Carbs, carbs, carbs

[Bstryker]

Hey all!

So... My bike was running decently and I wanted to mess around with it and get my idle smoother with no deceleration popping. Did a bit of research and found that it was most likely a lean mixture, though it could be a number of reasons. So I took the initiative to take off the carbs and drill into the cap to get to the mixture screw. Being impatient I drilled through the pilot screw threads.

Is there a way that I can get the pilot screw out (which doesn't have threads) instead of buying a new set of carbs?

If not I'm looking at the TC Bro carbs with the billet aluminum intake manifolds. Would I need to change the petcock to fit this mod?

I have read through all the older threads about carbs but I just wanted to reopen this discussion for 2018 in case there were new developments. Also would fuel injection be worth it? I heard probably not. Just talking out of my butt right now but anything helps!

 

[weekendrider]

A picture of where you drilled would be helpful. If you have drilled out the threads for the pilot jet or the mixture screw most likely you will need another set. But let us see what ya got going on.

 

[gggGary]

You drilled the threads or you drilled off the slot at the top? There is a way to make a new slot.... it's not hard just takes a reasonable amount of patience and dexterity. If you've toasted the stock carbs, the kawasaki 500 carb conversion is a popular well documented mod.
PS I rebuild and buy sell carb parts would interested in your set if you give up on them.

 

[grizld1]

TC Bros, huh? Their ad claims that their VM34 kits are "tuned for the XS650." Please get this straight: a vendor can baseline carburetors for an application with known factors such as exhaust, camshaft, intake, etc, but there is no plug-and-play setup for an aftermarket carburetor and no honest vendor would claim to sell one.

 

[5twins]

Asking for advice here first probably would have saved your bacon on this one. Many of us have removed these plugs and there's a proper technique to avoid damage to the mix screw. Obviously, too late now for you but maybe this will help others in the future .....

It helps to know a little about this plug we're dealing with, in particular how thick it is, because the trick to removing it without damaging the mix screw is not to drill all the way through it. It's about 3/16" thick, 1/4" at most .....

Notice that there is a small vent hole through the center of the plug. Use this to determine when to stop drilling .....

Drill a little bit and check the hole, look at the diameter of that little vent hole. Drill a little bit more and check again. Keep doing this and watch for the diameter of that little vent hole to just start getting larger. Stop drilling, you're almost through the plug. Now you can thread the sheet metal screw you've chosen into the hole. But you'll want to prep that screw first. Grind or file the point off it so it doesn't poke through the plug and damage the mix screw .....

I turn the screw in until it bottoms out then keep turning it until it breaks the plug free and spins it. Then I grab the screw head with vice grips and yank the plug out. If you didn't drill through the plug and you blunted the tip of the screw you used, you should find a nice, undamaged mix screw below the plug. But unfortunately, many don't stop drilling in time so damaged mix screw heads are quite common. Usually, most of the screwdriver slot gets drilled away and that makes adjustment and removal difficult. What we need is a good, cheap replacement, and I'll address that next .....

 

[5twins]

When searching for replacement BS34 mix screws, at first all I was finding were a couple aftermarket offerings at about $10 each. Yamaha never listed or sold the 650 BS34 mix screw, it's not even shown on the parts diagram. But, they do list and sell mix screws for many of their other Mikuni carb equipped bikes. Could one of those be the same screw? I think it is. I ran across this one, the 12R-14105-00 .....

An eBay seller conveniently listed all this screw's dimensions .....

I've compared them to actual BS34 mix screws I have and they're a perfect match. The only thing I can't be 100% sure of is the screw's thread pitch, but it does look like a match from the pics. The best thing is the price, only about $6 .....

https://www.partzilla.com/product/yamaha/12R-14105-00-00

I plan on buying one eventually and will confirm the fit once I do.

 

[650Skull]

Yamaha must have sold them as a replacement part. Japanese Parts Manual has a part # for those jets and shows them as adjustable with no block off cap, also shows an adjustable Jet needle.............Be obsolete now i would guess.

There were other countries where they weren't constrained by US EPA restrictions. Canada,Europe,Oceania....

 

[Bstryker]

You drilled the threads or you drilled off the slot at the top? There is a way to make a new slot.... it's not hard just takes a reasonable amount of patience and dexterity. If you've toasted the stock carbs, the kawasaki 500 carb conversion is a popular well documented mod.
PS I rebuild and buy sell carb parts would interested in your set if you give up on them.

I drilled through the flat head screw at the top. I didn't actually drill until the threads are gone. Is there a good way to take the stripped head screw out? That way I think I can just replace the mixture screw without having to spend a couple hundred for a new set of carbs.
Thanks, Bstryker

 

[Bstryker]

Also something to note. The mixture screw on my left carb is going into the throttle body where the butterfly valve is. So it seems to be in there tight. I think the mixture screws are brass so they are pretty soft but could they possibly increase the diameter of the hole because I screwed it in with the drill accidentally. I don't think it's supposed to be poking out of the hole. The right one isn't. Let me know if this stuff doesn't make sense. Might have time to get pictures tomorrow.

 

[weekendrider]

If you have the plugs out you might a left twist bit. Was the bit about the diameter of the mix screw head or smaller?

 

[Bstryker]

If you have the plugs out you might a left twist bit. Was the bit about the diameter of the mix screw head or smaller?

The drill bit diameter is smaller than the mix screw.

 

[hooser]

TC Bros, huh? Their ad claims that their VM34 kits are "tuned for the XS650." Please get this straight: a vendor can baseline carburetors for an application with known factors such as exhaust, camshaft, intake, etc, but there is no plug-and-play setup for an aftermarket carburetor and no honest vendor would claim to sell one.

I never say I can get it right on but usually very close. But sometime, we aftermarket guy get it right.

Usually don't get a lot of feed back from customer good or bad . But this was nice, Bill Steven wrote "its a non rephased 20 over bore,pamco, bigger valved mild ported motor it was 54 hp I think, didn’t really care about the power just tried to dial in the tuning only ended up changing the mains a couple, but couldn’t come up with anything better than your set up, you made life easy for us!

 

[grizld1]

Yeah, Gary, sometimes a guy gets lucky and nails it. Just for shit's 'n' grins I recently set up a pair of used and abused Mikuni 33 mm. flat slide 4-stroke pumpers on my D-model. I made a WAG at jetting, nothing more. Dropped the mains 1 step to get rid of a roll-off sputter and that was that. But I don't expect to get that close on the first shot very often!

Anyway, you and Michael Morse are the only vendors I recommend for guys who need guidance on VM carbies. I can only guess at the kind of tuning advice a customer would get after the sale from some outfit that specializes in chopper bling.

 

[weekendrider]

You might try driving a Torx bit into the hole. It may have enough bite to turn the screw out.

 

[grizld1]

The procedure that's worked for me is to drill a 3/32" hole, run in a 3 mm. tap, and pull. With a small bit it's easy to feel penetration and avoid damaging the mixture screw. The hole in the cap can be resealed with a dab of silicone and reinstalled to keep out moisture and debris.

 

[gggGary]

I custom grind the end of a piece of stainless steel from an old windshield wiper, the brass is soft and you can easily cut a new slot with the stainless then use a screw driver to remove. Yes it sounds like you seated the needle. That's a GOOD thing, means the needle threads are good, this really shouldn't be that hard. Seriously if it was on my bench i'd have it out in 15 minutes. DO NOT do any of the other hole, tap, LH drill bits until AFTER the slot forming is tried. There's at least one carb running around with the original needle and the reformed slot, happy as can be! I'll try to shoot up the procedure, I swear I've done it before but can't find it...
I am the freaking KING of repurposed windshield wiper stainless strips I pretty sure I've made well over 40 tools out of that stuff. Fine point the stainless is different sizes, big van wipers have heavier, thicker, wider, little cars thinner, narrower strips. do look in the hole, if any of the body threads are showing; you have avoid bunging them up with your tool and screw driver. The little orange screwdrivers found in the chainsaw/trimmer section of the local hardware are a perfect fit for these screws.

 

[gggGary]

Do it like this .

An actual recut screw slot. That carb body got split when i attempted to use a drill and easy out, afore I figured out this trick.
keywords; idle mixture screw slot straight bs34 bs34s 80 81 82 83 special carb carbs carburetor carburetors stainless windshield strip wiper tip tool trick homemade home made brass easyout left hand LH drill bit. stuck cap air bleed burr burred stripped drill drilled EPA plug

 

[Bstryker]

Jesus gggGary. That is awesome. So all I need to do is find a sharp hard metal to create my own flathead screw slot? After I do it, do I turn the screwdriver clockwise or counterclockwise to take it out? How many turns should I do? Is it possible to turn the mixture screw while the carbs are attached and the bike is running? You guys are awesome! I'll have time to work on it this weekend. Where should I be ordering my new mixture screws from or should I just use what I have?

 

[grizld1]

1. Leftie loosy, rightie tightie.
2. Take the mix screws, springs, washers, and O-rings all the way out and clean the carb bodies with carb cleaner spray followed up with compressed air.
3. Click "Tech," follow menu to link for Carb Guide, read.

 

[Bstryker]

Hey guys, I tried garys way and it is tough and not working as well as I thought it would. I'm looking to buy new carbs and the only options I've really seen is the TC Bros VM34 or the carbs that are on Mikes XS. Anyone know which are better to buy? Everything on my bike is stock and I will refer to the carbs section in tech for jetting when I get them.
Thanks!