pilot jet issues on xs650 bs34 carbs

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jonandjones

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I am rebuilding the carbs on my 80 Xs650. All the research that I have done tells me that I have bs34 carbs. I tear them apart pull all the jets and what not clean everything well , decide to go with the dyno jet kit from mikes xs. It comes and I find that the pilot jets that came with kit are different then the ones I pulled out of my carbs. I guess I'm supposed to have bs30/96's but the ones I pulled out look like vm22/210's Idk. My thoughts r someone redid these carbs and put the wrong jets in. Here's the thing I put the new pj's that came with the kit in and the bike ran like crap. So I put the jets that came with the carbs in and ran better. Anybody had this problem 80 bs34's with brass floats. I guess your not supposed to run the wrong pj's in these carbs so I'm confused. When I got the bike the motor was junk the lady that had it melted a piston. She had pods and two into one exhuast on it with stock jetting. She killed that motor. I just got done rebuilding the motor I don't want to end up the same way she did. Anyone shead any light I can post pic of the jets if someone wants to see.
 
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Mike's doesn't sell Dynojet products. His are a generic set from China or Japan. The jets are usually wrong. The needles are usually wrong. The gaskets sometime work.
Put all the parts out of your carbs back in. Just clean them up well.
Read this to, www.amckayltd.com/carbguide.pdf
This is the bible for your carbs. Readit, print it out, read it, read ut till it haunts your dreams.
It tells you how to test if your jets are the right sizes. If you need them jets , real Mikuni jets are availible locally at about the same price. If you look around you may find a local independent shop with a bunch of gently used jets in bins. Get them from the stock size up to two over on the pilots and up to three over on the mains.
Follow the guide and test them to see what your engine needs.
They might even buy back the ones you don't need.
Leo
 
Oh, I see your new here, let me say welcome to you, read and enjoy the site. It will help you get your bike running good.
Leo
 
Dyno tune kit I guess... I do have mixed feelings about mikes xs. But my town the shops around here aren't very helpful! The one yamaha shop e have the owner is a complete ass! I know hw prob has bins full of what I need but he says he don't. The othere shop we have is HD and he don't really care about old stuff. There is an old salt that does itout of his garage that has been helpful says he doesn't have jets and odd ball stuff plus he's more of a kaw nutt! Lol I took my kz440 to him and when I got it back 160 dollars later it ran worse and the tank was full of water! No lie... Well I didn't make a big deal of it tho I'm not sure how it got there?? He does know his shit tho it s fun to pick his brain. Back to the carbs it ran extremely lean stock tune. Are the pilot jets interchangable on the newer carbs. Or did mikuni I didn't know if maybe mikuni made a series that ran the older pj's. The metering orifices are different. Here's the kicker on the jets I pulled out of the carbs. They are stamped 42.5 I have some other bs34 doner carbs that I took the jets from and there 42.5. I can find a 42.5 in the vm22 style. I am completely stumped. I mentioned posting pics. Well I forgot I put thestock pj's back in the bike. I got
42.5. Pilots
135 main
The needle set in the middle.
Mix screw 2 turns
Runs good haven't rode it yet will today hopefully.
When I put the jets from mikes in there
45 pilot
145 main
Needle set in middle
3 turns on the screw
Lean at idle. No mid and rich at full...
So makes me think the jets that all the lit that I have red even the carb bible says supposed to be in there don't belong! Idk. I guess if it runs good should prob not worry I just don't want to run lean and melt again.
 
We can't really discuss jets until we know how your bike is set up filters exhaust valves and cam chain adjusted compression good on both sides charging system working. The BS34s are rather forgiving and will at least run most engine set ups with stock jetting. What needles are you running. The stock needles don't have the 4 slots.
 
BS34s have the float valves held in by screws. Float height on the brass floats is 27.3mm


CarbSpecsReducedSize.jpg
 
I have filter pods, valves are adjusted compression is good, chain is set. Floats set carb kits installed Top half just rebuild. Two into one exhuast. I got the dyno tune needle kit from mikes. Came with 135,145 mains 45 pilot and adjustable needles. I ran the bike today a bit , idles good throttle response good falls a bit on its face topend wise. The pipes seem to heat up fast plus they turn blue close to the head and then yellow a bit down the pipes. Rich?? The needle is set in the middle the rebuild was a walk in the park campared to these carbs. I swear I can take them off the bike with my eyes closed! Lol oh yeah I put the stock pjs back in
 
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Just going down the usual suspects list.
Float valve o-rings replaced.
rubber caps on pilot jets
idle screws cleaned replaced, good o-rings.
Choke circuit in float bowl clear.
carbs synched
carb cleaner check for throttle shaft, intake boot leaks
Diaphragms good, very slow drop with port blocked.
slides are correctly oriented to carb body.
Vacuum petcock diaphragms OK.
 
I have pretty much done all that. Except the throttle shaft I did soke them in b12 for about a week not realizing what that stuff will do to plasitic.haha what r your thoughts on the pipes ?
 
I think a 145 main is probably too big. And on the other end, a 135 may still be a tad small. There's been mixed reports on those dyno needle kits. Some report they don't work and end up going back to the stock needles. If you can't sort it with those new needles, that's what I'd do ..... and go one up on pilots, 2 to 3 on mains.

If you're set on installing new, adjustable needles, the Canadian needle with it's matching needle jet might be a better option.
 
Not to my knowledge. Like you said, a P.O. probably put them in by mistake.
 
What he said... I have only seen one pilot jet style in BS34s parts fiche says 42.5 stock
 
Yeah the bike ran like crap with the bs30 45 in idk maybe they wherent big enough. Im going to try and post pics of the two jets tomorrow I know people know the difference. Its just something is a miss idk Im wondering if they r completely different jets out some other mikuni. I hate to keep bringing these jets up people prob think this dude is dumb. Hopefully I get it figured out.
 
Yes, show us pics of the jets. I've never tried swapping the 2 types but, technically, it shouldn't work. The carb wasn't designed to use the VM22/210 type. As I mentioned, it may be that dyno kit needle. Others have had problems with them, some reporting they just plain don't work.
 
A heads up; some pod filters have a "too thick" lip that restricts entry ports on the carb creating running issues. And in general CV carbs need a little intake restriction "decent filter" to work well, some pod filters don't provide enough of that.
I think this is a pic of a stock jet for a BS34 :wink2:

jet.JPG
 
The pilot jets, I can't recall just now which way is which, but one type of jet has the orifice up at the threaded end, the other has the orifice down at the other end. The float bowls are designed to work with one style or the other. If you put the wrong jet in the wrong bowl the way the air flows around the jet will not draw the fuel through the jet.
On the one type of jet the air is drawn down and mixes with the fuel and is then drawn through the jet.
The other type draws fuel through the jet, then mixes the air with it.
You might get it to run, but never right.
Leo
 

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