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

ClassicBiker

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VOC Member
Morning Greg,
The barrels came with the bike 39 years ago. My father had them bored over by 0.020" and fitted new pistons. I believe they were original to the bike. I don't know if he checked to see relation between the rings and the oil feed hole. I do recall him lapping the head to liner and checking to make sure the head didn't contact the muff while doing it. Interesting thought about the liner being cracked radially. I hadn't considered that. I immediately jumped to it being an issue with the head. When you said about buying 6 new barrel/muff assemblies with matching pistons, I thought that must have cost a fortune, but checking the VOC Spare Co. They're quite reasonable. Do you buy them already bored and the oil hole already drilled or no?

Morning Albervin,
I also use the bridge as a gauge for my oil level. I try to keep the oil at the level of the bridge or just under it. I buy quality oil there isn't any economy in buying cheap stuff.

I'll update as I find out more. Thanks for the all the input.
Steven
 

Bill Thomas

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Hi there Bill, yes on standard rockers I grind the tops down then linish to a smooth finish. On the new rockers Neal Videan supplies over here you don't need to grind them down as he has allowed for this in the newer version he makes. Cheers................Greg.
Greg, I would love a photo of Neal's rocker, Just to show people what needs to be done. Cheers Bill.
 

davidd

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VOC Member
Guess I know what I'm doing this fall and winter.:( It is already sounding expensive.
Thoughts?

Steven,

Very nice work. Unfortunately, these old bikes seem to work on for years with some problems without too much complaining.

As for the leakdown, I violate the instructions regarding doing the test with the piston at TDC and do it with the piston at BDC, mostly because it is easy. I take out the pushrods and ease the pressure into the cylinder. The piston goes to BDC, but there is no need for anything elaborate to hold the piston at TDC. There could be more scratches up at TDC, which would lower the pressure, but, in general, if you know your engine, you should be close. I run aluminum liners with Nicasil, so scratches are less likely. I suspect that the guides would need replacing just to tighten them up a bit, so I would not spend a lot of time testing them.

David
 

vibrac

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Greg, I would love a photo of Neal's rocker, Just to show people what needs to be done. Cheers Bill.
upload_2017-8-16_17-3-57.jpeg
 

greg brillus

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VOC Member
Morning Greg,
The barrels came with the bike 39 years ago. My father had them bored over by 0.020" and fitted new pistons. I believe they were original to the bike. I don't know if he checked to see relation between the rings and the oil feed hole. I do recall him lapping the head to liner and checking to make sure the head didn't contact the muff while doing it. Interesting thought about the liner being cracked radially. I hadn't considered that. I immediately jumped to it being an issue with the head. When you said about buying 6 new barrel/muff assemblies with matching pistons, I thought that must have cost a fortune, but checking the VOC Spare Co. They're quite reasonable. Do you buy them already bored and the oil hole already drilled or no?

Morning Albervin,
I also use the bridge as a gauge for my oil level. I try to keep the oil at the level of the bridge or just under it. I buy quality oil there isn't any economy in buying cheap stuff.

I'll update as I find out more. Thanks for the all the input.
Steven
Hi there Steven, I buy them with the liners installed but not bored and honed as I have had instances where the clearance is way too small. I think the specs on the Omega piston say up to 0.003" but we give them 0.0035" just to be sure, remember we have a hot climate here in Australia and I don't want them to nip up. You won't really know what's going on until you strip it down. Just so you know, the recess in the head should be 0.125" in depth whereas the liner should sit above the top face of the muff by 0.128" when all is new, giving you about a 0.003" gap at the large surfaces of the muff and cylinder head. Over time and after several head/barrel removals and the lapping in of the two as you mentioned, this tolerance dissapears and this is where leaks start to occur. Sometimes people pull the head nuts down to stop the leak, and if they try really hard, it starts to collapse the alloy towers through the head..........:eek:............. Once you have it apart you will soon see what is going on. Cheers.............Greg.
 

stu spalding

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Hi there Steven, I buy them with the liners installed but not bored and honed as I have had instances where the clearance is way too small. I think the specs on the Omega piston say up to 0.003" but we give them 0.0035" just to be sure, remember we have a hot climate here in Australia and I don't want them to nip up. You won't really know what's going on until you strip it down. Just so you know, the recess in the head should be 0.125" in depth whereas the liner should sit above the top face of the muff by 0.128" when all is new, giving you about a 0.003" gap at the large surfaces of the muff and cylinder head. Over time and after several head/barrel removals and the lapping in of the two as you mentioned, this tolerance dissapears and this is where leaks start to occur. Sometimes people pull the head nuts down to stop the leak, and if they try really hard, it starts to collapse the alloy towers through the head..........:eek:............. Once you have it apart you will soon see what is going on. Cheers.............Greg.
Barrels should be checked to see that the top and bottom faces are square to the bore. In some new ones this is not the case. Cheers, Stu.
 

greg brillus

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VOC Member
Good point Stu, on old barrels it is not uncommon to find the muff heights completely different too. I had a set not so long ago that were 40 thou different from front to back.......That must affect the compression and make the engine less than smooth. Standard height is 3.062".............. Bill, if you PM me your email address I'll send you a pic of standard verses one of Neal's rockers, then you can post it on here if you want. Cheers...........Greg.
 

nkt267

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VOC Member
Good point Stu, on old barrels it is not uncommon to find the muff heights completely different too. I had a set not so long ago that were 40 thou different from front to back.......That must affect the compression and make the engine less than smooth. Standard height is 3.062"...........
I have had to check and skim new muffs as well
 

Black Flash

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Greg if you don't mind please post a picture of the two different rockers here as well.
I didn't know that there exist different rockers
Bernie
 

ClassicBiker

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VOC Member
Well personal circumstance didn't allow me to tear into the motor and find the cause of the problem. So I have resurrected this thread to bring everyone up to date. In another thread I mentioned I had purchased the new extended rockers to install when I figured out what was going on with the sudden smoking. Well over the Easter weekend I pulled the heads. Bur first I started the Shadow to see if by some miracle it had healed itself. Not. So I made a by pass on the oil line to the heads and rockers. That stopped the smoking and lead me to believe that the cause was an worn guide allowing excess oil into the cylinder and/or exhaust causing the smoking. When I removed the muffler/silencer I heard a rattle. I thought it was the baffle loose inside. Until a little something fell out. At first glance it appeared to be a lump of carbon. Closer inspection revealed it was metal. In fact it had a curve to it. I looked up the inlets and exhausts of both heads and could see the top of all the valve guides, except the front exhaust. I could see the valve guide retainers, except the front exhaust. This did not bode well. With both heads off, I removed the valves from the front head. The lower guide is completely gone. The little bit of shrapnel I found in the exhaust is all that remains. The threads for the guide retainer are completely fretted away, only the retainer remains.
Now I have to decide whether to repair the head by the methods I have seen on the forum of making an insert to retain the lower guide or purchase a new head. But first I must determine if the hole for the lower guide has been worn excessively or not. Does anyone know the standard o.d. of a lower guide?
Of interest the upper guide appears to have been sufficient to keep the valve aligned as there doesn't appear to be any damage to the valve or head in the seat area.
Steven
 
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