40 MM carb on 700 SP ??
 

Hello everyone ,

I'm new to this form , but have been watching it for a few days , and this is my first post , so here goes ,

I recently purchased an 04.5 Sportsman 700 [ carb ] for various uses in mind from plowing my driveway to pit vehicle at the drag strip , and just having fun !

Quick question , can anyone give me some detailed feedback on what to expect in performance boosts from installing a Mikuni 40mm flat slide carb , eg : seat of the pants feel , starting etc, etc ???

PS , Nice Site

40 MM carb on 700 SP ??
 

There must be someone out there with a coment on this ?

40 MM carb on 700 SP ??
 

since your going to a larger carb from a 34mm CV theres going to be a noticeable increase in power, id suggest while your at it to get a Dyno-Jet kit for that carb from Dyno-Jet and a K&N air filter.

40 MM carb on 700 SP ??
 

welcome,

sportsman7003 did this mod.
You may want to send him a PM if he dont respond to the thread.

40 MM carb on 700 SP ??
 

Welcome to the forums. I put a 40mm carb from a 500HO on my 700. It has a very noticeable gain in power and nice throttle response. It's easier to start now with the 40mm carb vs. the 34mm carb. There is a few modification you have to do to make it fit. Click here for a thread about the 40mm.. Let me now if you need more info.

40 MM carb on 700 SP ??
 

Thanks for the reply , the carb I already ordered from Aaen [should be here late this week ] is a 40mm flatslide Mikuni so I'm still a little curious

I've been doing some research and based on my past Motorcycle experiance , initially my guess it will only be worth a couple of HP , but other future mods I have planned should be maximized to there potential with this carb

Thanks

40 MM carb on 700 SP ??
 

Not to discourage you, but the carb Aaen sells will require significant tuning to work on your 700. I've been this route with their 36mm flatside. As delivered from Aaen, it was rich on all circuits and required a pretty significant investment in jets to get it right. However, the TMX series, which is likely what you've ordered is not as tunable with as the TM series I dealt with. The TMX and TM (non-pumper versions) are primarily 2 cycle carbs and are jetted accordingly, which is significantly richer than their 4 cycle counterpart. Aaen delivered the 36mm with changes in the main and the needle jet from the stock Mikuni jets. Both were too rich. No only did I have to change both of these jets, but I also had to go down several sizes on the pilot jet and starter jet. The TMX does not have a replacable needle jet, but relies on jet needles of different diameters. It could be expensive finding the right needle. There was another gentleman on another board that purchased the same carb for his 700 and ended up selling it as he couldn't get it dialed in, and his 700 got horrible gas mileage.

Hot Seat Performance has a 41mm Keihin FCR, which has an accelerator pump and is a 4-cycle carb. Their carb is sold for the sp 700 and the 500 preditor. It's too expensive for me. I just purched a 40mm Mikuni pumper carb that I intend to install on my 700. It's a Mikuni TM40-6, also referred to as the HS40. I haven't installed it, but I know it has similar dimensions to the stock carb, as the 36mm TM referred to previously that replaced the Mikuni 34mm BST on my old 500, the same carb on the 700, have the same dimensions. I know it will need jetting too, and just ordered a some jets today. I can keep you posted on my results.

40 MM carb on 700 SP ??
 

That's a well detailed explaination of your expierance with the TMX , I have no doult all of this is true , but was this tried on your 700 at the time with stock cam and EX ?

I question it as well , but I'm somewhat banking on the fact that it been a 700 Twin with a 360 degree crank[ even firing ] , drawing off one carb , there is going to be a more constant flow of air/fuel through the intake port at low RPM's then say a single or odd firing twin if it were engineered with a 180 degree crank

The other idea in mind was the posibility of putting a turbo on it , and blow through the carb [ Garrett T-12 ]

We'll have to supply a varible regulated fuel pressure to the carb , and make sure it well sealed
The concept has been showing up in the drag race scene [ blowing through holley carb ] with great success over the last few years , I know it's not a holley , but the same principals apply [ Not 100% sure yet though , time permitting ] I may spray 20-25 HP NOS instead

If I was going to suck through the carb with the Turbo , CV is the only way to go

I also orderd the 700 EFI rubber adapter between the carb and the head , because it's designed for a 40 mm throttle body , hav'nt picked it up at the dealer yet , but Aaen told me they thought the Spigot size is considerably bigger than the 40mm TMX , and to just force the new carb over the original adapter

I'm not conviced I want to do that till I see it myself and for the $25 the new flange is worth I'll check it out anyways

Best case scenirio I fully expect there to be calibration issues that I'll have to try to work through it

I do Know the 40 mm CV from the 500 HO is a sure bet

None the less , I've got my fingers crossed

All info and further comments greatly appreciated

Thanks

40 MM carb on 700 SP ??
 

What I referred to as pumper carbs are carburetors with accelerator pumps. Non-pumpers designs have no accelerator pump and will have a distinct bog when you hit the gas fast. You can see the effects on any carbed car or truck by removing the accelerator pump linkage. There will be a distinct hesitation on acceleration. You can modify the clutch to add more stall to hide the bog, but without an accelerator pump you will never eliminate it. 2-cycle engines are jetted considerably richer than 4-cycle engines and don't rely on accelerator pumps. The TMX, TMS and TM that are not pumper carbs are primarily intended for 2 cycle engines, so they present more than unique tunings challenge on a 4 cycle. The number of cylinders will have little to do with overcoming any of these issues.

Let me explain some other differences. The stock carb, and the what everyone refers to as the 40mm CV (500 H.O.) have a throttle shaft and throttle butterfly to regulate airflow and the jet neddle, a large metering rod, is mounted to a vacuum diapham inside the carb. Since it relies on engine vacuum to meter fuel, it likewise does not have an accelerator pump. A flatside has a throttle valve that is pulled up into the carb body to manage airflow and the needle jet is mounted to the throttle valve; whereby, the metering mechanism is controlled by the thottle, not engine vacuum. Essentially, a 36mm flatside will have the same flow capabilities as the 40mm CV, since the throttle shaft remains a restriction in the throttle bore. When the throttle valve is pulled up into the carb body, there is no restriction in the bore of the venturi. Not only is airflow better in the flatside, throttle response is better as well as engine vacuum is taken out of the equation with respect to fuel metering. Look to any aftermarket carb for an atv or motorcycle with four cycle engine and it will be a flatside design. While it took considerable effort to dial in the 36mm, and had a very slight bog on a jackrabbit start, it certainly performed circles around the stocker.

If anything, the vacuum diaphram in the CV carb should present some rather unique challenges in a blow-through forced air induction system. I fail to see how the CV would be superior to the flatside in either n/a or forced air applications.

Keep us updated on your results. Great things about these boards is you may indeed unlock the code to the 40mm TMX on a 700 and can pass that information on to the benefit of others. Even our failures can serve as warnings to others.

40 MM carb on 700 SP ??
 

Yes , I concur totally with your technical explanations , and I am familar with all these carb designs as I had worked as a Motorcycle mechanic in the Mid 80's for a Suzuki/Honda dealer for 3 years . I have owned close to 20 M/C over the years , however this is my first Quad , so I apreaciate any education you can give me [ I don't profess to know it all ]

One of the reasons I chose the TMX was because it should work in a " Blow Through " turbo set up for the future if I decide to go that route , we'll see how close Aaen get's it

The lack of an accelerator pump may not be that critcal with the timing bumped ahead a couple of degrees [ already done ] and because these machines have a snowmobile style clutch , unlike other machines that use a transmission and clutch , [ they can't be lugged down in RPM ] the polaris is always in it's torque band , even at a cruise

No question about it though , CV's do an awesome job at controlling mixture and velocity at all RPM


One other possible option I'm going to research a little further is the Keihen 44mm CV pumper carb that's often used on Harleys , this would be the cat's meow on a suck through Turbo setup , because it's big and can respond to as necessary to various demands and compensate for turbo Lag

I did a quick search and there are many suppliers out there , it may even work good as a replacement for the stock 34mm CV with the " apparently larger " adapter from the 700 EFI

And I may try this as well