new guy that needs help

[79beater]

just picked up my first xs400. Got it for nothing so i figured how can i go wrong. Ohh was i ever wrong.

a little back ground on myself

this is my 3rd road bike.... on top of about 15 dirtbikes. ive always done my own work and have more seat time on a bike than in a car. I figured a 1979 bike cant be very complicated and a quick clean of the carbs and she will be rolling in no time. ive always wanted a budget bobber or brat so i gave it a go.

After around 15 times of cleaning the carbs and reading basically every forum on here im lost and need guidance.

the symptoms are very strange

before cleaning the carbs the left cylinder did not want to run but the right would run like a champ. the left would spit and spudder but did not want to fire until the engine jumped up to 4k RPMs. both would run great there. if i tried to idle it down it would sit at 4k and then just die after trying every screw on the carb......(ive had it do different things on each screw) sometimes it would idle but will die when i try to give it any gas.

i boiled the carbs this last time and made sure everything was clean once again and put it all back together.

now the right cylinder is doing what the left was doing. wont idle and then will jump to 4k and run like a champ.

i dont know where to go from here. ive tried everything i can think of and find but nothing has helped.

some of what ive done.

tested for vacuum leaks
switched spark plugs
run it with no exhaust/airbox and different combos just to see if it would change anything

i know im missing more i looked at every thread i could find on here before i posted yet another thread on the same thing and nothing has helped.

any help is greatly appreciated and beers are on the house if you live close to Colorado springs

 

[Wolfe_11B]

Synched carbs? Have you checked to see if the plugs are getting spark while the issue is happening? If its not sparking, you can eliminate the carbs and look at the ignition side of things

 

[79beater]

thanks for the reply.

I have taken both plugs out and made sure I had spark. I want to sync the carbs but would it be possible to sync them at 4k RPMs? when its barely idling it wont run long enough to sync. im at work now but tomorrow I plan on pulling every wiring connector out and cleaning them hoping that will help.

ive never had this many problems with a motorcycle and ive probably cleaned carbs a few hundred times.

 

[Wolfe_11B]

Have you checked timing? Points? Valve adjustment? Just throwing out ideas

 

[79beater]

so I have not touched timing or points. I actually found a few posts on the points today not sure how to mess with that but will dive into all of it again tomorrow. the bike has 12000 miles so is timing a stretch or no?

 

[Wolfe_11B]

Get the valves right first

 

[79beater]

I will get that done but would that explain one cylinder running good and not the other and then it changing cylinders?

 

[Wolfe_11B]

Well it might be the carb synch. But to do that the valves need to be in spec, so you have to start there

 

[79beater]

awesome I will get that done tomorrow. I guess my last question is can it be synced at 4k rpms and maybe it lowers the idle or don't even try it?