Tuned Commando

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paulcali3
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Location: Somerset UK

Tuned Commando

Unread post by paulcali3 » Wed Dec 16, 2009 3:16 pm

I have two 34mm Amal Mk 1 carbs on my tuned 750 Commando engine..bike goes well enough, no flat spots or dodgy tickover but overall performance is a bit disappointing. It has been dyno tested at 48.8 BHP at around 5800rpm which seems about right for a 750 Commando. Don't know what else has been done internally but it has compression from Hell...starts first kick when hot (sometimes when cold too ) now I have the technique, but I'm not getting any younger...Dunstall silencers, doesn't leak oil. I don't like high revving engines, don't want to hammer it to get best performance, too much noise & vibration (I own a Guzzi 1100 and Harley Sportster too), wondering if I should lower the compression or test drive a standard 750 Commando to compare? Big subject I know, any thoughts? PS I live in Ireland and don't know any other Norton owners...
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Last edited by paulcali3 on Wed Dec 16, 2009 11:00 pm, edited 1 time in total.

Captain Custard
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Re: Tuned Commando

Unread post by Captain Custard » Wed Dec 16, 2009 7:40 pm

lower the compression. a couple of head gaskets? i did it years ago with a triumph, calmed down the vibes a treat.where in ireland are you? im in westport.

Triton Thrasher
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Re: Tuned Commando

Unread post by Triton Thrasher » Wed Dec 16, 2009 9:35 pm

The main effect of lowering compression will be less power.

You might get better response from 32mm carbs.

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Hooli
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Re: Tuned Commando

Unread post by Hooli » Wed Dec 16, 2009 10:36 pm

Triton Thrasher wrote:The main effect of lowering compression will be less power.
I was under the impression that lower compression also means the power peaks at lower revs? or is that just a function of it not working as well at higher revs?
Classics ain't built in Metric

paulcali3
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Location: Somerset UK

Re: Tuned Commando

Unread post by paulcali3 » Wed Dec 16, 2009 10:56 pm

Thanks for the advice. I'm in Blarney Co. Cork..long way from Westport but love that part of Ireland..Maybe I'll fit an extra head gasket..it's cheap anyway!

paulcali3
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Location: Somerset UK

Re: Tuned Commando

Unread post by paulcali3 » Wed Dec 16, 2009 10:59 pm

Actually just remembered I did have a pair of 32mm carbs...must have a dig in the garage...sure they're in there..

Triton Thrasher
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Re: Tuned Commando

Unread post by Triton Thrasher » Wed Dec 16, 2009 11:00 pm

Lower compression should never give more power at any rpm (in theory at least). If you have pinking or overheating caused by too high a comp ratio, lower ratio will make the engine run better though.

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Hooli
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Re: Tuned Commando

Unread post by Hooli » Wed Dec 16, 2009 11:14 pm

Triton Thrasher wrote:Lower compression should never give more power at any rpm (in theory at least).
No i realise it wont give more power, I just thought it gave a lower rev range to the peak power.
Classics ain't built in Metric

paulcali3
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Location: Somerset UK

Re: Tuned Commando

Unread post by paulcali3 » Wed Dec 16, 2009 11:39 pm

No pinking or overheating problems..quite a sweet engine really!

chilly
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Re: Tuned Commando

Unread post by chilly » Thu Dec 17, 2009 11:29 am

32 mill carbs would be a good start i would think,i reckon some of the 750s had 30 mill carbs but not 100% on that one .

If your running a boyer ignition and your battery is a bit low the ignition can go to full advance when you try to start it, making it hard to kick over.

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