over revving revisited

In regards to the over revving problem that I posted a thread about a awhile back. I pulled the carbs and
replaced the throttle control pivot, thinking that the old one was kind of beat up. Then I loosened the screws
on the butterfly valves, made sure they were centered properly and re tightened the screws. Then I bench synchronized the throttle valves with the thinnest sewing needle I could find. The carbs were clean, the slides
were closing with a snap. New fuel jets, new mixture adjustment screws, new float needle valves, float drop set
to recommended specs. But, when I started the bike, it still revved at 5 k rpms. Backtracking on my rebuild I
revisited everything I could have done wrong. I purchased a super cheap rebuild kit on Ebay. Gaskets,slide
needles and springs,mixture screws "0" rings and washers,float valves and seats, and fuel jets. All out of brass
made by a Japanese company and labeled For XJ650 maxim. The price was around $50. Was this kit
too cheap ? Should I reinstall the original components (all still in good shape) fuel jets etc. Could it be
the igniter ? (I have a spare). Or, some other component failure I have overlooked . I even pulled the air filter,
with no change. Any thoughts would be appreciated. By the way, does the idle control knob only control the
idle speed on #3 carb ? Or, will it slow the idle on all the carbs through the linkages ?

 

Did you replace the throttle shaft seals, 2 on each carb? Requires breaking the rack apart.

The idle adjustment knob does act on all 4 carbs through the linkage.

 

yes I separated the carbs and replaced the seals. but I had to pull the throttle shafts to do it and remove the butterfly
valves to get the shafts out. It was a real bear to get the butterflies back in and aligned right. thanks for the advice.
I'll try to back off on the idle control knob and see if it helps, but if the rpms don't slow down I may put the original
fuel jets and slide needles back in.

 

Happened to me recently. It may sound obvious but make sure the cable is correctly seated in the guide. Also back the idle off.
Good luck

 

Have you checked for air leaks using an unlit propane torch or some flammable spray such as starting fluid around the carb to head manifolds?

If no air leaks are found and the idle adjustment knob does not help you may want to revisit your bench sync. I used a thin strip from a business card to do my bench sync and it got me very close.

Did you wet set the float levels on all four carbs and did you check to make sure the throttle linkage is hooked up properly and not holding the butterflies open slightly? Also is the choke linkage hooked up properly and allowing the choke plungers to seat all the way?

 

By the way what model are we talking about?

 

1982 xj650 maxim

 

Who made the kit?
$50 for parts to do all four carbs is beyond inexpensive; suspiciously so.

You said slide needles were included. Swap the old (and likely still perfect) slide needles back in. That could be the problem. Those needles are very precicely ground, and any difference in their taper can effect fueling. If the new needles aren't closing the main fuel jet off when the slides are closed, that could be causing your idle to be high.

 

One other posibilty is the nut on the #3 carb is to tight ( don't ask me how this can happen ) if it is it can keep the butterflys from closing as fast as they should ...try loosing the nut with the tank off you can reach it with a 10mm wrench half a turn should do it. Just a thought. Good luck

 

I think you are right on again K-moe I'm going to swap out all the cheap brass parts for the originals. The old parts were all pretty Ok.
Also I think that making sure the throttle shaft nuts are not too tight is smart. I've always set the float drop with a homemade credit card
gauge and left it at that. I understand the wet set principle of the level in the tube equals the level in the bowl, but how do you adjust
the level with the carbs assembled. Aside from that I'm getting really good at pulling carbs out and putting them back.

 

You adjust the float levels by taking the float bowls back off, adjusting, installing the bowls, and re-checking (repeat as needed). Some people hav substituted a pyrex measuring cup in place of the float bowl to speed up the process, but I find that method to be a bit too smelly for me.
The entire wet-wet process is done with the carb rack offf of the bike, and mounted in a jig to keep the carbs level.

Link: http://www.xj4ever.com/setting fuel levels.pdf

 

Thanks again K-moe,I pulled the carbs yesterday and swapped out the new fuel jets and slide needles for the old ones, after a thorough cleaning.
The bike started right up and ran as smooth as silk at 1.5k rpms. Under a magnifying glass those parts looked identical and even had all the same markings.
a demonstration once again,that, you get wht you pay for.