450 desmo carb

[themoudie]

Dear Nigel and George,

Thank you for your comments and information.

Nigel, yes, the inlet port was polished to a mirror finish and I have not given it a scouring with any emery cloth. The exhaust port has a clean finish, but not polished smooth. Times and knowledge have changed since 1977, when the porting was carried out. So, the head will be coming off, after setting up the timing marks at TDC for easy replacement. The ports will receive some attention and the old OME 450 cam will be going in.

George, yes, the cam is going to be changed. I have checked the timing of the cam on both the inlet and exhaust valves three times since originaly checking, when the head was first replaced on the motor. Nigel, who supplied the Piper 173A cam was the first, if I rememeber correctly to ask if I had checked the cam timing and offered helpful advice on tolerances that would be acceptable. Whilst my 'measuring' may not be 'spot-on', my measurement readings fall within the parameters that Nigel has kindly supplied. So, I don't doubt the published figures of the cam correspond to those of the cam supplied to me.

Right, off to watch Ireland v England!

Good health, Bill

[BevelBitsaBrighton]

The comments about space are worth noting! I have fitted a 36mm Mikuni to my 450. The new manifold is straight so the carb no longer points at the airbox but at the frame tube. The Mikuni is bigger than the dell orto, so the bell mouth is also too close to the frame to fit the airbox pipe as well. I have found a kinked K&N which sits outside the frame. As I am not fitting rearsets it sits behind my leg! I have also had to raise the back of the tank 10mm to clear the throttle cable. I thought I had been clever turning the choke mechanism 90 degrees to make it more accessible until I put the tank back on & found it was sitting where the fuel tap goes... I am learning a lot about ducati singles the hard way...

[graeme]

Hello Bill,

How's the 450 going?
Haven't heard for a while,,,, I hope all is well ???
I have a recurring dream of a Scotsman in his underpants with a bottle of whisky dancing around a burning motorcycle, and swearing illegibly,,,

graeme

[themoudie]

G'day, Graeme,

My apologise for your recurring apocalyptic nightmare! My wife now says she has a similar "vision"!

As for being a "Scotsman", I must for the sake of honesty declare that is adoptive and I have enjoyed their tolerance for just shy of 50 years. Having "gone bush" in 1973, married one of their daughters and not returned to permamnent residence south of Hadrians Wall since.

After contemplation, temptation from BevelBob and a porter, I have lifted the head and dismantled it, taken some images and shared them with Nigel, who again, has kindly offered advice, experience and encouragement.

Lifting the head revealed a sticky soft carbon deposit inside the head, a poorly seating exhaust valve that appears to have become stuck in the collets and is not rotating in action, a polished inlet port that I knew about and not of a "good shape" to encourage cylinder filling, but more likely to encourage the fresh charge to skate through the combustion chamber and head for the exhaust port! Finally, some edgy rocker pad contact with the cam lobes

So, "Whaat to do Misser?". I am going to revert to the 450/250 SCR 'White' cam that is the OME profile. I will have to dress the rocker pads to improve the contact area with the cam lobes and if this is not possible have them stellite coated and re-finished. Maybe add another 'White' cam to the bundle for a re-grind as well. Re-cut the exhaust valve seat, roughen up the inlet port and possibly add an epoxy filler to change the airflow across the bottom of the port, to make the inlet charge fill the cylinder.

As is often the case and now makes the heading to this thread that I appear to have highjacked, inaccurate, is this is likely to be a porting job from 1977 finally revealing its inadequacies when a well designed cam is added to the equation of "Suck, Squeeze, Bang, Blow"!

Good health, Bill

[graeme]

is the red bit a lip up or just looks like that in the picture ?

[themoudie]

G'day Graeme,

I wish it were a lip! It might help to gain the desired lift and fall of the charge into the cylinder. Unfortunately, not, it is merely a mirage from the polishing of the port and shadows.

However, after soaking the head in 'Gunk' and giving it a good scrubbing the carbon deposits are shifting, to give a better view of what has been going on. Now to start the remedial work. £££££££

Good health, Bill

[Duccout]

It's only money (that is what I keep telling myself!).

[themoudie]

Aye Colin, and no worth a jot in a "savings" whatever!

Good health, Bill

[Bevel bob]

Hi Bill , Sounds like you are having far too much "fun" , I miss those days !, I'm going to up my offer and add a case of best malt to the deal. I have been bored witless over the last year ,but am now attacking the fitness and hope to get my 250 out this week . I have a head cam and will try for some entertaining footage , Just have to work out how to post it.

[themoudie]

Good afternoon Bob,

Thank you for your increased "Offer"! However, I shall resolutely stand by my washdown sink cleaning the head components, before making some "adjustments"! I hope that the results are positive this time.

As for the heed cam? I have thought about one these, but am feart about the mounting on the bonce and think that a chest harness might be a better option. But all of that is a distraction from getting the bike back on the road, which is the first priority. Viewing "my world" through a body cam might cause fellow "Scrubbers" to take unintended medical conditions and that wouldn't be benificial to a small group of individualists!

Keep doing the aerobics/yoga/bench presses/feng shui and enjoy your spring warmth, we are back to a 5°C, rain sodden, 20mph wind blast from the NE today!

Good health, Bill