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


greg brillus

Well Known and Active Website User
VOC Member
The hole in the cap is really the "Secondary" breather, the chain oiler is the main breather which most seam to blank off all together. You only need to wind the adjuster screw fully in to blank off the oil flow and leave the main outlet pipe open to vent the tank as it was designed. I feel the pin hole in the breather cap is barely able to vent the tank correctly especially at elevated speeds.
 

davidd

Well Known and Active Website User
VOC Member
The hole in the cap is really the "Secondary" breather, the chain oiler is the main breather which most seam to blank off all together. You only need to wind the adjuster screw fully in to blank off the oil flow and leave the main outlet pipe open to vent the tank as it was designed. I feel the pin hole in the breather cap is barely able to vent the tank correctly especially at elevated speeds.
I would not have guessed that. Other than opening up the hole in the cap a bit I have never had a problem. I block of the chain oiler at the rear of the UFM with an engine drain plug. This makes the cap the primary vent. Normal red line at 7,000 rpm.

I do use a shroud in the filler neck to divert all the oil down the filler neck, so nothing but some mist should make its way to the cap.

David
 

ossie

Well Known and Active Website User
VOC Member
you sure its not just the old oil and soot in the exhaust catching alight and causing a smoke screen like when the soot in our chimneys use to years ago?????
 

greg brillus

Well Known and Active Website User
VOC Member
For those that are unaware the opening for the tank breather on a "c" type upper frame is on the right side of the rectangular steel block where the oil return passageway is. The adjuster screw is a bleed from this return oil, same as a carb mixture screw. If you look down the filler neck at the right side of this steel block you will see a hole in the side of it, this is the vent line that runs to the rear of the upper frame where the T 29 screws in, then down the tube to oil the drive chain. I and a few others I know here at one time had this fitting blanked off all together, but we found at elevated speeds past say 80 mph, that oil would start coming out of the vent in the cap and all over the top of the fuel tank. This is what led me to believe that this vent should be left open, or perhaps extended via some flexible tubing out near the rear axle. I actually have mine connected via a "T" fitting with the engine breather on mine and it works fine.
 

timetraveller

Well Known and Active Website User
VOC Member
I'm with David on this. I have the hole at the rear of the tank for the chain oiler totally blocked off, a twin start oil pump and a deflector inside the oil filler cap, held in place with the adjuster screw mentioned by Greg. I can cruise at 80+mph, which is as much as I can manage without getting tired arms from clinging on against wind forces, and there is no oil coming out of the filler cap or out of the exhaust. I could not claim that the outside of the engine is totally oil free but it is certainly not dripping or running in oil. I had the same set up many years ago when racing and sprinting and, once again, there was no excessive oil leaking or smoking.
 

ClassicBiker

Well Known and Active Website User
VOC Member
Here's a little update. I unscrewed the crankcase drain plug. Approximately 250 cc ( 8 ounces in old money ;)) of oil poured out, I then unscrewed the chain case level screw. Normally nothing pours out of this but in this instance 125 cc did. I then checked whether the breather assembly was still an assembly or not. I removed the ATD cover and plugs and placed the bike in fourth gear. I placed my airline with about 20 psi up the breather pipe and listened as I rotated the rear wheel. The hiss of air entering the crankcase could be heard starting and stopping as the wheel rotated. Next to make sure the return pipe was clear I blew air through it with no problem.
Now the leak down test. The good news is my home made leak down tester works. :D After setting the line pressure to 100 psi I checked that both gauges either side of the restriction read the same. Now setting each piston at TDC and fiddling to get it so the air pressure didn't drive the piston down the bore was a big headache. Setting is close and wrapping a strong cord around the rear wheel with the bike again in fourth and tying the other end to the front wheel to stop rotation and gradually shortening the cord finally paid off. The line pressure on the feed side dropped to 90 psi when I opened the valve to allow air through. This is where it gets ugly.:( On the front cylinder the with feed side of 90 the air pressure on the down stream side dropped to 80 psi, with the air exiting from under the front right head nut. Trying to tighten is didn't help it was already tight. So that head will have to come off to see what's up there. The rear cylinder was 90 on the feed side and the downstream was a little over 80. Took me a bit to realize the air I could hear escaping wasn't going out through the valves because the air had moved the piston and thus opened the valves, but was escaping into the crankcase. When I took the ATD cover off again I could hear it clearly.
So now I'm wondering if it is worth temporarily bypassing the oil feed to the rockers to see if the excess oil is being sucked down the valve guides. If I'm taking the front head off to see why air is escaping from under the head nut I might as well double check the valves and install seals on the stems. Along with that I'll double check the radi (as mentioned in the latest MPH) on the rockers and probably install the modified rocker bearings and feed bolts from the VOCS for good measure. If doing that to the front head I'd be foolish not to do the same to the rear. At that point I might as well lift both the barrels and check all the ring gaps. Guess I know what I'm doing this fall and winter.:( It is already sounding expensive.
Thoughts?
Steven
 

greg brillus

Well Known and Active Website User
VOC Member
If the head to liner joint is leaking and the head bolts are tight my guess is the liners will be throw away items. The all important height that the liner sits above the alloy muff will be too short, and i have found trying to reclaim this is too hard. It is also possible that the top of the liner could be cracked radially around the top. Remove the barrels and first check I make is to see if the oil feed hole is too high feeding oil between the rings. This is often the case and another reason to replace the liners. Striping the heads to check the guides is normal practice, and I always fit the ET 100/1 locking feedbolt mod to all engines. It will be interesting to see what you find, but all the parts are readily available from the VOC spares co. I have quite recently bought 6 complete barrel/muff assemblies and all new standard pistons for same. It is easier and far quicker than mucking around trying to reclaim old parts mated to new parts which I have learnt the hard way before. Cheers.............Greg.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Morning Greg, Have you had to grind the top of the rocker, When fitting locking feed bolt ?, Cheers Bill.
 

greg brillus

Well Known and Active Website User
VOC Member
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.
 

Albervin

Well Known and Active Website User
VOC Member
I always find that most new owners of Vincents put way too much oil in the tank. This can lead to embarrassment. Just above the bridge at the bottom of the filler is enough. Even in Australia, in Summer, I do not go above that level and after 30,000+ miles no drama inside. Use a good quality oil, monitor levels and change regularly (along with the filter). SIMPLE.
 

ClassicBiker

Well Known and Active Website User
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
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
 

greg brillus

Well Known and Active Website User
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
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

Well Known and Active Website User
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
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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