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Old 03-20-2013, 09:07 PM   #75016
BergDonk
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FWIW, some more of my DRs FCR development is posted here and on:
http://www.advrider.com/forums/showt...646076&page=27
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Old 03-20-2013, 09:12 PM   #75017
shu
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Quote:
Originally Posted by BergDonk View Post

These carbs were developed originally for road racing......

If you are touring there is probably not much point, but the more technical the riding, the better it is.
Speaking of touring, we continue our way south in Mexico. The DR(stock carb) is doing great as usual from sea level to 12,000 feet.

We ran into some more of this cobblestone stuff again, but this time we turned back after about a mile of pounding- we'd like to avoid breaking stuff down here.



For those who think it's not that rough, come down here and try it. The riding is easy but the ride is extremely harsh.


So we took some easier roads, this farmland is at about 9,000 feet.



Lost or confused? Time to reprogram the GPS. Bicimapas coverage is pretty good but certainly not perfect.



I helped this guy tie his hand-truck to the back of his scooter with some twine. I know for sure he made it around the first corner.




Now here's a plug for the original, totally unmolested carb (except for carb mounted choke knob, and extended pilot fuel screw.) Never a problem, never lacks for power or response in touring situations: highway, twisties, in traffic, dirt roads, and rocky dirt roads. Reliably delivers 50-54 miles per gallon.



................shu (from Oaxaca, Mexico)
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Old 03-20-2013, 09:39 PM   #75018
motolab
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Quote:
Originally Posted by BergDonk View Post
As I said, with a slow revving bike like the DR, the AP isn't necessary at all, but its nice to have all the same, and does improve response.
It isn't necessary on any engine (just open the throttle slowly enough), and if it improves response, some might argue that it's therefore necessary.
Quote:
By all accounts the BST can be made to work OK and it has no AP.
That's because the BST is a CV carb.
Quote:
With my FE650 Berg with negligible flywheel and bigger bore, too much AP makes it unrideable in the bush.
Do you mean that it's too responsive?
Quote:
My 3 FCRs, Berg 501, 650 and DR650 all have an adjustable AP of some sort and is a definite advantage when setting them up.
Agreed. Being able to adjust pump shot volume and duration is a good thing.

Regards,

Derek
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Old 03-20-2013, 09:40 PM   #75019
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Quote:
Originally Posted by Bronco638 View Post
Dude! Hook us up!

Unless you're running really low air pressures, I wouldn't bother. That said, I did have 'em on my DR350SE but I don't think I ever really needed them.
I ran my dr hard in the dirt for several hours and the tube did not twist.
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Old 03-20-2013, 10:06 PM   #75020
NordieBoy
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Quote:
Originally Posted by MeterPig View Post
I ran my dr hard in the dirt for several hours and the tube did not twist.
It's in the rocks/roots where you may need them.
Knobs + embedded rock/root that the tyre can't spit out the back and violently grips on. Can cause issues...
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Old 03-20-2013, 10:56 PM   #75021
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Quote:
Originally Posted by shu View Post
Speaking of touring, we continue our way south in Mexico. The DR (stock carb) is doing great as usual from sea level to 12,000 feet.

We ran into some more of this cobblestone stuff again, but this time we turned back after about a mile of pounding- we'd like to avoid breaking stuff down here.



For those who think it's not that rough, come down here and try it. The riding is easy but the ride is extremely harsh.


Now here's a plug for the original, totally unmolested carb (except for carb mounted choke knob, and extended pilot fuel screw.) Never a problem, never lacks for power or response in touring situations: highway, twisties, in traffic, dirt roads, and rocky dirt roads. Reliably delivers 50-54 miles per gallon.

................shu (from Oaxaca, Mexico)
Crap, that looks bumpier than the road from Rollinsville to the tunnel. Not one of my more comfortable day rides. It does put me in my place though.

Totally unmolested carb..............are you knutz..........

Thanks for the pics and updates.
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"BTW, I don't do style. It's a dirt bike, not some girlie dress-up thing." -
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Old 03-20-2013, 11:06 PM   #75022
BergDonk
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Quote:
Originally Posted by BergDonk View Post
.......... With my FE650 Berg with negligible flywheel and bigger bore, too much AP makes it unrideable in the bush. .........
Quote:
Originally Posted by motolab View Post
Do you mean that it's too responsive?..........

Derek
Yes, 122 kgs wet and blinged and 63 hp at the knobs. I have not ridden anything that has close to the hit, or linearity this has, including the latest EFI stuff. For single track and fire trailing, its awesome, but only with the AP dialed right back. You also ride it using lots of clutch, not the throttle. In slower going, its far easier to fine tune drive modulating the clutch than it is a throttle that is super responsive, even with the AP backed off. Totally different to the DR650 to ride. On dirt, the FE650 will light up the rear at any speed up to about 140 kph and launch, its like a huge puppy, just wants to go at the slightest provocation stretching the leash all the time. The DR even with the FCR and stuff, is like the old dog who just wants to lounge in the shade, but if you insist, well OK it'll go and cruise if you insist.
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Old 03-21-2013, 05:57 AM   #75023
Rusty Rocket
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Quote:
Originally Posted by NordieBoy View Post
It's in the rocks/roots where you may need them.
Knobs + embedded rock/root that the tyre can't spit out the back and violently grips on. Can cause issues...

Exactly. I spun a tire when I wheelied over a ditch and made contact on the far side with the rear tire under hard acceleration. Pulled the stem right out of the tube. I had a rimlock the next time out.
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Old 03-21-2013, 10:10 AM   #75024
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Regarding the accelerator pump you said:
Quote:
Originally Posted by motolab View Post
It isn't necessary on any engine (just open the throttle slowly enough), and if it improves response, some might argue that it's therefore necessary.
Seems to me that's the point of a lot of this thread. I think most people would agree that a properly jetted CV carb performs reasonably well as long as the inherit lag in throttle response is acceptable. A slow(er) roll on makes that lag imperceptible and while maximum power output will ultimately be achieved to the rider it can feel a bit sluggish. Anyone who has ever ridden a modern 2-stroke understands what throttle response is all about. You best be holding on when you snap open the throttle open on something like a RM250. I don't think anyone expects that kind of instantaneous kick from a big 4-stroke single but it is definitely big time fun in the dirt. I think a lot of the crazy stuff people do to their DRs is to try and move them in that direction. Hence the cutout airboxes, drilled slides, and often grossly rich jetting we read so much about.
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Old 03-21-2013, 10:22 AM   #75025
motolab
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Quote:
Originally Posted by BergDonk View Post
For single track and fire trailing, its awesome, but only with the AP dialed right back. You also ride it using lots of clutch, not the throttle. In slower going, its far easier to fine tune drive modulating the clutch than it is a throttle that is super responsive, even with the AP backed off.
Is it that the accelerator pump makes the engine too responsive when there are large/quick changes in throttle opening, and also when they are small/slow?

Regards,

Derek
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Old 03-21-2013, 10:26 AM   #75026
motolab
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Originally Posted by thump! View Post
I think a lot of the crazy stuff people do to their DRs is to try and move them in that direction.
I'm sure you're absolutely right.

Regards,

Derek
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Old 03-21-2013, 10:30 AM   #75027
Adv Grifter
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Quote:
Originally Posted by shu View Post
Speaking of touring, we continue our way south in Mexico. The DR(stock carb) is doing great as usual from sea level to 12,000 feet.

We ran into some more of this cobblestone stuff again, but this time we turned back after about a mile of pounding- we'd like to avoid breaking stuff down here.


For those who think it's not that rough, come down here and try it.
The riding is easy but the ride is extremely harsh.
................shu (from Oaxaca, Mexico)
I've ridden cobblestone like that ... usually what works is MORE SPEED!
Go fast and you float over most of it. This is the real test of your suspension. But certainly easier said than done.

In Death Valley there is this Volcanic rock section that is also tough on a heavy bike. On a dirt bike I can hammer through. On the DR had to slow down ... which makes it worse. You try to keep pace UP but tricky on this stuff. You have to avoid the BIG rocks that are everywhere on the track. Lots worse than it looks in pic.


Hope all is will in and around Oaxaca! One of my favorite areas! Hope you get to ride over the mountains out to Puerto Escondido/Puerto Angel. Lots of dirt roads in those
mountains.
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Old 03-21-2013, 10:39 AM   #75028
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Quote:
Originally Posted by thump! View Post
Regarding the accelerator pump you said:

Seems to me that's the point of a lot of this thread.
I think most people would agree that a properly jetted CV carb performs reasonably well as long as the inherit lag in throttle response is acceptable.
A slow(er) roll on makes that lag imperceptible and while maximum power output will ultimately be achieved to the rider it can feel a bit sluggish. Anyone who has ever ridden a modern 2-stroke understands what throttle response is all about. You best be holding on when you snap open the throttle open on something like a RM250. I don't think anyone expects that kind of instantaneous kick from a big 4-stroke single but it is definitely big time fun in the dirt. I think a lot of the crazy stuff people do to their DRs is to try and move them in that direction. Hence the cutout airboxes, drilled slides, and often grossly rich jetting we read so much about.

After some mods the lag in mine is non existent (or at least imperceptible), even when opening the throttle quickly. And it will pull without hesitation from a low close to 2000 rpm (if the tiny tach is to be believed). The stock low rpm shutters and shakes are pretty much gone. Patience and a little luck got it there, and mileage is still 50mpg.
I am sure it doesn't have the snap of the aftermarket carbs, but I am pretty happy with it.

Rumlover screwed with this post 03-21-2013 at 10:52 AM
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Old 03-21-2013, 11:20 AM   #75029
BenYork
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Quote:
Originally Posted by Greaslife View Post
Rusty. I did top it off



Yay it did after I got home.

Is there any thing I can do to stop this ? I'm not against any mods.

If you have stock junk do not top off. If you must top off you can keep the stock tank and remove emissions stuff, plugging carp ports with Vacuum caps. Your gonna need to plug the port in the right side of the tank with something gas proof. Your cap is still going to have a tough time venting with gas in it.

The way I dealt with the issue is put the acerbis tank on and strip all the emissions stuff. Now the only thing that needs to vent is the cap, which it does thru a long hose. Still need to cap all vacuum ports etc. Its quite easy, and you have a bigger better tank.
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Old 03-21-2013, 04:26 PM   #75030
BergDonk
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Quote:
Originally Posted by motolab View Post
Is it that the accelerator pump makes the engine too responsive when there are large/quick changes in throttle opening, and also when they are small/slow?

Regards,

Derek
Yes

Using the BK mod, I currently have the stroke set at <> 0.1 mm



The way I set it up is that the washers are the same thickness as the plasitc cover, and with the bolt length, the exposed thread is about equal to the stroke, or the gap between the end of the bolt and the lever. Here its at <> 1 mm, which was OK until I got the jetting sorted, then way too much. Readily adjustable from the outside with 2 x 8 mm open end spanners.
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