Power, RPM and MPH

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Power, RPM and MPH

Postby Pharisee » Mon Jul 23, 2018 12:40 pm

Is there published anywhere what power the G3 engine develops and at what R.P.M. ? Really, I'm just curios as to what the max recommended revs are.

My '54 G3 has a non-standard overall gear ratio as I have an AMC gearbox and clutch fitted. The clutch drum has 42 teeth as opposed to the original Burman item that has 40. The engine sprocket has the normal 18 tooth so the primary ratio is slightly lower. To (over) compensate, the gearbox sprocket is 18 tooth instead of the standard 16 tooth. That gives me an overall top gear ratio of 5.444:1 instead of the standard 5.833:1

I've just wrapped a tape measure around the rear tyre and the circumference is approximately 84". Not exactly an accurate rolling circumference but close enough for me to work out that the engine is doing approximately 3,400 r.p.m. at 50 m.p.h.

Has anyone got a tachometer fitted... Does that sound about right?

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Re: Power, RPM and MPH

Postby SPRIDDLER » Mon Jul 23, 2018 1:58 pm

For a '54 this website says 16hp @ 5600 rpm.

http://www.motorcyclespecs.co.za/model/ ... 3%20LS.htm

I put a chalk mark on the tyre and a corresponding one on the ground, move forward one revolution and measure the distance travelled.
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Re: Power, RPM and MPH

Postby Rob Harknett » Mon Jul 23, 2018 2:07 pm

Do they really rev 5,600? my car will redline just over that. But never done it as it would be doing almost double the speed limit. 70 in the car is just over 3,000 in 5th. I could never go flat out in 3rd on my 55 G3LS as valve springs would float. Don't know what RPM that happened.

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Re: Power, RPM and MPH

Postby Mick D » Mon Jul 23, 2018 2:47 pm

Hi

You can get acoustic tachometer apps if you're a smart phone user.

Regards Mick

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Re: Power, RPM and MPH

Postby SPRIDDLER » Mon Jul 23, 2018 3:42 pm

Seems about right..........

Spec'n 54, 58 and 62 G3.JPG


Extract from a 1991 Classic Bike road test and specs for the '54, '58 and 63 350's here:

http://archives.jampot.dk/editorial/Roa ... adtest.pdf
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Re: Power, RPM and MPH

Postby Jonny Astro » Mon Jul 23, 2018 4:31 pm

I confess I've been wondering about rpm/road speed on my '53 G3LS...

Having been riding carefully for a few hundred miles since I got it from the chap who restored/rebuilt it I've not pushed it yet, but even at 50mph it seems a bit "frantic".

Am I just being a bit soft? I would have thought that a 55-60mph cruise would have been acceptable, (assuming standard gearing of course) ?

Jon

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Re: Power, RPM and MPH

Postby SPRIDDLER » Mon Jul 23, 2018 5:02 pm

Jonny Astro wrote: I would have thought that a 55-60mph cruise would have been acceptable, (assuming standard gearing of course) ?

Your bike may have sidecar gearing....... :?
However,
I've cruised my '54 350 for thousands of miles (with camping gear), mostly abroad, much of it cruising at around 55 to 60mph. When a pal with a P11 and me travelled to the IJR at Milan some of the time was spent following a pal driving a (foreign) motorhome. We instructed him to stick to a cruising speed of 100kph (62mph) max which he did on dual carriageways and open roads for many hours at a time, only slowing when necessary or on long inclines. My bike and most others have a 'sweet spot' at around 55 to 60 'ish when the engine smooths out and runs like a turbine.
On long trips I stuffed rag into the gap 'twixt seat nose and petrol tank as the carb induction hiss and chatter and general engine/rocker noise funnels up there and can get very tedious after a few hours.

Motorhome, G3LS and P11 somewhere en route to Milan....

CNV00030 (640x429).jpg
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Last edited by SPRIDDLER on Mon Jul 23, 2018 8:58 pm, edited 6 times in total.
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Re: Power, RPM and MPH

Postby Mick D » Mon Jul 23, 2018 5:07 pm

Hi

I wonder how many of these concerns are perceived? I have noticed a marked increase in exhaust note from my 'pattern' silencer.

I tend to ride at around 50mph and whilst it's a bit noisier than I remember of old I've not changed anything significant other than the silencer, it sounds more 'manic' but it must be revving the same.

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Re: Power, RPM and MPH

Postby Pharisee » Mon Jul 23, 2018 8:33 pm

My engine was rebuilt... new main bearings, new big end assembly, new bore and a new piston so I've been taking it fairly easy. Ran it at around 40mph for a couple of hundred miles and with 350 on the clock now, pushing it up to 50mph or so. There is no sign of any tightness and I'm sure it will run faster. There was a noticeable reduction in vibration from 40 to 50 and it seems very willing to go faster. I'll give it a while longer and give then give it a few more beans. Promising to be a fine motor... :D

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Re: Power, RPM and MPH

Postby Pharisee » Tue Sep 11, 2018 4:20 pm

Pharisee wrote:My engine was rebuilt... new main bearings, new big end assembly, new bore and a new piston so I've been taking it fairly easy. Ran it at around 40mph for a couple of hundred miles and with 350 on the clock now, pushing it up to 50mph or so. There is no sign of any tightness and I'm sure it will run faster. There was a noticeable reduction in vibration from 40 to 50 and it seems very willing to go faster. I'll give it a while longer and give then give it a few more beans. Promising to be a fine motor... :D


650 miles on the clock now and not just promising to be a fine motor, it is a fine motor. Very willing to rev and simply purrs (loudly) along at 60 m.p.h. on the flat with a bit to spare for the occasional overtake. Takes a while to get there; she won't win any 'traffic light grands prix' and she slows down a bit on steeper inclines but is never-the-less an absolute joy to ride. This one is a keeper unless someone is prepared to part with some serious wedge!!!

20180626_123443.jpg
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