PS. Here is a tip for the duel carbs. Remove the breather pipes on the stock carbs and install a breather filter to each one. It helps bottom end power and on the dyno will give about 1 to 3 HP more. It does not add to top end power.

Freez, can you tell me how it helps the bottom end and will work on modded stock carbs?

 

with dual carbs you are "feeding" each port and have to stagger the jetting. With a single carb, the ports "pull" and mixture balances before the "Y".

 

You are right sixsixt. I do not know if the dual carbs deliver the correct mixture. Here I am going by what Yamaha recommends, since I am not changing their setup.

What I do know, is that every turn and every bump or curve in the flow of the intake port causes problems. The straighter it is, the better. All high performance heads have very straight intakes. With he single carb setup you are introducing lots of additional bends, that is not good for air flow.

The crossover port will not help much with the cross over of the bunched up air inside the intake. The reason for this is simple. The restriction is the port size on the head where it joins the intake manifold. The crossover is further back inside the port. Air bunched up between the head and the carb cannot flow thru the crossover port in the head as it is behind the restriction.

I know it all theory, and I admit I might be very wrong here. All I know for a fact is that bending air and making it change direction is not good for an intake.

Next, why I say the breather pipe removal will add more HP low down.

The stock carbs work on a vacuum created by the air flowing under the slider and causing a vacuum in the chamber above the slider and the plastic lid of the carb. This pulls the slider up and allows more air thru the carb. The slider will match the motors demand.

The breather pipes on the stock setup connect to the intake pipes feeding the carbs. If you have two pipes than join at a 90 degree angle, air flowing thru the main pipe will cause a vacuum in the other. That is exactly the way the slider works.

Since the breather pipe connects at a 90 degree angle to the main intake pipes, it will cause a vacuum inside the pipe. This is bad. Above the slider you need a vacuum to lift the slider, The breather pipe feeds a passage under the slider vacuum chamber and if it has a vacuum to, the two vacuums will compete against each other. Remove the vacuum under the slider diaphragm and the slider vacuum have no competition to move more freely and faster. This in turn gives the slider much better response to the changing engine demands thru the carb. The vacuum under the slider diaphragm will slow down the upwards movement of the slider. Without it the slider can shoot up or down as it pleases, without restriction. On the dyno you can see it very clearly. At low RPM ,when you hit the throttle, the "open" breather set creates better response and more HP low down. It purely helps with acceleration. Once the throttle is held in one position, it does not add more power compared to the stock setup.

PS. On the Predator, that uses the same carb as the DS 650, and the Yamaha Grizzley, they use a small filter and an open connection. It’s the same make as the stock carbs on the Raptor.

 

hi my name is dennis and i am a forum addict

just wanted you guys to know this so hopfully some more can come out a treat the problem

 

some people get real deep in this forum but some of it is just there foot in a deep pile of **** lol just messing

 

Thanks Freez.

 

I'm researching old posts on single carb set-ups for raptors, this one came up as the most iteresting, notice it is old news as the previous post before mine is 8 months old.

Anyway, those of you who have been running the single carb for a while now, how do you like it?
I see that edelbrok is being used, along with lectron, but why no large mikuni flatslides like the TM42, TM45, and TM48's commonly used on the DS?

I noticed in this discussion that most of the talk centered around which setup makes the most peak HP. While this is a very important issue, the main reason I am looking at the setup is for a friend who is seeking a more convenient setup to make altitude changes with. We travel all over the country and hit every altitude from sea level to 10K in a single trip sometimes, and ease of tuning for each situation is very important. When it takes me 35 seconds to rejet for altitude, and a raptor guy with stock carbs over an hour, its easy to recognize the benefits of a single carb setup.

And I don't think the trade-off has to be a loss of power either, some of the fastest DS's in the country are running single carbs up to 48mm in diameter. Very few DS's run dual carbs actually. there are several out there, but compared to single carb set-ups the numbers are few. there's just too much convenience to a single carb set-up and duals do not have a large enough incentive. Of the dual carb DS's out there, the most common setup is dual FCR 39mm. It would take an awefully huge single carb to equal the flow of those, but the single 45mm is very close to that of the dual 33's on a raptor. Seems to me the Mikuni TM45 would be an ideal choice for a Raptor, since it works so great on DS's, including my own.

So what do you guys think? I am very familiar with how lectron carbs are constructed and work, and I am equally aware of the pros and cons of lectron and mikuni alike, as well as the hp differences between the two, so I don't wanna end up making a big deal battling between those two brands. But the main thing I wanna find out is if the single carb set-ups on the raptors are working out given their unusual head and intake port design, along with finding out if there are any physical constraints as far as space is concerned with fitting a big single in the space provided under the seat of a raptor.

Thanks in advance!
HT

 

I would like to know as well, if there are peeps running the TM45 on their Raptors........ and how you like 'em?!?

 

oops, double post..... sorry!
[img]i/expressions/face-icon-small-blush.gif[/img]

 

Maybe Duncan Racing know something what other guy somehow miss.

Duncan Racing

rnuts