high revs

I just got finished rebuilding a set of carbs, New jets, new float needle valves and seats,new slide needles, new
mixture needles ( set at 2 1/2 turns out) new gaskets, new throttle shaft seals and fuel tube "0" rings. cleaned
all the parts imaculately . I bench synced the throttle vaves with a small sewing needle. then I scrubbed and
lubed the throttle return springs. The slides worked perfectly. The choke and throttle cables were freshly lubed
and had proper clearence gaps. But although the bike started right up, It revved up to 6,000 rpms every time.
I shut it off quickly each time. So no damage. the rpms didn't drop when I backed off the idle speed wheel. I'm
going to pull the carbs and go through them again. any ideas on what to look for first ?

 

Disconnect the throttle cable and start it.

Then disconnect the choke cable and start it.

What happens each time?

When you hook it back up, make sure that the throttle cable sleeve is fuly seated into the holder on the carb body, and that the choke cable sleeve is clamped so the choke plungers fully close.

Does the idle speed knob have any effect on lowering the engine speed?

 

Idle knob had no effect on slowing the engine down. there was a few mm. of slop on the throttle cable
before it started to take up slack on the throttle actuating lever. It was the same with the choke lever .
A few mm. of slop before the cable started taking up slack. This was a frame up rebuild out of parts
from several bikes. Just completed assembly this morning, threw a battery in and it fired up right away
with no choke. My bench sync might not be right. Could the mixture screw be turned out to far ?( 2 1/2 from bottom )
I used a Japanese rebuild kit from ebay. All the parts seemed identical to the old parts. I pulled the carbs off the racks,
stripped them completely and soaked them all in laquer thinner for a couple of days before blowing everything out with
compressed air. I have 2 other carb sets, so, I had a model to follow during reassembly. This build was pretty spotless.
I reassembled with new throttle shaft seals and fuel tube "0" rings. I wonder if the idle speed control system is out of whack ?

 

Check for vacuum leaks.

Which model and year of XJ are you working on?

 

Might have to bench sync because one or two of the throttle blades are open too far causing a high idle condition. Even with using a needle something must be off. Try using a 1/4 in wide strip from a business card. Then check for a source of an air leak in the carb manifold boots.

 

He did bench synch.

 

It seems weird the throttle screw wont do anything when he backs it out.
Something is not closing off all the way

 

It's an 82 maxim. As soon as I can I'll pull the carbs and check whether the throttle linkage is hanging up
or whether the throttle valves are sticking open before I take the carbs apart. Fortunately I can pull a set
of carbs now in about 15 minutes and reinstall them in 45 minutes.

 

So when carbs are on or off the bike do you hear a definite "slap" when you let them close
And you mentioned that you are using parts from other bikes is it them correct cable ?

 

The throttle cable came with a set of right hand controls in good shape, with an original
hand grip, off of ebay. Everything matched the "82" maxim I already have. I coiled up
the cable and let it sit submerged in shallow drain pan full of atf, kerosene,and motor oil.
Sat overnight, The next day it slid back and forth in the jacket slickly. I think Im going to find
Somthing like a burr or rust in the carb linkage keeping it from returning to the bottom, or
maladjusted throttle plates. The slides move up and down freely and they all slap at the bottom.

 

OK ....what happened on mine one of the butterfly's was not quite centered (#1 carb) I agree a business card works real well. What I did backed all synch screws out till all were closed , held up to light if all are set right you should not see light ( my #1 carb you could see light ) lossen butterfly screws just a little open throttle and close your plate should move to close... thighten one screw down , remove other put a dab of lock tight on screw reinstall now do other screw same steps. Re check and then do bench synch. I had same high revs after redoing this I had nice idle (1050) and was easy to use my synch gauges .