Thanks Diploman .Nfsnfs, Since your bike is new and not yet broken in, before you start thinking about changing the front forks you should get them operating well. As delivered, the 390 front forks are often misaligned at the factory.
Diploman, does this apply to all 390 dukes?Experience has shown that many/most 390's are delivered from the factory with a misalignment of the forks which causes binding and stiction. Apparently, at the factory the right (looking forward) fork leg is tightened on the spindle/axle first, then the spindle nut on the left leg is tightened down. This procedure - which really should go in the opposite sequence - results in a tension between the two fork legs that tends to pull each towards the center, and perturbs the alignment of the fork sliders with their respective legs.
The remedy: On the right fork leg there are two pinch bolts that tighten down on the spindle/axle. Loosen these bolts. Then, grasping the handlebar grips and applying the front brake, pump the forks up and down 6-8 times. Then retighten the pinch bolts. This allows the tension to release on the fork sliders and permits them to align naturally with the upper fork legs. The improvement in fork compliance is astonishing.
The Duke already has above average suspension travel with 150mm at both ends, but the stock suspension is horrible. The rear is harsh and the front end sags a huge amount. My forks dropped 75mm with me and gear on the bike. I've swapped to an R6 shock and now have some stiffer fork springs on the way. Handled the dirt very well with just the R6 shock but the front bottomed out way too easily which is why I've got for upgraded springs. They haven't arrived yet though so I'll have to report back.Did you ever change these forks? I've been thinking of the same concept, throwing some long travel dirt bike 43mm forks on. I honestly know nothing about how hard this would be or if it's a good or bad idea, but it seems like a fun project to turn a 390 into an adventure bike.
Because it's fun. Simple as that. Motorcycling doesn't have to be about getting from A to B in the easiest manner possible. For a lot of people it's about the journey.I will never understand why humans purchase a machine that is meant for a purpose, then Attempt to turn it into something that it is not. Is it because you liked the looks of it sitting on the showroom floor? Was it the price?
If you want a DRZ400 or Africa Twin, why not purchase one rather than convince others about the shortcomings/inadequacies of the machine that you own and are using for a purpose other than it was designed for?
Hey Cedar Drew,Can't comment on why the original poster wants enduro forks on the Duke. But for me, I run a group for riders dedicated to custom scrambler builds. We do it for the fun of it. We have Ducati's, MT03's, a W800, Triumph Bonevilles, SV650's, basically any naked bikes that have been converted to run a mix of road and dirt (aka Scramblers). It's incredibly fun and you have just as much fun riding to the dirt roads as you do on them. I've had plenty of Scramblers in the past as I tend to build, ride and then sell every couple of months just to keep things interesting. For my latest build, I specifically picked the Duke 390 for a number of reasons.
Size and weight - It's small and light. Much smaller and lighter than what the others guys in my group run. I'm a small/light guy and I don't like wrestling with 200kg bikes.
Ergonomics - It has a great riding position which lends itself well to off-road style riding, albeit it's too cramped to be able to comfortably ride standing on the pegs.
Power - Just the right amount to make road riding fun and not so much that you're constantly wheel spinning whilst on the dirt.
Ground clearance - No nasty header pipes or oil filters hanging underneath the engine, and you can buy bash plates already made.
Suspension travel - This little thing has 150mm front and rear. That's well above average for a road bike. It actually has more than the CB500X and Versys 300X.
Price - Second hand these are dirt cheap. I got mine for $2,600 AUD because it had a few scratches already from a carpark fall.
So those are the reasons I chose the bike before actually owning one. Once I bought it and test rode it a few things were realised. On road this bike is incredibly fun and one of the most fun bikes I've owned. The rear suspension felt cheap and harsh, but other than that I couldn't fault it. Based on this, I sourced an R6 shock and threw it on expecting that it would not only improve road riding performance and comfort, but that it would also benefit off road riding by being slightly longer and allowing me to tune the damping for additional comfort. Then it came to testing the bike off road. Almost everything from my above list was spot on. Size, weight, ergos, power, ground clearance. Where it fell quite short of expectations was suspension travel at the front end. 150mm should be plenty of travel. At the rear it was more than enough to never bottom out even loaded with a bit of gear, but when you take into account the highly excessive sag (especially for myself as a lightweight rider at 75kg), I was left with an effective travel at the front end that was far short of this number. This should be an easy fix. The travel is there, the valving is competent enough, it just needs more suitable springs. And so I've sourced some 0.75kg/mm fork springs to swap out with the 0.62kg/mm standard springs. If I set these up with about 30-40mm rider sag then I'll have an addional 110-120mm usable travel at 0.75kg/mm before I bottom out, which is significantly better than the 75-85mm of travel at 0.62kg/mm that I have now. This should be plenty enough to allow my bike to do what I'm asking of it and be a **** of a lot of fun to ride while doing so.
The reason I've specifically picked on the front forks of the standard Duke 390 is because I haven't had this issue before with any other road bike being used off road. And all of the other road bikes I've ridden off road have had LESS suspension travel and so my conclusion that the standard front springs are very sloppy is based on the ease at which they bottom out especially considering their long travel. If you Google or search on this site for the standard front sag numbers people are getting on this bike you pretty much come up with nothing, but take some measurements yourself and you'll be surprised.
Your forks are different to mine since I have an older Gen 1 Duke. As mine were closed cartridge forks I was able to gain about 20mm more height at the front by adding the YSS fork caps as they push the whole assembly further down through the fork outers, but with a fork like yours these will increase preload and not height. Finding someone to machine some extensions sounds like the way to go. I have a mate of mine who off roads his XSR700 up in Brisbane (where I'm from) and he's getting some extensions made up to give him more length at the front since he already has a longer shock a the rear (height adjustable Bitubo).Where are you guys based? I'm in Point Cook near Melbourne...
I’m running the std forks but with added preload (same effect as changing springs) plus have added thicker oil to counter the increased spring rate..I'm not sure what springs they run in the little Husky but check how much you're sagging at the front because where I made up most of my extra length was by using the stiffer springs so I wasn't losing all that height just by sitting on the bike.
I will never understand why humans purchase a machine that is meant for a purpose, then Attempt to turn it into something that it is not. Is it because you liked the looks of it sitting on the showroom floor? Was it the price?
If you want a DRZ400 or Africa Twin, why not purchase one rather than convince others about the shortcomings/inadequacies of the machine that you own and are using for a purpose other than it was designed for?
