BS34 carbs rich

bassgoat1979

bassgoat1979

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I have 1980 BS34 carbs and when jetted 1 up pilot 2 up main with stock headers straight piped and XS performance filters it worked fine. I got a set of 1/2" pipes (longer but bigger ID) and now it is running rich on the midrange. I tried a small pilot jet, too lean at idle, 1 bigger than stock is perfect with the screw 1 turn out. The main is down to just one size bigger than stock, top end is great. Anybody alse have this problem?
 
"Anybody alse have this problem?" Yes I have!
I am totally focusing on getting my BS34s Jetted correctly 81 special. My setup a bit different yours but maybe what i have been going though can help you.
I have mikes XS1 Type Exhaust System and stock air boxes with more air inlets and am at 4500ft.(higher=leaner) I am also running xsJohns custom Needles.
I would say you need to Lower your needles.
After messing with this setup and trying all combinations this is what i did last night its a Huge improvement. I've got 75 miles on it today I am finley making progress, not all the way there yet but closer. , 60-65 was top speed I would up the main then the midrange 35-55 would be to rich.
I have stock jets except, I have the MainJets at 137.5 today with lowered needles it would cruse 70 freeway! but still lean, now my midrange is leaned down with the lower needles I am going to try a bigger Main
Your stock needles are not adjustable (down anyway)
heres some links that helped keep me sane working though this, go slow use your head and ride it alot and read the plugs, think, read more and try the next step.
http://www.iwt.com.au/mikunicarb.htm
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html

This is excellent direct info about our xs650s and takes a while to digest. need a login to read it.
http://xs650temp.proboards.com/index.cgi?board=carbfaq&action=display&thread=731
Have fun! I am and its a great excuse to Ride!
Me and the Carbs know each other very well.
 
'83 Heritage - 17:30 gearing, K&N air cleaners, 2 into 1 low restriction exhaust at sea level, 90 F.
137.5 mains, 47.5 pilots, XSJohns needles - All is well had it over 85, no flat spots, crisp throttle response. Don't forget to check or change the CV diaphrams. A simple test is to raise them up with your finger they should drop with a slight dampened feal. If they fall like a stone they need replacing.
 
The thing is they worked fine with the stock headers and richend up main and pilot. I know they were only desighned to be fuel saver for 80's and up, it's a battle. I gave up and going to get them on ebay, just won a set of 78 BS38s that are suppose to be in excellent condition. If they are it will work good. I got them for $100 and will get a couple kits and intakes. I've jetted quite a few bikes and NEVER had it take more than a couple hours to get right, these BS34's have been a experience! from what I've seen with the 38s is there is a lot less issues with jetting.

You may be right about the diphrams, I just don't want to spend the $130 for new ones unless it is for the 38s. Somebody told me the slide weren't rising fast enough and to drill them out .109", tried that and it did nothing. They do come down slow enough from my experience though.
 
I got a set of 1979 BS38's coming, I'll order the boots and jets monday. I was surprised I found out my bs34's sold on ebay for $60! That's more than I thought I would get. They don't sell nere as high as the BS38's. I will be glad to ship those headaches away for good!
 
Pandorasglocks said:
Haha I did the same with my bs34's bassgoat. I never looked back once I got my '79 BS38s tuned right.
Click to expand...

What pipes and filters did you use? Stock headers or single walled? What jetting to you end up going with? I just what to know the approxamate jets to buy. I was thinking two sets of pilots two up and same with the mains.
 
Check the floats in the BS38s the brass floats are a bit prone to leaking. $12 at mikes. Which boots are you going to use?
 
gggGary said:
Check the floats in the BS38s the brass floats are a bit prone to leaking. $12 at mikes. Which boots are you going to use?
Click to expand...

The floats are good, I checked the levels on both and both plugs get the some darkness. Plus I shook them. They are gone now though!:D I'm ordering parts from XS650 central from now on, and getting the ethanol safe no vaccum barbs ones. I don't really trust some of the stuff mikes sell, wouldn't trust his floats for sure. I got foot peg rubbers 3 months ago and they are pretty much cracked up junk now, not happy. His clear fuel fiters leaked and had return customers becuse of them, cost me a lot of time. They sent on set of VM pilots istead of BS ones and cost me a lot of time untill I figued it out. The compact gauges are bobby and inacurate. One thing after another and I only ever got nasty emails for him, or just no reply. I will never buy from him again unless it's a part ONLY he sells and I have to have it. XS650 central actuly will talk on the Phone! I never seen a business like Mike's with no phone number to call. Wonder why?!
 
I am confused, you have the BS38s already? I have not seen a different source than mike$X$ for BS38 floats yet. Since I exploded a float last night I will need one. Do you know of one? Yeah I am aware of the issues with mikes, I am pretty careful about what I order from him, but his markups are reasonable so I order "known makers" parts from him. I did roll the dice and ordered a set of his knock off cartridge emulators, not sure which bike will get them yet. I will probably try 650 central soon.
 
The 38's will be here Tuesday or Wednesday. But I refused to spend one more minuet working on those BS34's and sold them this morning. XS650 central should have the floats, some of the parts you have to call, leave a message and he does get back with you. As long as mikes is selling Mikuni brand, they'll be good. I just wish is there was a problem he would take care of it or at least be decent about it. I guess if I do order from him again and he won't take care of a problem, I'll just file a PayPal claim, that will get it taken care of!
 
I got the BS38's in and and have the pilot stock, the needle down one (2nd grove down from the top) and one up on the main. I got rid of the mid range stutter and for sure has excellent power after idle (pilot) clears, but now the pilot is rich. I will have to go lower than stock on the pilot I guess. Befor I buy the pilots, has anybody else had the pilot too rich when running aftermarket staight pipes (not stock headers) and XS performance pods? I always had to richen the pilot circut with more flow unless it a 2-stroke.

I'll add the carbs are completely cleaned and new needle and seats & floats are mint. The fuel level is perfect.
 

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