Suzuki DR650 Regearing

Regearing a chain-driven motorcycle involves changing the Final Drive Ratio that, in turn, changes the engine's performance characteristics. Increasing the final drive ratio (i.e. gearing down) improves acceleration and low end torque. Decreasing the final drive ratio (i.e. gearing up) smooths top end performance generally increasing speed for highway applications. 

Chain driven motorcycles have three drive ratios. They are the Primary Drive Ratio, the Gear Box Ratios (one for each of gears 1 thru 5) and the Final Drive Ratios. The Final Drive Ratio is the relationship between the countershaft (front) sprocket and the drive (rear wheel) sprocket.

Below is a summary of all ratios as provided in the DR650 Service Manual.

• Primary Drive Ratio: 61:28, 2.178
• Gear Box Ratio (1st Gear): 29:12, 2.416
• Gear Box Ratio (2nd Gear): 26:16, 1.625
• Gear Box Ratio (3rd Gear): 26:21, 1.238
• Gear Box Ratio (4th Gear): 21:21, 1.00
• Gear Box Ratio (5th Gear): 19:23, 0.826
• Final Drive Ratio: 42:15, 2.80

The Final Drive Ratio of the post-1995 Suzuki DR650 is 2.80 which is calculated simply as the number of teeth of the drive sprocket (42) divided by the number of teeth of the countershaft sprocket (15).

As mentioned in other posts, I previously had a 2016 model DR650 and recently purchased a 2012 model year. As it related to the 2016 gearing, I retained and was perfectly satisfied with the stock gearing (42:15) over the term that I owned it. That ratio supported my dual sport rally hobby that generally requires 50% on-road and 50% off-road riding. 

As it relates to the 2012, the prior owner had changed the countershaft sprocket to a 14T, increasing the final drive ratio from 2.8 to 3.0. Increasing the ratio (i.e. gearing down) naturally has the affect of increasing the low-end torque/acceleration (good for off road; more rpms and grunt in the low gears) at a cost of top speed reduction and a loss in the smoothness of engine operation at the top end of the powerband (bad for on road; requires more rpms to achieve the lower top speed). 

Top Speed with 42T Drive Sprocket (Source - Gearing Commander):

• 13T Countershaft = 84.8 mph
• 14T Countershaft = 91.4 mph
• 15T Countershaft = 97.9 mph
• 16T Countershaft = 104.4 mph

Back in April 2016, I put my DR650 (stock gearing) to the top-speed test and after multiple attempts the motorcycle topped out at 93 mph, measured using a GPS device. (Suzuki DR650 Top Speed)

I ran the 42:14 ratio on my 2012 model year DR650 for about the first 750 miles, which included the two-day, 500 mile 2021 Trans Florida Dual Sport and Adventure Rally. Overall, as you may expect, the better grunt in the low end of the powerband was better on the trails. However, those improvements did not outweigh the cost on the top end. As mentioned, increasing the ratio deceases speed and engine smoothness in the upper powerband. The speed wasn't the issue. The issue was the loss of smooth engine performance as the motorcycle began to hit highway speeds (around 65 mph). This is how final drive ratios are weighed and it's an individual, case-by-case situation. I went back to the 42:15.

Good news/bad news:

The good news is that changing out countershaft sprockets is all of cheap, easy, and quick. One could change in and out of sprockets that are suitable for different rides quite easily. The sprockets run around $15 for a good aftermarket branded sprocket, like JT, and it's all of 3 bolts to remove/replace. That doesn't include the fact that the rear axle and chain pullers also require adjustment. 

The JTF.1448.15 Countershaft Sprocket was $15.25 on Amazon. 

The bad news is that there's a school of thought out there in motorcycle circles that it is preferable to address "increases" in Final Drive Ratios (i.e. generally installing smaller countershaft sprockets) by changing only the rear drive sprocket. The thought runs that smaller countershaft sprockets are bad in that they require a tighter turn at the drive shaft that affects both the chain life and tension on the drive shaft.

 Not to worry...

Ratios come down to simple math. 

A desired ratio of 3.0, the result of a 42/14 sprocket configuration, can be accomplished a number of ways. If 3.0 is desired and one feels it necessary to retain the 15 tooth (or higher) countershaft sprocket, then the desired ratio is achieved my multiplying that ratio x the countershaft sprocket teeth: 3.0 x 15 = 45 tooth drive sprocket. 

Similarly, a desired ratio of 3.2, the result of a 42/13 sprocket configuration, can be accomplished using the 15 tooth countershaft sprocket and a 48 tooth drive sprocket: 3.2 x 15 = 48 tooth drive sprocket.

You can do the math on other configurations. Or, JT Sprockets has a useful Gearing Ratio Cross Reference Chart available on their website that can be downloaded in .pdf and used as a reference.

Chain Length Considerations:

The stock chain on the post 1995 Suzuki DR650 is a DID525, 110 Links. Changes in sprockets may result in different chain lengths. For determining whether more (or less) links are required, consult the Gearing Commander Chain Links Calculator. 

Tusk D-Sports for the DR650

My recently purchased (used) 2012 Suzuki DR650 came with a set of Shinko 804/805 Big Block Tires (40% on road/60% off road). The 804 (front) was near new, the rear was a thousand miles away from replacement. 

I'm very familiar with the Shinkos. I had a set on a past KLR650 and the Shinkos were the tires that I purchased to replace the Original Equipment Tires on my former 2016 Suzuki DR650 that I purchased new. My problem with the Shinkos is, bottom line, I never liked them; not so much the 805 (rear) as the 804. Likely a great tire for more intermediate terrains, such as gravels and hardpans, the 804 isn't suitable for the soft sand, loam, mud that we have in Florida. Here are the Shinkos on my 2016 DR tearing up a muddy trail out on Devils Creek (Brooksville, Florida).

Notwithstanding my feelings for the Shinko, I gave them, as installed on my recently purchased DR, a shot on the 500 mile Trans Florida Rally in mid-November, first rally on the 2012 DR. Only to confirm what I used to think of them as stated above

So, between the Trans Florida Rally and upcoming Polar Bear Rally, I've slipped on a fresh set of tires more suitable for my needs. Those are the Tusk D-Sports (Front: 90/90-21 $54 @ RMATV, Rear: 130/90-17 $64 @ RMATV). Since RMATV released the D-Sport under it's Tusk Brand, I've had two sets of the D-Sports, these will be my third.

 

The width of the outermost knob is:

• Rear 135mm
• Front 90mm

The D-Sports are generally believed to fall into the 30% on road/70% off road category of dual sport tires, which seems right based on my experience with them. The tread pattern provides thick knobs that hookup and wide/deep grooves that channel the soft materials out the sides, thus maintaining traction on the sandy and muddy Florida trails and forest roads. 

Online reviews and comments can be found that suggest the D-Sport front isn't effective on soft surfaces, basically capable of washing. Well, all tires wash in sand and mud, but as a generality, those comments are simply not true. All you need to do is look at the tread pattern to see that those comments are wildly exaggerated. I believe the reason behind disparaging comments about this tire (and certain others) are that the comments are coming from riders that don't have experience riding in sand and mud as do I. That stuff is difficult for everyone.

The D-Sport tire compound seems very similar to the D-606 and has a consistent wear life to the Dunlops. The D-Sport carcass is relatively stiff compared to other aggressive DOT knobby tires such as the Kenda K760 TrakMasters, but I find it's stiffness to be similar to the D-606. 

Online reviews and comments that indicate stiffness to the point of difficulty in spooning or limited air-down levels are wildly exaggerated. I've spooned three sets with my basic hand spooning tools outlined for you below, no problemo.

As for on-road, the D-Sports, like the D-606 and K760s, are a long way from a smooth ride on the pavement. Rough and noisy. Similarly, like all other DOT knobby tread designs, caution should be exercised on wet pavement. Other than that, the the D-Sports hold-the-road pretty good. Here are the D-Sports (mounted on my classic 1985 KLR600) sticking to the off-camber hairpin turns of the Tail of the Dragon. 

Onward...

Off with the Shinkos and on with the D-Sports. 

The front, having only recently been installed came off easy; the fresh D-Sport spoon on just as easy. The rear, on the other hand, was a miserable job getting off the bead. Such is the case when they've been sitting a long time and compound wears off on the metal. I would not have been able to break the bead on the trail. It's a good thing I did the change.

Cleaning a rim in this condition this requires a combination of wire wheel and solvent. 

I use the same tire tools in my garage as I use on the trails. Specifically, those are the Stockton 3-Piece Tire Iron Kit ($30 at Revzilla and Cycle Gear) and the very popular Motion Pro Bead Buddy ($17 at many stores). 

Removing the tire carcass requires all three of the tools in the Stockton Kit (see below). The longer bar has a bend on one side for breaking a bead; a normal bead, not like the one I needed my 6" clamp to break. Spooning the tire on the rim requires only the longer bar and the Bead Buddy as shown in the photo above. The Bead Buddy holds the bead in place at one point, then the long bar is used to spoon it on. The long bar in the Stockton Kit is the key to successful spooning. It has a bead breaker bend on one side and a special lip on the other that avoids needing to push the bar under the bead too much and possibly pinch the tube. I never pinch a tube sticking to these two tools. 

Spooning the D-Sport onto the nicely cleaned rim, with a fresh strip and tube, was a cake walk. As I previously mentioned, online reviews and comments that indicate that the sidewalls and carcass are so stiff as to interfere with spooning are wildly exaggerated. .

I'm looking forward to reacclimating myself with the Tusk D-Sports in early January 2022 at the Polar Bear Dual Sport and Adventure Rally. 

Final thoughts on Dual Sport Tire Pricing:

Continental Twinduro TKC80:

When I first got into dual sport in a very serious way, there was only one tire that I consistently used: Continental Twinduro TKC80. I consider the 40/60 class Twinduro to be the gold standard in dual sport tires from a pure performance perspective. Unfortunately, as time passed, Continental took advantage of the tire's popularity and following and all but priced the tire out of the market. While I just paid $118 for the set of D-Sports, a set of Conti's would have run me $250. That wouldn't necessarily be the end of the world; However, the one issue that the Conti's have is a poor wear life relative to other options. In a pure 50-50 road vs trail riding environment, the lifespan of the Conti is no more than 2,500 miles. I will get twice the miles under the same conditions with the D-Sports. 

Look at it like this, if the $132 price delta between the D-Sport and the Conti were projected to an average 10,000 mile year, tire costs would be $264 for the D-Sports (two sets) and $1,000 for the Continentals (four sets). I'll leave out tubes and strips that need to be replaced with every tire change.

Dunlop D-606:

Another tire worthy of mention is the 10/90 Class Dunlop D-606. An excellent dual sport tire, although a more gnarly tread pattern for serious off road work. The D-606s represent another example of popular tires who's price went off the scale in response to a broadening dual sport following. In fact, I was running the D-606 on my 2016 Suzuki DR650 when I sold it in 2016. Like the Conti's, I actually can't remember what I paid for them; however, today the set is $235. I will mention that the D606s actually had an excellent wear life for a 10/90, perhaps the best I've had in that category. 

One interesting observation that I had while reviewing some old photos of my 2016 Suzuki DR650 was how close the 10/90 Dunlop D-606 (right) and 30/70D-Sport (left) Tread Patterns are. From my first hand experience, I think its safe to say that the compound (stiffness) is equally similar.

Shinko 804/805 Big Blocks:

Since this post started with a discussion of the Shinkos, I will add that the Shinkos are another tire where popularity and following resulted in a massive price increase. A set of Shinkos for the DR, although not under consideration for the reasons mentioned, would have run $236. For the record, their wear lives exceed all other tires mentioned in this post.

Tuning (Jetting) Suzuki DR650

I've just completed tuning (aka jetting) the stock Mikuni BST40 Constant Velocity ("CV") type carburetor on my recently purchased 2012 Suzuki DR650 (15,000 miles) using the James Dean JDJetting Kit No. JDS013. I have experience tuning my first DR650s, although the first involved a new, fresh off the showroom floor, 2016 model. I used the JD Kit on that one as well, based on information and reviews that I considered on the DR650 Forum.

I actually have quite a little experience tuning and jetting CV-type carburetors, having owned the two DRs, two KLRs and two Super Sherpas. When it comes to tuning normally aspirated fueling systems, I believe jetting kits are the way to go. Of course, there are several brands of kits other than the JD on the market for our consideration. In general, though, with jetting kits you typically get the following:

• A selection of Jets: A number of different jets sizes for different applications. The JD Kit came with Mikuni #140, #145, #150, #155 Main Jets and a replacement #42.5 Pilot Jet. With all those jets, the Kit supports future mods.

• Needles: Often kits include a motorcycle specific, or selection, of needles with different lengths and tappers. The JD Kit came with two height-adjustable needles with tappers to fit differing climates and altitudes.

• Guidance on tuning parts selection. 

ProCycle offers a bunch of nice kits, including one of their own design.

Essentially, tuning/jetting a carburetor encompasses configuring the fueling flow level (i.e. amount of gas) and the fueling ratio (i.e. the mix of fuel to air, usually around 1 part fuel to 15 part air) to a motorcycle in either it's stock form or modified form. Tuning/jetting involves selecting a combination of jets, needle, needle height, and fueling mixture. In some instances, it may also other involve physical modifications to the carburetor (e.g. the ProCycle Kit recommends drilling a small hole in the slide to adjust the CV vacuum level).  

Why jet/tune the DR (and many other brands/models)? The general answer is that carburetors do not provide constant and correct air-fuel mixtures to the engines they serve ... period!

• No-Modifications: It is widely believed (including by me) that the stock configuration of naturally aspirated motorcycles is designed too heavily in response to governmental fuel and emission standards resulting an excessively lean fueling mixtures. Tuning a richer mix (more fuel + less air) improves engine performance, but at the cost of fuel efficiency. I jetted my new, fresh off the showroom floor 2016 DR650 for this reason. 

• Modifications: Jetting is considered appropriate and may, in fact, be necessary when modifications are made to the motorcycle design. The BST40 is configured (fitted, so to speak) to work with the stock motorcycle and all it's parts. However, there are changes to the motorcycle that can interrupt that stock configuration (e.g. exhaust, air box, motor cams). The most common modifications are (i) air box modifications and (ii) installing performance enhancing exhaust systems. Modifications have the affect of changing the engine's needs in terms of the amount of fuel, the mix of fuel/air or both. Tuning and jetting adjusts the carburetor to accommodate a better running powertrain.

• Horsepower: NO! As some may suggest, jetting does not increase horsepower. Perhaps whatever modification giving rise to the jetting increases horses. But the jetting itself only reconfigures the carburetor to allow those performance enhancing modifications to work on the motorcycle.

In this most recent exercise, one issue on my recently purchased 2012 DR650 was Airbox Modifications. Generally, airbox modifications involve one or more of (i) removing the snorkel, (ii) cutting a hole in the air box, (iii) removing the airbox door, altogether and/or (iv) adding a hi-flow air filter. These modifications naturally increase airflow into the carburetor. Since the motorcycle engine ignites a specific mix (or ratio) of fuel and air (usually around 1 part air to 15 parts fuel), an increase in airflow will result in leaning the mix. Generally, we don't want to lean the mix, as the factory settings seem to result in too lean a mixture in stock configuration. 

The leaner mix arising from the air box modification requires adjustment to the mixture to "enrichen" by individually or a combination of (i) a larger main jet, (ii) raising the needle height, (iii) reducing the needles taper, and/or (iii) opening the fuel screw (aka mixture screw).

As it relates to my 2012 DR650, both the snorkel and airbox cover had been removed. Carburetor tuning changes by prior owners that I encountered, presumably to adjust the mix for the air box mods, included (i) increasing the main jet from a stock #140 to a #160 (increasing jet aperture and, therefore, fuel amount) and (ii) increasing the fuel to air mix to "richer" by turning the fuel mix screw out from 1 1/2 turns (stock configuration) to 2 1/4 turns. Both of these tuning actions pointed to enriching the fueling mix to compensation for the additional airflow from the modified airbox. 

I decided to replace the airbox cover with a new cover due to the dusty/sandy conditions that I encounter on the trails, but left the snorkel off. In addition, the motorcycle had a stutter/sputter in the upper end of the powertrain that was clearly a fueling mixture problem that needed correction. The condition is a symptom of an overly rich mixture. For these combined conditions, I set out to jet and tune the BST40.

As previously mentioned, I used the James Dean JDJetting Kit #JDS013 on both my 2016 and 2012 Suzuki DR650s; around $85 and available at ProCycle.

Here is a link to the Instructions from the JDS013 Kit. Kit components are:

• Main Jets (Mikuni Brand): 140 (Stock), 145, 150,155
• Pilot Jet (Mikuni Brand): 42.5
• Needles: Blue Coded (Rich), Red Coded (Lean)
• Needle Clip
• 4 Replacement Cap Screws
• Drill Bit for Slide Modification

My final configuration was: 

• 145 Main Jet
• 42.5 Pilot Jet
• Red Coded Needle @ #3 Groove
• 1.5 Turns on the Fueling Screw (note 1.5 is stock)

I followed the guidance in the JDJetting instructions (see link above) related to modification-types, climate and elevation. Jet selection and Fueling Screw adjustments, on the other hand, is and was a matter of trial and error irrespective of their instructions. The following procedural points and considerations may help through the trials:

1. Test Your Mods: Determine the affects of the modifications and performance parts along the entire powerband before jumping into jetting. Don't assume that a new pipe or a air box mod will require re-jetting; they may not. Understand what the affects are with some long test rides. A sluggish/sputtering throttle is the result of an overly rich mixture. Bogging is the result of an overly lean mixture. Jetting is dealing with the amount and mix of air and fuel so defining the issue before fixing it (or not) sort of goes without saying.

2. Clean It: Don't tune/jet a dirty carburetor. Make sure the carburetor on a used motorcycle is properly cleaned before jetting and tuning. Consider the guidance in The BST40 Bible on Adventure Rider. The author of that post did a better job on the disassembly and cleaning that I could do here.

3. Warm it Up: The ultimate tuning decisions and fine tuning adjustments need to be done when the motorcycle is in the state that it normally operates. That is, hot.

4. Ride It: You can not jet or tune your carburetor without taking it out on the road and testing it along the entire powerband. It may run fine at idle or twisting the throttle sitting on the stand. It would be different out on the road and, for that matter, pure luck to get the tuning zeroed in the first time. Consider this, when I used to work at the powersport dealerships our service personnel would advise service customers that the carb may have to be removed up to three times (and re-jetted) following road testing to get zeroed in on the proper tuning.

5. Needle Selection: In my opinion, needle adjustment and selection is low-hanging fruit in the tuning process. The needle, being right in the middle of things going on the carburetor, controls the majority of all throttle settings up and down the powerband. Needle height and taper affect mixture. Lowering the needs or expanding the taper make the mix leaner. Raising the needle or thinning the taper makes the mix richer. The needle taper is not adjustable; rather, some kits (including the JD) offer different needles with different tapers. All needles (for the BST40) have grooves to allow for lowering and raising using a simple C-clip. Start the trek on tuning the BST40 with the C-clip in the middle groove. 

6. Jet Selection: Jet selection governs the amount of fuel based on the size of its aperture (i.e. the hole going through the middle). Generally, the goal of jet selection is ultimately to select the smallest Main Jet (smallest aperture) that supports fueling adjustments necessary for the modifications or objectives. There may, in fact be a range of main jet sizes that seem to work, but fine tuning is going to result in better performance if the smallest in that range can be selected. The fueling screw, as discussed in the next point, can help identify the best jet for the job.

6. Fueling Screw: The fueling screw governs the air/fuel mixture (turn out = more fuel = richer; turn in = more air = leaner). Fueling mix is the "finest" of fine tuning the carburetor. It should be noted that, irrespective of the modifications, the fueling screw should generally be kept at or near the stock setting. In the case of the Suzuki DR650, that setting is 1 1/2 turns out (also the recommended initial setting in the JDJetting Kit). If the tuning requires turning the screw too far out or in from that setting (say 1/2 turn either way), the jet selection is probably incorrect. For example, if I needed to turn the fueling screw out 2 1/2 turns to zero in on a #145 Main Jet, I would bump the jet to a #150 (more fuel flow) and put the turns back to 1 1/2.

This photo ^ shared from The BST40 Bible.

Overall, tuning the BST40 is a process of understanding the affects that modifications have on the motorcycles performance along the entire powerband and then tuning them in. It's important to understand how the individual tuning elements interact in achieving the proper amount of fuel and the proper mixture of air and fuel ... and not going too far.

TransFlorida 2021 Part 2

 The first serious work for my DR650 Part 2 (this is my second DR650) was the November version of the 2021 Semi-Annual Trans Florida Adventure Rally, i.e. Part 2. 

The Rally launched out of Palatka, Florida (east cost) on Day 1 and terminated 250 miles later in Monticello, Florida. Day 2 was a different 230 mile track back to Palatka. I've ridden the TF for several years and, while the starting/finish has always been Palatka, the organizers place the mid-point in a different city; normally one of the cities along the Gulf, this track had us all the way up near Tallahassee!

Overall, I estimate a better than 50-50 dirt to pavement ratio, but that still equates to being in the gravel, dirt, sand and dust much longer. I've ridden the Trans Florida for several years and, quite frankly, this event was the best of the tracks they've prepared for us. 

While I stayed in a hotel in Monticello the first night, I had camp set up at Rodman Campground throughout the weekend. A little fishing on Friday and Monday in the Rodman Reserve and Rallying over the weekend.

Light and nimble being the best way to handle these types of events, I stripped the DR650 down to bare bones. No need for boxes and center stands and whatever else. Generally, all I need is one change of cloths and tube replacement tools for the Trans Florida.

I have some video of the starting line in Palatka.

The next event we're registered for is the Polar Bear Adventure Rally out of Keystone Heights, Florida on January 6-9.

Stay tuned.

Devils Creek DR (Part 2)

It's been a little over three years since selling my 2016 Suzuki DR650 (Devils Creek DR) in June 2018. Yesterday, after deciding to move back into the larger bore thumper, I purchased another DR650. This one is a 2012 model year with 16,000 miles. 

The seller listed the motorcycle for $5,500 on Facebook Market Place. We agreed on $4,500 for the 2012 DR that came with a load of adventure accessories, as follows:

• Acerbis 6.6 Gallon Tank (Seller said it was a 6.6 gallon tank. DR Group members believe it's a 5.3 gallon Acerbis Tank)
• Sargent Comfort Seat
• Tusk Pannier
• DirtRacks Sidecase Brackets and Tail Rack
• Pelican Top Case
• RallyWorx Screen
• Barkbuster Handguards
• JNS Bash Plate
• Warp 9 RacingWide Foot Pegs
• Unknown Brand Accessory Fog Lights
• SW Motech Center Stand
• Many recent maintenance and servicing items including the countershaft oil seal cover, but excluding the neutral sending unit modification, were also included. New battery, chain. The seller advises that it's using a 13t front and standard rear sprocket. However, I pulled the cover and it's a 14 tooth countershaft sprocket.

Hours-old Shinko 804 on the front. Desperate for a replacement on the rear. 

The KBB and NADA pricing put this model year at around $3,500--$3,800 in a retail setting, but the additional accessories, most of which I intend to keep, move the value into the price I paid. So, I'm fairly satisfied with the price. 

Additional photos:

The seller said the DR was running a 13/42 final drive ratio and included a new 14 tooth Sunstar Countershaft Sprocket in the deal. When I finally got the cover off and counted teeth, the countershaft sprocket had 14.

The front tire is a fresh Shinko E-804. The rear is a 75% worn E-805. In a private sale transaction, new tires are usually a good indicator as sellers usually don't go to the the expense of fresh rubber on a motorcycle that they plan to sell. 

The seller said he was not the first owner, but he did include in the listing that he rode the bike to California. When I checked the title at the transaction, I didn't notice that the last transfer was 12/3/2020 and the mileage on that date was 15,472. That indicates that he only put 894 miles on this DR; not exactly enough miles to get to Cali and back. 

Well, the true test will be on the trail and ...

The first serious ride will be the two-day Fall TransFlorida Adventure Rally that kicks off in Palatka, Florida on November 18.