Keihin vs. Edelbrock

[dave76]

My stock BTM has a machanical flat slide with jet needle attactched, and also has a butterfly at the exit of the carb, the choke works via an enrichener plunger, plus the carb dose have a small accelerator pump.

 

[griff]

My stock BTM has a machanical flat slide with jet needle attactched, and also has a butterfly at the exit of the carb, the choke works via an enrichener plunger, plus the carb dose have a small accelerator pump.

Hmmm, does the butterfly open and close with the slide and throttle? It really shouldnt as FS carbs have no use for it in that manner.

However...

If not, then its only part of the choke system, and should open/close with the choke plunger. Old design FS carbs will have a butterfly for a choke system (if it has a choke). That BTM is kind of an odd carb anyways, and IIRC it was Yamaha spec'd to Mikuni.

 

[jasonp]

Well holy ****!! Now that I think back about it the stock carb does have the slide directly linked to the linkage of the throttle and same goes for the butterfly valve. Thank you for pointing this out dave and griff. WOW do I feel like an idiot right now!! This is why you see the accel. pump used on this carb. I wonder though what the hell there trying to do by this design? There is no vaccum operated diaphram, slide. I was wrong.

 

[griff]

Well holy ****!! Now that I think back about it the stock carb does have the slide directly linked to the linkage of the throttle and same goes for the butterfly valve. Thank you for pointing this out dave and griff. WOW do I feel like an idiot right now!! This is why you see the accel. pump used on this carb. I wonder though what the hell there trying to do by this design? There is no vaccum operated diaphram, slide. I was wrong.

Dont feel bad Dude, I messed that up too. I've seen Warriors with CV carbs before, but at this point I have to grant those were not stock. Every year I looked at in the fiche shows that BTM Flatslide stock.

I'm pretty sure any butterfly in the BTM is for the choke system, theres NO design reason to have one in a FS carb otherwise. The butterfly should remain open at all times (regardless of throttle position), and should only actuate via the choke plunger. That would be normal.

Whats odd is that a butterfly doesnt show in the parts schematic, so its a little bit of a mystery.

I emailed my friend who works for Sudco, he'll know the low-down on the BTM.

 

[jasonp]

Dont feel bad Dude, I messed that up too. I've seen Warriors with CV carbs before, but at this point I have to grant those were not stock. Every year I looked at in the fiche shows that BTM Flatslide stock.

I'm pretty sure any butterfly in the BTM is for the choke system, theres NO design reason to have one in a FS carb otherwise. The butterfly should remain open at all times (regardless of throttle position), and should only actuate via the choke plunger. That would be normal.

Whats odd is that a butterfly doesnt show in the parts schematic, so its a little bit of a mystery.

I emailed my friend who works for Sudco, he'll know the low-down on the BTM.

I just hate to miss lead people, thats all. I'm glad we cleared it up. Does the raptors have the BTM as well?
I'm almost positive that the stock carb uses both butterfly valve and flat slide much like a CV carb but with out the diaphram. I'm not sure the reason behind this as it really doesn't make any sense to me. Maybe wanted a flat slide design but with out the disadvantages...?? Will have to see what sudco says as I do trust in them.
I just ran out side and checked my old carb out. The butterfly is connected to the throttle along with the slide. Has the port for the diaphram (but not used) and goes through the upper part of the carb to. Very weird.

 

[madcow]

The butterly isn't operated by the choke, it's just linked to the throttle. I think it's not in the schematic because you can't take it out. It looks like it was put in before the 2 halves of the carb case were attached.

 

[griff]

[quote:yq8o65om]

Dont feel bad Dude, I messed that up too. I've seen Warriors with CV carbs before, but at this point I have to grant those were not stock. Every year I looked at in the fiche shows that BTM Flatslide stock.

I'm pretty sure any butterfly in the BTM is for the choke system, theres NO design reason to have one in a FS carb otherwise. The butterfly should remain open at all times (regardless of throttle position), and should only actuate via the choke plunger. That would be normal.

Whats odd is that a butterfly doesnt show in the parts schematic, so its a little bit of a mystery.

I emailed my friend who works for Sudco, he'll know the low-down on the BTM.

I just hate to miss lead people, thats all. I'm glad we cleared it up. Does the raptors have the BTM as well?
I'm almost positive that the stock carb uses both butterfly valve and flat slide much like a CV carb but with out the diaphram. I'm not sure the reason behind this as it really doesn't make any sense to me. Maybe wanted a flat slide design but with out the disadvantages...?? Will have to see what sudco says as I do trust in them.
I just ran out side and checked my old carb out. The butterfly is connected to the throttle along with the slide. Has the port for the diaphram (but not used) and goes through the upper part of the carb to. Very weird.[/quote:yq8o65om]

Yeah, me too

I have a sneaking suspicion of why that BTM is designed like that, but I'll wait to see what my bud says.

The Raptor 350 does have a BSR, and that IS a traditional CV carb thats been used on quite a few other bikes (et all). Its an excellent carb.

 

[griff]

The butterly isn't operated by the choke, it's just linked to the throttle. I think it's not in the schematic because you can't take it out. It looks like it was put in before the 2 halves of the carb case were attached.

Yikes, thats scary...

 

[jasonp]

The butterly isn't operated by the choke, it's just linked to the throttle. I think it's not in the schematic because you can't take it out. It looks like it was put in before the 2 halves of the carb case were attached.

The butterfly valve is screwed into the shaft from what I can tell on my carb.

 

[jasonp]

[quote:54vealtw]
I just hate to miss lead people, thats all. I'm glad we cleared it up. Does the raptors have the BTM as well?
I'm almost positive that the stock carb uses both butterfly valve and flat slide much like a CV carb but with out the diaphram. I'm not sure the reason behind this as it really doesn't make any sense to me. Maybe wanted a flat slide design but with out the disadvantages...?? Will have to see what sudco says as I do trust in them.
I just ran out side and checked my old carb out. The butterfly is connected to the throttle along with the slide. Has the port for the diaphram (but not used) and goes through the upper part of the carb to. Very weird.

Yeah, me too

I have a sneaking suspicion of why that BTM is designed like that, but I'll wait to see what my bud says.

The Raptor 350 does have a BSR, and that IS a traditional CV carb thats been used on quite a few other bikes (et all). Its an excellent carb.[/quote:54vealtw]

Ah yes. I bet this carb also helps the raptor make more torque and hp over the warrior stock along with the smaller header? Does the raptors carb have an accel pump?

 

[jasonp]

ok this carb is freaking weird... on the side of the carb, it's got this small plastic cover with a diaphram and spring inside the carb. Connected to the diaphram is a piston which looks to get vaccum from the inside of the slide cavity or where the slide rides inside the carb. It's on the oppsite side of the throttle lever assembly. I've never seen anything like this before.
also pictures.. http://www.bluetraxx.com/phpBB/viewtopic.php?t=37378//url

 

[madcow]

I think that's the accel pump assembly. At least that's what I remember from reading the manual.

 

[jasonp]

that diaphram is a freaking coasting enricher. Now what is that used for as it does look to have a 2nd air jet inside of it.

 

[dave76]

I'll take a pic of the stock carb griff, the butterfly works directly with the FS in sinc. It's mechanically conected by linkage.

 

[griff]

OK, this is what I got back guys:

That carb is a design clustf**k Griff. It incorporates the worst aspects of an rs and cv for one stupid reason: california emissions requirements, which the rest of the states also had to suffer with. Its almost impossible to get a normal flat slide tuned for emissions as you know - flat slides dont like lean conditions - which is how most manufacturers get by C.A.R.B. requirements. For some reason yamaha wanted a flat slide for the warrior, and had mikuni design that abortion btm soley from an emissions stand point. Its a piece of junk, and if you have one, get rid of it! Any after market, or retrofit carb will work better. People will use a RS36 conversion, or a TM36 if they really like mikunis, and I've heard of keihin fcr's and pwk's being used too, but I dont know whats involved with those. With some tweaking a raptor 350 carb will work well too if a cv is preferred, but think a different cable is needed.

There was some other misc stuff, but nothin much to do about this topic. FYI, "CARB" is "California Air Resource Board", the bastards who do smog equipment certifications, etc.

He has an excellent point about FS carbs and emissions (that was my sneaking suspicion). See, with a CV carb you can tune lean and the carb will put up with it to some extent (and basically run OK, like a Raptor 350), but a normal FS carb will not put up with a lean condition at all, it will run like total ****. You guys who have tuned something like an Edel know what I mean, if its lean, it hates it.

That butterfly must be for velocity/flow control, i.e. keep it intentionally restricted so that a simple lean condition persists, and viola... it passes 4-stroke emissions standards.

Seems like a lot of effort went into that by Yamaha, and I'm still scratching my head as to WHY... maybe they were stuck in a contract with Mikuni for those carbs or something, I dunno. Would have been a lot easier just to use a CV carb than put in that screwy BTM.

What a bizarre carb....

 

[jasonp]

I got a laugh out of that. Thanks griff for posting that.

 

[griff]

I got a laugh out of that. Thanks griff for posting that.

No problem Dude I kinda laughed too, I was just more stunned at how truly weird that BTM carb is.