Edison approach to alerantive XR400 carbs

[FChaves]

I purchased a Mikuni 167.5 Main Jet and a 1.75mm drill goes through and even has a little play. You should be ok.

I'm going to purchase some too. Drilled a 150 Main jet to 1.8mm, sould be around a 170/175 Main. 

 

But I need to drill it wider to keep testing. 

 

XR400 '96

No exhaust baffle

sea level

Hiflo Green filter

No snorkel

Bsr42 with 170/175main and 45 Pilot at 3 turns out.

 

I have a feeling that the bike's low end response was snappier with the 167.5 Main jet. Does the main jet affect so much the low end?

 

Cheers everyone

[xrikester]

I am attempting to install a 42 carb off a Predator. I can make it fit into the airbox boot, but the intake is another story. I had an old broken intake and I shaved some of the rubber out of it and was able to get the carb in, but it would barely fit. And these pieces were off the bike, don't know how I could ever do it on the bike.

Any advice from those who have done it?

[FChaves]

Xrikester, my intake boot is fairly new. And I pressed and twisted the carb until it snaped in, try lubing the rubber with some silicone grease inside and out and give it some heat with a hair drier. Quickly clean the excess lube inside the boot and press and twist it in. It takes some force. It is doable with some persistance.

If it doesnt work the first time, repeat process.

Cheers

[mudguy]

I purchased a Mikuni 167.5 Main Jet and a 1.75mm drill goes through and even has a little play. You should be ok.

I'm going to purchase some too. Drilled a 150 Main jet to 1.8mm, sould be around a 170/175 Main. 

 

But I need to drill it wider to keep testing. 

 

XR400 '96

No exhaust baffle

sea level

Hiflo Green filter

No snorkel

Bsr42 with 170/175main and 45 Pilot at 3 turns out.

 

I have a feeling that the bike's low end response was snappier with the 167.5 Main jet. Does the main jet affect so much the low end?

 

Cheers everyone

 

The main jet in the BSR42 affects the entire range, and making big swings makes it necessary to change the pilot jet size at approximately -3:1 ratio. So if you go up 3 sizes on the main you go down one size on the pilot, approximately. 

 

All those stupid carb chart have been wrong for years on this. Main jet feeds fuel to some extent in all throttle ranges

 

45/175 is pretty close, I would try moving the needle up or down. If the bike makes a boooowahhh sound when you whack open the throttle, drop the needle a clip. If it flames out then raise it a clip

 

Main jet is hard to set on the CV carb, you need WOT throttle + high RPM to get the slide all the way up and to get the bike completely off the needle to do a plug chop. A long steep uphill freeway is about the only way to do it.

[xrikester]

I am attempting to install a 42 Predator carb and I can make the airboot fit, but the intake is another story. I can't see how you guys are making it fit. I had an old broken intake and I removed some of the rubber, but even then it barely fit and didn't slide in enough IMO. And I didn't even attempt this with the parts on the bike, that would be another story.

I read the suggestion to put the carb in the airboot and remove the intake from the engine and attach it too, and then as it is bolted to the engine it will stretch the airboot enough to fit. Comparing the old and new carb I guess I can see how this would work, but the attaching it to the intake is really the issue that bothers me.

Any suggestions would be appreciated.

[xrikester]

Ignore above post, don't know why the other one wasn't showing up until after I posted it.

[mudguy]

A bit of grease or wd-40 and it slides right on.

[FChaves]

I will be doing some more testing, increasing only on the main jet and play with the fuel screw. Thanks for the input mudguy!

Cheers

[Baja trail Rider]

I am attempting to install a 42 carb off a Predator. I can make it fit into the airbox boot, but the intake is another story. I had an old broken intake and I shaved some of the rubber out of it and was able to get the carb in, but it would barely fit. And these pieces were off the bike, don't know how I could ever do it on the bike.

Any advice from those who have done it?

Here is how I did it.Took intake manifold off  bike in vise,heated with heat gun.lubed it ,pushed carb it.Let it sit 3 days,heating it few more times with carb in. Then removed air box with boot ,again heat gun.Pushed carb in,let it sit 3 days.Heat gun few more times.

[mtngoat]

What they said.

 

Once you get it together and ride for a season it will get MUCH easier as well. It's just getting it set initially that's a pain. After a year and a half mine goes back together easy peasy when I have to adjust the needle for elevation.

[xrikester]

Thanks for the input.  I will give it a try and let you know how it worked out.  I'm using it on a electric start X4 I'm putting together.

[FChaves]

Well it seems that 45p and 170mj has been working out well for me at sea level with my stocker.

Just drilled out the main jet to 195mm(dont know what mikuni size it resembles to) and pilot to 0.72mm. She fired right up with 2 turns out on the pilot screw. Tomorrow I'll be testing it out and play with the pilot screw to find the sweet spot. The funny thing is that, its my first time ever tuning a carb and I'm feeling good for giving it a go with some success. I BET THIS CARB IS VERY FORGIVING EHEHEHEH.

Cheers you all. Would never start to mess with it if it wasnt for all you guys. Thank you for all your help

[FChaves]

Well, a little update.

 

Couldn't get the bike to idle right (rough idle) The pilot jet was toooo rich, at 40ºF the bike started first kick with the pilot screw 2 turns out. When the bike warmed up, it began to stumble and had to turn the pilot screw at 1 turn out.

Went for a ride and tested the bike on a long uphill road and brrrrraaaaaaaaaaaaaaaaaaap - the main jet is approved ?

 

Rode it back home and let it cool down and switched the pilot to stock 45.

 

After the next ride I'll post up some more updates!

 

Cheers everyone!

[mudguy]

I run the 50 because I use the bike as a dual sport and don't want to mess with the choke early in the morning or changing jetting or flame outs EVER, so I picked a jet slightly to the rich side. The 50 is perfect when it is cold and humid and I just close the fuel screw a bit when it is warmer and dry. The fuel screw is very very sensitive.

[FChaves]

Hey folks! 

 

Well I've been riding with the BSR42 and the only thing odd that I feel is when I WOT for a wheelie it cuts out! 

 

Is this needle related or main too rich? Or even float related?

 

Cheers guys

[mudguy]

Raise the needle 1 clip - it will make better midrange power and not cut out when pulling a wheelie.

The stock position was probably selected to be lean for emissions compliance, max power will be richer.

Also, confirm that you have the proper spacers under the needle. One washer and a plastic donut under the needle.

I'm guessing it is a lean bog, I assume you whack the throttle and it acts like you hit the kill switch.

You should be able to open the throttle extremely fast with no hesitation.

Edited March 7, 2015 by mudguy

[FChaves]

Thanks for the input mudguy !

 

I thought it was lean, so I moved the clip down. Big mistake, it cut out on the wheelie and if I kept WOT it started sputtering!

 

Even accelerating progressively to WOT it sputtered.

 

Is this a sign I need to go down on the main? or just move the clip up on the needle?

 

Cheers!

[Manlaw]

I would like to try the bst40 on a 280 kit. Anyone with one willing to sell one? I live in Las Vegas NV.

Seems no one has tried it yet, if you have please give me your 2cents.

[afm774]

Mudguy, do you have any more spacers for the bsr42? If you do I could really use one.

[Integrapollyon]

Hello everyone, long time reader of this forum and first time with anything to say. Recently installed a bsr42 from a predator 500 on my 96 xr406r with Gordon's mods, uni-filter and exhaust baffle removed. I am running 50 pilot and 180 main with pilot screw one turn out plus jets r us pullchoke. Had to receive a pull start to get it started as couldn't figure out why it wouldn't start. Figured out I had the idle set extremely high after she fired and that's why it wouldn't start. Now it starts first or second kick hot or cold (went out before typing this and started it in flip flops to make sure before posting haha). I live at 1100' and have only taken her to 3000' so far. I ride up to 5100' regularly so will have to update with how that goes. This carb seems to have livened my bike up through all phases of riding. It leaks at the bowl gasket a bit but that will be easy fix. Thank you all for all the info posted as it helped immensely.