continually looking for 6th gear

jerry · 24-09-2019, 05:46 PM

both my carby 750 monsters pull like trains powered by 2 strokes now they are well tuned ,, i am continually searching for the non existant 6th gear both have 15-41 sprockets so as a 6th gear is unlikely maybe going for a 39 rear might be the way to go

a rear sprocket is cheap so might be worth an experiment ,,,

Flip · 24-09-2019, 08:56 PM

I'm sure Utopia will be along shortly on this one as I believe he has raised the gearing of his 750 for the very same reasons you mention.

350TSS · 24-09-2019, 11:30 PM

what are the relevant numbers for a 750SS? - mine would if revved hard in 4th not quite pull top revs in 5th on a level road - obviously with a fairing so you would need an extra tooth for none on the Monster.

Darkness · 25-09-2019, 06:49 AM

Take a look where the back wheel is in the swing arm.
You may be able to squeeze in an extra tooth on the front sprocket if the chain is long enough?
That would improve chain swingarm clearance (Marginally) rather than reducing it.

Darkness · 25-09-2019, 06:59 AM

Quote:

Originally Posted by 350TSS

what are the relevant numbers for a 750SS? - mine would if revved hard in 4th not quite pull top revs in 5th on a level road - obviously with a fairing so you would need an extra tooth for none on the Monster.

15/37 on SS 750
15/41 on Monster 750

A 39t is standard on an M900, so should be readily available to try (But may need chain shortening).

350TSS · 25-09-2019, 08:51 AM

Both are 520 pitch so a 39 would be just about right for the Monster - I will try a 39 when I rebuild my 750SS as only about 3 times in 30k miles have I found a road long enough to worry that I was not getting top revs in top and it would sharpen it up in the important 50 to 90 mph range

utopia · 25-09-2019, 01:52 PM

Like Jerry, on std 15/41 sprockets I often found myself searching for a non-existent sixth gear on my 750.
For a while I toyed with fitting a gear indicator.

When the carbon wheels went on I was obliged to fit a new rear sprocket so I specified a 40t, which I ran for a couple of years.
This was much better in fifth gear, keeping the revs down a bit when fast cruising was required and reducing the tendency to search for that extra sixth gear.
It also had the additional benefit of making first gear more usable in town traffic as it was that bit taller and lasted longer, such that in stop/start traffic you could hang on to it rather than constantly changing in and out of second gear.

By this time the weight of the bike was down to just a tad over 160kg.
The ultralight wheels span up quickly too, due to their reduced inertia .. an effect which was more noticeable than I had expected.
Therefore I reckoned I could go to 15/39.
I've tried that for the last couple of months but its still a bit early to be certain whether I prefer it or not.
Motorway cruising is now a nicely relaxed affair though, and I seldom if ever hunt for that extra gear.
First gear is even longer, which personally I quite like but it may not suit all tastes.
I also quite like where that puts fourth gear, which seems just about right for your average twisty road (which I remember thinking on my way through from Douglas to Kirkmichael at this year's TT).

Its never that simple though, is it ?
Lately my attention has been directed towards the front sprocket.
I've had a casesaver fitted for a few years but there is almost no room for it in the 750 crankcases with the 15t sprocket fitted.
It will fit but the chain has a tendency to scrape it sometimes.
This happens mostly on the overrun when the top run of the chain goes slack and it is made worse as the chain ages, wears a little and develops the odd tighter spot .. which they all do to some extent.
Checking the bike over before leaving for the TT, I noticed some wear marks on a couple of inner link plates of the chain.
It was too late to do much about it, but as the 39t rear sprocket was hanging on the shed wall awaiting fitment, I stuck that on and also made a fine tweek to the chain alignment.
Well, I snapped that chain on that trip.
Luckily, at walking pace and only 50yds from my tent at the campsite, rather than half way up the motorway at speed.

Sorry for the long story but I mention all this because my latest decision has been to change to a 14t front sprocket, to give a bit more clearance on the casesaver.
I could of course remove the casesaver and keep the 15/39 or 15/40 gearing that I like but .. well .. I daren't.

And so, the upshot so far is that I'll be going to 14/39 and exploring the implications for chain/swingarm clearance with that set-up (I've had no clearance issues with the 15/39 btw ).

Drive ratios for these various sprocket combos are as follows ...
15/41 = 2.73:1
15/40 = 2.67:1
15/39 = 2.60:1
14/39 = 2,79:1

So you can see that my latest 14/39 set-up will be slightly worse than the original 15/41 ....doh !
I may try and squeeze a 38 rear on at some stage, but I suspect chain clearance on the swingarm will be critical by then.
Oh btw, this is with an ally swingarm fitted.

So there you go.
That's as much as I know, so far.
Personally I think that a casesaver is a pretty essential bit of kit and I don't want to ditch it.
Maybe I'll have to go back to sixth gear hunting or else fit that gear position indicator (just a top gear indicator would do, tbh).
But note .. Jerry in particular .. the casesaver clearance issues above relate to the later style 750 crankcases with separate clutch slave. .. like your original 750, Jerry.
It could be that the earlier style cases with integral clutch slave .. I believe, like your new 750, Jerry ? .. have more clearance around the front sprocket and might allow the 15t sprocket with casesaver to be fitted.

utopia · 25-09-2019, 01:56 PM

Oh, and the 15/39 combo will fit with the std, 100 links chain, but it leaves chain adjustment a bit marginal.
After I snapped my chain I fitted a 98 link, which was better.

jerry · 25-09-2019, 07:02 PM

Thanks utopia , i have a case saver on my M750 and the 15t never seems t mark it ,,i think 39 t is what i will try on one of the 2 M750 bikes ,,

my 750ss 1991 has a 39 t on rear and 15 on front seem to hit 130mph indicated on speedo ?? but it does have fairing runs sweet ,

utopia · 25-09-2019, 09:28 PM

Quote:

Originally Posted by jerry

.....I have a case saver on my M750 and the 15t never seems t mark it.

Do you know the manufacturer of your casesaver, Jerry ?

I would much rather stick with 15/39 if I can get a casesaver in there with enough clearance.

Also, it turns out that 15/39 with a 98 link chain is an ideal combo for evening out wear in the final drive ... it takes 15 full chain rotations before a tooth on the front sprocket returns to a link with which it has previously engaged ....and 39 full chain rotations in the case of a tooth on the rear sprocket.
See here for a calculator ...https://www.blocklayer.com/chain-sprocket.aspx

The 14t front sprocket fares much worse in those stakes.
Fortunately I think the 98 link chain will do for either set-up, so I can still switch back to the 15t if I can solve the casesaver issue.

Dukedesmo · 25-09-2019, 09:33 PM

Quote:

Originally Posted by utopia

Oh, and the 15/39 combo will fit with the std, 100 links chain, but it leaves chain adjustment a bit marginal.
After I snapped my chain I fitted a 98 link, which was better.

I can confirm this.

Whilst I have a 900, the swingarm/sprocket positioning are the same and I originally fitted a 15/41 combination as I thought it might be an improvement. However it left me looking for a 7th gear as I found it too 'buzzy'.

I went back to the standard setup of 15/39 but left the 100 link chain that I had fitted with the 15/41 setup as I wanted to try the the longest possible wheelbase, but it was right at the end of the adjusters with the chain still a bit loose so I changed to 98 links which fits perfectly with the 15/41 combo.

Actually if you are continually looking for 6th gear, you could always fit one - my understanding is that a 6-speed box will fit in the 'small block' casing? t'would be a fairly major job though...

jerry · 26-09-2019, 06:29 AM

Utopia , i cant remember the case saver supplier sorry ,, I think it was desmo times ???

fitting a 6 speed cluster would be lovely ,, could it be done ????

on my S4 i went the opposite way was 15-39 but lousy at slow speed buy could hit 150mph changed to 15-43 much better low speed and still cabable of 130mph

Dukedesmo · 26-09-2019, 01:48 PM

Quote:

Originally Posted by jerry

fitting a 6 speed cluster would be lovely ,, could it be done ????

I'm fairly certain it can be done although you may need to use a six speed mechanism specifically from a 'small case' engine such as an 800 rather than the 900/1000?

I remember reading on another Ducati forum that a lot of DesmoDue race bikes have it done for better acceleration.

Hopefully someone more knowledgeable can confirm?

Edited to add, more info here; https://www.ducati.ms/forums/57-supe...peed-case.html

jerry · 26-09-2019, 02:52 PM

so a 6 speed cluster and selectors from a 620 or 800 or 695 would likely fit ok ?????

,,,400 was only 5 speed and im not sure a later 696 ,797 or scrambler 800 would be same line up

Flip · 26-09-2019, 05:00 PM

This may or may not help in your search but either way it’s an interesting read if you’re that way inclined

http://bradthebikeboy.blogspot.com/2...speed.html?m=1

24-09-2019, 05:46 PM	#1
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,803	continually looking for 6th gear both my carby 750 monsters pull like trains powered by 2 strokes now they are well tuned ,, i am continually searching for the non existant 6th gear both have 15-41 sprockets so as a 6th gear is unlikely maybe going for a 39 rear might be the way to go a rear sprocket is cheap so might be worth an experiment ,,, __________________ MONSTERMAN

24-09-2019, 08:56 PM	#2
Flip Registered User Join Date: Mar 2010 Location: Beachtown Bike: M900 Posts: 2,188	I'm sure Utopia will be along shortly on this one as I believe he has raised the gearing of his 750 for the very same reasons you mention. __________________ You're perfect, yes, it's true- But without me you're only you!

25-09-2019, 06:49 AM	#4
Darkness . Join Date: May 2007 Location: Stockbridge Bike: M900 Posts: 1,984	Take a look where the back wheel is in the swing arm. You may be able to squeeze in an extra tooth on the front sprocket if the chain is long enough? That would improve chain swingarm clearance (Marginally) rather than reducing it. __________________ Original and Best since 1993

25-09-2019, 07:02 PM	#9
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,803	Thanks utopia , i have a case saver on my M750 and the 15t never seems t mark it ,,i think 39 t is what i will try on one of the 2 M750 bikes ,, my 750ss 1991 has a 39 t on rear and 15 on front seem to hit 130mph indicated on speedo ?? but it does have fairing runs sweet , __________________ MONSTERMAN

26-09-2019, 06:29 AM	#12
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,803	Utopia , i cant remember the case saver supplier sorry ,, I think it was desmo times ??? fitting a 6 speed cluster would be lovely ,, could it be done ???? on my S4 i went the opposite way was 15-39 but lousy at slow speed buy could hit 150mph changed to 15-43 much better low speed and still cabable of 130mph __________________ MONSTERMAN

24-09-2019, 11:30 PM	#3
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	what are the relevant numbers for a 750SS? - mine would if revved hard in 4th not quite pull top revs in 5th on a level road - obviously with a fairing so you would need an extra tooth for none on the Monster.

25-09-2019, 08:51 AM	#6
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	Both are 520 pitch so a 39 would be just about right for the Monster - I will try a 39 when I rebuild my 750SS as only about 3 times in 30k miles have I found a road long enough to worry that I was not getting top revs in top and it would sharpen it up in the important 50 to 90 mph range

25-09-2019, 01:52 PM	#7
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,545	Like Jerry, on std 15/41 sprockets I often found myself searching for a non-existent sixth gear on my 750. For a while I toyed with fitting a gear indicator. When the carbon wheels went on I was obliged to fit a new rear sprocket so I specified a 40t, which I ran for a couple of years. This was much better in fifth gear, keeping the revs down a bit when fast cruising was required and reducing the tendency to search for that extra sixth gear. It also had the additional benefit of making first gear more usable in town traffic as it was that bit taller and lasted longer, such that in stop/start traffic you could hang on to it rather than constantly changing in and out of second gear. By this time the weight of the bike was down to just a tad over 160kg. The ultralight wheels span up quickly too, due to their reduced inertia .. an effect which was more noticeable than I had expected. Therefore I reckoned I could go to 15/39. I've tried that for the last couple of months but its still a bit early to be certain whether I prefer it or not. Motorway cruising is now a nicely relaxed affair though, and I seldom if ever hunt for that extra gear. First gear is even longer, which personally I quite like but it may not suit all tastes. I also quite like where that puts fourth gear, which seems just about right for your average twisty road (which I remember thinking on my way through from Douglas to Kirkmichael at this year's TT). Its never that simple though, is it ? Lately my attention has been directed towards the front sprocket. I've had a casesaver fitted for a few years but there is almost no room for it in the 750 crankcases with the 15t sprocket fitted. It will fit but the chain has a tendency to scrape it sometimes. This happens mostly on the overrun when the top run of the chain goes slack and it is made worse as the chain ages, wears a little and develops the odd tighter spot .. which they all do to some extent. Checking the bike over before leaving for the TT, I noticed some wear marks on a couple of inner link plates of the chain. It was too late to do much about it, but as the 39t rear sprocket was hanging on the shed wall awaiting fitment, I stuck that on and also made a fine tweek to the chain alignment. Well, I snapped that chain on that trip. Luckily, at walking pace and only 50yds from my tent at the campsite, rather than half way up the motorway at speed. Sorry for the long story but I mention all this because my latest decision has been to change to a 14t front sprocket, to give a bit more clearance on the casesaver. I could of course remove the casesaver and keep the 15/39 or 15/40 gearing that I like but .. well .. I daren't. And so, the upshot so far is that I'll be going to 14/39 and exploring the implications for chain/swingarm clearance with that set-up (I've had no clearance issues with the 15/39 btw ). Drive ratios for these various sprocket combos are as follows ... 15/41 = 2.73:1 15/40 = 2.67:1 15/39 = 2.60:1 14/39 = 2,79:1 So you can see that my latest 14/39 set-up will be slightly worse than the original 15/41 ....doh ! I may try and squeeze a 38 rear on at some stage, but I suspect chain clearance on the swingarm will be critical by then. Oh btw, this is with an ally swingarm fitted. So there you go. That's as much as I know, so far. Personally I think that a casesaver is a pretty essential bit of kit and I don't want to ditch it. Maybe I'll have to go back to sixth gear hunting or else fit that gear position indicator (just a top gear indicator would do, tbh). But note .. Jerry in particular .. the casesaver clearance issues above relate to the later style 750 crankcases with separate clutch slave. .. like your original 750, Jerry. It could be that the earlier style cases with integral clutch slave .. I believe, like your new 750, Jerry ? .. have more clearance around the front sprocket and might allow the 15t sprocket with casesaver to be fitted.

25-09-2019, 01:56 PM	#8
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,545	Oh, and the 15/39 combo will fit with the std, 100 links chain, but it leaves chain adjustment a bit marginal. After I snapped my chain I fitted a 98 link, which was better.

26-09-2019, 02:52 PM	#14
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,803	so a 6 speed cluster and selectors from a 620 or 800 or 695 would likely fit ok ????? ,,,400 was only 5 speed and im not sure a later 696 ,797 or scrambler 800 would be same line up __________________ MONSTERMAN

26-09-2019, 05:00 PM	#15
Flip Registered User Join Date: Mar 2010 Location: Beachtown Bike: M900 Posts: 2,188	This may or may not help in your search but either way it’s an interesting read if you’re that way inclined http://bradthebikeboy.blogspot.com/2...speed.html?m=1 __________________ You're perfect, yes, it's true- But without me you're only you!