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Old 03-31-2011, 01:20 PM   #196
Pablo83 OP
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BOXING THE DR350 SWINGARM (Swingarm redux)

I'm going to review the swingarm modification so I'll have it all in one post...

The stock DR swingarm:


The swingarm is made from three pieces. There is the cast front section that houses the bearings and there are two forged arms. They are connected with four square-drive bolts per side. In addition to the bolts, the arms are also epoxied to the front piece. The epoxy looks just like JBweld. After thoroughly destroying my first swingarm I discovered the joints that hold the three pieces together are incredibly strong and don't need to be reinforced. Even welding on the swingarm did not seem to effect the epoxy.

Here is the main problem:



The arms are C-sections where most swingarms are fully boxed. This allows a lot of flex.

Another aspect of the swingarm that might be causing flex is this E-section on the outside:



After the whole thing is boxed, the swingarm will be strong enough that much of this E-section will be unnecessary. Since I don't want to add much weight, first I drilled a decent sized lightening hole and then I ground out the center fin of the E-section.





I don't know what alloy the swingarm is made out of so this leaves a lot of guess work. I have chosen 5052 Alu for boxing the rear swingarm. 5052 provides the best as-welded (no temper) strength. ESAB recommends 5356 filler rod for the least chance of cracking when welding 5052, so that's what I'm going with.

I made the shape in cardboard first, then aluminum







And then I welded it all up.





It was difficult welding the section around the brake bracket due to the difference in thickness of the pieces. I later had to grind down the welds around the two chain-stay hole to get it to mount.

I weighted the swingarm before and after. These modifications added 13oz.

Boxing in the swingarm has significantly stiffened the chassis. The bike now handles like you would expect a dirt bike to.

After I started this project I found out that replacing the DR swingarm with one from an RMX was not difficult and is reported to give the same result. If I wanted to stiffen another bike, I would try the RMX swingarm first.

Pablo83 screwed with this post 03-31-2011 at 01:36 PM
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Old 04-03-2011, 07:16 PM   #197
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Quote:
Originally Posted by pablo83 View Post

Can someone post a pic of a known good cam profile? I'd like to know if this is normal, or due to wear.

Thanks.
Here is a picture of my cam -- bike runs fine (except for the stator, which is currently broken.)

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Old 04-03-2011, 07:41 PM   #198
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Thanks. That's a very good picture of the cam profile.

So is it just me, or does the right side look like it has a flat spot?

Quote:
Originally Posted by juda5 View Post
Here is a picture of my cam -- bike runs fine (except for the stator, which is currently broken.)

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Old 04-03-2011, 07:54 PM   #199
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Thanks. That's a very good picture of the cam profile.

So is it just me, or does the right side look like it has a flat spot?
Yes, the profiles are definitely different, apparently stock DR cams are asymmetrical.

This page offers a pretty good explanation of cam terms, specifically:

ASYMMETRICAL refers to a camshaft lobe profile where the opening and closing ramps are not exactly the same. The reason some camshafts are this way is to try to achieve an opening ramp profile that has a high velocity and a closing ramp profile that has a slower velocity. In this way the valve can be set down more "gently" than the rate at which it was first opened.
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Old 04-04-2011, 08:48 AM   #200
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The DR in Moab:



The bike did great in Moab. It went right up Guardian Hill. I've ridden it a couple times since that trip and some other flaws have popped up.

Things to do:
new carb (arriving tomorrow) - mine seems leaky
15 wt fork oil - I need more rebound damping, but it's dialed all the way up, so I'll put in heavier fluid
Heavier rear spring
More shock rebound damping - this is also dialed all the way up, so this will probably require re-valving
longer shift lever
shorter clutch lever - I need one of those two-finger levers with a quick adjust perch
Less rear sag
fork brace - still no signs of anyone who makes these
new rear tire - I'm thinking I'll go trials
bigger chain and 47t rear sprocket

Pablo83 screwed with this post 04-05-2011 at 06:54 AM
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Old 04-07-2011, 08:53 AM   #201
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shifter

I finally got around to lengthening my shift lever. Pretty straight forward: cut, add more metal, weld. I extended it 22mm to give it the same peg-to-shifter length as my WR. I'll test it this afternoon.



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Old 04-07-2011, 08:58 AM   #202
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Thats some great metal work there pablo. Nice riding too! Looks like you know how to make that DR move. I laughed my ass off when your camera guy got caught up on the sand hill.

Keep up with the updates!
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Old 04-07-2011, 01:56 PM   #203
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Thats some great metal work there pablo. Nice riding too! Looks like you know how to make that DR move. I laughed my ass off when your camera guy got caught up on the sand hill.

Keep up with the updates!
Apparently it was a rough get-off for him. He was done trying that dune after that attempt.

Things I've done recently:
- Installed the new carb (same model), but still needs jetting worked out. Jetting for this carb seems different than the old one.
- 15 wt fork oil: done but needs testing.
- longer shift lever: it now has a much more natural feel for a size 12 boot.
- Less rear sag: I dialed in as much as I could and it feels much better, but still needs more. I probably just need a stiffer spring
- New rear tire: Perelli MT43 trials tire, very grippy
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Old 04-09-2011, 11:53 AM   #204
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Quote:
Originally Posted by pablo83 View Post
Apparently it was a rough get-off for him. He was done trying that dune after that attempt.

Things I've done recently:
- Installed the new carb (same model), but still needs jetting worked out. Jetting for this carb seems different than the old one.
- 15 wt fork oil: done but needs testing.
- longer shift lever: it now has a much more natural feel for a size 12 boot.
- Less rear sag: I dialed in as much as I could and it feels much better, but still needs more. I probably just need a stiffer spring
- New rear tire: Perelli MT43 trials tire, very grippy
Yeah, it sounded like he got the bars right in his chest. Thats never fun.

How does a trials tire handle sand?

Let us know how that 15wt oil works for you. I think stock weight is 5w for the cartridge forks. Id like a bit more compression too, was thinking about going to a 10wt
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Old 04-09-2011, 01:14 PM   #205
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Quote:
Originally Posted by pablo83 View Post
The DR in Moab:


Oh, shit yes.
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Old 04-10-2011, 01:55 PM   #206
Pablo83 OP
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Quote:
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How does a trials tire handle sand?
I don't know. I had a worn out MX knobby on the bike in Moab. I installed the trials tire last week. I've been on two rides since (no sand) and it's been great. Ask me again at the end of the summer and I'll have a better answer.

Quote:
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Let us know how that 15wt oil works for you. I think stock weight is 5w for the cartridge forks. Id like a bit more compression too, was thinking about going to a 10wt
Interesting. My Clymer manual says the forks take 10w, so that's what I was assuming was in them. Of course my manual is for the '90-94 DR. I just checked the factory manual and your are right, the bike came with 5w. Thanks for pointing that out. During the build, I had replaced it with Bel Ray 10w, thinking this was close to stock.

One thing to note regarding fork oil is they are not all measured the same. 15w of some brands can be lighter than 10w of others, so you can only compare weights of the same brand. Currently I am running 15w Bel Ray with the following setting:
Compression - 13 clicks out
Rebound - 9 clicks out

These settings have been very comfortable and predictable over roots and whoops on my last two rides, BUT... I don't think that the heavier fork oil is what fixed my front end bouncy-ness. The manual says when refilling the fork, to cover the top with your hand and compress it hard. This builds pressure in the shock and forces oil into the cartridge. I did this and reassembled the forks and tested them and it was clear that the damping was letting go near the top of the stroke. It turns out it really takes a lot of pressure to force the cartridge to fill and the only way I could get it done was to assemble the forks with the springs and compress them quite a few times with my full body weight, then removed the cap and spring and refill the fork to the proper level.

In conclusion: I'm guessing Bel Ray 10w would be just fine with .47 springs but a lot of attention needs to be paid to insuring the forks have been properly filled.
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Old 04-17-2011, 08:27 AM   #207
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Transmission analysis

Below is one of the longer lists of bikes in Montesa's transmission thread. The first number is the first gear ratio divided by the top gear ratio. This gives you a general idea of how wide the gearbox is. This list is not exactly an apples-to-apples comparison, because the feel of the gearbox width has a lot to do with the torque curve of the engine that it's matched to, but it still makes and nice comparison.

I've inserted the two different DR trannies. The DR350 was already on this list, but it is listed as 3.03, and I calculate it to be 2.92. Either way, it's clear there's a big difference between the DR350 and the DR250S trannies.


5.00 Montesa Cota 349 (6 speed) 25.25
4.97 Fantic 300 25.12
4.41 Yamaha TY250L 22.26
4.38 Yamaha DT175E (6 speed) 22.08
4.00 Honda TL250 (5 speed) 20.20
3.90 Yamaha XT225 (6 speed) 19.69
3.82 Montesa V75 Enduro (5 speed) 19.29
3.80 Hercules 250 (7 speed) 19.19
3.78 Honda CRF230L (6 speed) 19.12 (current widest ratio dual sport)
3.75 Suzuki DR125 (6 speed) 18.95
3.74 Can-Am 175 ASE 18.85
3.69 Montesa Enduro 360H (6 speed) 18.63
3.63 Kawasaki Sherpa 250 (6 speed) 18.30
3.54 Husqvarna 500XC 17.89
3.53 Suzuki RS175Z 17.85
3.53 Husqvarna 400WR 1984 17.82
3.53 Honda XR200R (6 speed) 17.81
3.51 Honda XR250R (6 speed) 17.69
3.47 Kawasaki KE125A5 (6 speed) 17.49
3.46 Yamaha XT250 2008 (5 speed) 17.50
3.45 Yamaha TW200 (5 speed) 17.43
3.45 Suzuki PE175D (6 speed) 17.42
3.41 90-92 Suzuki DR250S
3.40 Husqvarna TE610 (6 speed) 17.16
3.40 Honda XR200R 1984 17.16
3.36 Yamaha WR250R/WR250X (6-speed) 16.99
3.32 Kawasaki KLR250 (6 speed) 16.76
3.29 Yamaha Tenere (5 speed) 16.61
3.27 BMW G650X (5 speed) 16.54
3.25 Pegaso 650 (5 speed) 16.41
3.19 Husqvarna 175XC 16.10
3.18 Kawasaki KDX200 (6 speed) 16.08
3.18 KTM 530 E/XC-R (6 speed) 16.07
3.18 Husaberg FE650E (6 speed) 16.07
3.18 Husaberg FE450/570 (6 speed) 16.07
3.18 Honda XR650L (5 speed) 16.07
3.15 Kawasaki KLX250 (6 speed) 15.91
3.14 Yamaha IT200 (6 speed) 15.88
3.14 Honda XR350R (6 speed) 15.86
3.13 BMW F650GS (5 speed) 15.79
3.06 KTM 640 Adventure (5 speed) 15.44
3.04 KTM 950 (6 speed) 15.37
3.03 Yamaha XT500G (5 speed) 15.29
3.03 Suzuki DR350 (6 speed) 15.28
3.01 KTM 520 E/XC (6 speed) 15.16
2.93 Suzuki DR650 (5 speed) 14.77
2.91 Suzuki DR350
2.88 Yamaha WR450 (5 speed) 14.52
2.88 KTM 690 (6 speed) 14.51
2.86 Kawasaki KLR650, KLX650 (5 speed) 14.42
2.82 Honda XR400 (5 speed) 14.27
2.80 BMW G450X (5 speed) 14.10
2.68 Kawasaki KLX450R (5 speed) 13.51
2.66 Honda XR650R (5 speed) 13.43
2.65 Suzuki DRZ400 (5 speed) 13.36
2.47 Aprilia RXV 550 (5 speed) 12.46
2.45 Husqvarna TE250 (6 speed) 12.40
2.21 Honda CR500R (5 speed) 11.17
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Old 04-18-2011, 03:03 PM   #208
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I noticed the circlip that holds the CS sprocket on was loose so I ordered a new one, but it didn't come in time for my ride today so I went anyway. As soon as I got way out in the middle of nowhere it all went to hell.

The case saver took a fair amount of damage:


So did the chain tensioner:


The circlip was nowhere to be found. I don't know how long I was riding without it. I was kind of screwed. I hadn't seen anyone one else in hours. Searching around for a solution, I considered using the key ring.



The first full turn of the ring fit in the groove perfectly. The second turn had to sit on the outer diameter of the shaft.



It worked perfectly. I started to head home at first, but it was such a solid fit that I ended up riding a bunch more trails on the way home. I was awfully lucky to have that size key ring on the bike.

[NOTE] Since writing this post I have have seen another guy on ADV have this problem and today a friend called who wanted to know if I had an extra circlip because he lost his on the trail today. So go check your circlip and make sure it's in good shape.

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Old 04-18-2011, 03:08 PM   #209
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Nice to hear a happy-ending-story. Don't ride alone next time
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Old 04-18-2011, 03:20 PM   #210
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Nice to hear a happy-ending-story. Don't ride alone next time
That's another reason I wanted to move to a more reliable bike: I ride alone all the time. I live in a small town and I ride mid-week a lot, so it's tough finding a riding partner for every trip. I leave an itinerary with my wife and last year I got a PLB, but it's still risky and I know it. I've hiked out of the middle of nowhere a couple of times. It can suck, but it's all well worth it.
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