Carb Adjustments

[Josh_TN]

I know that this subject is one that is brought up over and over again. But after spending hours reading post after post I have a question or two. I am wanting to get just a little more out of my new 08 DR 650. I would like to keep close to stock fuel mileage. I know that when you add power that mileage is the cost of that. But I know that there is some that are still getting good power without killing mileage.

Would shimming the stock needle, removing the snorkel, and richening the mixture be a good way to start? Or would I be wasting my time and should just bite the bullet and call Jesse? Also I would like to keep the stock exhaust.

[snb92]

I'm not sure how much more you're wanting to get out of it, but I have done exactly what you have described and was very impressed with the results. Don't get me wrong, it wasn't front wheel lifting, hang the #@*# on type of power added, but what a difference it makes. So much smoother with none of the chuff and puff surging and gone is the header glow. I also did not want to take a brand new bike and start hacking the lid off of the airbox, etc. The mods you refer to are also incredibly simple to do, and the best part is, if it proves not to be enough, you can easily go the DJ route.

[Rick Blunden]

Josh -

I agree with Carp.

Check out:

https://www.thumpertalk.com/forum/showthread.php?t=566238&highlight=procycle+dyno

Looks like a good way to go to me.

Rick

[NVDESERTKID]

You wouldn't be wasting you time by doing that. Your gas mileage shouldn't have any dramatic change from this mod and if anything your engine will thank you.

[FishHound]

I suggest trying this simple stuff I did all of it last weekend and I'm real happy. Grinding that headder weld would be a good idea also mine was a real mess.

[the1wizard]

I agree with all the previous ideas and add drilling the hole in the slide. No cost, more response. All these mods together add up to more fun, better seat of the pants power. Enjoy.

[dr1445]

for sure dito on the above comments. i did the washer, snorkel, and adjust pilot jet. milage went from around 60 down to 58mpg. well worth the exchange for the increased response and smoothness. plus the bike doesn't smell anymore.

[J_T]

...plus the bike doesn't smell anymore.

Hmmm...You should have told him that up front! That probably would have sold him, it did me!

[Josh_TN]

what thickness shim did ya'll use? Also when drilling the slide, how many holes? and what size. Forgive the ignorance but you gotta be a noob at some point right?

[ronm12]

a washer for the needle came with dyno jet kit,i don,t know how thick it was.the extra hole in slide is a #39 or .099.it goes across from existing hole that is next to and diagonal from needle hole.easy to see where when slide is removed.

[ttsquirrel]

TTT

I am wanting to do just this little mod also as I dont have the money for a pipe right now. besides, i am a complete noob when it comes to the carb work so this will start me looking at what I will be doing when i get a cab kit and pipe.

where would I be able to get the washer for the needle?

if anyone is in fresno/visalia area and would like to help me out, I would appreciate it and reciprocate with some brew or something:thumbsup:

CG

[Rick Blunden]

TT -

> where would I be able to get the washer for the needle?

Get a #4 brass washer from your local Ace Hardware Store. The washer will be about .030" thick. Because of inflation, it might set you back a dime or so.

Rick

[NVDESERTKID]

a washer for the needle came with dyno jet kit,i don,t know how thick it was.the extra hole in slide is a #39 or .099.it goes across from existing hole that is next to and diagonal from needle hole.easy to see where when slide is removed.

You'll see once you get the slide out, it's pretty obvious what needs to be done. There will be a hole in the middle and one hole on the left (depending on how you hold it) you just want to match that left hole on the right so it becomes a "mirror image". A tip too is that once you have the correct drillbit (i forget what size) it's easier to drill from the inside out; there is a "groove" inside that the drill bit can sit right in to make sure the hole is lined up perfect... your average drillbit is going to be too short and this will mean that you have to drill it from the outside, no worries there but you'll need a steady hand. Don't fret too hard on getting it perfect, but don't get sloppy either.

Good luck!

[Josh_TN]

does the extra hole in the slide have any effect on anything except throttle response?

[J_T]

You'll see once you get the slide out, it's pretty obvious what needs to be done. There will be a hole in the middle and one hole on the left (depending on how you hold it) you just want to match that left hole on the right so it becomes a "mirror image". A tip too is that once you have the correct drillbit (i forget what size) it's easier to drill from the inside out; there is a "groove" inside that the drill bit can sit right in to make sure the hole is lined up perfect... your average drillbit is going to be too short and this will mean that you have to drill it from the outside, no worries there but you'll need a steady hand. Don't fret too hard on getting it perfect, but don't get sloppy either.

Good luck!

I know drilling isn't reversible...but if for some reason it was objectionable after the fact...could just filling the hole with epoxy or JB-weld return the performance back to original? (I haven't looked physically at the slide...trying to picture it mentally) ?

does the extra hole in the slide have any effect on anything except throttle response?

and +1 for Josh's question...any noticeable difference on anything besides throttle response (and is it wheel popping noticeable?). Like MPG, Tuneability, ideling, torque...etc?

[Blankwaffe]

I know drilling isn't reversible...but if for some reason it was objectionable after the fact...could just filling the hole with epoxy or JB-weld return the performance back to original? (I haven't looked physically at the slide...trying to picture it mentally) ?

and +1 for Josh's question...any noticeable difference on anything besides throttle response (and is it wheel popping noticeable?). Like MPG, Tuneability, ideling, torque...etc?

Personally I could tell absolutely no difference in the drilled slide.I dont think it was worth the effort.

[tklm539]

Ok,

After reading all this I tried it on my 07.

I drilled the slide, and added 3 #4 s.s. washers to the needle. I also turned the fuel out to 2 turns (500ft.) elevation.

Ground out Header (real mess inside)

Results:

The poping on decel is much quieter.

Engine is running about 20 degrees cooler

On the low end, it seems to pull harder (not sure if it was me driving harder or the mod's

On the top, with one one washer and 2 turns from the factory setting. I was topping out at 80-82 mph. No poping at all. I came back closed the fuel down all the way and brought it out 2 turns and added 2 more washers.

Second test run, the low end seemed the same. Slight poping (nothing like unmodded) 1500rpm's warmed up. Top end was at 85 when I ran out of road and it was still pulling. I do not need to know (for now) how much is left.

I am am not sure what I was expecting, It seems snappier.

Do these results sound about right? I have a new screw on order from Jesse. Should make adjustments much more handy.

Thanks

Tom

[Icelander-DR650]

When you have the carb apart you can also cut the spring for the vacuum slide. In the "MX_Rob Needle Comparison" the instructions are given. I drilled my slide and cut my spring(3 coils). The bike responds more quickly to a throttle snap. For a $5.00 spring I thought I'd give it a shot and am pleased with the results.

[NVDESERTKID]

Yes, if for some reason you decide that you don't like the effect of the extra hole in the slide it can easily be filled/eliminated with a good epoxy.

I couldn't tell you if it had any affect on my bike, I drilled the slide at the same time I did a bunch of other carb/intake/exhaust stuff, but my throttle response is much better. The power to the wheel is exactly proportionate to how much I twist the throttle whether I twist it fast or slow; I can really only attribute the extra slide hole to that change in throttle response. As to what it did to my MPG, no idea. I Don't think the slide drilling will have any affect to power/torque etc., just throttle response: If you go from zero to 1/4 throttle with it drilled it goes straight to 1/4 throttle, whereas now (undrilled)it will kind of work its way to 1/4 (supposedly). How much power/torque you get when at that 1/4 throttle will depend on other factors: intake, exhaust, air/fuel amount and ratios etc.

You should be the pioneer on the forum: go out an ONLY drill the slide, note the differance (if any) and settle this once and for all for all future DR owners. HA!

Good luck!

[IdahoJim]

Personally I could tell absolutely no difference in the drilled slide.I dont think it was worth the effort.

There isn't really much effect. All that drilling the slide does is give the vaccuum in the venturi a bit less restriction to the diaphragm that moves the slide. I'd bet money you couldn't see a difference on a dyno. I hooked my carb to a vaccuum cleaner and watched the slide movement while opening and closing the throttle plate.....I could see no difference in how well the slide tracked the movement of the throttle, both with 2 holes and then closing off the extra hole. It's a good idea, in theory, but has very little practical benefit. On the other hand, it also doesn't hurt anything, so if you want the extra hole...go for it....LOL. Also, since the air at lower elevations, is denser, there may be more benefit at sea level than the 4,500' elevation where I live. I'd still bet there'd be no measurable difference on a dyno. ?

Jim