Vent the rear drive filler cap?

[Guest drknow]

I found this tip on wildguzzi.com. I wonder if it would work for the spiney bikes. With 200cc of oil in my Centauro, I still get a little leaking, and would love to quit cleaning the rear wheel all the time. There's a pic of the mod on the site as well:

 

Wild Guzzi Tip

 

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Final Drive Pressure Tip from Bob Echoff:

 

Final Drive leaks and pressure.

 

I have been riding since 1967. For the first 20 years I rode assorted English bikes. That taught me to fix things that leak. I have been in the auto repair business since 1970. Things that build up pressure need someplace for that pressure to go. So here is my Guzzi Final drive story.

 

Two years ago I did a ground up restoration on a 1976 850 T3. When I put new seals in the final drive, a little wear was apparent, but nothing I was going to buy hundreds of dollars worth of gears for.

 

Sure enough, when it built up pressure, it leaked. Being cheap I vented the system using Guzzi parts. I have ridden it over 10,000 miles since the modification and no it does not blow oil out from the vent and contrary to what a dealer told me, it is getting all the oil it ever did. I even took it on vacation riding it over 1700 miles in 5 days

 

I do not claim that this will work on any other bike, it is just what I did.. If you want to try it, here you go:

 

The object it to fit a 1984 Guzzi small block final drive vent to your existing filler cap. The vent costs about 21.00 from your dealer.

 

My fill plug is concave on top. After you get all of your supplies together the actual operation should take about an hour. If you use epoxy rather than solder it will of course take as long as it takes for it to cure.

 

 

 

You will need:

 

Propane torch & solder, or 2 part epoxy

 

A 1/32 inch drill bit

 

Drill or drill press

 

Final drive vent from 1984 Moto Guzzi small block.

 

A bottoming tap to fit the threads of the 1984 final drive vent. Make sure it is a bottoming tap.

 

A drill bit to drill the hole for the bottoming tap

 

Course sandpaper

 

Teflon tape like plumbers use

 

3 or 4 rubber washers to fit threads of vent Get at hardware store

 

 

 

How to:

 

Remove the stock fill plug. Put it on bench or table.

 

Use the sandpaper in the concave part of the top to roughen up the metal. Rough it up good!

 

Clean it. Use your favorite solvent but clean it really good.

 

Now get out either the propane torch and solder or epoxy

 

If using solder, put the plug lightly back in a vise. Heat the plug until your solder flows easily then fill the concave top of the plug with the solder. Do not overheat it. When done let it air cool to room temperature.

 

If using epoxy, mix according to manufacturers directions and fill the concave top of the plug. Let harden.

 

When the lead is cool or the epoxy is hard, find dead center of the top of the plug & mark the spot with a punch or awl.

 

Put the plug lightly in a vice or better yet use a drill press

 

Take a 1/32 inch drill bit, and drill all the way through until it emerges from the bottom of the plug .

 

Remove any material left over. I removed the entire magnet as it did virtually nothing anyway.

 

Now take the big drill bit, the one for the bottoming tap, and using the 1/32 inch hole as the guide, drill just through the epoxy or solder. Go slow. Do not over drill it

 

Next take the tap and cut threads in the epoxy or solder. Go slow. Remove the tap every so often to see where you are.

 

Clean the new threads of any shavings.

 

Make sure the 1/ 32 inch hole is clear.

 

Screw the vent into the threaded plug by hand. Note the amount of thread sticking out after the vent has seated.

 

Unscrew the vent and install enough rubber washers on 1984 vent to fill that space.

 

Wrap the threads of the 1984 vent in Teflon tape and thread it into the original fill plug Do not overtighten! & leave enough room at the bottom so that you are not blocking the air hole

 

Blow through the bottom of the new assembly to make sure air passes through

 

Install new assembly on bike.

 

All done.

[Pierre]

Yea, I'd love to find a fix as well. So why does he fill in the concave part and then only tap that? Is there not enough plug to accept the length of the vent? Guess I don't understand the dynamics of the vent.

 

Will Creedon asys he's solved the issue with a vent that I think he got from a BMW. At least it wasn't a Guzzi OEM part.

[docc]

Was the 1999/2000 V11 Sport the first to have a vent?

[Guest drknow]

Yea, I'd love to find a fix as well. So why does he fill in the concave part and then only tap that? Is there not enough plug to accept the length of the vent? Guess I don't understand the dynamics of the vent.

 

Will Creedon asys he's solved the issue with a vent that I think he got from a BMW. At least it wasn't a Guzzi OEM part.

 

We should ask Will. I got the impression that he tapped the whole thing, only but up the concave bit to have more material to tap, but I'm guessing.

 

dk

[Pierre]

Was the 1999/2000 V11 Sport the first to have a vent?

If those models are vented (I've never owned one, so don't know) then I agree with Kevin H. that would seem to be the way to go.

[mason]

My 02 Lemans is leaking at the right hand final drive seal. I am told this is not common by tyhe folks at Moto Int. I checked the vinted cap on mine, seems fine. Not overfilled, any other suggestions. (I did receive a bump from a car a couple months back nothing major but I am starting to wonder)

[richard100t]

My 02 Lemans is leaking at the right hand final drive seal. I am told this is not common by tyhe folks at Moto Int. I checked the vinted cap on mine, seems fine. Not overfilled, any other suggestions. (I did receive a bump from a car a couple months back nothing major but I am starting to wonder)

Mine was leaking from the right hand side seal as well. What I did was remove the vent cap & I found that it was "stuck" in one position. Its supposed to rotate freely. I just gave it a gentle turn with pliers, lubed it a little & put it back in. Its never leaked since then.

[Ryland3210]

Here is another tip from Wildguzzi just after the one referred to earlier:

 

Another Final Drive Pressure Tip from Dave Phillips:

 

To keep my 74 Eldo transmission from slobbering oil all over the place I adapted a plastic tube to the vent and ran it to a square 4.5OZ plastic bottle laying on it's side and held atop the battery with stick-on VELCRO pads. I drilled a small vent hole in top side of the bottle. Once the bottle filled to the level of the tube the excess oil flows into the bottle while ridding and vacuums back into the tranny as it cools down. It works great.

 

I'm interested in comments on this. I set up my boat's outdrive with a similar reservoir. It is mounted on the transom higher than the outdrive. One of the main reasons I did it was to create a constant pressure at the bottom end of the outdrive where the propellor seal is. That way, if there is any leakage, oil will seep out, instead of water seeping in. I will know if it happens by watching the oil level in the clear plastic reservoir.

 

OK, the point of this background is that the outdrive is designed to have its gears flooded, whereas the main drive on the Guzzi is not. So the question I pose is, how much horsepower is lost in a flooded, versus a non-flooded Guzzi gear case? Same question on the transmission.

 

Any takers?

[Guest ratchethack]

. . .So the question I pose is, how much horsepower is lost in a flooded, versus a non-flooded Guzzi gear case? Same question on the transmission.

 

Any takers?

Hm. Assuming the question is a serious one, I reckon there's only one person who would be more than overjoyed to respond to this. My only wonder is why it's taken this long.

[Paul Minnaert]

Well, my daytona rear drive never sweated. I just filled it until oil came out the back screw. The 5 speed rear drives have the filler just inline with the gear, so putting a v11 vent in might get more oil out. And putting a tube on it might need a long one, you don't want it to loose oil over time, so in the end you have to low level.

[dlaing]

Hm. Assuming the question is a serious one, I reckon there's only one person who would be more than overjoyed to respond to this. My only wonder is why it's taken this long.

Excellent question!

I know with the engine crankcase, all those running the oil up at the top of the sump are losing some HP, but I have no idea how much.

How much of the loss would be windage, and how much crankcase pressure, I could only speculate.

Mr. Ratchet on the other hand has claimed he felt more power through reduction of windage.

As for the transmission, case pressure is a none issue, but fluid friction is an issue. Fluid friction can increase heat and decrease power. The factory recommended levels are probably fine.

[dlaing]

None of the hose/tube solutions work very well, unless the objective is to sling gear oil up the tube.

On my V65 I popped the cap off of the gear box vent, attached a hose, ran it up just a few inches and arched it over.

It helped greatly. Some recommended a catch bottle, but it was not necessary.

[pete roper]

None of the five speed spineys have a vent. This *can* cause pressurisation problems.

 

On Earlier bikes, Loops and Tonti's, the box can *theoretically* vent through the pinion bearings, up into the swingarm and eventually any excess pressure should be able to creep past the UJ and driveshaft splines where it can simply swell the boot between the gearbox and the swingarm a bit. In practice even they sometimes pressurise themselves, (I've seen it, prying out a leaking seal I've heard the 'Hiss' as the box de-pressurises!) but itseems rare.

 

With the early spineys the bevelbox is sealed at the pinion so when it gets hot the air inside will expand and can in some cases overwhelm the seal. Why some do it and some seem not to is beyond me. The only thing I can think is that a box that is set up less accurately will produce more frictional losses and therefore heat so the pressure rise will be greater.

 

In most cases the seals can be oprotected by 'Burping' the box. After it has been re-filled after an oil change it can be take for a good thrash to get it hot and then the filler plug loosened to release the pressure. As it cools it will de-pressurise but hopefully the seals work well enough in *reverse* to prevent the ingress of too much air when cold. Probably regular 'Burping' every couple of weeks or so would be the way to go but this is simply conjecture on my part.

 

As for fitting a vent? as others have said, if this is done in a place where the vent is in the direct trajectory of oil being flung off the crownwheel the box WILL tend to expell oil, even if the tube is taken a long way away from the box, (I've even tried running them to the steering head and got covered in gear oil for my trouble! ) The best sollution I've found is to tap one of the FILLER plugs that doesn't have a magnet in it (One of the tall, hexagonal types as used on Ambo's and the like.) with the correct thread to fit one of the breather pipes off a late five speed gearbox. These have a (?) 13mm hex with a pipe coming off it. Screw this into the top of the filler plug with an o-ring around the threaded bit to seal it. You can then run the hose off somewhere up the swingarm and under the seat. Block the end of the hose with a ball bearing and make a slit in the hose and stick it into a small catch bottle next to the battery or whatever. The slit acts like a 'Duck Bill' valve allowing the box to de-pressurise but not being so easy to force open or allow air to pass that it will encourage the oil to escape BUT!!!!! The main thing is that by having the breather on top of the deep, hexagonal, top of the filler plug it is shielded from direct spray from the crownwheel, if you want to be doubly certain you could solder or weld a further shield on the bottom of the filler spigot and put a small hole in it towards the front of the plug as it is fitted.

 

Certain spineys *may* have problems the height of this arrangement, it might foul the torque arm bracket, I'm not sure. If that is the case then some other fitment other than the gearbox breather pipe should be used but I have done this to a couple of blurty Sport 1100's and Daytonas with good results.

 

Pete

[dlaing]

Your V65 rear end already had a vent, Dave. What we're talking about here is venting a SEALED rear drive as on a Sport 1100i or Centauro, if you'd bothered to read the preceding posts. That's what I was referring to. There should be no need to add a hose to the small Guzzi V's.

I did read, but you were not specific, cretin.

The tube solution kept my V65 gear oil from spewing all over the rear tire.