Do yourself a BIG favor

yyub · Full Member Joined: Nov 17, 2007 Posts: 24

If you own a set of bs34 carbs you've GOT to try John's needles.I've had VM34's (bored out to 35.2) on my bike for the last 3 years and spent about half that time trying to sort out the jetting.My guess is that if Mikuni (or any body for that matter)would make a needle specific for the XS650 it would save us all a lot of headaches (and$) but instead you have to take what you can get and try to make it work. Just about the time I got them sorted pretty well John posted He had some custom needles for the BS34's .I'll make a long story short... I bought them, installed them,made the adjustments recommended by John(I've got Alphabet 2 into 1 exhaust and no air boxes ,just K&N pods) and was really impressed at how clean they run . With my setup now when I grab a handful of throttle the clutch slips. Without a doubt, it's the best $42.00 I could have invested to make my XS run so sweet!

ukie.eagle · Posted: March 11, 2008, 10:47 pm Post subject: Re: Do yourself a BIG favor

Glad to hear this YYUB: I also bought a set of the custom needles from John for the 34s on my '80...Unfortunately, the bike's been sitting at my buddies all winter [two counties away], so I haven't been able to get the carbs to do all the modifications that John suggested Sad

Just a couple of questions for you, seeing as you already did your carbs: 1)what tips could you offer for a complete beginning carb re-builder? Embarassed

and 2) did you 'un-plug' your mixture screws, & how?..I've read some people using a drill press, others a hand drill, and others say just use a self-tapping screw Confused

weekendrider · Posted: March 12, 2008, 4:48 am Post subject: Re: Do yourself a BIG favor

If you have access to a drill press it would be better to drill them. You need to limit the depth. So it doesn't trash the jet.

xsjohn · Posted: March 12, 2008, 5:05 am Post subject: Re: Do yourself a BIG favor

All of my needles also compensate for the hotter running right cylinder......Makes summer riding a lot more fun.........

xsjohn

yyub · Full Member Joined: Nov 17, 2007 Posts: 24

Mikes XS sells a kit to cover the air screws once the brass plug is removed(48-5012) which includes a new o-ring to go around the air screw. Mine were removed when I bought the bike so I haven't had any experience doing it. There are rubber plugs to cover the pilot jets in the float bowl( Mikes XS # 48-5002), these pugs also make great covers for the air screws once they have had the plug removed. When I rebuild my carbs I usually check to see if there's any wear between the needle and needle jet, if it looks questionable replace them or you'll get a rich midrange. If the float bowl has sat dry very long you should replace the pilot jet rubber plugs or you can get a rich running pilot circuit.

74yamabob · Full Member Joined: Mar 08, 2008 Posts: 24

Any sugestions on setting up the eailier carbs from a 73-74.I'm running K&N filters with a 2in 1 and stock carbs. It seems to bog down when i hit the throttle but then takes off like a scalded dog.

yyub · Full Member Joined: Nov 17, 2007 Posts: 24

Big difference between 73 carbs and 74 carbs. If you have 73 carbs make sure you have the correct choke plunger, it should have a hole in the side of it to feed the right hand carb . 74 has a plunger without the hole in it. In both cases make sure you have a gasket between the choke cover and the carb body. I assume you have different year carbs on the bike, what year is the bike?

yyub · Full Member Joined: Nov 17, 2007 Posts: 24

I have to correct myself The choke plunger changed on the 76 model, but if you have 73 or 74 carbs make sure the plunger has a hole in it.I have a 73 and when I didn't have the correct plunger in it , it ran like crap mid throttle. My brother has a 78 which ran erratically for years and we finally traced the problem to the choke covers missing their gaskets. Once replaced it was one of the sweetest running 650's I've ridden

xsjohn · Posted: March 12, 2008, 10:52 am Post subject: Re: Do yourself a BIG favor

74yamabob..........take the air filters off and try it.......

xsjohn

KYLEPRESTON · Posted: March 12, 2008, 11:12 am Post subject: Re: Do yourself a BIG favor

JOHN I have traced out a template for my batter box,
do you know how much space I need to leave the stacks to breath?

xsjohn · Posted: March 12, 2008, 11:32 am Post subject: Re: Do yourself a BIG favor

Would think an area equal to the opening.....could be from the sides too.....

KYLEPRESTON · Posted: March 12, 2008, 11:40 am Post subject: Re: Do yourself a BIG favor

I have left about 1/2 inch my battery box looks like the state of texas from profile. I was thinking of incoroporating a small air ram setup on the side to get flow when going. it looked to make sense. I know they are going to breath. they are a pain in the butt, they trumpet wider vs the pods that taper to a point. I am relocating my ignition under my tank at the front. I think my relay and reserve lighting device are going up there as well.

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

I was one of the original "guinea pigs" for john - and I can say is "wow!" Once you get them tuned in - it's like turbo charging your bike!

I constantly look down and am surprised how much faster I am going for the same amount of throttle!

yyub · Full Member Joined: Nov 17, 2007 Posts: 24

I've got stock bikes and the one with Johns needles and WOW is a good way to describe the improvement

xsjohn · Posted: March 22, 2008, 8:57 pm Post subject: Re: Do yourself a BIG favor

You guys has been a big help and I thank you for working with me in establishing the base line for these BS34's.....and everyone else involved too.......38's are next and we will see how that pans......... some good people are working on some ideas now.......getting the right straightened out is a major improvement all by itself ........especially a full operating temperatures then add the summer........

xsjohn

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

Just a reminder - in the 34's under the tin tops - below the diaphram - there is a small casting hole about 1/8" with a brass BB plug in it. - My left side had a small leak in it - allowing extra gas to bleed into the mix - richening it up. This extra gas was responsible for not only fowling my left plug sooner but also cooling the left side faster than the right. Once I plugged it with some JB weld - my right and left side temps evened out real quick.

nj1639 · Posted: March 29, 2008, 12:13 pm Post subject: Re: Do yourself a BIG favor

Still working the bugs out on my'83. Just got done making some clutch changes and took it for a spin. Slow cruise @ 3000 rpm in 5th gear and then cranked the throttle. Whoa! G force! Instant response and put me back in the seat. I'm smiling!
Thanks, John!

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

jimdi wrote:

Just a reminder - in the 34's under the tin tops - below the diaphram - there is a small casting hole about 1/8" with a brass BB plug in it. - My left side had a small leak in it - allowing extra gas to bleed into the mix - richening it up. This extra gas was responsible for not only fowling my left plug sooner but also cooling the left side faster than the right. Once I plugged it with some JB weld - my right and left side temps evened out real quick.

I'm not sure what this is is it an air port of some sort. I'll have too look into that is the original bb plug to completly stopit any one esel ahve info or piks on this. Because my rt and left on my 80 special ran same plug collor allways now the left is geting allot more carbon on it sudenly.

xsjohn · Last edited by xsjohn on March 29, 2008, 1:27 pm; edited 2 times in total

Mixture screw out a bit to far on that side maybe........I have the same bigger pilots as you do and just a bit of a turn goes a long way........they are like 46.5's....

Sorry if I repeat this too much…assuming that all else it correct….the best way for me to set the mixture screws is to check the outer ring on the plug for soot with the end of my finger……if there is lots of soot crank the pilots in a bit and try it….if there is no soot at all then the pilots may be in a bit much and lean……mine seems to run the best and smoothest with just a faint trace of soot……faint…..setting each side independently....

john

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

Ok - sorry I don't have pic's but take off the tin top - pull out the slider and diaphram - look straight down - you have the big hole that the slider went down - at 12o'clock you have the choke openings - at 6o'clock there is an oval opening for pressure equalization - at about 1 or 2 o'clock there is a small 1/16" hole that if you look down you will see either dirt or if clean - a brass BB. that should be plugged. If you follow the hole under the "cast top" you see the passages for the choke circuit - the brassk BB just blocks a casting opening from the manufacturing process. If it leaks - it lets in gas from the choke circuit into the diaphram area and it makes it's way into the mix.

If I have mine apart again - I will take a picture.

just hold them choke up at it's at about 1 or 2 o'clock.

Jim

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