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DisTech 03-16-2013 10:12 PM

DisTech's DR790 build
Hello friends!

Sent ProCycle my DR650 head and jug last week.

Taking advantage of the super easy access to the starter

and finally remove the goose honk by greasing the "self lubricating" sleeve.

Going to split the case to check bearings and transmission. Ordered a flywheel puller, but damn if ProCycle didn't get everything back to me before the puller arrived! :eek1
  • DR790 Big Bore Kit
  • Big Valve Head
  • Web Cam 190


DisTech 03-16-2013 10:27 PM

Picked up a 2006 RMZ450 front end last year. Before bolting them on the DR790 I'll replace the seals and see if I need different springs.

RockyMountainATV has video's that show exactly how to rebuild these forks,
Fork seals, change on motorcycle part 1 (of 2), twin chamber,
Fork seals, change on motorcycle part 2 (of 2), twin chamber.

wrk2surf 03-16-2013 10:40 PM

All these DR BIG jobs are making me want one.. looking forward to this one

DisTech 03-16-2013 11:36 PM

Fork Springs
So how do you figure out what rate your ebay fork springs have? Not being the first person to ask this, Google lead me here
My variation on the ThumperTalk designs for putting load on the spring. 1" EMT in vise, 5/8" ATR, nuts and washers.

One of the calcs wants a measurement at 20% deflection so 2.5" of 12.2" travel works for me.

2.5" deflection was from a BOSS 302 head (50.5lb) and 10lb dumbbell.

Zip tied a caliper to a stick and zeroed it at this point.

Changed the 10lb out for a 50lb.

Caliper reads 39.28mm difference.

<iframe width='860' height='960' frameborder='0' src=' 1E&output=html&widget=true'></iframe>

The stock 2006 RMZ450 fork spring rate is .47kg/mm.

In the red shaded section you don't need to weigh anything or build the contraption and that calc look like it worked pretty well. Depending on what modulus of rigidity you use, either side of .47kg/mm.

The blue shaded section requires weighing and measuring via the contraption. calc used the delta between two measurements showed a rate of .4619kg/mm. ThumperTalk simple rate calc's suffered from my ability to accurately weigh things. I ordered a digital fish hand scale that can measure down to the ounce and will update the sheet with accurate weights.

Anyway, it looks like the forks have stock springs in them. Ordered .52kg/mm springs, seals, wipers and 5wt oil today.

The fish scale arrived so I re-weighed the weights and head for more accurate data. The spring rate calc sheet has been updated and now the simple rates are close to the rate of the springs I ordered :bluduh... I'm betting the rate calc that uses a delta between two points is correct, but we'll see when the new springs arrive.

Update! Update!
RaceTech .52 springs are finally here! :clap

Here is the exciting fish scale! From Cabellas, works pretty good, pounds and ounces or kilograms, 50lbs max.

The rate calc sheet now has accurate numbers from both pair of springs.
  • Red: No weighing neccissary, easy and accurate. :thumbup
  • Blue: Two sets of measurements required. :thumbup
  • Tan: One measurement, not so accurate. This calc is essentially the same as the two measurement method with one measurement assumed to be at 0". This means you include the end portion of the spring which is much stiffer and fouls your results.

So the ebay forks had the stock .47 springs, good! Ordering RaceTech .52's was correct, back to the build!

Kawidad 03-17-2013 08:03 AM


DisTech 03-17-2013 04:35 PM

Steering lock
The RMZ triple will not work with the stock steering lock and I've always wanted to get rid of the DR650 boat anchor ignition switch. Going to use a DRZ400 key switch. The lock is also in the way of other planned features :evil. So its gotta go!


jessepitt 03-17-2013 08:18 PM


That should be a different bike alltogether when its finished.

rpet 03-17-2013 08:51 PM

looking good!

is the DRZ key switch plug and play?

DisTech 03-17-2013 09:14 PM


Originally Posted by DisTech (Post 20972136)
Gotta add a resistor, so it will be similar to the push button mod. Links and pics when I get to it.

...when I get to it...pffft
What kind of jerk writes that?

The data I'm going to start with to figure out the resistor wiring is ER70S-2's Post #25 in Krusty's DR650SE Index Topic # 9 ELECTRICAL/LIGHTING and Greg@RME's post linked there.

Cumbacheech 03-23-2013 04:16 AM


bobbed06 03-23-2013 06:54 AM


Originally Posted by DisTech (Post 20970231)
The RMZ triple will not work with the stock steering lock and I've always wanted to get rid of the DR650 boat anchor ignition switch. Going to use a DRZ400 key switch. The lock is also in the way of other planned features :evil. So its gotta go!


Just a heads up......I had to rework the steering stop on my DRZ 400/ RM 250 fork conversion. The DR steer stop barely touches the triple clamp and is so thin its like a knife anyway.

DisTech 03-23-2013 08:28 AM


Originally Posted by bobbed06 (Post 21014975)
Just a heads up......I had to rework the steering stop on my DRZ 400/ RM 250 fork conversion. The DR steer stop barely touches the triple clamp and is so thin its like a knife anyway.

Thanks, good info.

My flywheel puller has been lost in transit bah! But when I told the ebay seller about it she said, "i have 1 more....ill ship immediately......". Must say that was a nice surprise, but it still delay's everything.

Fork seals showed up, but still waiting on the springs.

DisTech 03-24-2013 05:27 PM

Rear wheel
Going to have The Wheel Master put a Excel 18x2.5 on my rear hub. Going from a 4.25" wide rim to a 2.5" had me worried, but the Tire Sizes Explained page on Dennis Kirk helped me. This table is at the bottom of that page and shows what tire sizes are recommended for different rim widths. 130/90-18 D606 will work!

<table class="tire-table" cellpadding="0" cellspacing="0" border="1"><tbody><tr><th>Permissible Rim Widths</th><th>Metric</th><th>Alpha</th><th>Standard Inch</th><th>Low Profile Inch</th></tr><tr><td>1.60, 1.85</td><td>70</td><td>MG</td><td>2.75</td><td>-</td></tr><tr><td>1.60, 1.85</td><td>80</td><td>MH</td><td>3.00</td><td>3.60</td></tr><tr><td>1.85, 2.15</td><td>90</td><td>MJ</td><td>3.25</td><td>3.60</td></tr><tr><td>1.85, 2.15</td><td>90</td><td>ML</td><td>3.50</td><td>4.10</td></tr><tr><td>2.15, 2.50</td><td>100</td><td>MM</td><td>3.75</td><td>4.10</td></tr><tr><td>2.15, 2.50, 2.75</td><td>110</td><td>MN</td><td>4.00</td><td>4.60</td></tr><tr><td>2.15, 2.50, 2.75</td><td>110</td><td>MP</td><td>4.25</td><td>4.25/85</td></tr><tr><td>2.15, 2.50, 2.75</td><td>120</td><td>MR</td><td>4.50</td><td>4.25/85</td></tr><tr><td>2.15, 2.50, 2.75</td><td>120</td><td>MS</td><td>4.75</td><td>5.10</td></tr><tr><td>2.50, 2.75, 3.00</td><td>130</td><td>MT</td><td>5.00</td><td>5.10</td></tr><tr><td>2.75, 3.00, 3.50</td><td>140</td><td> MU</td><td>5.50</td><td>-</td></tr><tr><td>3.50, 4.00</td><td>150</td><td>MV</td><td>6.00</td><td>-</td></tr><tr><td>4.00, 4.50</td><td>160</td><td>-</td><td>6.25</td><td>-</td></tr></tbody></table>

Off the bike.

Getting the brake disc off required heat and the hand impact driver. For the bearings, the Blind Hole Bearing puller is the ticket! One bearing seamed OK, one did not...

Drove the cush bearing out with the socket and extension. The bearing looked pretty crusty but spun free, maybe a bit sloppy.

Bearings and 520 conversion are on order from ProCycle.

DisTech 03-24-2013 05:29 PM

Occasionally my DR produces an unsettling moan/groan/honk/bad bearing kind of noise when hitting a large whoop. Didn't replace bearings on the first rebuild, just greased them up. So they are probably overdue.

Patient is on the table ready for swingarm-ectomy.

Operation successful.

Things that are not obvious from the exploded view:
  • Spacer #5 has a larger OD than spacers #10.
  • Spacer #5 and spacers #10 have the same ID.
  • Spacers #10 act as an inner sleeve for bearings #7.

I used the smaller Blind Hole Bearing puller to pull spacers #10. They came right out, no slide hammer required. Once they were out of the way I tried to drive out a bearing #7 by hammering spacer #5 through... does not work. The pile of needle bearings and wrecked bearing cage is the result. But the 5/8" - 1" Blind Hole Bearing pulled yanked them out just fine.

New bearings are on order from ProCycle.

greener556 03-24-2013 05:58 PM


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