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Hello

Right I'm stuck in the middle of a disagreement between my parts supplier and my scooter shop. Both are saying that they are right and the other is wrong.
Now none of this is my area of expertise and I'm stuck in the middle. Not knowing who is right. But it's rapidly heading to the point where each is going " well go on do what they say and see where it gets you !". ………. Each wanting the other to fail.
now I obviously don't want this as I've already spent a fortune on parts and if I'm totally honest I'm now flying on vapours. So I need to get it right first time round.
So it's come to me either choosing one over the other or saying " look just fit this ".
But I'm not going to lie I don't have a clue about gearings on hotted up motors.
I've tried to look it up but I'm not getting anywhere.
I hate these situations as both people are nice and I'm going to have to choose one. If I choose the wrong one the other is just going to say " ha see ".
I want or can afford that.


In the interests of world peace I'm not going to mention any names. As that's not fair on either and we all make mistakes. I would rather we were on the same team.

Hopefully someone has done a similar build , with wanting similar results, who can say this is what worked for them.

Here are the details

i have a '07 Vespa PX125 ( Disc )

These are the parts I have about to be fitted . Sent to me by my supplier after a lengthy chat about what I wanted my ride to do. My mechanic was like get the parts and I'll do it. So at that time no advice from him.

BGM 177
BGM 60 stroke crank
BGM Bigbox exhaust
24 carb
23 tooth banded clutch PX200 coda
BGM 36 tooth 4th gear
12 spring Cush drive primary repair kit

ideally what I want my scooter to do is be nice and torquie ( as torquie as possible ) but still give a higher top speed late 70s-early 80s if possible.
But I also will be doing a lot of twos up.

now I chatted to a very helpful bloke about short 4ths to give a smoother powerband and really liked the idea of that. So told my supplier and these parts are what he recommends and they were purchased.

Now the parts are here and there is a dispute. This is what I'm being told by the mechanic

That a 23 tooth clutch is wrong for this set up ( 125 )
the Cush repair won't work unless cog is changed.
the px125 comes with a 36 tooth 4th as stock so why buy another.

I've tried looking up this stuff but can't get a straight answer. I'm at a loss here.

if you've done this build or something similar and you wanted the same results as I'm after then I'd really appreciate your advice ?

cheers
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The 23 tooth won't fit the stock primary. Just a 20 or 22 tooth will I believe.

That said, I installed this overdrive kit on my PX and have been very happy with it.

https://www.sip-scootershop.com/en/product/gearbox-23-64-teeth-malossi-cosa-2-clutch_67167210?q=23/64%20Cosa

Comes with the bits to rebuild the Cush drive and made for the Cosa style clutches.

A quick search shows PX125s came with the 36 tooth 4th gear but it's also labeled as a short 4th for 200 gearboxes. With the stock 125 gearbox and the overdrive kit change, I can cruise 65mph all day long and get 72 mph full tuck (200lbs).

Didn't build my PX for two up riding but wanted higher top speeds without making the engine scream. If you are open to options, I'm a new fan of the SIP Road 3.0
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Molto Verboso
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125/150's come with the lower 4th gear, commonly swapped into tuned 200's to close up the 3rd-4th gap. Your 2007 late px125 does indeed already have this part.

There are even shorter 4th gears available aftermarket, but I don't think you will really need that nor be able to use it to any advantage.

Regarding primary gearing-

Your late px would have come with a 21/68 primary set, and a cosa style clutch assembly. Higher gearing would indeed be advantageous to your setup, however the 23 tooth cog on a stock 200 clutch is too large of a diameter to mesh with the 68 tooth gear on your Christmas tree.

This problem has two solutions- one, is an aftermarket 23 tooth cog sold by DRT, this will fit your clutch and mesh with the 68 tooth gear.

The other is to swap your Christmas tree gear with the 65 tooth gear from a 200. This will enable you to run the stock 23 tooth clutch cog from a 200.

Now, it is also worth noting that from my experience the 23/65 is usually just a hair high for a mildly tuned 125/150 setup. I usually recommend a 22/65 or a 23/68 or in more revvy setups or less touring oriented setups a 22/68.
Because of this, and because of what you have already bought, I would recommend just getting the 23 tooth drt cog, As that path will be cheaper and easier for you. If you want options to play around, you can get the 22 tooth cog as well.

As for top speed, in these gearing setups and the state of time you have described, expect 75mph, 80 might be a bit optimistic.
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Rob, I'm almost sure my 125GTR (VNL2T 1977) still has the original 67 teeth Christmas tree, now with a 23 teeth clutch BGM superstrong ... I was a bit surprised to know that the original clutch was only 19 teeth! Afaik GTR had a reduced gear ratio compared to 150 sprints.

Now, I don't hear anything strange, everything fine so far but, how can an original 67 accommodate such a wide spread of 19-23 teeth? I assume the cog diameter must be the same so this has only to do with shape/spacing of teeth no?

TIA
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A standard stlyle 23 tooth will not mesh with a stock 67 or 68 tooth gear.

Also, Piaggio never made a 19 tooth clutch gear, so you've got something miscounted there.

The 67 primary only ever shipped mated to a 22 tooth clutch gear. The factory ratios are 20/68, 21/68, 22/67, and 23/65

As far as working with a variety of gears, you can go down a few teeth from stock as they just mesh a little looser, and the 67 and 68 tooth gears are just slightly different, so a 22/68 works, but is just a hair tighter than factory tolerances.

In short, the 22/67 can work with any of the smaller gears than stock, it just engages slightly less of the gear teeth.

23/67 or 23/68 will not mesh, unless a looser aftermarket DRT gear is used that is designed to fit with the 67 and 68 tooth gears.
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Thanks for your input.

I think these reduced 19 teeth clutches were only for the EU market? all them say a 19/67 mesh:
https://www.vespa.name/vespa-model/vespa-125-gtr
http://www.scooterhelp.com/scooters/VNL2T.125gtr.html

And I have indeed a 23 teeth clutch on my 67 primary, bought on SC:
https://www.scooter-center.com/en/search?sSearch=BGM8098D
Clutch -BGM Pro Superstrong CNC, type Cosa2/FL - for primary gear 67/68 tooth- Vespa PX80, PX125, PX150, T5 125cc, Cosa, Sprint150, Rally180, GT125/GTR125, TS125, GL150, Super125 (VNC1, 11001-), Super150 - 23 tooth
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Cush drive primary repair kit will fit. Drilling out the rivets is sometimes easy.

Swap the new 36 cog (if yours is in good condition) for either a P200 65 ring gear or a DRT 23 cosa cog (made for 68 primary)
https://www.sip-scootershop.com/en/product/clutch-gear-cog-23-teeth-primary-drt-65-teeth-standard-67-68-teeth-drt-cosa-2-clutch_87475000
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PSMA wrote:
Thanks for your input.

I think these reduced 19 teeth clutches were only for the EU market? all them say a 19/67 mesh:
https://www.vespa.name/vespa-model/vespa-125-gtr
http://www.scooterhelp.com/scooters/VNL2T.125gtr.html
I'd be very careful on relying on secondary sources like that.

I've had my hands in numerous GT and GTR engines, and I have had to extensive research into cross references and what changes happened when. I wrote the model cross reference data that two major US shops use in their catalogs and/or website. It is very common for bits of heresay and incorrect tidbits to get out on the internet and be repeated, as is the case on these as not only are the numbers the same, the copy describing the models are, too.

That being said, if you have it, I'd love to see a picture of that 19 tooth gear.
Quote:
And I have indeed a 23 teeth clutch on my 67 primary, bought on SC:
https://www.scooter-center.com/en/search?sSearch=BGM8098D
Clutch -BGM Pro Superstrong CNC, type Cosa2/FL - for primary gear 67/68 tooth- Vespa PX80, PX125, PX150, T5 125cc, Cosa, Sprint150, Rally180, GT125/GTR125, TS125, GL150, Super125 (VNC1, 11001-), Super150 - 23 tooth
This is consistent with what I have said.
Rob Hodge wrote:
23/67 or 23/68 will not mesh, unless a looser aftermarket DRT gear is used that is designed to fit with the 67 and 68 tooth gears.
This is exactly what you have linked to- an aftermarket clutch with an aftermarket 23 tooth cog specifically designed to mesh with a 67 or 68 tooth Christmas tree gear.

A stock, OEM style 23 tooth clutch cog will not mesh with anything besides a 65 tooth gear.
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I've been through this a few times, you really want to mess with someone, put a p200 primary gear in there with a DRT 24 tooth clutch cog.

https://www.sip-scootershop.com/en/product/clutch-gear-cog-24-teeth-cosa-2-primary-standard-65-teeth_87478000
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Because of this, and because of what you have already bought, I would recommend just getting the 23 tooth drt cog, As that path will be cheaper and easier for you. If you want options to play around, you can get the 22 tooth cog as well.

As for top speed, in these gearing setups and the state of time you have described, expect 75mph, 80 might be a bit optimistic.
[/quote]

Cheers Rob I really appreciate your input.
Right so just to clarify a 23/68 ( the 68 being stock ) would give me a better result for a more touring set up. So would I be correct to say higher top speed less torque.
22/68 for more torque. But how much difference would you say there would be in top speed ? Would the 22/68 help keep me in the so called power band between 3rd and 4th ?

Just to throw another question in the mix. If I was riding two up what would be the better set up.

Thanks again
P.S I'm always optimistic when MPH is the conversation.
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rob hodge wrote:
That being said, if you have it, I'd love to see a picture of that 19 tooth gear. […] This is exactly what you have linked to- an aftermarket clutch with an aftermarket 23 tooth cog specifically designed to mesh with a 67 or 68 tooth Christmas tree gear.

A stock, OEM style 23 tooth clutch cog will not mesh with anything besides a 65 tooth gear.
Many thanks again Rob, that was very elucidating. I can't backup the 19 teeth info, I only got that from web, mine was already a 22 before the tune up to 177.

Ps: Sorry GET SOME for the OT, this didn't help with your problem
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PSMA wrote:
Sorry GET SOME for the OT, this didn't help with your problem
We're all part of the same gang mate 😃
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Molto Verboso
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GET SOME wrote:
Cheers Rob I really appreciate your input.
Right so just to clarify a 23/68 ( the 68 being stock ) would give me a better result for a more touring set up. So would I be correct to say higher top speed less torque.
22/68 for more torque. But how much difference would you say there would be in top speed ? Would the 22/68 help keep me in the so called power band between 3rd and 4th ?

Just to throw another question in the mix. If I was riding two up what would be the better set up.

Thanks again
P.S I'm always optimistic when MPH is the conversation.
Honestly, if your bike shipped with the 68, I would go with the 22, and if it shipped with the 67, go 23.

This has less to do with the primary gears themselves, but more to do with the gearbox they shipped with. The 67 gears were used on a gearbox with lower overall gearing and the 68 gears shipped on bikes that used the same gearbox as a 200.

Gearing is always a trade of top speed vs acceleration, untill you run out of power to keep the bike in the powerband and then higher gearing just gets slower. 23/68 would be right on the edge of that with your gearbox

If you do a 23/68 on your late gearbox 150, you will have too high gearing, you may find yourself dropping into 3rd to maintain speed up hills or into headwinds. This will be even more so when running two-up.

PMSA, It is worth noting that 22/67 is the stock gearing for the GT and GTR when looking at any source besides scoot.net, and that is what you're had when you got it.......
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Gears turn my cogs, in a good way.

Wanna get all hot n flustered? All turned around? Here, have a play with this baby... hours of fun to be had
http://gearingcalc.free.fr/

Just remember hills go up as well as down, wind resists & total tare loads make incalculable differences.


Final Gearing in Speedy - VBC1 2-port, with PX-efl box & 3.50x8" tyres.
Primary Drive: 24/63 Malossi (as they were the only ones that did it!)
PX xmas, with following: 12/57 (12.4), 13/40 (8.1), 17/37 (5.73), 21/37 (4.63)
1st is standard, 2nd is exceptionally long, 3rd is standard, 4th is exceptionally short
There is about 1800-2000rpm drop between 2nd & 3rd, & only 1200-1500rpm drop between 3rd & 4th
Is was hard to work out which gear I was in at times... but ohh soo much power from about 45km/h to 120km/h!

I had to completely change the style of how i was riding & how/when i changed gears...
This is from my early rides with that setup:
GPS said top was 117km/hr on first day, & it was quicker on day 2... Or so the GPS told me as it seized...

Hardest bit was remembering if i was in 3rd or 4th... 1200rpm rev drop between gears sure ensures the power stays on!
Im stoked at the final gearing setup... But for higher speed it would be tempting to get a longer primary.... But for twisties going 2-3-4 while under full power was simply awesome... Damn impressive!
Try to make yours quicker...
Try to make yours quicker...
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Wanna get all hot n flustered? All turned around?


You've just completely fried my brain ! I just thought I was figuring it all out and now you done this !!!!
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rob hodge wrote:
Now, it is also worth noting that from my experience the 23/65 is usually just a hair high for a mildly tuned 125/150 setup.
Hi Rob

Just one thing . When you say mildly tuned ( obviously there are out and out mentally tune engines out there ). But would you class a Bgm 177 kit with the 60 stroke crank pushing it to late 180s early 190s, ported with 24 carb and Bgm bigbox a mild tuned or the higher end of mild ? Ie maybe the hair high might work ? Or even a 64 ?

I was looking at the 23/64-65 set up.
As BGM were saying they had great results with the 64. But I don't want to run out of steam as it were.

Even with everyone's advice I'm still a bit lost .
But I really do appreciate all the advice I've received.
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GET SOME wrote:
Wanna get all hot n flustered? All turned around?


You've just completely fried my brain ! I just thought I was figuring it all out and now you done this !!!!
I'm here to help... what I'm helping is still unknown, but frying is some of it!
If you really want to cook the bacon as well, read this... modify VBC1. 2-port - Fuel... Gimme MORE FUEL ! (Page 2)
(Page 2-4 is mostly about gearing)

But basically, my thoughts are to get 3rd & 4th as CLOSE AS POSSIBLE together, then you can remain on the powerband no matter what happens.
hills, 2-up, headwind =mostly 3rd
Speed =4th & if you ever feel you are dropping off in speed or torque, then drop down a gear & keep going!
Only problem is taking off at lights can be a but slow, but you will quickly catch up & pass most others... then change into 2nd & leave em for dead!
⚠️ Last edited by SubEtherBASS on UTC; edited 1 time
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SubEtherBASS wrote:
Here is how I see it...

Grunt;
Highest = 14.4 hp
Amount in "usable rev range" = 10 hp

& the all important... SPEED !

1st = 34km/h (defo not full throttle)
2nd = 61 km/h (ditto)
3rd = 32 km/h to 108 km/h (fuk yeah!)
4th = about 45 km/h to 132 km/h (OMG that sounds fun, yet mildly scary)


Not bad for a wee 2-port VBC 150 motor!

Note: 1st & 2nd didn't get seperate runs, as only 3rd & 4th are checked... Ohh well.

I'm amazed that the calcs worked, it just appears to be revving about 8500 rpm, but I only calculated 7000rpm.

As you may see... In 4th I was watching the Dyno speed & saw.. 120, 125, 128... Revs getting higher... Then thought: Ohh well may as well see if it will go 130... Yip, damn that's really revving now... Button off time, I've got about 3000km to ride in a few days... That's enough.
Result: 132 km/h & STILL pushing 10 hp ! YEEHAA !
[/u]
Basically: about 97-98km/h is the sweetest spot to change between 3rd & 4th... you don't even notice the power difference! It's easy to forget which gear you are in!
Actual DYNO results.
Actual DYNO results.
With pretty colours , just coz it made more sense!
With pretty colours , just coz it made more sense!
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I live in the Yorkshire Dales so it is all up and down therefore I went 22/68. I still get 75mph on GPS and I've not gave it the full WOT yet. The TS1/RB25 guys were wondering how I could keep up with their 90mph machines. They were not 90mph machines!

22/68 will suit you if you are carrying weight/passenger. I call it semi automatic because I can leave it in 4th for the majority of a journey. Same spec as yours.
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Well I've bitten the bullet and made a choice. Be it right or wrong .
I had to make the jump as it's at the workshop and they can't have things sitting about.
So I've purchased a BGM 64 to go with my 23 clutch. I was going to go for either a 65 or 68 but BGM said they had good results with the 64 when using their kit and exhaust. As they make and sell all 3 I guess they'd have some experience without being bias.

If it's wrong well I guess I'll can mess about a bit as I'm a lot more wised up now than I was before this thread.

Anyone have any thoughts on this ?

Thanks for all the replies. I really is appreciated.
I'll report back when it goes tits up.
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It's probably a good choice. Can you go 22 with the 64 if need be? Changing clutches is easy compared with Christmas tree gears.
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I will pitch in my .2 c based on gearing, testing and comparisson between my own scooters with different gearing and even swapping 3 powerplants on a single scooter with various cylinder kits and gears.

In summary the larger displacement and shorter gears will give you that awesome torque. I recently opened a post on the geranal forum bragging that I picked up my 175lb son from school the entire year on 4 scooters and I talked about each scooter and how it felt.

The shorter geared PX150 Malossi 166 and Sprint Veloce (LML engine with new Malossi 177) felt the best. I was accelerating from traffic lights effortlessly with the short gears. The PX wasn't a slouch either because I was hitting 68mph speedometer with the two of us sitting upright in just a 1/4 mile distance.

My P200E is quick with the malossi 210 but it has a TERRIBLE rpm spot in 4th. It hits a brick wall of air at around 65 -70 mph. You have to tuck down a bit to get to pass that narrow RPM range otherwise the engine strugles to keep reving. In other words, the 4th gear is super tall.

Having a tall gear might not be a bad idea if you want to cruise at 60-65 mph. On the other hand, with the vespas with the 4th short gears, I can get to top speed relatively quick the problem is that at 65 mph(GPS) I am reving the hell out of them and therefore the Head temps are probably too high.

Having been on the two ends of the spectrum my next option is to try the aftermarket 23/64 gearing kit which i heard from many people that the 8% gearing increase is the sweet spot.

You have to determine what works best for you, figure out the type of riding that you do and go from there. Your BGM 177 from what I read is a decently torquey cylinder kit, my Malossi 166cc for instance is very weak on torque but it will certainly rev well in the higher rpm band.
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Thanks that useful input.

Yes I've heard good things about the BGM kit and I'm hoping that the 60 stroke crank will give it an extra kick up the backside too.

Theres just so many different riding styles and requirements that it's hard to figure it out. Until a week ago I hadn't even thought about it. So I'm jumping in at the deep end.
But as the kits about to go on I might as well do this at the same time.
Hopefully I've made the right decision.
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To an extent these choices are a matter of rider preference. Having read many tuning posts, it seems common to read that any given kit or gearing either sucks or is the absolute tits.

It's hard to know what's best for you until you get whatever you build running well and do some testing on the butt dino. Then you will have a baseline and be able to decide whether you need more of this or less of that.
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orwell84 wrote:
Tits.
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orwell84 wrote:
To an extent these choices are a matter of rider preference. Having read many tuning posts, it seems common to read that any given kit or gearing either sucks or is the absolute tits.

It's hard to know what's best for you until you get whatever you build running well and do some testing on the butt dino. Then you will have a baseline and be able to decide whether you need more of this or less of that.
Yes 100% correct. So let see. Hopefully we close first time round.
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I think you'll like the BGM. I've only put a few miles on this one since I installed it over the weekend, but it has lots of torque, a wide power band, and respectable peak horsepower. I'll guess it's 17-18HP off the butt dyno with a 60mm cut crank and 24/24 carb. I only have a SIP Road 2.0 on it for clearance (a downside of rolling on 8"s), but still quite respectable and was really nice riding last night.
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Interesting topic, just an FYI.
2011 onward px150 euro models come out with 20/68 primary and stock px200 gearbox
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jimscoot wrote:
Interesting topic, just an FYI.
2011 onward px150 euro models come out with 20/68 primary and stock px200 gearbox
20/68? Even the Stella came with a 21/68.
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chandlerman wrote:
20/68? Even the Stella came with a 21/68.
Yep piaggio euro spec 2011 onwards.
Early px150 yes 21/68
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chandlerman wrote:
I think you'll like the BGM. I've only put a few miles on this one since I installed it over the weekend, but it has lots of torque, a wide power band, and respectable peak horsepower. I'll guess it's 17-18HP off the butt dyno with a 60mm cut crank and 24/24 carb. I only have a SIP Road 2.0 on it for clearance (a downside of rolling on 8"s), but still quite respectable and was really nice riding last night.
Well that's given me some reassurance. I'll report back from the hospital !
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GET SOME wrote:
Well that's given me some reassurance. I'll report back from the hospital !
My motor is similar enough to yours that it should give you some idea of the power curve and how it performs.

Lucky for you, I needed to run an errand this morning so I took the VBB and grabbed a quick GSF Dyno recording. I'll have to double-check all the inputs, but it's about what I was expecting.

The peak power comes in way lower than it should (like...1500-2000 RPM's ) and it's not smooth once it gets up there, so I need to figure out what's up with that, but you get the general idea.
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chandlerman wrote:
The peak power comes in way lower than it should (like...1500-2000 RPM's ) and it's not smooth once it gets up there, so I need to figure out what's up with that, but you get the general idea.
Exhaust. SR II peaks early like that. Enough reason to buy another pipe
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Jack221 wrote:
Exhaust. SR II peaks early like that. Enough reason to buy another pipe
Polini box? SR 3? Sito+ Razz emoticon?

What's the brain trust say is my best option for a low-profile (8"-friendly) box these days?
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GET SOME wrote:
Hi Rob

Just one thing . When you say mildly tuned ( obviously there are out and out mentally tune engines out there ). But would you class a Bgm 177 kit with the 60 stroke crank pushing it to late 180s early 190s, ported with 24 carb and Bgm bigbox a mild tuned or the higher end of mild ? Ie maybe the hair high might work ? Or even a 64 ?

I was looking at the 23/64-65 set up.
As BGM were saying they had great results with the 64. But I don't want to run out of steam as it were.

Even with everyone's advice I'm still a bit lost .
But I really do appreciate all the advice I've received.
Honestly, sometimes the higher tuned setups require lower gearing; if they make their power at a higher RPM then the gearing can be too high and the 3-4 gap gets too large and the effective power band in 4th gear gets too narrow for the bike to be rideable.
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Thanks Rob

Well we're trying the 23/64 and a 36 4th.
Let's see.
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