OMR,
So here is an update. I'm now on a Mikuni 182.5 jet. It seems to run fine. I haven't done a full on high speed plug check, just rode with a friend & his kid. Went kinda slow. But the quad ran Ok & the plug looked OK for that. Rode again with a friend & his kid again. Runs reliable but haven't checked full on plugs yet.

Also, I bounced this off Freeze since he seems really bright. What do you think? Anything you can add is great. BTW, I have a stock intake on the way since I got overzealous with mine.

I ported my intake 2 years ago. I just did it a little bit, I was scared of botching it. I did a nice job for what little I did. Anyway I couldn't really tell a difference. So last year I did it again with really aggresive bits & I really botched it up. But again I really didn't think it felt better or worse. 9maybe it did & I just got used to it?) I had a friend clean it up good last week. It looks nice but is "hogged" out real big. it's 48mm across the opening.! Anyway I haven't had a chance to ride yet but my friend is afraid with just a stock carb it's too big & won't flow well because of that. I see his point, what is your take on something like that?

Thanks for your time as usual OMR.

 

hey 01ds650. listen i did omr carb mods and i have a ported intake that is huge. i know it will accept a tm48. i did all of omr's mods and i have a 172.5 main along with a 45 pilot. my bike is running better than it ever has. i have a mild high comp piston/uni/hmf/barnett 9 disc and it pulls great. i am competitive with bikes with bigger carbs. they pull me at the end but i do better than most would think. as long as your intake is semi smooth and not all scarred up it should be fine.

 

Anyone ever think of running duall stock 42mm??? I sure would like to try it just for the heck of it. You could spec out the duall fcr's for base line jetting to get it close maybe. Just a thought. Maybe an in-expensive way to flow some more air.

 

where would they fit? sounds cool though.

 

Thats what i call a superCARB! Is it needed a dual?

 

Other big dualls fit so I dont see why these wouldnt.



I dont want to hijack OMR's thread. He does wonders for a stock carb, I might start a new thread on this concept. Im willing to bet it would be a smooth curve with duall.

The dualls would be recomended on a built motor.

 

The DS650 head was originally designed to run with two carbs. I speak under correction, but the motor used on the BMW650, had 2 x 36mm carbs on it.

Running a dual 42mm carb setup on a stock motor is an overkill, but if you have an aftermarket cam, ported head and a few other bits in the motor, those duals will sure add some more ponies.

About 2 years back I had this "argument/discussion" with MisterHP, and told him to use duals on his big bore DS motors. I told him that his big bore motor was down on power, by about 7HP, and he laughed. A while later he tried my suggestion to run duals, and he gained the 7HP I told him was in the motor. The single carb setup, will restrict high end power output.

One more thing, I have tested a few DS's on my dyno now, and every single one I tested, made more HP without the lid. I am about to do a full set of test on a stock DS, to see what each mod adds, and will update you guys soon, showing you the gains after each run.

But, so far, my dyno consistently indicates that no lid setup rules, when it comes to making high end power. With the lid on, even with larger intake tubes to the airbox, you loose about 1 to 1.5HP at peak.

 

Freez, I always admire your opinion. I agree on the dualls. For the stock motor the single 42 was very smooth and yes on a stock motor 2 would be overkill. I was considering testing the dualls on my built stock bore 14:1 comp with cams, bigger valves, race ported, drag pipe etc. I sure would like to run a set on the dyno back to back with other carbs just to see what happens. 2 Stock snorkles and 2 giant air filters.

 

It is one of my pet projects to work with the DS's and raptor 660's. Both bikes have virtually identical bore and stroke, but the raptors consistently produce higher HP numbers than the DS.

Up till about 4500 to 5000 RPM, there is nothing between the two motors, but after 5000 rpm, the raptor's hp output keep climbing at a steady rate, while the DS is starting to flatten out. In the end, the raptors produce about 3 to 5HP more, when both motors are stock

Now, I honestly believe that this loss in power on the DS side at high RPM is due to the single carb, not being able to flow the air the motor needs.

As you all know, a larger single carb will up the hp on the stock DS, but a massive single carb also tends to drop low end throttle response, and might even hurt low end power. Especially when you don't use a CV carb. The FCR, or slide type carbs with an accelerator pump, can mess up the low RPM acceleration in a big way, and getting that thing set up right takes a while, and you have to know what you are doing. Most riders live with the low down rpm bog these carbs tend to create, since they don't know how to fix it.

Two smaller 33 or 36mm duals will not harm throttle response, especially if you can get a set of CV carbs in that size, plus if will outflow a massive 49mm single carb any day. You will also get rid of that stupid "V" shaped intake and will be able to run straight intakes, helping airflow.

Apparently the dual BMW carbs used on the "DS" motor, will not fit, due to the DS frame being in the way. Has anyone tried to make a set of stock raptor carbs fit the DS?

 

I know there are arguments for lid on and off, I just just wondering about no airbox at all with a stock carb, has anyone dynoed a stock carb with just the snorkle tube?