easily obtain 7075-T6 in 1-1/4" diameter. I'm going to measure the valve guide bores and see if I need oversize or standard size guides. If I cannot get a suitably sized guide to replace the AWOL guide, I can buy C630 bronze to make my own. If all else fails my fall back plan is new heads.
Stay tuned.
Steven
 

timetraveller

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Steven, if you make guides with a flange, like the original but larger, then my modification can be made so that it sits directly on that flange. The protruding part at the bottom of the new part can be made to sit within the damaged space where the lock ring was and it can even be machined to take an oil seal. If it is difficult to get the ring exactly the correct length to exert a force on the top of the guide then a shim on top of my mod would ensure that there cannot be any movement of the replacement guide
 

Bill Thomas

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Can't remember if you have to keep the bottom guide short for Mk2 Cams ?, Is it Exhaust your problem ?
Good Luck. Bill.
 

ClassicBiker

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Bill, I replaced my Mk2 cams with Mk1 a couple of years back as the cams and the rockers were very badly worn. I had originally thought that perhaps when my father had rebuilt the bike back in the late 70s early 80s that he had neglected to shorten the guides, but when I was replacing the cams, I could clearly see the top of the guides were all nearly flush with the top of the lock rings. Now that I have the heads apart I can see the three remaining guide tops are not damaged in anyway. Which leads me to believe the guide self destructing is just the luck of the draw.

TT, I had intended to replace all the guides and lock rings with the new type that take the oil seal. I had also read in the other thread where you posted the dimensions that someone had managed to fit an oil seal to your modified part, so I was going to do the same. But shimming it to make sure that pressure is exerted had not occurred to me.
Steven
 

Bill Thomas

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I think it's how deep the valve seats are cut, New valve seats would make the collar come nearer to the top of the guide ?. Cheers Bill.
 

ClassicBiker

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Bill, I suspect you are absolutely correct. The valve seats appear to be about middle of the road. Nothing is pocketed and therefore masked nor are the valve faces extremely proud. I would suspect that if the collars were hitting the guides there would be witness marks on the collars. What I find confusing is I haven't found a piece of the shoulder of the guide that would have been trapped by the retaining ring. I'm also pleasantly surprised by the lack of damage. Except for the small length of cylindrical body of the guide the rest is gone. As if it turned to dust and disappeared and this piece just slipped out the exhaust port.
Steven
 

Bill Thomas

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VOC Member
We have been told of this before, As you say, Strange.
I have looked up the Exhaust hole on one of my bikes, And can see a lot of oil Running down ! But as long as it still goes, That's good enough for me, I don't go far !!, Joke.
I have a lot of respect for OUR Trev', But if the top guide was not there, I would think the valve would be all over the place ?.
I remember dear old Dave Dock at a Sprint, His Bike was not going well, He stripped it out in the padock,
And found the valve seat had been going up and down, Resting on the valve head !.
Cheers Bill.
 
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