OP
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1978 Vespa p200e, Rally 200, 1980 Bajaj Chetak
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Location: Colorado Springs, CO
 
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1978 Vespa p200e, Rally 200, 1980 Bajaj Chetak
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Location: Colorado Springs, CO
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Hey! I'll start off and just admit I don't know much about gearing and, frankly, don't know where to start to learn more.

I'm rebuilding my 1978 p200e engine and, in addition to bearings and gaskets etc etc, new parts include:

1: Polini 210 cast iron w/ the aluminum head
2: Polini Box exhaust
3: 26/26 spaco carb (and a couple 24/24's)
4: Polini Venturi kit
5: Mazzucheli 57mm crank
6: that ridiculous tall Pinasco carb cover

Standard p200 gearing, standard clutch

I am at altitude and don't want to sacrifice too much top speed, so my question is:

Do I need to look at T5 short 4ths, cosa clutches, Upgear kits, different gearing at all?

While it's open I might as well get some information on that. Thanks!
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parallelogramerist
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parallelogramerist
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That old cast iron Polini kit has TONS of torque. It's probably the only cylinder kit out there that i probably would not swap a short 36 tooth 4th into. It should be totally fine with the stock 35T 4th....but you said say that you do live at elevation, and that does rob a fair amount of power. So it probably wouldn't hurt to toss in a 36T 4th (out of a P125)? You might sacrifice a couple mph on a flat road, but you would probably gain 5mph on any sort of hill. Other than that, you don't have to switch out any other gears or clutches on your engine.

And be aware that the cast iron polini doesn't dissipate the heat very well, so make sure your jetting is spot on! An ignition kit with variable timing would help with that.
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Molto Verboso
One or two fun scoots....nothing too precious
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Molto Verboso
One or two fun scoots....nothing too precious
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whodatschrome wrote:
That old cast iron Polini kit has TONS of torque. It's probably the only cylinder kit out there that i probably would not swap a short 36 tooth 4th into. It should be totally fine with the stock 35T 4th....but you said say that you do live at elevation, and that does rob a fair amount of power. So it probably wouldn't hurt to toss in a 36T 4th (out of a P125)? You might sacrifice a couple mph on a flat road, but you would probably gain 5mph on any sort of hill. Other than that, you don't have to switch out any other gears or clutches on your engine.

And be aware that the cast iron polini doesn't dissipate the heat very well, so make sure your jetting is spot on! An ignition kit with variable timing would help with that.
I agree with whodat, adding that the Pinasco is the other torquey kit where this applies. I have installed a 36T 4th in my Pinasco 225, purely to bring 3rd and 4th closer together, but then I upgeared the whole lot with 24/63 Malossi gearing. With your Polini 210 and a 36T 4th in place, you do have the option to go 24T on the clutch, without changing the primary. This will counter the slight loss of top end on the flat, and if you don't like it, it's very easy to change back to 23T clutch. Changing the primary is a PITA IMHO.
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parallelogramerist
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parallelogramerist
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swa45 wrote:
I agree with whodat, adding that the Pinasco is the other torquey kit where this applies. I have installed a 36T 4th in my Pinasco 225, purely to bring 3rd and 4th closer together, but then I upgeared the whole lot with 24/63 Malossi gearing. With your Polini 210 and a 36T 4th in place, you do have the option to go 24T on the clutch, without changing the primary. This will counter the slight loss of top end on the flat, and if you don't like it, it's very easy to change back to 23T clutch. Changing the primary is a PITA IMHO.
I agree that a 24T clutch could be a great match with a Polini 210 along with a 36T 4th. The only variable for me would be while elevation thing. But at sea level, i think it would be a great combo.
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Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
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Lucky
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Knowing nothing about how or where you ride, we can't actually provide you any useful advice. Are you intending to race from stoplight to stoplight? Running out to the taco truck and liquor store? Long, leisurely cruising? Jumping onto the highway, then trying not to get steamrolled by a semi? Trying not to annoy the neighbors? Trying to piss off the neighbors?

All of those suggest potentially different gearing setups.

Personally, I'd stick with the stock gearing if I were you, until you *know* that it's not a good fit for how you're actually riding. If you decide you don't like it, you can tweak things effectively by changing the clutch cog, which is an easy and relatively cheap swap.

But you might also decide you're fine with it, so no need to fix what ain't broken.
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1978 Vespa p200e, Rally 200, 1980 Bajaj Chetak
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1978 Vespa p200e, Rally 200, 1980 Bajaj Chetak
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This is all great advice. Thank you!

It's the "new" cast-iron 2022 Polini 210, which I think just means a different piston and fancy aluminum head. Which, I'm hoping helps a little with the heat dissipation.

Riding style: Typically short runs in Denver but we also have big rallies and long rides. I was leaning toward a relatively basic set up for reliability and a little bump in power. I won't be drag racing anytime soon haha.

I also found a 37t DRT 4th gear cog in a parts bin, but it's sounding like that might be pretty short.

So, if I'm understanding correctly, go with stock gearing with maybe a 24t clutch. Is that correct? Or would I need the 36t 4th in there as well?

This is helping me demystify gearing a little bit, so thanks again everyone
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UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
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I went and found ScooterCenter's dyno curve for the Polini 210. It's a little more aggressively set up than you're going for, but it's a nice wide curve. I don't think you need to worry about struggling to make power on the low end of 4th with it.

I think for your purposes, I'd recommend stock gearing. With careful setup and proper port timings, you'll be able to hit 70 MPH, at last on the flat, without 50-60 feeling like something might explode. The problem with dropping 4th down is that it makes cruising speed slower or louder than it would be normally.

I like the stock P200 gearing, even with a racy top end on mine (and no other upgrades but a SIP Road 3). It's not crazy-fast like my other bikes, but is a really nice bike to get out and eat up miles on, while still having plenty of peak power when I want/need it.

If you add a bellmouth/venturi to your carb, it'll draw as much air as the rotary valve will let you can push through the motor, too, thus making the altitude piece basically irrelevant.

And all these cylinders have both aluminum pistons and heads, regardless of barrel composition. You'll still have all the limitations of cast iron (nothing over 350F on the CHT), but all the benefits, too (muriatic acid to remove the smeared aluminum from the barrel, clean up the piston and rings, then you're back on the road).
Thanks, Scooter-Center!
Thanks, Scooter-Center!
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Johnny Two Tone
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Johnny Two Tone
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my standard reply = if you live near and deal with hills, you want the 36t 4th
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Molto Verboso
One or two fun scoots....nothing too precious
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Molto Verboso
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I favour the 36T 4th on an otherwise stock P200 gearbox, but that's just personal preference. It brings 4th gear closer to 3rd. I've then used a 24T clutch to compensate at the top end, and to give it longer legs across the range.

As Chandler said, the Polini will pull the 35T 4th no problem, even with a 24T clutch.
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Johnny Two Tone
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swa45 wrote:
I favour the 36T 4th on an otherwise stock P200 gearbox, but that's just personal preference. It brings 4th gear closer to 3rd. I've then used a 24T clutch to compensate at the top end, and to give it longer legs across the range.

As Chandler said, the Polini will pull the 35T 4th no problem, even with a 24T clutch.
this is the way. bring 4th closer to 3rd and move the whole thing up or down as needed. so much easier to fix it when it's all apart and make it right. you'll never go wrong with the 36t if you can adjust your primary drive with the clutch.
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parallelogramerist
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parallelogramerist
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I have to admit i'm not familiar with the new cast iron kit. I had the old version on my P2. My setup at the time was 24/24 carb, stock air filter, Sito+, 35 tooth 4th, stock cylinder head. It had plenty of torque near sea level. I rode over a Mt. Hood (in oregon) a couple times (5000') and it pulled the steep climbs with no problems. No doubt it would have been more optimal to have a 36T 4th and a 24T clutch, but i was ignorant of gearing options at the time. I now automatically install short 4th gears in all of my builds...whether they have a cylinder kit or not.

And hard pass on the DRT 37 tooth 4th gear unless you're planning on building a high RPM engine for the track. I've also heard that that the 37T isn't recommended for higher horsepower builds. I think it's because the sprocket teeth get smaller as the gearing goes down (and the tooth count goes up). I do have a 37t in my T5 and it does work fantastic for my particular build.
⚠️ Last edited by whodatschrome on UTC; edited 1 time
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Ossessionato
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Ossessionato
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for what is it worth and works well for me with the pre 2016 Malossi 210

24.24g HRS vortex.
Polini BOX ceramic coated.

now what i did for gearing was to use a long 3rd and a short 4th. The malossi is an absolute monster in 3rd and pulls is damn well. The gap is even shorter between 3rd and 4th.

Just something to think about for your Polini setup!
⚠️ Last edited by GickSpeed on UTC; edited 1 time
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bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
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Quote:
use a long 3rd and a short 4th
This makes a ton of sense, and is probably the way I'd go. With most kits, you run out of gearing in third way before you run out in fourth.
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Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
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Jet Eye Master
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Back in the day, the iron polini 207 with a malossi 210 piston was the ultimate set up. Even with a longstroke crank and tuned cylinder it still had torque to pull a 35 tooth.

If you have a rev counter it's fairly easy to tell how appropriate your gearing is.
Go WOT in 3rd, check the max rpm. Same in 4th, check the max rpm. 500 rpm difference is the ideal for general use.
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