Euro Spares — The high-performance (or at least higher performance) V50II…

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Moto Guzzi V50 C

The high-performance (or at least higher V50II (and V65 Lario) Guzzi article

Note: I all the smallblock Guzzis at the end of August Their time had come and and it was better that they to a new home.

By Michael Moore, 1996-2000

The V50II is another of my hop up projects. At present I’ve to V50III pistons and valves/springs. the later piston uses a wristpin I put in Carrillo rods of spending the money on stock I’ve lightened the flywheel a bit and had all the rotating/thrashing parts balanced.

has increased the flow in the head a lot over the stock small II head if I remember correctly) and I had do a regrind on the cam. I think I had do a lobe profile that don’t normally show in the (Craig was working at Megacycle at time, so he could check to see was available — Megacycle has a lot of not listed in the catalog.)

I’ve a set of 30mm Dell’Orto carbs out to for use on the bike, and I’ll also a 2-1 pipe. I’ve been at putting on a Lucas alternator as I for my SP, and mounting a RITA ignition on the as per the III model. This will an electronic tach, but that a problem.

The above mods let me shorten the front of the motor a bit, allowing it to be moved to the front wheel.

‘ll do a different frame. The stock design doesn’t impress me too and the stock forks are junk. A is easy to do on the little twins the swing arm mounts on the transmission, things noticeably.

I’ve got a set of from a Honda CB-1 which are 3/4 x 17, and I keep looking at the drive to see if I can adapt them. will require a new swing arm but what the heck, the stock arm isn’t particularly wonderful

Craig wants to pull the wheels and short leading front end off of his 450 Honda single racer to put on his V50, and I haven’t what to do on the front end of mine. got all the parts for a hub-center front end I’m trying to get around to (the Laverda 750 race has higher priority at the moment) maybe I’ll stick it on the or I’ve got all the tubing on hand to another leading link end like Craig has.

Then again, I could do a front end as used on the Swallower race bike. Sometimes, you can too many options!

Here are fairly large-scale scans of the the diagram for the V50II (Bosch ignition version) that may be of to some of you.

New addition as of 2000

The following is a compilation of a of posts I made to the Moto email list after back into the V50 project at the of 2000.

V65 Lario 4 valve

I found a 650 Lario engine dropped exhaust valves on one that is otherwise supposed to be in good shape. I hope to that here in a few weeks and then get a cylinder head up to for analysis. Remember how much flow the 4v Honda head vs the 2v Guzzi head?

There be some possibilities with a … 500cc Lario.

The engine arrived. I did most of the welding on the damaged Lario after removing the valve and Craig will finish the (I have a small 50A electrical into the house and the TIG welder start tripping the breaker welding big chunks of aluminum a cylinder head). He’ll see about sending the cylinder that side off for repair/replating.

If you nigasil/nikasil cylinders that are internally you can get them welded/machined and generally for under $200/cylinder (I that is accurate — it with bore size and of welding needed) so keep in mind.

The cam lobe for the exhaust that lost their was looking pretty sad. told me that what happened was that the lobe bad and got the valves chattering bad enough they ended up failing, as to the valves failing on their I don’t think that any of the looked really bad so it may have a soft cam rather than a that caused the wear.


I spoke with today and he says the 36mm valve does look it will fit, though it is to need a new intake valve — the V50II intake is actually just a bit small for the Monza valve we were to use, and these new valves are a of mm bigger than that. He get the valves/seats ordered today or if no crisis erupts in his shop.

A conversation has brought up the power of the V50, and how unlikely it seems it could pull a very skin from a very rice pudding.

Herron heads can perform — the Cosworth SCA, a 4 cylinder with Herron from 1964 had these (pulled from the Ginetta website — isn’t the wonderful?):

Bore 81.0 mm 74mm)

Stroke 48.36 mm 57mm)

Rod ratio 2.85:1 (vs for the V50 — longer would be

Compression Ratio 12.5:1

Horse Power 115 bhp minimum @ rpm

Gross Torque 76 lb ft @ 6800 rpm

two 40 DCM2 Weber Choke 32mm

36.8mm intake and 31.75 exhaust valves 7.15mm stems.

That had built heads designed for but Craig has been doing a lot of in the V50II heads which have valves nearly as big but 1.65mm smaller stems restriction).

So if, in 2000, we can come to matching the bhp of a 26 year old race car (and I bet a lot of the internals were a lot than the V50 parts), then we are at a possible 57 bhp, which is darn good.

We’ll to spend some time on the (Craig is working on getting one set up) but if we can get 50 bhp at the rear wheel that still be comparable to a bevel 750 Ducati which weren’t layabouts (not to mention a lot than a V50).

The flow records show the modified head with Monza is doing 87.5 cfm @ 15 of water at (intake) valve lift. I write down what the II head measured out at, but I think the max was around 50 cfm, so big progress has made (I don’t know a stock V50III/Monza head Craig doesn’t plan on any welding in the exhaust port he says that side is quite well as it is.

He is going to get a intake valve and seat to put in, and that 95 cfm is pretty likely, and an 100 cfm may happen.

36mm Dell’Ortos be sufficient for that level of

For comparison a very nice MX BSA B25 was doing 96 cfm at .400 lift, and a XL250 4/v single head 115 cfm with a pretty nice flat tracker head 124 cfm.

Obviously, more are handy to have.

I made a fixture for the Lario heads for the valves open on the flow and we did make several test on the good stock Lario Craig’s comment was that the person who did the ports on the 2v head have done the Lario as as both flow pretty stock.

The first run on the stock head (15 of vacuum) showed:

You’ll that the exhaust flows than the intake for the first of valve lift and is nearly the as the intake for the rest of the lift bad, bad, bad.

The Lario cam gives right at valve lift (which is the stock port flow out), and since the port flow appreciably more that point there much reason to put a hot cam into a with a stock head. The cam (which I’m not going to further until we get the head a lot better) will give .380 valve lift.

The valves (27/24mm) are smaller the stock valves in a 1972 XL250 4v single (same as a V50). The stock seats allow a bit bigger valve there may not be enough room, with new seats, to put the size a powerful 325cc single twin) would want.

then did a little bit of grinding less than 5 minutes. He the ridges around the valve in the combustion chamber (bad for low flow) and relieved the intake a bit in the area around the valve as well as smoothing out a noticeable combo in the port.

The second run

As you can see, that little bit of made some significant in air flow. These were not big in the ports and could have been incorporated in the casting the factory. The intake at low lifts is not sufficiently better than the flow so more work is to bring things into

The balance between the ports at and higher is looking better. The head still needs to up

15 cfm on the intake side to match a XL250, and 25 cfm to get close to a nice XL250 head.

Craig is of the that for this year we just stick with the 2v especially since we’ve got the already in hand for that. work on the Lario heads as a upgrade for the future.

The V50II came back with the diameter intake valve Craig also has the new stainless valve blanks that are

2mm than the V50III/Monza valves so he gets a chance to shorten and cut the valve seats in he’ll be to put the 2v heads back on the flow He’s expecting a fair in flow from the bigger plus the old valve seats too large an inner diameter for the size, and that has been with the bigger valves/seats.

The V50II cam with new Megacycle grind has .308 cam lift, 106 lobe centers, and 19/51, timing.

We’ll be running Precision Machining valve (nice AMPCO 45 bronze and I think the valve springs decided on are R/D Spring kits for an Honda single.

Cylinders, and bottom end

Pistons — A burette check of the Monza makes it appear that it give about 11:1 That is presuming no more .040 squish clearance. magazine listed 10.5:1 for the so that seems to check our numbers. Craig says should be fine for the street, but we’ll want to have new made for Bonneville to help for the high altitude.

He had an opportunity to to Keith Duckworth of Cosworth the Cosworth SCA engine (1 litre with Heron heads) and was they ended up with a top piston with two pockets for the and a little pocket under the plug — all of those connected. Duckworth said maximized the SCA compression ratio probably in the 14:1 area or

Arias will make any as long as 4 are ordered, so after we can get a roughly assembled we’ll a piston with clay and out the minimum clearances we’ll In any event the bowl in the Monza is likely to disappear. Thinner will also be sought at time, along with a wall wrist pin.

the high compression I’ll to be careful about not applying throttle at lower RPM so as not to induce

The Lario engine has the 15mm oil pump and there are some different for chain sizes, of the sprockets from the base of the etc that will have to be at if we decide to upgrade the V50II to the pump. However, Craig that the stock oil pump, combined with some in the rest of the oil system and the oil control we’ll put in the crankcase, may be sufficient. it will be a bit less prone to at high speeds(that is a reason the Butler Smith BMW race went with a smaller stock oil pump).

Moto Guzzi V50 C

I’ve hearing stories about the twins being prone to their oil out the breather, and a quick inside the crankcases reveals a reason — a complete of any semblance of oil control mechanisms.

The poor oil probably stays wrapped around the crankshaft, beaten to a froth by the rods. It like the main way oil would get back into the sump be from the cylinder head

I’ll be constructing a scraper for the crank — this is NOT a flat plate sticking out to the crank. Craig made I understood just what to do for a system which should see the oil from the crank while not any drag to things that are around in the crankcase.

Some holes will probably to be drilled in the floor of the crankcase to the oil back into the sump. have to also deal a method for securely fastening the system in place — it to fit quite closely to the crankshaft in locations.

Our usual exhaust and assisted crankcase breather will be installed to help down the cases.

Eliminating the pressures and battering of the oil will some wasted energy.

and transmission

Clutch — has concerns about the V50 clutch the increased power, especially at speeds where the drag is He’ll be contacting a manufacturer of car clutches this coming to get some drawings/data on 4.5-5 A small clutch like (and that is the OD of the basket) take about 200 bhp from a 4 car, but we may need a little to accomodate torque spikes in a

When I talked to Tilton years ago about clutches said that on the Wittner bike they had to go to a bigger than was needed for the bhp to deal the torque spikes. I think ended up with a 7 clutch, I can’t recall if it was a single or plate unit.

Craig the clutch guys will install whatever spline is in the clutch plates, though we always rob the centers out of V50 plates if and rivet them in ourselves.

of the clutches are now available with a type of heaver, as used by the We’ll also look to see if is enough room for an annular pusher as used by many cars.

However, the V65 clutch is a option (though it might the V65 transmission to go with it).

Gearing — the Monza ratios may prove to be the best — and at this time it known for sure if the taller gears will fit or can be made to I may have to have different wheels set up with different OD to use to make minor gearing The II/Monza/Lario primary ratios some pretty big jumps in

A chain final drive certainly be handy!

This is I was able to extract from my V50

Monza primary drive 1.4666

5th gear .909

drive 3.875

overall — 1:5.1661

A typical 110/90×18 rear tire is

OD which would have a of 82.31

Some rpm/speed would then be:

8000 rpm = rear wheel rpm = 120.70 mph

rpm = 1645.342 rwrpm = 128.24 mph

rpm = 1742.126 rwrpm = 135.79 mph

As mentioned before, the 2v heads outflow the 36mm Dell’Orto so that’s what they’ll end up The carbs will be mounted on manifolds as the stockers are quite in diameter.

I’ll build a 2-1 to Craig’s specifications — work well on all the other 90 twins he’s built for (600-950cc Ducatis, 500-1000cc Guzzis) and I have no doubts it work well here


Chassis — have to try and get a roller mocked up so we can looking at that. I’ve got a set of Kawasaki KR250RR fork and both Ceriani and Guzzi T3 clamps to play with. now I’m thinking about the steering head off entirely and a new one in that will have a lower top. If I don’t do I’ll just shorten the top of the steering head and make new cups to take taper bearings.

The forks will be shorter — we want to the bike as low as possible and reduce the area. Back to the home #169 1996-2009 Michael last update for this 01 September 2009

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