New Mikuni Carb for 2003-06 Big Bear

[Gwbarm]

Just found this on eBay, OEM carb for 2003-06 Yamaha Big Bear, $165.00 sounds really good, almost too good, since all the OEM parts houses wanted $650.00 for them. Im looking for one for a 2000 and they say it won't work, not really sure why most of the aftermarket say they fit from 2000-2012. Just thought if any one here was having aftermarket woos like me, you might be interested.

Genuine Mikuni OEM Carburetor for Yamaha Big Bear 400 03-06 BSR33-P48 | eBay.webarchive

For got to convert the file

Genuine Mikuni OEM Carburetor for Yamaha Big Bear 400 03-06 BSR33-P48 | eBay.pdf

 

[kp3004x4]

I myself just bought an aftermarket carb from ebay ,for a 2000 Kawasaki prairie,came in looked the same but when put on the choke was different than originally had,took off and got the mighty Dremel out and  cut the extra tabs off to fit my cable ends.stil not running yet had to work on others that came in shop.  I've come across that before on accelerator cables also ,but on Yamahas mostly.

[Gwbarm]

I have contacted the seller to try to find out why it won't fit a 2000 model, I have a lot of trouble with aftermarket carbs, already having trouble with the one I put on my Eiger 4 months ago, ran good when I first put it on, im really thinking about getting one anyway.

[kp3004x4]

They have really flooded the market with aftermarket everything these days seems most look like the item your replacing but but won't last,there is something to say about OEM parts. Straight from dealer that is. Some are quality some are aftermarket themselves and selling you substitute parts for OEM dealer prices. 

[Gwbarm]

I am a little skeptical although the company has aa 5 star rating, it does say Mikuni on the carb, but is it, there are fake everything out there now. The seller did get back with me almost immediately haven't read the email yet, I will let you know what he had to say, curious to see why it doesnt fit a 2000, all of the aftermarket says they fit Big Bear all, wolverine, timber Wolfe, warrior, so that pretty much sums up why they don't perform well, no way they are a perfect match for all those bikes.

[Gwbarm]

The guy got back to me on the Mikuni carb. There is one carb that fits 2000-2002  3 years, then they changed it. They seem very knowledgable on Mikuni Carbs. It used these jet sizes:

Jetting:

112.5 Main jet
17.5 Pilot Jet
70 Starter jet
 

Not surprised the aftermarket carbs perform badly. I am going to check the jet sizes on my aftermarket carb that is leaking and see if it even comes close to that.

[kp3004x4]

Just wondering are they the same diameter as the old ,so that you could clean oem carb to about new specs with new brass.?

[Gwbarm]

I thought about doing that to the aftermarket carb I have , just buy the jets and the needle, yamaha doesn't seem to offer a kit from OEM dealer, so I was looking at the parts and the needle by itself was 44.00, that's why so many good OEM carbs get trashed because you can buy a new carb that kind of works for less, but you don't know its not as good until you really push it, my biggest complaint with them is hesitation and throttle response. There are aftermarket kits but there you are again, are they good enough, or better than buying an aftermarket carb, probably. 

[kp3004x4]

Yes sir completely agree with you on that.anyways good luck

[Mech]

You have to be careful swapping jets. Not all jets use the same threads or size classification. Not all cheap jets are accurate. at all.

Even if the old jets do fit a new aftermarket carb, the idle mixture screw may not.. It may have different threads, or have a different tapered or diameter pin on it's end.

If you do buy a cheap aftermarket carb it will always run better if it's tuned to suit your bike and climate, fuel, altitude etc. The trouble is that if you want to buy different jets, or slide needle, you can never be sure the jets are the thread you need, or are going to be that 5 up from the jet you are holding in your hand.

Edited April 14, 2023 by Mech

[Gwbarm]

I decided I didn't want to fool with it, and bought the Mikuni.  

[Gwbarm]

The correct jet sizes for the 2000-2002 big bear was:

112.5 Main jet
17.5 Pilot Jet
70 Starter jet

I took my aftermarket carb back apart and there was no markings on any of the jets

[Mech]

Ha..  yeah that too Gw. I've got spare jets in the packet that were all different numbered, but looked to me like the same size.

The fuel jets alone don't dictate the tune, the fuel jets, air jets, emulsion tube, discharge tube, slide, and slide needle all have to be chosen to work together.

[Gwbarm]

Good point! My thoughts were you don't know what size they are even if you wanted to replace them  

[Mech]

Yeah, the cheap carbs have inaccurate jet sizes, and they use threads of their own sometimes.

Stahlwille use to sell bike jet measuring and reaming kits which went down to the small sizes, but they don't seem to make them any more which is a pity. I should have got one years ago.