This is ALMOST correct.

Yes everything is matched, but not for power/performance. The stock setup is developed to produce the best performance it can while still meeting minimum emissions laws. The stock setup is FAR from efficient in developing power. The stock engine has ALOT of potential power to be unleashed just by bolting on external parts and rejetting.

 

Sam

i will read that with interest when my copy gets here

what you were saying about the needle i have a slight hesitation on mid throttle only at certain RPMS
that i have never been able to shake no matter what set up i have tried It is very slight now but i have been thinking a different taper might afect it . Have you or do you know any one who has tried different taper needles in the stock carb ?

 

I am not seeing where he says it is "efficient in develoing power". I am not trying to deffend anyone. just dont see what you are. in fact, he has said basically the same thing you just posted. in other words.in other post. did you read the whole thread?

 

as for a differnt taper no I havent. dyno jet is the only one that Ive ever heard of any one using other than stock. you would need to get the numbers off the stock and get ahold of a mikuni distributor and see whats avalable. THE BOMB might be able to help you get what your looking for. PM him

 

busmechanic
I was thinking the same

Sam
Im not sure if i will go down that road right now, maybe if some one had already done the hard work i would follow there lead[img]i/expressions/face-icon-small-blush.gif[/img]
i am thinking of a carb transplant so i will wait and see, but if not the needle thing will be worth a try

 

I dont blame you

 

there is a tm45 on ebay right now. it sounds like the guy is not sure what it is for sure. he is calling it a "mikuni bsr42". I dont know. maybe I am wrong. here

 

yea, thats a tm45....looks like someones going to get it for next to nothing.

 

Ok, so let me put my spin of things on this article.

When you restrict the airbox flow, creating vacuum inside the intake tube, that vacuum is present from the air cleaner right thru to the cylinder head. Now, since the slider works on vacuum, the additional air inside the slider chamber will be sucked out, due to the vacuum, thus razing the slider more. Now, looking at this you will think, the carb is opened more and yes you might have the right mixture, since the carb and needle was designed to work like this from the factory. So, you have a big carb opening and you have the right mixture. This will give you good power, no question about it, BUT you still have the problem of a nice big old vacuum inside the intake and this robs power output.

Now, here is the other side of the coin. Rip that airbox lid off and you have much less vacuum inside the intake. So, the less vacuum inside the intake might reduce the slider movement, resulting in a smaller opening. Now ask yourself this question. Does the carb opening determine the power output, OR, the amount of air (oxygen) that goes into the motor? If you thought carb opening your wrong. It's the amount of air that can flow into the motor.

Now, a max carb opening with a vacuum, can flow less air than a carb with a smaller opening and no vacuum. Ever thought of that? The fact is that you can make the same power with a smaller carb opening, as long as the airflow (oxygen intake) is more than the bigger opening with a vacuum. The problem here is that since the carb opening is smaller, the stock needle might be completely wrong and cause a very lean condition. For the uninformed, they will see a drop in HP and think the "lid on" setup works better. Get the needle shape and mixture right and you can make the same HP with a smaller opening. So, I agree with the article. Needle have to be changed to get the right mixture.

Now to take this further. When you reduce the vacuum, the slider might open smaller since it was designed to work with a vacuum created by the motor. So, how do we increase the opening of the slider, without restricting airflow into the motor? Simple! You need to play with the slider spring tension and the holes sizes in the bottom of the slider. If you have lots of air flowing thru the carb, the 90 degree opening in the slider will cause a vacuum in the slider chamber. Instead of the vacuum of the motor sucking the slider open, you can make the air flowing thru the carb to do the same. Generate a vacuum, but in a differant way. Playing around with the hole and spring tension, you can create the same slider opening, without using the vacuum created by the motor. It's a matter of finding the right hole and spring tension. I am nto sure of the article mentions how to adjust the way the slider behaves, but it is possible and takes lots of trail and error. The spring tension, hole size and then lastly finding a needle to match it all is not something most tuner have time for. You need to start with a stock slider, try different holes sizes to get the best possible HP increase. In the process you might be throwing away a few sliders. Then you need to get the spring tension to work with the new hole setup, and lastly you need a needle to match the way the slider operates. Ask yourself this question. What is the easier way to get the right mixture? Adding duct tape to an opening or trying slider modification and spending lots of time and money to get the right slider setup? The duct tape will give you the quickest and easiest way to get things working right, BUT its not the best way to get max power output.

Now, if you get the same opening as with the vacuum in place, you now may be able to use the same needle AND, you have very little vacuum, thus adding much more airflow into the motor.

I state again. There is two ways of getting the carb to give the right mixture. You can either try and restrict the airflow to get the mixture right, but lose power due to the low airflow of running a lid on, OR, you can get the intake to flow correctly and fix the real problem of the slider setting.

Now I ask you again, which one will give you more power? Fixing the cause of the problem or addressing the symptoms? Adding the lid addresses the symptoms, but they never fix the problem!

It’s like having a very bad pain. You have to ways of getting rid of it. Drink pain pills for the rest of your life or fix the cause of the pain. Adding the lid is like drinking pain pills.

Restricting airflow to make a carb work better is madness. It defeats the object of making HP.

Now for the last thing.

I believe the shape and size of the rubber intake tube on the DS was designed to increase airflow. Longer intakes are designed to increase low RPM intake velocity, while short intakes increase high RPM intake velocity. You can change the length of the intake to give you a boost where you need max power. Making the intake to long or to short will not add any benefit. This might be a reason why running a direct bolt on K&N to the carb might not give the best power output. Note I have not tested this, so don’t take this as gospel, but plan to test this setup next year and I will tell you what the dyno says.

Now, since when do people design intakes to increase velocity, but the “tuners” try and get more vacuum inside the intake to make the carbs work better. Are these intakes not designed to increase airflow? Increasing airflow will NOT cause vacuums. It will REDUCE vacuum.

Note that the stock DS was designed to work with a puny little exhaust and an intake system that will match it. You add a new exhaust, put you keep the intake stock? Does this sound like the best way to make HP?

I want to ask you a question here, and I will use myself as an example.

I don't race, but I like to kick someones butt if he takes me on. I found some very interesting mods after spending lots of time on the dyno and with trail and error. One of the mods I found adds 3HP to a stock raptor, plus it kept the power output going for a 1000 RPM longer, without even changing jet sizes. For a very long time I kept it to myself. It gave me the edge and it made me win each time I raced another raptor with the same mods. I did this same mods for some of my friends and they have been told to keep it quite. In the end a shared this with another forum, but it took me a long time to get over the fact of keeping some stuff to myself. In the end I am not selling anything. All the testing I do is for writing technical articles for a local quad mag.

Is it not possible that the people telling you to try this and that might keep a little bit to themselves? They might not give you ALL you need and leave some for themselves to keep them winning. Now add people to this list that are selling you more goodies to give you more power. Are they going to tell you that you can get more power by drilling a hole here and there and make the stuff they sell useless and a waist of money?

It’s all about winning and making money.

I don't sell anything, I ride a raptor, I am not a Yamaha fanatic, I like the DS and was it not for the weigh, size and price of the DS, I would have bought one and I will never race one of you guys. Why would I keep anything back about DS mods? I have nothing to gain, or to fear from you guys, except maybe opening a few eyes to look at things a bit differently.

 

Busmechanic
Thu December 09, 2004 10:06 PM (NEW!)



"there is a tm45 on ebay right now. it sounds like the guy is not sure what it is for sure. he is calling it a "mikuni bsr42". I dont know. maybe I am wrong. "


I was hopeing no one would spot that with the description,
looks like it will get more expensive now [img]i/expressions/face-icon-small-sad.gif[/img][img]i/expressions/face-icon-small-wink.gif[/img]