Join Date: Sep 2011
Location: Queensland, Australia
Thanked 84 Times in 35 Posts
Sharing my impressions of C90 into C50 final drive mod.
I've had this mod installed for about 500km now. This post is only going to echo much that's already been said on the subject, but I'll chip in my two cents worth of feedback for the benefit of anybody contemplating a conversion but hasn't done it yet and may be wondering what to expect.
Why I did it in the first place? Lots of open highway and relatively few hills in my area left me feeling that my C50 was about one gear short of a full box at the top end. Problem solved. C90 gearing is worth near-as-dammit one full gear more. Quieter, smoother, less vibration in handlebars and mirrors at cruise. And cruise faster than before if you want, with little apparent effort. Gotta be a reduction in engine wear, too, I figure.
Sluggishness with the higher gearing? Sometimes mentioned, but this is actually a misconception. Sure, the acceleration in 5th gear is less lively than before, but remember this is now a whole gear higher like having 6th so it's to be expected. Kick down to 4th, you're about almost exactly where "old" 5th used to be in the gear range, and turn up the wick; you've lost nothing! all the former zip is still there.
The maybe unexpected fringe benefit of the drive mod is how much more useful the lower gears become as well. 4th comes up as only about 4% lower than "old" 5th and as such becomes an excellent gear for overtaking slower traffic on long roads, plenty of poke but no feeling of urgency to change up straight after. First gear becomes smoother an less inclined to jerk and snatch. There seems to be smoother progression through the gears and each gear seems to fit a situation more aptly.
My previous riding style with stock drive seemed to be; start in 1st/click up to 5th in no time flat/ stay there til next time I stop. Now I feel like I've got a practical five speed gearbox and I can work it to my best advantage. Engine braking is a little smoother and I can confidently go well down in gears at corners without so much backlash or risk of lockup if the road's slippery.
Some have mentioned a little more clutch feathering to get moving from standstill, but honestly I've found the difference generally so little as to be almost un-noticeable, and only mildly apparent even starting with a trailer.
Hill starts may tell a different story but I can't comment as I don't have a lot of 'em around here.
I sometimes tow a trailer, moderate size and weight old school steel construction, and the higher top gear handles this no problem, steady cruise 110km/hr - 68mph actual (not Suzi speedo-error indicated) is quite comfortable and unstressed on a reasonably flat highway.
Fuel economy? A very open question! Depends on riding style and use. I've not undertaken any stringent tests on this. When I first got the new drive up and running, I tended to give the bike some stick to try it out and see if anything broke before I got too far from home, and also dragged my trailer around a bit to check how it handled it. After the first couple of tank top-ups it appeared that I was getting very similar figures with the trailer on as I used to get with the trailer off. I did not refine that into a specific figure but I think that counts as an improvement. It certainly did not get worse!
Worth the cost? (variable) In most cases I think more than likely yes. Unless you ride your bike only very little and local short haul. Some, like me, have done the mod when our stock drives have chewed out the rear coupling and we had to buy parts and do work anyway, in which case the difference between stock and mod refitment might be as little as 100-150 bucks or so, well worth it if you do it that way.
This conversion works very well on the VL800, so well one could wonder why Suzuki hasn't offered something same or similar at least as an OEM alternative option, bearing in mind this is a cruiser and tourer?
And I'm left with an odd thought, don't know if anybody else has pondered this, but if C90 gearing works so well on a C50, why is a C90 so relatively undergeared? With bags more hp and torque than a VL800, you'd think it would have much longer legs. I confess I've never ridden a C90 so I don't know how they feel.
'08 Boulevard C50
'84 Kwaka GPZ900R
No, sir, it's not a leak, it's a protective oily sheen