gearbox for SPR

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Hi,

I am an owner of a SPR. I wanted to know what the best thing is to make the bike accelerate right away. Change the gearbox? as the first gear is long or would an other rear sprocket do the trick. The gear box is probably the most expensive thing to do and if so wich gearbox woulb be the best to fit?

Thanks,

Helmut SPR 34

-- Helmut Lampaert (contact_muty@hotmail.com), December 29, 2004

Answers

Helmut,

for your reference I have standard gear boxes in '02 F4 monopostos. One with the stock gearing, with no modifications and a second with higher gearing, RG3 exhaust, WTC chip. That is the basis for my offering here.

To move power down in the rev range (more grunt-less top end) either increase the tooth count on the rear sprocket or decrease the tooth count of the front. To Move the power up in the rev range (less grunt-more top end) the opposite is true. A rule of thumb is that a three tooth increase in the rear is approximately equal (though not mathimatically) to a 1 tooth decrease in the front. Changing the front will achieve larger differences in gearing than changes to the rear. Or changing the rear allows for finer adjustment of the gearing. Front changes are generally more complex/difficult than changes to the rear. Quick change and modular carrier/sprocket comdinations are available for rear gearing changes. This is especially true for the F4S

My info is that 15 teeth is the "better" front option as 14 teeth will cause the chain to wear at a higher rate due to the decreased radius of the smaller sprocket. How much more the chain will wear? I do not know. Figure in the quality of the chain and the level/intensity of the riding and for moderate to spirted riding with a highest quality chain that is well maintained and I would trust the smaller front sprocket option. I have however found the front sprockets available only thru dealers or MV special parts.

I have used the modular carrier/sprocket combination with sucess. I run 3 teeth higher on the rear primarily for a bit more power out of a corner, when lower (say 5000 to 6000 rpm) in the rev range. As far as making gearing changes to affect performance from a stop or from very low in the revs in first, gearing changes will make a noticable difference but will probably not completely cure the problem. Please experiment with the gearing. Work on finding where with each setup the power STARTS to come on, where it IS on and how far up the revs she pulls HARD. Working with the power characteristics of the bike will actually do more for your "sense" and "feel" than moving the power around mechanically for on the fly riding.

The gear box of the SPR may however contribute to this issue as well. FYI I have a standard gear box with less than 7000 miles on it (might even be under 6000) well maintained and unabused. I have posted here that I am interested in aquiring a close ratio gear box. New if available, dealer says I can build one from parts but as a unit it is not provided as an assembly by MV. Used from an SPR would be fine.

As I say above, please experiment with the gearing. However if you should find that option not to your liking. Go test ride a standard F4S 750 and see if the transmission gearing is more to your liking and need. If that were the case please contact me if you would be interested in working on the terms for an exchange?

I hope you find something here helpful. Good luck and as always...

Good Roads, Ride Well,

Scot/NC

-- Scot Hennon (smhennon@alltel.net), December 29, 2004.


hi helmut

i have a quick change sprocket carrier for all f4s on my website...not yet posted for the mv but its basically the same as the ducati model that i do have posted on my website. take a look at: www.norton-special-parts.de cheers and happy new year all

-- kelvin (norton-sp@gmx.com), December 30, 2004.


Hi Helmut, You have been given some very comprehensive advice so I wont waffle. The problem you are experiencing is also common on the Ducati 916/996 SPS. This is primarily due to the fact that like your SPR these bikes were designed with track work in mind. All that said and done I dropped only one tooth off the front sprocket of my SPS Duc and that fixed the proble spot on. I did not notice any undue chain or sprocket wear (though it makes sense it would add a small amount). A front sproket change is worth a try given the minimal cost. Let us know how you go. Cheers Brett

-- Brett (bfitzpatrick@psm.net .au), December 30, 2004.

Hi hemut, I am an owner of a SPR too! N 219/300 What is your number? Best regards Arnaud

-- (agustamv2003@yahoo.com), January 05, 2005.

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