If I didn't have this kit in the shop I would have ordered a nicer kit (around $50). I cut the top off and welded a fat nut on the plate to accept my cable end.
#Manual for a bst40 carb mod#
Just had to mod the cable mount plate on the carb (red arrow). I had the cheap-o Motion-Pro kit and it was scary close. I went another route and used a twist kit for a 400EX.
#Manual for a bst40 carb pro#
I have talked to Motion pro and for $70 they'll make you a set of cables to connect this carb to your stock twist throttle.
Okay, so far it's just been some fun with regular tools. Do the same for the emission port next to the mixture screw (red arrow). It's a real easy clean up and accessible.Ĭap the right side vent (blue arrow) with a vacuum cap. Be sure to blow out all shavings (green arrow and pic 2). In pic 2 you can see up in where you are drilling through. You're just drilling out the blank on the left side of the carb (blue arrow). The middle has already been drilled out my Mikuni. Take the bowl off the carb and if you have a long enough bit you can do what I did and drill from one side to the other for perfect alignment(red arrow). In pic 1 find a drill bit close to the vent hole diameter but not bigger, a little smaller isn't a bad thing. The good thing is Mikuni casted in what we need once again. The hose is a little kinked and although would work it doesn't look good. The bowl vent on the right side of the carb runs right into the right frame rail too. In pic 2 the bell created from the breather should be trimmed off with a knife and then when the carb is mounted on the bike you connect that end to your 90. The red pic indicates the breather filter and it simply needs to be moved to the other end of the tube where the green arrow is. The OEM unit can be purchased separately, works very nice, sits right on top of the air box and only needs a simple mod.įirst pic shows the original configuration. It's kind of a must have unless you want to make an aftermarket set-up. I was able to get the breather tube and filter from the previous owner. IDK why but I put some red loctite on this too. You don't need to sink in all the way, just make sure it's secure. Start it in by hand and tap it the rest of the way with a hammer. This will help with routing your breather assembly later. line it up so it points near the center line of the carb. Now you can re-use the 90 you pulled out of the other hole. Line up your drill bit the best you can and keep a clean hole. Easily found in most hardware stores or possibly where you bought the 1/4" plug for the previous step.
The correct drill bit needed is a 15/32". You will need to be accurate with your drilling here. Tighten up the plug and move on to drilling out the new hole. I Used a big glob of red loctite because I never plan on taking it out again. Now that we have a nice tapped hole you can use either pipe thread sealer or a generous amount of loctite. Run the tap in far enough that the plug will mount flush when installed.
You will NOT need to re-drill the hole you just opened up for the tapping. To plug this hole you need a 1/4" pipe thread tap and a 1/4" allen head plug.
#Manual for a bst40 carb full#
Tape off anything you don't want shavings in unless you're doing a full teardown and cleaning later. Comes out easy once you get it moving and it won't hurt anything for our next step. The 90 has little barbs on is and you're basically ripping the aluminum up getting it out. The KTMs use the hole we need but I have a DR650 carb here.įirst thing you do is remove the top, spring, slide and needle/ Then stick something big and solid in the 90 and twist it out. The good thing is the place it needed to go was already casted in the housing (blue arrow) and just needs to be drilled out. All the credit goes to him.įirst thing we need to do is move this big 90 degree elbow (red arrow) that feeds a breather for the slide. The following intructions and pictures have been copied (and some edited slightly) from ATJ_Number_1's original thread and Facebook page. The original thread where all of this information came from (and where the performance results can be found) is located HERE. I suggest reading the original THREAD, as there is more info in there pertaining to the KTM version of the BST40 and various jetting recommendations. If using one from a KTM, the vent line modifications aren't needed so you may want to research exactly what needs to be done, in that case. These pictures and instructions apply if you are using a BST40 from a DR650. I thought I'd take the time to try to put it all together for anyone wanting to do this in the future. Luckily they are all available on his Facebook page, but do not have all the captions with instructions. Since his original post, most of the pictures aren't showing up. First of all, I would like to thank ATJ_Number_1 for taking the time to figure all of this out.
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