Pulled my carbs - Couple of questions....

Bike: 1985 XJ700

Is this buildup indicative of bad throttle seals? Carbs were very clean otherwise.




What is this tar looking crap in the bottom of the bowl? Two bowls had it.


Thanks.

 

The tar comes from the fuel.
The brown around the seals could mean they are shot, or perhaps the PO has shot some lube round there, also as the rack generally is so clean, maybe the PO soaked the rack in carb cleaner without removing the seals.

 

Does that build up on the end smell like fuel?

Regardless, you are going to need to clean and rebuild those bad boys. The throttle shaft seals are not that hard to replace, and you are going to have to replace them eventually.

Here are some links you should read, and read again if you haven't or if you have :

Church of Clean: http://xjbikes.com/Forums/viewtopic/t=14692.html

Rick's Walkthrough (Whole 9 Yards): http://xjbikes.com/Forums/viewtopic/t=2908.html

Throttle Shaft Seal Replacement: http://www.xj4ever.com/hitachi%20throttle%20shaft%20seals.pdf

For bench syncing I would strongly recommend Polock's method of lining up all 4 butterflies with the 2nd hole in the top of the venturi (to where only 2 of the 3 holes are visible).

Also if you do go about the throttle shaft seal replacement, make sure to check the action of each butterfly to make sure they close fully and snap shut completely before you re-assemble.

Also, don't forget to get your valve clearances in spec first! Good luck!

 

Yep, buildup smells like fuel.

I went through these carbs about 4 years ago or 3-4K miles and also set the valve clearances. I didn't have a colortune or a YICS tool then so I want to do it right this time.

Thanks for the links, read most of those the first time I did the carbs. Sucks the pics are gone now but once you do them it goes pretty easy the second time. I had them off the bike and the top and bottom ends apart in about an hour.

Guess I'll break down the stack.

 

Definitely sounds like it's time to replace them.

It's getting close to time to do them again Might as well check them while you are getting your hands dirty!

 

The buildup doesn't necessarily mean they're leaking. Remember, if they leak they pull air in, not out. The varnish buildup is fuel, as you smelled. When you shut you motor off there is still going to be a small amount of wet fuel in the carb throats and capillary action will pull some out the shafts. The seals are V shaped with the open side of the V facing outward and it won't seal this direction. At least that's my theory.

All that gibberish now over as long as you have them off replace the seals anyway. They are 30 years old and if they aren't leaking now they will be soon. Follow the links Shah posted above and you'll be done in no time.