New and trying not to pull my hair out. Help!!!

[WICKIDSIX]

I picked up a 82 xs650 a couple weeks ago. Someone had already attempted a bobber project and failed. Most of the parts were in boxes. over the past couple weeks I have been going through it working out the bugs. I got it to run but shitty. I pulled the carbs apart and cleaned and inspected them. everything looks intack and they didnt seem to be too dirty. However I did not soak them. Put them back on with a nice clean tank and fired it up. Fired right up with the choke and idled fine after about 30 seconds. let it warm up and went to take it for a spin. if I peg the throttle it will shut off. if i ease into it it acts like its only running on two cylinders and slowly starts to get better. then while still holding the throttle it will go fine. If i keep it in the upper rpm i can go through all the gears and it runs great. if i let the rpm drop it will start studdering again. I dont know if it makes a difference but i am currently running with the back half(including crossover) of the exhaust off. I have tried it with the four cone filters and with no filters. Any help or ideas would be great. Thanks

 

[blackbetty]

I'd check your float level and go from there. Inventory the jets, do a diaphragm test, bench sync.

 

[deadchef]

sounds like you have a 4 cylinder xs650. that could be your problem...

pics?

 

[hotrdd]

We need some pictures and need to know more about the bike. What carbs, what intakes, what ignition. Have you rejetted for the changes? Have you set the Cam Chain Tension, valve's and timing?

Check the Tech Section for some of these items.

 

[WICKIDSIX]

Thanks for the insight. Yes it is a 4cyl 650. As fas as i know everything is stock. Carbs, intakes, jetting, etc. I will start checking stuff and marking it off the list. Just hoping someone had this same issue and I could avoid some extra hair pulling. Thanks and ill check out some tech sections.

 

[Inevitable]

Errr...xs650's are 2cyl bikes?

 

[visimpact]

I thought that was gonna go a bit longer then one post.

 

[WICKIDSIX]

well it's definitely a 4 cylinder. I'm fairly new to the bike game. the guy I got the bike from didn't know much about it. I'm still in the figuring out process too. I know based off the title it's an 82 Maxim. definitely 4 cylinders with 4 carbs

 

[Adrenaline-Junkie]

Then its not an xs650, its an xj650. They may look similar but they are two different bikes with very different motors. The xj650 isnt even chain drive.

 

[weekendrider]

It is an XJ. The wiki page tells more.
http://en.wikipedia.org/wiki/Yamaha_XJ650_Maxim

My best guess is you have a restricted (fuzzy) pilot circuit.
It isn't suppling enough fuel and the air only is about to shut it down.
That is why opened quickly it dies.
Opened slowly it can supply enough fuel to make it to the next stage of fuel in the carbs and it will run well as long as you are running at that higher rpm.

There are some other sites that may be a bit more helpful as the XJ and the XS have very little in common. Even if it was to be the XS's replacement.

 

[WICKIDSIX]

Thanks alot weekendrider. Learn something new everyday.

 

[jd750ace]

Try this forum for particulars.

http://xjbikes.com/Forums

 

[WICKIDSIX]

sweet Thanks

 

[Adrenaline-Junkie]

Out of curiousity did you think you were buying an xs and got an xj?

 

[gggGary]

Wasn't there a very low volume experimental XS650 4 cylinder in 82?

 

[Adrenaline-Junkie]

Idk but since his is titled as a maxim i doubt thats what it is. If its chain drive maybe it is something special.

 

[WICKIDSIX]

Its shaft drive and I got it in a trade. Xs, xj, it doesnt matter to me. Thanks for all the info.

 

[Adrenaline-Junkie]

As long as you dont care thats all that matters i guess.

 

[weekendrider]

If he looks around here long, he'll be lookin to trade up.
gggGary you aren't thinking of the 71 GL750 prototype are you?
http://hooniverse.com/2011/06/28/two-wheel-tuesday-yamaha-gl750/
Note the reference to the 73 TX750(though not by name)