What is the difference in '85 and 86 Hitachi HSC33 Carbs?

I just pulled the carbs on a '85 XJ700N parts bike I bought and except for missing one bowl screw, they look very good and mostly clean. According to Chacal, the carbs presently on my '85 XJ700N are 1986 carbs since the outer carb bodies are painted. Since I want the bike as close to stock as possible I plan to use carbs off the parts bike. Other than the painted carbs bodies the only difference I have seen is that the parts carbs have 4 additional tubes which I assume are vents of some sort since each comes out from the left top of each carb. So my question is, are there any other differences I should be aware of and is there any particular way these vent tubes should be routed?

 

The difference between the 85 and 86... are the vac ports, and the outer 2 carbs are painted on the 86.

Is your engine black or silver? that's the biggest difference between the 86 and 85

 

Re: What is the difference in '85 and 86 Hitachi HSC33 Carbs

my engine is silver, but the #1 & 4 carbs on it are black, and only has two vent tubes. The carb I bought is all silver and has the same two vent tubes as mine plus 4 more coming out near the top or each carb. I think the po put a set of '86 carbs on my '85 bike--or I have an '86 bike that has always been titled as an '85.

There doesn't seem to be any special routing for the 4 extra vent tubes and other than that are there any functional differences?

 

What is the VIN of your bike? BTW, round tank emblems = 1985, long oval tank emblems = 1986

The HSC33 carbs without any vac ports (by the idle mixture screw area) are 1986 model carbs. The ones with the vac ports are 1985 models carbs.

All XJ700 airhead (HSC33) carbs that have a large, "pointing towards the sky" vac port on the #2 carb (only) are California model carbs...that large vac port has a hose that runs to the evaporative control emissions canister under the RH side cover.

VAC HOSE:

- the HCP5349, HCP16280, or HCP16275 (color) vacuum hose is used on the emissions control system canister on all California-only XJ700 models. A total length of 30" of hose is used: 12" for the hose running from the emissions canister to the fuel tank anti-roller valve, and a 18" length of hose from the emissions canister to the vacuum port at the very front of the #2 carb body.


FUEL HOSE:

7.95mm ID Bowl Vent Lines:

All XJ700 non-X (air-cooled models) with Hitachi carbs use two pieces of 7.95mm ID fuel line, each about 10" long, on the fuel overflow lines coming off the aluminum T-fittings located in-between the #1/2 and the #3/4 carb bodies. Be aware that these vent lines run from those t-fitting to "nowhere"; that is, their other ends do not attach to any component, and are merely vented to the atmosphere. These lines just "hang free" and point downward, exiting below the bottom of the carb rack. Yes---for these carbs, there is a virtual rats-nest of fuel lines going everywhere!


and

6.35mm ID Fuel Supply or Bowl Vent Lines:

ALL XJ-series models use 6.35mm main fuel line from the petcock fuel outlet to the carb fuel inlet(s) (on XJ650 Turbo models, this would be the short line from the fuel pressure check valve to the carb inlet). Additionally, the following models also used this same size fuel line as the bowl vent (overflow) lines:

1985 XJ700 non-X (air-cooled models) and all XJ750RL models with the original HSC33-series Hitachi carbs use four sections of 6.35mm fuel line, each about 10" long, on the short brass vacuum port coming off (horizontal and angled towards the rear) of the front left of each carb body. These hoses are routed "upwards" and backwards of the carb rack, and their open end rests below the airbox.

 

Thanks Chacal. The VIN is JYA1FG00XFA001215, and I have round tank emblems, and my carbs do not have the vac ports, but the ones on the parts bike do. It definitely appears that I have an '85 bike with '86 carbs. So I am going to clean up the '85 carbs and put them on and see what happens. I assume that the float settings on both carbs are the same. Who knows maybe these will help out with the fuel consumption--now that would be nice.

 

Re: What is the difference in '85 and 86 Hitachi HSC33 Carbs

Got the 85 carbs on and made an initial pilot screw adjustment. They are out anywhere between slightly less than 2 to slightly more than 3. the plugs are still a little dark, but the bike runs better than it ever has, and the initial check of mpg has added approx 4 mpg. Hopefully, when I get the pilot screws set correctly I'll be over 40 mpg.