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I've just rebuilt top and bottom end of my 150 Special (Pacemaker) and was wondering what top speed I can realistically expect with different gearboxes.

Spec is: AF 200cc Aluminium cylinder kit (for smallblock), GP race crank, standard weight SIL flywheel, 22mm Jetex, RAM air filter on normal air hose and an AF 42mm sloping Clubman. Gearbox is the original Pacemaker but I have an SX200 gearbox on my shelf which I'm thinking of using instead and I also have an AF lightweight flywheel on the shelf.

According to ScooterHelp website on the Pacemaker gearbox at 6krevs my speed will be 54mph and with an SX200 gearbox my speed will be 63mph at 6k revs. So is 63mph at 6k revs realistic with the SX200 gearbox???

I appreciate that time will tell but I've only just started running in today.

Only if there is enough power / torque to pull that gearing.

Your pacemaker box will be 5.65 with 15x46 - the SX with the same sprockets is 4.8 - that's a big jump.

I'd be inclined to use the pacemaker and if you're finding it too revvy, fit a larger front sprocket (46 x17 would give you just under 5 for your final drive).

I'd use the Sx box it should pull that gearing nee bother. My 186 did/does, when it's on the road and not in bits again, ffs.

I reckon the SX box would be a good way to limit wear on 4th gear

MickYork wrote:I'd be inclined to use the pacemaker and if you're finding it too revvy, fit a larger front sprocket (46 x17 would give you just under 5 for your final drive).

Aye, that.

I'd be tempted to go 16/47 (5.29) and enjoy letting it rev easily, which will suit the clubman, rather than struggling to pull 4th correctly. Don't forget that 5.2 is the correct ratio for both the Innocenti GP200 and SIL factory stage 4 motor with bigbore (similar to clubman), and that tuning and power delivery should be similar to yours. 5.29 allows for the CCA that you lack compared to the 200s.

Either way, good luck with it.

Adam

Cheers for the suggestions guys, so I’ll either go for 5.65, 5.29, 4.98 or 4.81 final drive

Adam_Winstone wrote:I'd be tempted to go 16/47 (5.29) and enjoy letting it rev easily, which will suit the clubman, rather than struggling to pull 4th correctly. Don't forget that 5.2 is the correct ratio for both the Innocenti GP200 and SIL factory stage 4 motor with bigbore (similar to clubman), and that tuning and power delivery should be similar to yours. 5.29 allows for the CCA that you lack compared to the 200s.

Either way, good luck with it.

Adam

Cheers Adam but what is CCA??

davla wrote:Cheers for the suggestions guys, so I’ll either go for 5.65, 5.29, 4.98 or 4.81 final drive

Yes definitely.

Seriously, Adam knows what he's on about and to be honest I hadn't read what I was agreeing with properly. I was thinking about 46 and 16, which is nearly what Adam is suggesting anyway.

It's a common mistake to use gearbox calculators and think time you can get a speed from up-gearing. I've done it myself a couple of times and had to change it back to something lower.

With the set up you have I'd definitely not drop below 5:1

CCA means that Adam has fat fingers that are no good for porting

It was simply meant to read CC

Adam

Many years ago the first course of action after tuning was to upgear by raising the front sprocket to 16. This is a nice ride on a Pacemaker box. This is still good advice today and is the least expensive way of raising the gearing. If your chain has enough slack it will fit or otherwise you will need a longer chain.
The temptation is to go too far and it's embarrassing when you then get left behind on inclines because there is not enough power to drive the higher gear ratio. Been there, done it and got lots of T shirts !

^... me too

if your after a higher top speed then a close ratio gearbox would help to achieve this, an af close ratio is a good gearbox, based on the indian gp 200 gearbox, although they are about to release there own 5 speed gearbox which would allow you to go even faster, but remember that the engine will need to have enough power to pull the final drive ratio that you use, how the engine is set up and tuned will affect how much pulling power its got and over what rev range, personally i prefer an expansion exhaust as the extra power higher in the revs is nice, and with the right final drive ratio your can stay in the powerband after you have changed up to the next gear and it will pull nicely, obviously you must take into account how big and heavy you are. do you ride 2 up and is the area you mostly ride in flat, all things to take into account when selecting your final drive ratio, as others have said its easy to think your engine will pull higher gearing until you try it, then you find its fast in gear 1, 2 and 3 but dies when you put it in 4th .
holty

Cheers again for the replies. I'll stick with the Pacemaker box until I've run it in and then throw in the SX200 box to see how it goes. If it struggles I'll go back to the Pacemaker and change the front sprocket and go somewhere in-between.

im running pacemaker box with 18 x47 on a small block so you finish with sx final drive 4.8 well worth trying ,im pleased with the overall performace in every gear

I did the C2c quite a few years ago on my Series 3 with my Tv2 motor Mugello 186, 42 mil clubman and it pulled like a train and coped remarkably well with all the passes in 3rd/ 4th gear I must add. It was going that well I was asked if the barrel had been tuned? Which was a no, just bolted straight on. While I respect other people's opinions and knowledge in these matters please don't take the piss out of other people's own experiences it really fucks me off.

Anyway the very best of luck in your quest of gearing correctly.

Have a nice evening everyone.

Cgt75b............................

Cgt75b wrote:... and coped remarkably well with all the passes in 3rd/ 4th gear I must add...

That mustn't have been a year that it went over Hardknott Pass, Paddy

I think most years back in the day it went over hardknott Paul. It seems to have softened somewhat in recent years.

Still a great riding event though.

Cgt75b.

davla wrote:Cheers again for the replies. I'll stick with the Pacemaker box until I've run it in and then throw in the SX200 box to see how it goes. If it struggles I'll go back to the Pacemaker and change the front sprocket and go somewhere in-between.

This all depends on the specification of the porting and any changes that you might make to your set-up configuration (pipe etc.). Capacity alone is almost impossible to judge gearing requirement from as it all depends on the rev range that the motor and pipe produce power at, which is why a 225's requirement can range from 5.2 (recommendation for a TS1225 with revvy pipe) to 4.4 (same TS1 225 with very torque'y pipe)... and depending on 1-up, 2-up, large 1-up + luggage, flat area, hilly area, riding style, etc.

You could well find that the Pacemaker (15/46) is too short, depending on the above factors, and/or the SX200 15/46 too long (again depending on the above factors). The Pacemaker 16/46 (stretched 80 chain or 81 with pull down tensioner) is the a half way house that should perform pretty well for all of those factors. That said, a pal in my local club had one of the 175 steel lined alloy kits from AF, which he used very reliably for about 6K miles (and it was fast on the standard Pacemaker 15/46, as the AF porting revved well with the extended exhaust period)... but then ran into repeated piston/ring failures as the hard chrome thin rings kept wearing the soft iron liner. My pal went through about 10 pistons and a couple of rebore at 175, then took it to 200 to reduce the % exhaust width to bore ratio, had the same happen, then went back to an iron barrel and used it reliably from then on. Strange that this kit ran so well for 6K, then had so many repeat wear and ring breakage issues (the port was a good oval shape to start with but after a while the rings would wear the port square until it couldn't cope anymore, then...!).

Adam

PS - If Cgt75b or others though that my previous comment was intended to 'take the piss' then I apologise as that was not my intention.