It Runs!!! Well too! But...

I bought a set of carbs off fleaBay and worked them over very well. Nice and clean and turned the mixture screws 3 turns from bottomed out. Life is great.

However, when I connect the throttle cable to the linkage, the bike ramps up to 4-5K rpm and hangs there. Unhook it and life is great. Nice even idle at 1K.

My question is regarding the new carbs I bought. They were labeled as 81-82 XJ750 carbs while my bike is an 83. Is it possible that the linkage for the 83 is longer than for the 81-82?

Did anyone run into this problem swapping carbs from different years?

 

Check your adjustment screw/nut right under the throttle handle. The more you screw it IN (toward the handle/outside of the bike) the lower your throttle will go, until the screw is bottomed out. At least that's been my experience.

Just a thought.

 

No problem swoping carbs from my 82 to my wifes 83. As shnuffy said check your adjustments.

 

make sure you dont have the throttle and choke cables swapped

 

The throttle adjustment on the handle is bottomed out. So that isn't the issue. I discovered that the hard way by making it go towards the bike, firing it up and it made the problem worse.

I know the choke is hooked up right because I witness it activate the enrichment circuit.

I think I need to lubricate the linkage. It might be simply binding and not moving properly.

Thanks for the help fellas.

 

i'm having the same problem too. i'm in the middle of resurrecting this bike from many years of sitting and have it running well at this point when i have the gas tank removed and manually work the throttle cable.
when i mount the gas tank, it's as if i suddenly put tension on the cable but i haven't.
when manually working the throttle cable when tank is off the bike, the throttle will go up and stay there or come down slow.
interesting.....

 

Is it possible that you have the wrong throttle cable. So many things can happen over the years and PO's syndrome.

MN

 

i'm thinking wrong cable could affect idle speed but not it's ability to drop back down. it's just wants to rev up to 5000 or so....

 

fwiw.....success!
by futzing with all 3 carb idle adjustment points (throttle cable, sync screw, and idle adjustment wheel), i've found a setting that just had me on my first inaugural ride around the block!
yippee!

 

also meant to apologize to "marshallnoise" for hijacking his thread. i was having the exact same symptoms and wanted to chime in.
i hope you meet with success today also.

 

Thorin, as it so happens, I did have success today. The linkage needed a bit of lubrication and the cable needed to be re-set in the linkage assembly. Between those two, life is awesome on the engine side.

I have been debating on taking it around the block too today. Decided against it because I need a headlight (i know its day time) and the tires are probably...20 years old!

 

Good decision.

My 650 is sitting in the garage on brand new 15-year old Dunlops that will have to be replaced before it turns a wheel.

 

Now that frigging hurts! But, with tires so cheap and being able to do them yourself, its a no brainer to be on the safe side.

 

never being accused of being the brightest bulb on the tree i not only took the bike out yesterday but rode it on 2 separate excursions, the last one thru a rainstorm that passed thru the area. i had the rain jacket that was stuffed in 1 of the saddlebags i got with the bike and away i went.
well, she got me back home and i'm thankful.