Butterfly

After rebuilding my carbs on my 82 XJ650, I'm finding it very hard to get the butterfly on the first carb I'm putting back together re-installed so that there's no light coming around it in the carb throat. I put it on with the screws very lightly tightened and work the throttle shaft. I've tried and tried and can't seem to get a complete seal. I think it's really close but not perfect. Is there a secret or should I just get it as good as I can? I am using a really bright flashlight shining from the intake side so maybe I'm trying to be too perfect. Any suggestions?

 

Stop trying to be perfect!!!!

It may not be 100% crucial to be able to block 100% at the butterfly.

However, if you are OCD, then you will have to analyze the gaps it does not seal. Then message either the butterfly or the carb body to align the two properly.

However, I think you will be fine to do a bench sync and the running sync will perfect your setup.

 

Ideally the closed throttle plates will not allow light to pass.
In practice, the closed throttle plates should not allow light to pass.

Did you number ant mark the plates for correct orientation before you removed them?
If not, then you'll have to do several dy fits to find where they go. The plates were fitted by hand to each carb body when the carbs were made. Throttle plates that are not fittted correctly will bind, and cause all sorts of trouble.

 

I'm doing one carb at a time but I went ahead and numbered them and marked the up position. The one I just put together is positioned correctly but no amount of adjusting gets it perfect. It's very close but not perfect. If I just hold it up to a lamp or outside light, I don't see any light but with my very bright flashlight shining in the intake side, I see a tiny little bit. I'm not sure that I can get it any better.

 

I've been messing around with some carbs recently and I to am close. I have now got all to fully closed . When there close I started to slowly tighten the screws. Every little turn I would open the butterfly and let it snap close on its own a few times till they were completely sealed and then fully tightened them up.

This probably isn't the correct way to do it but it did work for me.

So maybe if you haven't figured it out give it a try.

Also the butterflies are very soft metal so they can get damaged very easily.

 

If it takes a flashlight directly aft of the throttle plates to show light, then you're golden. Typical test is just with daylight.
Xjrider has the right technique for getting the plates to center and not bind.

 

Ok, good. I did it just like Xjrider said so I'm thinking I should be good. Thanks guys.