painfully long carburetor jetting

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jasonrblank

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First off. Have ya momma pipes, open. Mikes xs intake filters with the chrome caps. I've set the cam chain, valves and timing in that order. Tried going up two in the idol and 3 in the mains. Spark plugs said it was too lean. Went one up 1 in the idle and 2 up in the main. Ran better but no perfect. Went 1 up in idle and 3 up in main. Sputtering stoped and ran alot better but I have no power. If I wanted to get in the freeway I'd be too slow. Maybe go 50 miles an hour. My adjuster screws on the top of carbs seem to do nothing when turned in or out. Oh, the bike is an 81 with bs34 carbs. I've read the carb guide over and over. Pulled the carbs multiple times in multiple days in a row playing with the jet sizes. I can't seem to get this bike to scream down the road as it should. The bike idles great. Just has no power. Any advice please?
 
I feel like everything I do or need to do to the carbs is backwards too. So frustrating. I also feel like my motor get to hot. I have no guages what so ever. Im using 10w40 yamalube. My first xs650 as a project build. Any info will help.
 
I think your air filter's aren't helping either. Most recommend the Unipod filters (Foam) vs. pleated.
 
These are both very good questions. I say becuses I feel like my air filters are just too open for these carbs. Also, I checked the floats twice now but I still wonder about them. I will check them again to be 100%. Doesn't take long. Do those foam filters you talk about restrict air flow a little more. I tried wrapping mine in some rags just to see and I thought maybe it helped. Jets were bigger at that time though too. I love the insight. Please keep it coming.
 
Alright. Bought the uni pods from tc bros and will check floats tommorow and install pods first thing when they arrive. Any mo re thoughts? Will keep you updated.
 
When you oil your UNI pods, just use a 50-50 mix of gas and motor oil. Don't use the special foam filter oil, it's too thick and will clog them.

If your carb set is '81 just like the bike then they will have the plastic floats. The setting for them is 22mm±1mm. Are you using the correct BS30/96 type pilot jets? The other style, the VM22/210, will fit in there but not work right. Do you have the rubber plugs in place over the pilot jets? They won't function right without them.

All your jetting attempts so far have been in the ball park, in the range of what usually works for your carbs and your mods. Although those MikesXS filters may have hindered your tuning some, I think the bike should be running better and stronger than it is. What condition is the motor in? Have you done a compression check?
 
Before pulling the carbs again maybe slip the filters off and start the bike and see if it makes a difference. Those filters you have have been known to block a passage on the carbs. 5T will know the one I mean, lol.
 
OK! Had to check back in becuses I said I would. I've got this bike screaming down the road now. Didn't even know they were this fas! Lol. What I did. First; using unipod airfilters now. Shimed needles in carbs with a home made washer from a beer can. Running 47.5 idle jets, 137.5 main jets. Biggest part here, springs from Mikes XS for the timing advance weights were tight. They were not advancing. Toolk them out and stretched them a little to make them weaker. Put them back and fired the bike up. Idles great aND pulls hard through the entire gear box. I was impressed! Just wanted to follow up for anyone else that might be struggling. I cleaned and went threw these carbs so much and it turned out to be my springs. Takes time. Enjoy the process. Thanks guys!
 
Well, we never would have guessed you had an advance unit because the bike is an '81. Normally they didn't have one. With the timing stuck in the retarded position, it's no wonder you had no power.
 
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Hey there guys! Totally new here, was going through a few forums trying to find a similar problem Im having with my first bike (81' xs650) just got it about a month ago, PO already had it as a bobber project.

What I've got going on is, it starts right up first kick, or turn of the key, idles fine, idle screw seems to work going up and down til I find that sweet sound

But... when I'm riding, when I get to what I think the top of each gear is, it seems to flatten out and kind of sputter. like I'm not getting the power this thing should have out of each gear.

PO said to get a size bigger main jets. He thought it had 137.5's but it had 140's so I put in 142.5's this morning. Still same problem. I didn't see much of s difference with backing those screws on the top out 1/8 of a turn at a time. Also has these fishtail pipes and these metal screen air pods. ANY advice at all would be great. Started riding dirtbikes last year, this is my first road bike so I'm very new to this, but also very handy if anyone can point me in the right direction. Thanks!!
 
Start by getting rid of those cone air filters. Replace them with full size Uni foam pods or better yet, the OE air box. It would help if you indicated the year/model of your bike. Rear wheel indicates a Standard but carbs indicate 80-83 Special, something has been changed. What ignition is in place, and what have you done to inspect it?
 
It's an 81 xs650. Not sure about the ignition, it's a kick start or push the button. Yeah I was just told to get rid of those cone shaped air pods and get the unipod air filters. Also just read that I should order the Canadian needle with the 3 different settings, as the one I have in it only has one setting. And may be causing it to run too rich and flatten out.
 
Gavin, you're new here so let me make a suggestion... you started this thread for this problem. Take all your info and post it there... and let everyone make suggestions there.... instead of getting confused trying to follow two different threads. Makes life much simpler. :)
 
Forget what the PO said...........Not just forget...... reset your brain so the info is gone.........

Have you read the carb guide. Tech Menu; Carbs: http://www.xs650.com/threads/carbs-carburetors.43/ first link is the carb guide..........Read the first page and links ...This is the starting point for setting up the BS34's you have. On the first page is a graph for the carb jet sizes from Factory. ..............May need to go back to original settings and start from there. ............The non adjustable needles can be set and run ok without having to change to the adjustable type. some have just used a shim to raise the needle

You may need to balance your carbs......have you done this???...........

Check the butterfly plates for wear in the throat, (scouring in the venture sides) even if there is no obvious wear there the butterfly shaft seals may be worn.

As Griz says the bike needs to be ID'd properly. There has been changes made. More pics encompassing the whole bike would help.

May not be carbs............If the bike is not revving out the mechanical advance may need checking along with the timing to make sure it is advancing properly.....
 
Don't start jumping back and forward on 2 different threads now. Incorporate old relevant, and new information into this one.
 

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