Advice on DR177 and clutch
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Member
PX
Joined: 28 May 2020
Posts: 24
Location: Bognor Regis
Sat Sep 12, 2020 6:59 am quote
Apologies if this has been covered before. Wondered if anybody can help?

Ive finally run in my PX125 MY Disc 2003 having had a DR177 fitted (has a SIP Road 2.0 exhaust, 24mm carb, drilled air filter).

Performance wise i was not expecting a thrill machine from this setup but im getting loads of torque, no problem with head wind and it screams along at 62mph GPS verified (speedo is way out, stating 110kmh when it isnt).

When i say scream, its not noisy, but im clearly at the end of my gearing, as if its thrashing the balls of it.

I have heard much about the teeth of the clutch increasing gearing. I know the MY was fitted with a cosa clutch as standard, but does anybody know if it was a 20 or 21 tooth as standard. If its a 20 tooth, what can i expect from a 21 tooth, meaning will i be able to push maybe 5 mph more on my top end which would place me in the same position as my old p200 which would sit about 65/67 mph all day long.

Im happy with the upgrade but would like to sit at 60mph without thinking im trashing my 4th gear's peak. Cheers all malc
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2289

Sat Sep 12, 2020 7:35 am quote
Welcome to MV , I too was curious about the gains or what has to be done to get a bit bit higher on the speedo.
Hopefully someone will come along thats alot smarter than me and provide some insight.
Ossessionato
73 & 74 Rally, 76 ET3, 80 P200, 06 PX150, 61 Ser 2, 65 Silver Special, 86 & 96 Elite 80s, 2015 HD Road Glide Special, 2011 Ural Tourist
Joined: 18 Jan 2012
Posts: 3783
Location: Oceanside, CA
Sat Sep 12, 2020 8:07 am quote
I had nearly the same setup installed on my 2006 PX150. Clutch cog was a 20 tooth Cosa which gave me a top speed of 62. I now switched to a 22 tooth. Whatever clutch you have you can go 2 teeth higher without meshing problems. So if you have 21 like a 06 Stella you can jump to 23. 20 a 22.

For now I have a bolt on Malossi kit, 22 tooth clutch cog, 24/24 with heart drilled and I peg out at 66 GPS. For me I have to either port the cases to match or buy an overdrive ($250).

Check your clutch tooth count and maybe you can change it. Otherwise you’re in the same boat as me.
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2289

Sat Sep 12, 2020 8:18 am quote
MJRally wrote:
I had nearly the same setup installed on my 2006 PX150. Clutch cog was a 20 tooth Cosa which gave me a top speed of 62. I now switched to a 22 tooth. Whatever clutch you have you can go 2 teeth higher without meshing problems. So if you have 21 like a 06 Stella you can jump to 23. 20 a 22.

For now I have a bolt on Malossi kit, 22 tooth clutch cog, 24/24 with heart drilled and I peg out at 66 GPS. For me I have to either port the cases to match or buy an overdrive ($250).

Check your clutch tooth count and maybe you can change it. Otherwise you’re in the same boat as me.
MJ does this apply the same to the Vintage Vespa's? Thats all it takes is the replacement clutch? I'm interested.
Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 2903
Location: Nashville
Sat Sep 12, 2020 9:33 am quote
Lynnb wrote:
MJ does this apply the same to the Vintage Vespa's? Thats all it takes is the replacement clutch? I'm interested.
A replacement clutch and a motor powerful enough to drive it that much faster

If you want to figure out if you would benefit from some sort of upgearing, i.e. a toothier clutch, first thing you want to do is get a GSF Dyno graph to determine how much power you're getting. (Check out the Tips on Using GSF Dyno thread for how to do this).

Based on that, you can then determine if your motor has enough power to drive you that much faster (I have a spreadsheet that will calculate that, but that piece seems to have broken with a recent LibreOffice update and I haven't had a chance to debug it yet).

You might also consider adjusting just 4th gear if you're looking for a bit of an "overdrive" gear for distance riding, but that's obviously more involved than just swapping out clutches.
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2289

Sat Sep 12, 2020 9:47 am quote
chandlerman wrote:
Lynnb wrote:
MJ does this apply the same to the Vintage Vespa's? Thats all it takes is the replacement clutch? I'm interested.
A replacement clutch and a motor powerful enough to drive it that much faster

If you want to figure out if you would benefit from some sort of upgearing, i.e. a toothier clutch, first thing you want to do is get a GSF Dyno graph to determine how much power you're getting. (Check out the Tips on Using GSF Dyno thread for how to do this).

Based on that, you can then determine if your motor has enough power to drive you that much faster (I have a spreadsheet that will calculate that, but that piece seems to have broken with a recent LibreOffice update and I haven't had a chance to debug it yet).

You might also consider adjusting just 4th gear if you're looking for a bit of an "overdrive" gear for distance riding, but that's obviously more involved than just swapping out clutches.
Thanks Chandler , yes I think I just need some top end speed gearing so I can drop the revs a bit and gain 5 mph, gotta get the jetting correct first of course , but postal guys are 2-3 weeks anyway so ordering is a must now. These gents that are changing their carb setups is just mind boggling.
Member
PX
Joined: 28 May 2020
Posts: 24
Location: Bognor Regis
Sat Sep 12, 2020 10:40 am quote
MJRally wrote:
I had nearly the same setup installed on my 2006 PX150. Clutch cog was a 20 tooth Cosa which gave me a top speed of 62. I now switched to a 22 tooth. Whatever clutch you have you can go 2 teeth higher without meshing problems. So if you have 21 like a 06 Stella you can jump to 23. 20 a 22.

For now I have a bolt on Malossi kit, 22 tooth clutch cog, 24/24 with heart drilled and I peg out at 66 GPS. For me I have to either port the cases to match or buy an overdrive ($250).

Check your clutch tooth count and maybe you can change it. Otherwise you’re in the same boat as me.
Thanks for sharing this. Thats a pretty good speed for a bolt on setup without porting. Since yours isnt ported and comparable to my setup im gonna go ahead and do this 22 tooth setup. Can anybody recommend what cosa clutch on the market is the most reliable at the moment? As im only on a bolt on setup without radical tuning i dont think im gonna blow up a new clutch. I know i can just get the 22 clutch cog but i will replace the whole unit at the same time as after 17 years its due a new one.
Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1557
Location: UK (South East)
Sat Sep 12, 2020 10:05 pm quote
For that setup, a standard Cosa clutch would work well enough, but get the proper Piaggio or a SIP one. A 2003 PX125 should have a 20T clutch as standard, so choosing 21T or 22T will come down to power output and total weight
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2504
Location: London UK
Sun Sep 13, 2020 1:43 am quote
Get the best clutch that you can afford. Cheaper than buying it twice.

If you are a big guy get a 21 tooth. If you plan on porting the DR kit get a 22 tooth.
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