siphon tubes and carburetor rebuilding

Rebuilt the petcock and carburetors on my XJ650, put new o-rings on the transfer tubes between the carburetors, carburetor kits, new throttle cable, the whole nine yards. When rebuilding the carbs I noticed that the siphon tube on one carburetor was missing, either broken off or removed by a previous owner I assume. Whatever the case I reassembled the carbs hooked everything up, started the bike, and it appears to run pretty good. Question is what purpose does the siphon tube have and will running the bike with one missing have any adverse affects? While running I did have some problems with throttle control until I adjusted the idle, now it seems to work properly.

Also the float valve seats in the carburetor kits didn't have the mesh screens on them and no way to secure the old ones on. I hope this isn't something that is critical.

The rubber connectors between the carburetor and the air box have shrunk over time and won't seal properly so I've got to do something about those. Looking into buying replacements unless someone out there has figured out a way to renew the old ones.

 

Some aftermarket Carb Kits come with Seats and NO Beenie Screens.
Normal.

Run a inline Fuel Filter.

In warmer weather, you might get-by with one missing siphon tube.

I have a Carb Body with broken Hinge Pillars. I'll see if the Siphon Tube will come out.

 

Thanks Rick! I couldn't tell whether siphon tube was pressed in, swaged in or silver soldered. Thought about trying to drill out and make new one but anxious to get on the road again so decided to postpone until winter and check out alternatives.

 

Thanks Rick! I couldn't tell whether siphon tube was pressed in, swaged in or silver soldered. Thought about trying to drill out and make new one but anxious to get on the road again so decided to postpone until winter and check out alternatives.

 

Is the Tube "Missing"?

Or, is it Broken-off?

 

If it broke off it was a very clean break flush with the surface. Thats why I thought that it may have been soldered in and it was the solder I was looking at and not the remainder of the siphon tube. My original idea was to drill the hole out and silver solder a small brass tube in the hole. Whatever the case the tube is completely missing down to the surface of the carb.

 

The siphon tube is for the enrichment circuit, AKA choke. As Rick said in warm weather shouldn't be a problem but in cold weather starting could be a bit more difficult seeing as only 3 cylinders are getting enough fuel.

As far as the airbox to carb joints there is a 10mm bolt on top of your airbox that secures it to the frame. Loosen this and you should be able to slide the airbox forward.

 

Thanks Red! Removed subject bolt but rubber connectors still too short and stiff so took the easy way out, broke out the credit card and ordered new ones.

When engine is cold it's a little difficult to start , runs like a scalded dog after it warms up for a few minutes. Also starts up first try after warmed up.
Difficulty could be due to missing siphon tube I guess.

Getting an occasional backfire when I let off the throttle so going to take a look at the timing before I try to synchronize the carbs. Just an occasional little pop but still a concern. Not sure if that could be caused by ill fitting air box connectors.

 

Exhaust leak?
Check Plugs for uniform coloration.
Tight Intake Valve?

If it's the "Popitees" Pop, pop, poppity-pop.
Or, ...
Rum-rum, pop, rum-rum-rum, poppity, rum ...
> A marginally lean hole, ... TWEAK it out.

TWEAK
Stopwatch: 60 seconds.
15 Seconds = 1/4 Turn.
Tweak = 2 -to- 5 seconds.

 

Thanks Rick! Will check plugs tonight.
Its more of the Rum-rum-rum, pop, rum-rum-rum-rum, pop.
Please educate me, when you say "a marginally lean hole" are you referring to the pilot mixture screws? The ones the manual says not to mess with or I'll bring on the wrath of the EPA and possibly other Gov agencies like the DOJ, DOT, HSA, CIA, IRS, FBI and ATF?

Exhaust leak? I did replace the gaskets where the headers connect to the head. For fear of breaking off studs have been tightening down to recomended torque a little at a time after running. The gaskets seem to compress easier when heated up.