possibly carbs?

[youngandlearning]

I have finally finished my 77 hardtail. she cranks up after a kick or two or three, how ever she does not want to sit at idle. I'm also pretty sure my left cylnder isnt firing as good as my right side. Before I installed my bs38 carbs I disassmbled them completley, cleaned like crazy blew out every hole with an air chuck, put new gasket/float/ and float valve in. im currently running with my needle clip 2nd from the bottom (position 4 I believe) along with 27.5 pilot jets.(live in fl so no crazy altitude) I have uni pods on also along with cut off exhaust at the footpeg from mikes with 1.65 inside dia (sorry but yes im one of those guys with the cut offs haha and Ive read it has a lot to do with air flow). ive made sure my mixture screws are at 1.75 +/- .25. my bs38s are the 584 type, ive got brand new battery, plugs, coils, condensor, points. I've tried reading past post several times and ive read through the " xs650 garage carb guide" a few times but my head wants to explode. any help would be greatly appriciated !

 

[retiredgentleman]

Could be:

-needle jet O rings are worn out, allows extra gas and causes wandering idle
-ATU sticking advanced
-air leaks around intakes to carbs
-carbs not synced

 

[wherearewe]

I would try a sync first and foremost. That can make it seem one side isnt as strong.

 

[TwoManyXS1Bs]

After that, do a compression test...

 

[5twins]

You make no mention of changing main jets. Although they usually don't have much effect on idle, on this carb set they just might. The '76-'77 carb set came with the smallest mains (122.5) ever used on the 650. This works just fine on a stock bike because the the needle jets are the richest ever installed in a 650. However, once you start modding things, you quickly out pace those little mains.

I would recommend getting mains in the low to mid 130s. Get two consecutive sizes (130 and 132.5 or 132.5 and 135). Try them both and if neither is right, this will at least point you in the direction you need to go (bigger or smaller). This is a 3 to 5 size jump which is more than the other carb sets usually require but this particular set needs this because the originals were so small. Set your needles back to the middle or one step leaner (#2 slot) once you install the bigger mains.

 

[youngandlearning]

thanks for all the advice, today I bought a compression tester. my right side is at 145 and left is 155 which from research that sounds pretty good?? I thought at one point I had it idling pretty decent but then my dream got crushed Im wondering if I should do a valve lashing on the intake, I feel like its a pretty easy process and at least I could eliminate it if all checked out well? thanks for the suggestions 5twins ill order a couple sizes tonight, is mikes an ok place to get them from or do you recommend some one else?

 

[5twins]

I prefer to use only genuine Mikuni jets, which Mike's are not. You might try some of your local shops. Many have these jets on hand. I found several shops in my area that cater to dirt bikes, ATVs, and snowmobiles that have large assortment boxes of the Mikuni jets.

Yes, check your valves. For these bikes to run right, everything must be set properly. Set, in this order, the cam chain tension, the valves, the points and timing (if you have them), and finally do the carbs. Notice the carbs are last. You could just be wasting your time setting (or trying to set) the carbs if all the other stuff isn't right.

Yes, your compression sounds good. A complete tune-up and you should have a pretty good running bike.