Rear Sprocket Question N/S/R
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Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1954
Location: Not really sure but I think somewhere down South, in the engineering dept at Starfleet's UK HQ
Mon Aug 12, 2019 7:22 am quote
I understand what you want to do Bill. Lower revs to reduce stress on the motor. You could take off a tooth or two but really it's usually not a good idea because usually it increases stress on the motor. It'll be a bit like asking the engine to go uphill all the time.

Modern motors like to rev, they are designed that way, well most are especially the smaller ones. They all have short stroke low piston speed motors. My GTS revs high but the motor is not stressed at 70mph because the piston speed is low. If I lowered the engine revs the lower revs would bring the piston speed down increasing the bmep (pressure in the cylinder) for any given speed compared to the original gearing. In short it's normally best to let her rev as she'll be less stressed. Could go in to lots of technical stuff Bill but my surgeon has just walked in, I'm going down!!
eeee-bip
Benelli TNT 125 "Bean Alley" Kymco AK550 The War to end all Wars
Joined: 15 Apr 2008
Posts: 16572
Location: South East Great England of Britishland
Mon Aug 12, 2019 7:29 am quote
Click
Sleep tight little one.

I'm inclined to agree with you.

It's more trouble than it's worth but I think that we've all learnt something.

Lowering the revs will load the engine more than letting run free at the rpms it was designed to produce its peak power.......at.

Bill x
Enthusiast
Joined: 09 Aug 2019
Posts: 80
Location: Aberdeenshire Scotland
Mon Aug 12, 2019 1:58 pm quote
Re: Lips
Bill Dog wrote:
Difficult to compare and contrast heights though.
Its easy enough.

140/70-12

140 = width in millimetres

70 = height expressed as a percentage of width

So 70% (seven tenths) of 140.... 7x14= 98mm

A 130/70-12 would be 13x7 = 91mm

So the radius of a 130/70 is 7mm less than a 140/70 making the circumference (and gear development) 44mm shorter. (3.14xD)
eeee-bip
Benelli TNT 125 "Bean Alley" Kymco AK550 The War to end all Wars
Joined: 15 Apr 2008
Posts: 16572
Location: South East Great England of Britishland
Mon Aug 12, 2019 11:05 pm quote
Missed
Difficult comparing the profiles, not the little numbers on the side because that would be easy.

A Heidenau K91 profile when new is more like a lipstick where as a Continental or a Metzeller is more like a thumb nail and even though the numbers are the same its actually taller which is why it feels like riding on a knife edge.

Been riding scooters long ? Oh, I forgot, you don't have one.

Bill x
eeee-bip
Benelli TNT 125 "Bean Alley" Kymco AK550 The War to end all Wars
Joined: 15 Apr 2008
Posts: 16572
Location: South East Great England of Britishland
Sat Aug 17, 2019 4:54 am quote
Call
I've just asked those nice people at DEP if they can make complete pipe for the Benelli.

Oh dear.

It's a slippery slope.

Bill x
Ossessionato
LXV 150 Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 2781
Location: Bangkok
Sun Aug 18, 2019 4:41 pm quote
Re: Lips
Bill Dog wrote:
Actually you raise a very fair point and it's a shame that I've just had City Grips fitted as a tyre with a higher profile may well have created the same affect.

Difficult to compare and contrast heights though.

Bill x
Not so difficult.

https://www.tacomaworld.com/tirecalc
eeee-bip
Benelli TNT 125 "Bean Alley" Kymco AK550 The War to end all Wars
Joined: 15 Apr 2008
Posts: 16572
Location: South East Great England of Britishland
Sun Aug 18, 2019 9:45 pm quote
See above
Nope, you're still not getting it.

Bill x
Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1954
Location: Not really sure but I think somewhere down South, in the engineering dept at Starfleet's UK HQ
Mon Aug 19, 2019 12:42 am quote
Re: Click
Bill Dog wrote:
Sleep tight little one.

I'm inclined to agree with you.

It's more trouble than it's worth but I think that we've all learnt something.

Lowering the revs will load the engine more than letting run free at the rpms it was designed to produce its peak power.......at.

Bill x
Yep, thanks, I slept tight Bill. Surgery a complete success! Now home and recovering with my wife who earlier in the year had two brain surgeries to save her life. We're recovering together. The road ahead now looks smooth for both of us.

As you say Bill, it's difficult to compare like for like regarding size and specs of tyres. They can be very different when you actually measure them side by side even with the same numbers.
eeee-bip
Benelli TNT 125 "Bean Alley" Kymco AK550 The War to end all Wars
Joined: 15 Apr 2008
Posts: 16572
Location: South East Great England of Britishland
Mon Aug 19, 2019 1:14 am quote
Ticks
Good Man.

At least someone else gets it.

Bill x
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Benelli TNT 125 "Bean Alley" Kymco AK550 The War to end all Wars
Joined: 15 Apr 2008
Posts: 16572
Location: South East Great England of Britishland
Wed Aug 21, 2019 10:48 pm quote
Tidy
Just in case anyone doesn't what I was getting at it came from wondering if I was going to ride the Benelli on an endurance run could I reduce the revs to give the engine an easier time over the distance of say 12 to 24 hours.

From what I've read it seems that if the sprockets are changed the engine will be reving below it's optimum which means it will be loaded rather than reving freely while delivering it's maximum output of an incredible 11hp.

It will probably do more damage to do that rather than leave it the way it is.

Thanks all.

Bill x
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