(Fuel) line sizing for 1981 KZ305 CSR

Hello, recently purchased a 1981 KZ305 CSR with what appears all original parts. Obviously the fuel lines, carb vent and fuel lines, etc. are all toast and hard and need replacing. I have a digital copy of the maintenance manual, but am having a very hard time locating the inner diameter (ID) of any of the lines for this bike. Is anyone able to provide this info? Any help or sources is appreciated.

retka wrote:

Hello, recently purchased a 1981 KZ305 CSR with what appears all original parts. Obviously the fuel lines, carb vent and fuel lines, etc. are all toast and hard and need replacing. I have a digital copy of the maintenance manual, but am having a very hard time locating the inner diameter (ID) of any of the lines for this bike. Is anyone able to provide this info? Any help or sources is appreciated.

I don't have specific experience with the 305, but most other KZ bikes use 7mm ID fuel hose.

Realize, the OEM fuel hose is thin and stretchy.  Totally different from car fuel line, which is thick, and has an internal, no stretch, woven casing inside, to keep the hose from expanding under high pressure.  Car fuel line typically comes in english fractional sizes also, like 1/4" and 5/16" size.  This type of fuel hose requires a clamp, whereas the stretchy OEM stuff doesn't.  

If you have some calipers, I strongly suggest measuring the hose at the carb inlet Tee.  If the measurement suggests 7mm ID hose, this Suzuki hose is the best I've found.  As a bonus, they provide about 5' of the stuff, so you can have lots of spare hanging around, which is quite useful.

www.partzilla.com/product/suzuki/09352-7...5f12eb99bdfbc7e11823

how tight does the suzuki fuel line fit the fuel tee? 7mm is between 1/4" and 5/16". I'm using 1/4 on the vac line and 5/16 for the fuel. both seem to be a good fit.

Thanks for the answers folks. I'll check these and give them a try / get off my lazy butt and measure the OD of the fittings. Might put together a table of the things that work for me so there's a single go to resource.

H1Vindicator wrote:

how tight does the suzuki fuel line fit the fuel tee? 7mm is between 1/4" and 5/16". I'm using 1/4 on the vac line and 5/16 for the fuel. both seem to be a good fit.

Tight enough that it's easy to install, but won't pull off.  Repeating myself, no clamp needed.  I use a screwdriver to push off the hose when trying to remove the hose from the petcock, for example.  

The lip of the intake T is 7mm but the stem is 6

You have the smaller size, 5.5 X 6.4ishmm. A couple companies dominated the Petcock market back then, Mikuni or Taiyo Giken as supplied thru various brands. I'm betting you have the TG product. Ed is Correct for the Suzuki Hose but it only fits the Larger 7mm style barbs. If you're not concerned with a splash of color, use 1/4' Tygon fuel line. Readily available at "most" hardware/lawn mower shops. Like the hose Ed mentioned and original, it's thin-walled so assembly won't be a fight. It also is a friction fit but would suggest some sort of clamp. Tygon shrinks as it ages, contrary to what most person's don't care to admit. A couple of pictures to help you distinguish the difference, Have Fun!     

Whoops, just noticed You said 'Tee" so i guess you're referring to the carb tee? I just read your initial post and it didn't mention that but..regardless, it'll work on that too.

yes my measurement was at the carb T...and my digital caliper is MIA so I had to use a plastic one, but it was my best guess