keihin 38mm carb questions

[duneracerweston]

Fst recomends the dg carbs eather 38 or 39mm for the 446 so I imagine its going to work good

 

[duneracerweston]

Ok I'm going to revise my previos statements about the round slide

Round slides are built for mid to top end with great increases in the bottom end as well works best on big bore motors

Flat slides are for mid range with great throttle respoce and ok increase on the topend and are notorious about wearingout the slides guides out quicker then any of the 3

D shaped slides are allaroud carbs lacking in the big bore flow but has slightly better throttle responce

My fav is still the round slide its just so smooth in the power band the flat seems to be really jumpy and the D is a pain in the ass to get tuned correctly

 

[1998yamahawarrior]

So in the end the million dollar question, Is it a good idea on woods riding where I will be in and out of the throttle alot.

 

[duneracerweston]

Id say so the power curve is sooooo smothe on it its rediculis the stock one kindof jumps when you lay in the throttle the round slide just starts pulling like a tracktor on steriods !! I mean it jumps but not like its trying to run out from under you or get away from you

 

[1998yamahawarrior]

If I do pick this up then it would probably be a good idea to go 366 then I guess. That way I can get its full potential.

 

[duneracerweston]

Yep it won't dis apoint any way you do it I promis you and if it dosent doo al you want it to send it to me and I will work it over to make it like you want it

 

[1998yamahawarrior]

Thanks weston. Anyone else have any input, let me know.

 

[beastlywarrior228]

I dont think youl gain any performance on this carb.(38mm round slide no acc.pump 1970 vintage) ther are a lot better carbs out there. the best carbs for 4 stroke performance you need a acc. pump and flat slide like the keihin fcr37mm, even the 400ex carb is a upgrade(38mm flat slide acc. pump), And to make the 38mm perform better, the stock 36mm warrior port needs to be inlarged and you need a +1mm intake valve installed. Im now trying to install a FCR 37mm off a crf250 on my Raptor 350.

no **** dang ive been wanting to try a fcr off a 250 because i know the 39mm off a 450 is awesome on the 400ex and the fcr has that cool signature whistle

but ive got a mikuni 38mm waiting to go on mine

 

[duneracerweston]

Btw 98 if you really really don't like the carb I want dibs on it

 

[1998yamahawarrior]

I might hold off, checking out link that elwood put in my rebiuld thread.

 

[zazman513]

i got that exact same carb on my warrior and i love it!:tup: it seems to pull pretty good all around.I would say not so much on the top end but most riding i do is all turny and up and down hills so it works. I would reccomend it anyday compared to the stock one. Some times it can be a little tricky to start if its cold but once she starts she runs like a champ.

 

[duneracerweston]

They are more finiky though you will have to adjust the air fuel screw once a moth for it to run a optimum

 

[jasonp]

Look at what the racing 450's are using. FCR. Best carb out there.

 

[1998yamahawarrior]

Ok call me stupid but what does FCR mean

 

[jasonp]

Ok call me stupid but what does FCR mean

http://www.motorcyclecarbs.com/keihin_fcr_W60.cfm


Also Mikuni makes a good flat slide as well...

 

[duneracerweston]

Flat slids don't last nearly as long as a round slide but I guess I'm just a fan of the ultra smooth power band of a round slide

 

[jasonp]

Flat slids don't last nearly as long as a round slide but I guess I'm just a fan of the ultra smooth power band of a round slide

Dude... First off the whole slide wearing out is not going to happen because FCR uses roller bearings at all 4 points.
While a flat slide, with no bearings will wear out slightly faster then a round side, you'd have to put many many hours on both machines for this to happen.. not unless you are running with no airfilter. Really a round slide can wear out so that argument is null..

Second if you want a smooth power band then you should go with a CV style carb that the raptor 350 uses as it uses a vaccum flat slide to control 1/4-and above for constant volecity. The round slide carb is like the lowest tech out there as far as fuel delivery goes.

 

[1998yamahawarrior]

If I wanted to pick up an FCR carb, what would be the best motor to get one off of.

 

[beastlywarrior228]

If I wanted to pick up an FCR carb, what would be the best motor to get one off of.

idk any 250 dirt bike, itll be a 37mm. i think one off a 450 might be too big