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Old 03-28-2013, 08:23 AM   #15226
ShaneInDenver
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Carb question?

So I am going through this new to me DR350 dirt model I just got. I emailed Jesse about some carburetor settings. The bike has stock exhaust, with the Jesse airbox mod and a K&N filter.

I live in Denver, CO 5,000' and plan on being up in the mountains with this bike as high as 12,000', but I would like to do some passes above 14,000' too.

The bike has a 122.5 main jet in it and Jesse recommended going up to 140 main jet. Will this be too rich for my altitude? I am new to this, but have read you want roughly 8-12% less fuel here in Denver. 8% less would be a 128.8 main jet, but we could probably round up to 130.

Also he recommended making sure my needle is in the 3rd groove. I'm afraid I don't really know what he is talking about here.

Thanks
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Old 03-28-2013, 08:30 AM   #15227
slartidbartfast
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Originally Posted by boardforever View Post
... and my ride to work is only a mile each way. Is there any thing else to look for?
Nope! There's your answer right there. In a one mile ride the bike does not get hot enough to drive off the moisture in the oil. It forms that white emulsion which collects in the high spots in the crank case. It won't really do much harm and one long hard run will most likely get rid of it. If you never or only very rearely do such a long run, consider changing the oil at less than the recommended interval.
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Old 03-28-2013, 08:57 AM   #15228
Greg Bender
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Quote:
Originally Posted by ShaneInDenver View Post
So I am going through this new to me DR350 dirt model I just got. I emailed Jesse about some carburetor settings. The bike has stock exhaust, with the Jesse airbox mod and a K&N filter.

I live in Denver, CO 5,000' and plan on being up in the mountains with this bike as high as 12,000', but I would like to do some passes above 14,000' too.

The bike has a 122.5 main jet in it and Jesse recommended going up to 140 main jet. Will this be too rich for my altitude? I am new to this, but have read you want roughly 8-12% less fuel here in Denver. 8% less would be a 128.8 main jet, but we could probably round up to 130.

Also he recommended making sure my needle is in the 3rd groove. I'm afraid I don't really know what he is talking about here.

Thanks
Hi Shane,

Welcome! I live at 2000 feet and generally ride up higher from here. I have a 1993 DR350 dirt model that originally came with a pumper carburetor (I've since switched to the CV carburetor). When I had the pumper installed, I also had the airbox cut (came that way from the previous owner). I have one of the original stock mufflers that Jesse has modified. I ran the stock idle jet and needed to increase the main jet to 132.5 (stock size was 127.5 for my model). I would have been wallowing in fuel at 140.

Now that I run a CV carburetor, I use the stock settings for my model year and I am very happy with it (I'm using an uncut airbox with the snorkel installed).

Personally, I would only ever fit a K&N filter for pavement use only. Riding in the dirt, I would fit a foam filter such as the UNI. Much better filtration and they flow great.

As for aftermarket mufflers and cutting the airbox: My *opinion* is that they make a lot more noise with negligible (if any) performance benefits. I've yet to see anyone do back-to-back dyno runs showing differences.

Disclaimer: my experience is limited to my DR350 riding almost exclusively at 2000 feet and much higher elevations (over 12,000 feet). Other locations/elevations may be very different.

I hope this helps!

Regards,

Gregory Bender
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Old 03-28-2013, 09:10 AM   #15229
2bold2getold
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Quote:
Originally Posted by ShaneInDenver View Post
So I am going through this new to me DR350 dirt model I just got. I emailed Jesse about some carburetor settings. The bike has stock exhaust, with the Jesse airbox mod and a K&N filter.

I live in Denver, CO 5,000' and plan on being up in the mountains with this bike as high as 12,000', but I would like to do some passes above 14,000' too.

The bike has a 122.5 main jet in it and Jesse recommended going up to 140 main jet. Will this be too rich for my altitude? I am new to this, but have read you want roughly 8-12% less fuel here in Denver. 8% less would be a 128.8 main jet, but we could probably round up to 130.

Also he recommended making sure my needle is in the 3rd groove. I'm afraid I don't really know what he is talking about here.

Thanks
My book says stock is 132.5 and 3rd groove. If this is correct, that 140 may be a little rich at 6k to 13k ft. Not many passes much higher than that. So 122.5 might be close. How does it run. Most of us will not have a dyno or exhaust gas analyzer. You're gonna have to try it. How does it: sound... deep/throaty or tinny/pinging. smell...lots of gas smell or not. respond....quick or sluggish. Run hot or not. Plug color...white or black. Every bike is a little different depending on condition and set up. Get some jets and a manual and some help if you need it.

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Old 03-28-2013, 10:46 AM   #15230
thump!
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Quote:
Originally Posted by ShaneInDenver View Post
So I am going through this new to me DR350 dirt model I just got. I emailed Jesse about some carburetor settings. The bike has stock exhaust, with the Jesse airbox mod and a K&N filter.

I live in Denver, CO 5,000' and plan on being up in the mountains with this bike as high as 12,000', but I would like to do some passes above 14,000' too.

The bike has a 122.5 main jet in it and Jesse recommended going up to 140 main jet. Will this be too rich for my altitude? I am new to this, but have read you want roughly 8-12% less fuel here in Denver. 8% less would be a 128.8 main jet, but we could probably round up to 130.

Also he recommended making sure my needle is in the 3rd groove. I'm afraid I don't really know what he is talking about here.



Thanks
Mr DR350 is running a stock muffler and airbox with the TM33 pumper carb. I'm also running the TM33 snorkel which is substantially larger than the CV carb snorkel. Air filter is a Uni. Except for the filter (and I agree that K&Ns aren't for me off pavement) it's probably just like yours. This bike runs well at 2000 feet with a 132.5 main and the needle in the center notch (that's the 3rd from the bottom as I recall) A couple of years ago I spent a week riding out of Silverton doing all the high passes into Ourey, Telluride, Lake City. My bike ran poorly when I took it off the trailer and simply would NOT run above 12000 feet. I don't mean it ran bad above 12K, I mean it quit! I had to rejet to a 130 main, needle in the 4th (from bottom) notch AND disable the accelerator pump in order to ride up there. It was still a bit rich and if we hadn't been planning on going on to Moab after Silverton, I would have gone even leaner. FWIW, my friends with CV carbs and low altitude jetting were little down on power at altitude but their bikes continued to run without problems. Hence, the next time I take the DR350 up there it will have the CV carb on it. (I have both) The pumper works well when jetted correctly but it doesn't like big changes in altitude!



Trust me when I tell you Imogene Pass is NOT a good place to disassemble a carburetor!

thump! screwed with this post 03-28-2013 at 11:14 AM
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Old 03-28-2013, 12:01 PM   #15231
Greg Bender
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Originally Posted by thump! View Post
FWIW, my friends with CV carbs and low altitude jetting were little down on power at altitude but their bikes continued to run without problems. Hence, the next time I take the DR350 up there it will have the CV carb on it. (I have both) The pumper works well when jetted correctly but it doesn't like big changes in altitude!
Yep! That is where I am at, too. I can leave for a 10 day trip that spans 2,000 - 12,000 feet and the CV carb handles it better than the pumper carb (and no fiddling with jets). The CV returns better fuel economy (range), too.

Great photo, BTW :>

Regards,

Gregory Bender
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Old 03-28-2013, 01:05 PM   #15232
e28rusty
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So does anyone want to trade an almost new pumper carb for a cv?
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Old 03-28-2013, 01:06 PM   #15233
boardforever
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Originally Posted by e28rusty View Post
So does anyone want to trade an almost new pumper carb for a cv?
You have a pumper you are looking to get rid of? Is there something wrong with it?
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Old 03-28-2013, 01:18 PM   #15234
2bold2getold
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I agree. That Lake City, Silverton, Ouray, Teluride area is some of the best riding there is. Imogene has collected a lot of bikes and for that matter jeeps. A few years ago we came up on an old guy and is wife in a rented jeep near the top, where that step used to be on the Camp Bird side. He hit it kinda hard and jumped up in the air and almost went off the side. Must be at least 1500 ft straight down. Every body was standing around scratching their heads about how to get it back on the trail, It had two wheels on the edge. Finally I suggested we just pick it up and move it. So about 10 of us kinda scootted it 4 or 5 ft back on the trail. He got back in and gunned it again and did the same thing, but this time it landed on the trail and made it on up. His wife, though, had already walked on up to the top. Not sure she ever got back in. The CV carb on the DR350 seems to work better than any carb on any other bike I've had for altitude compensation. Most are down on power about 1 gear even jetted properly, ( less air....less power) but I couldn't tell much difference on the DR at altitude.
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Old 03-28-2013, 01:21 PM   #15235
MrPulldown
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Not to talk Shit about Jesse as he knows WAY more about DR's than I EVER will. But he ALWAYS reccomends a 140 main with a cut air box. I do not think that you can go from a 122 to a 140 by jsut cutting the airbox and run well. I am sure it will run pig rich at 5K. I think he is slightly hard of hearing and did not hear 5k.

As far as what is stock jetting on a DR. They changed in 94. The early years ran a 135 main (CV) and the 94+ (SE) went to a 127.5. Some say it was because of emmision regs. I think a kick start would be hard to start with such lean jetting.

Greg do you run the modified Exhuast wiih the 93 stock jetting?

Thump. Another way to get around elavation change is to mess with the air box opening. Before changing jets I would have removed the snorkle, the either crack or remove the air filter hatch. This often is enough to cheat your way to a running bike. Even losening and pulling the air filter slightly off the sealing base if you jsut need it for a short period.

I had a little chinese 150cc scooter for my wife. I live at 6k'. The airbox had all these foam insterts covering intake hole in several different locations. Scoot ran rich stock. Kept pulling foam till it ran right. It acutally ran a little lean with all of them removed so I put one back.
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Old 03-28-2013, 01:23 PM   #15236
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Originally Posted by 2bold2getold View Post
...but I couldn't tell much difference on the DR at altitude.

Because it has SOOOO much extra power to spare.
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Old 03-28-2013, 01:33 PM   #15237
Greg Bender
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Originally Posted by MrPulldown View Post
Greg do you run the modified Exhuast wiih the 93 stock jetting?
Hi MrPulldown,

When I bought my DR350, it had a SuperTrapp muffler on it. I hated that thing. Really loud, always popping on deceleration, I couldn't get it tuned right even throwing jets in it and fiddling with the "tuning" discs. At the time I was looking for a stock muffler and there weren't any on eBay. I called Jesse and he sold me one he had modified. I don't know what a truly stock muffler is like. I've been using Jesse's modified stock muffler ever since: both with the pumper and the CV carb. Yes, I run the stock jetting (for my model year) with the CV carb, uncut airbox, CV snorkel in place, and Jesse's modified muffler. This combo works great for me.

It has been mentioned previously that Jesse *may* recommend the 140 jet because it is very safe to go too rich rather than too lean. If this is the case, then I don't blame him one bit. It is a whole lot better to have a reputation for running too rich, than for recommending jets that are too small and holing pistons, etc. Alternatively, the way he tunes his carburetors for where he rides may justify 140 main jets. Honestly, this is all conjecture and I really don't know.

Regards,

Gregory Bender
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Old 03-28-2013, 01:52 PM   #15238
e28rusty
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I've been fighting jetting since adding bigger exhaust, I'm ready to try something different. I don't know what else to try. I may go back to stock exhaust
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Old 03-28-2013, 02:08 PM   #15239
MrPulldown
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Originally Posted by Greg Bender View Post

It has been mentioned previously that Jesse *may* recommend the 140 jet because it is very safe to go too rich rather than too lean. If this is the case, then I don't blame him one bit. It is a whole lot better to have a reputation for running too rich, than for recommending jets that are too small and holing pistons, etc.
This^ Makes sense. It jsut seems that there have been several mentions of speaking with Jesse and him reccomemding a 140, and the set up are all slightly differents with the only commonality being the cut airbox. And he is proably tired off listening to everyones what jetting should I use and this is a SAFE jetting he knows will work.

Friend of mine runs a CV with a 140 and cut airbox. HE lives at sea level and says he is a bit rich. When he comes up here to ride, I have to lead cuase his bike is a choking fume machine.
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Old 03-28-2013, 02:12 PM   #15240
slartidbartfast
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Originally Posted by e28rusty View Post
I've been fighting jetting since adding bigger exhaust, I'm ready to try something different. I don't know what else to try. I may go back to stock exhaust
Did you follow conventional wisdom and go for a bigger and bigger jet with every modification? If this is the case, you probably went too big (see previous post RE Jesse)
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Summer 2009 UK to Alps ride
Summer 2008 UK End-to-End ride
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