XJ750 Carb hoses.

I recently bought a XJ750 off ebay. I only paid £280 for it, as it wasn't running too good. the previous owner had fitted replacement carbs. I found that the carbs had a hose coming from the left hand side of each carb .near to the top of the carb body. The other end of the hoses were open,and the carbs appeared to be drawing air through the hoses. I plugged the ends of the hoses, balanced the carbs and the bike runs OK. But where should these hoses be connected to. They are not the drain pipes, they are in addition to these. I have noticed that they are not present on earlier bikes. Mine is a 1984.

 

A BIG welcome to you Bill!
Possibly an atmospheric vent perchance? Photos would be most helpful.

 

I am just going to take photos, and attempt to upload them. Not too good with these things.

 

Could these be the synch ports? There shouldn't have been hoses attached to them though and plugging them would explain making the bike run better.

Greg

 

I have a set as well. I was wondering also what the extra tubes were for. On mine looks to be vents. My set is on my xj700. Any one.

 

I think those only came on HSC33 carbs and there was another post on the forums about what those are for but for the life of me I can't remember.....perhaps fuel or air vents????

 

Did we ever figure this one out. I have a set like this on my 85 maxim and would like to know what they are for. Right now mine are just dangling there. Bike runs awsome.

 

They're Vacuum breaks and vents.

Run the hoses down so they vent below the airbox.
They vent to the atmosphere allowing the vacuum pressure to draw fuel.
They vent fuel out of the fuel bowls preventing flooding when the boogey-man make da bike faw donn!

 

Arent the two other ones mounted forther down used for that. I understand the whole venting to the stmosphere thing. But if they are used for that then shouldn't they have a filter on them so the engine wont ingest dust? There are four of these mounted way on the top of the carbs.

 

We need a wide shot of the carbs to identify them.

 

I am 99 percent sure they are hsc 33 carbs. Just for the life of me grasp why they have the hose at the top of them that goes nowhere. Seems to me like they should have a filter on them or at least be routed to the air box. I dont mean to keep asking this same question, but it is one of those things that knaws on you like dog eating a bone. keeps me wondering if these being open to the atmosphere will hurt the engine eventually. I would like to keep my xj around for a long time. Sorry to be such a bother. Maybe this carb should be on the show. How It Works

 

Dunno if this info will help or not......

If you go to http://www.drpiston.com/hitachicarbs.html it's based on Virago's, but may contain some information to help. Click on the Hitachi Carb Versions 2/3 on the top right of the page to open up a picture of a carb with a tube coming out of the top.

Back to the main page in the history section, version 2 carbs had "A port added on the outside of the right carb (California models) to pull fumes from the charcoal canister back into the engine for burning."

Further down version 3 carbs had "the addition of a "Coasting Enricher" circuit which had the effect of richening up the pilot circuit on deceleration by cutting off half of the "premix" air supply to that circuit."

 

I had a set of those get mailed-in to me, today ...

They're 1985-86 XJ-700 Max-X Carbs.

The 4 Rubber hoses attached to the Carb bodies at ports close to the Top of the Carbs are:

Fuel Bowl Vents.
Let's air into the Fuel Bowl -- Drain if the bike falls over.

 

Wierd but Cool. They have my bike bike sceamin down the road. Not fun to set the float levels on, but good little runners when adjusted right. Thanks for the info. It is one of those things that, if I understand how they work they will be easier to work on. Must be the mechanic in me.