Compression ratio

[Bill Cannon]

3mm is about 120 thou, so you are probably right Glen, although Terry said it wouldn't be that noticeable on a road bike.

I'll be happy to just have it running, if I don't feel it's sharp enough I'll order some different pistons and remove the plates.

Bill

 

[clevtrev]

Thanks for the new input guys.
I have been in contact with Terry and he confirmed that the pistons are not 9:1 as expected.
I have just picked up some 3mm compression plates which should be fitted during the coming week. These should bring it down to about 8.3:1 compression.
Terry supplied one new liner to replace the one I damaged by dropping the cylinder on the workshop floor! This should be back from boring/honing tomorrow.
I haven't currently got the kickstart mechanism fitted so I am expecting the Grosset starter to do the business.
I'll post if it starts and slit my wrists if it doesn't!
Regards Bill

Hopefully you`ve taken off the Gardner carbs, as instructed by François ?

 

[Bill Thomas]

Has anybody proved how good these funny heads and pistons are, With back to back tests, Bill is not the only person to have had trouble starting ! Cheers Bill.

 

[Monkeypants]

I was forewarned that mine would be tough to kick over, however much to my relief, it is doable.
As far as power goes, I have nothing to compare it to other than my 161 hp Triumph Daytona. It is not really a fair comparison to put it against a standard Vincent.
The Vincent with the funny heads, pistons and cams definitely comes on harder than the Triumph down low, almost brutal like a 490 Maico, but as that Triple starts to wail.... I'm not sure which is the faster of the two.
I can imagine that a 1360 cc Vincent with conventional head, pistons and cam in a 348 pound bike would also create some acceleration g's.

 

[Bill Cannon]

Hopefully you`ve taken off the Gardner carbs, as instructed by François ?

No I haven't Trev. Francois has had no experience of these carbs. Mine have been modified to include idle screws and perform well at all speeds so I don't believe they contribute to the problem. It's more likely to be the ignition, which is electronic with manual advance.
I have modified the starter reduction gears to disengage the drive once the bike is running thus preventing possible damage to the gears.
Next project will be to relocate the starter to the clutch side and devise either a sprag clutch or a gear train that is easily detachable.
Bill

 

[Bill Thomas]

Hello Bill, I would love to see a photo of a Gardner with idle screws, I ran three sets years ago, Funny thing was the very early one that was held together with lots of screws, And very square, Ran the best !! Cheers Bill.

 

[davidd]

Has anybody proved how good these funny heads and pistons are, With back to back tests, Bill is not the only person to have had trouble starting ! Cheers Bill.

Bill,

I think the answer is yes. It would have been Ian Hamilton, at least for the combustion chamber and piston Carleton and I used. As I understand, it is a copy of the Manx style combustion chambers and pistons that worked so well many years ago. It is often very expensive and time consuming to do this development work. It was why the Vincent was never developed. There were no funds. So, we all tend to do very unscientific things if someone else has done the hard work. Often we do them even if there was no hard work done!

The Terry Prince head is essentially a big port head with a squish combustion chamber and a "D" shaped anti-reversion exhaust port. The head was in part developed by John Trease. He is the bloke who got 58 BHP from Ian Boyd's Vinton, so he knows his way around an engine. I have never had any starting issues, but I have always used Amals and I have no experience with Gardner carbs. I know Stuart Hooper always liked the twin plug ignition not because it made more power, but because it started the bike so easily. Stuart used an Amal also with his funny head and piston.

David

 

[Monkeypants]

"58 hp from Ian Boyd's Vinton"

which is a 500 cc machine! Some of the fellows on the Norton site had difficulty believing this until David provided me with the graph showing 58 rwhp.

 

[Bill Thomas]

Hello David, I am just being Grumpy !! because I have no money and too old to do any of this stuff now !!. I got 99.8 out of a standard ish road Comet, And I have enough bits to build a 560cc, But I don't know when !!. Whats a D shape ex' port ?. Cheers Bill.

 

[davidd]

Hello David, I am just being Grumpy !! because I have no money and too old to do any of this stuff now !!. I got 99.8 out of a standard ish road Comet, And I have enough bits to build a 560cc, But I don't know when !!. Whats a D shape ex' port ?. Cheers Bill.

Yes, Grumpy is what we expect! That is quite a good speed for the Comet.

David