Fuel Hose routing, non-CA 3CV

[Bankerdanny]

So yesterday I pulled my carbs to give them a good cleaning. Been having issues with surging revs when the engine gets hot in traffic. It had mostly sat for 10 years before I bought it in late 2008 and I was overdue to clean them. Before I launch into my problem, I would like to curse the person at Mikuni who though philips head screws were a better idea than hex head bolts. 6 of the screws at the top of the carb had to be removed by using a hacksaw to cat a groove so I could use a regular screw driver.

On with the problem. I reinstalled the clean carbs and started it up and gas comes pouring out of a fitting in between carbs 1-2 (left side). I think this is partially due to an incorrect float adjustment in carb 1, which I will deal with this week, but it also appears that there is supposed to be a fuel line attached to this fitting as well as the fitting between carbs 3-4. I swear, no such fuel line was there when I took it apart.

The photo in the Clymer manual appears to show that these two fittings each have a fuel hose attached running to a T fitting, then a single hose routed...well, somewhere, I can't tell where. The photo shows the fittings pointing straight back. Mine point down and there doesn't appear to be room to install a hose and they can't rotate to point back because of the throttle shafts on the engine side and the connecting rods on the back. The only way to get them parallel to the groung would be to separate the carbs, rotate them, then re-connect.

I would appreciate any guidance I can get.

[Pat Conlon]

Those are vent lines for your fuel bowls. You want a hose on those 2 T's to help keep any dirt and grime away from the bowls. The route of the 2 hoses are over the back of the motor ending in front of, and slightly below, the swing arm pivot. The hoses need to be sloped to drain and with no kinks so atmospheric pressure gets to the bowls. If space is a problem you can install 1 more T and tie the 2 vent hoses together and run 1 hose out the back.
The vent T's between carbs 1/2 and 3/4 should point down for drainage so you're ok there. 

Cheers amigo!

[andyb]

First piece of help for you is this.  Unquestionably one of the mods that should be done to every FJ (actually to any bike with carbs on it).

In the defense of the designers at mikuni, those aren't phillips head screws.  They are JIS heads.  Looks the same and strips like butter when a phillips driver is used.  A set of JIS drivers will go a long way (doubly so if you get them to fit your impact driver) when working on older Japanese carbs (or anywhere else these are used, case covers and such).

(Yeah, I use phillips drivers on them and replace them if they piss me off.  We all do it.)


The second part Pat has right as far as the routing.  Bigger problem is why are they flowing fuel, those are vents!  The problem is you have a stuck float.  Hit them with a mallet (gently!) once they're mounted, using a stick of wood as a drift.  Don't dent things when you're trying, the aluminum is soft, and the diaphram covers are just thin steel stampings.  If that doesn't fix it, a wheelie with a hard landing, riding off a curb, or any other solid impact can handle it.

Gluck!

[Bankerdanny]

I haven't had to mess with float setting in a while thanks to fuel injected cars and a multiple year gap with no bike. But it seems to me that the floats on the FJ are harder to set than others I have worked with over the years.

Clymer says measure the height with the adjuster tab touching, but not depressing, the valve. But the slightest touch makes the valve start to slide in. I used to have a tool for setting float height, but it's long gone.

I may have to give it another shot. The cleaning definitely helped. The bike runs better (though it didn't really run bad before). But I still get a strong odor of fuel sitting at a light, which I shouldn't.

[andyb]

Clymer is correct there.  The trick is to hold the carbs at a pretty decent angle so that they're nearly balanced vertically and putting no pressure on the little pin things.

If you pull the float needle seats out entirely though, you can then replace the orings on them, as they're a semi-frequent cause of issue on these old machines.  The seats just pull straight out, but expect it to be on the difficult side.  It's pretty hard to do without distorting them.  When they're really stuck badly, i usually find a piece of steel that fits inside them as a spacer, then you can grab on pretty hard without crushing/distorting their shape.  The butt end of a drill bit can work, or a ream, but a set of measuring pins would be nicest.  The spacer has to be exactly the right size or you WILL distort the soft brass seat.

[Bankerdanny]

Hmm, I guess off come the carbs again over the long weekend. Maybe I will separate the carbs. It is easier to hold one at a time than the bank of 4.

I swapped out the float valve and its o-ring on the #1 carb, but I had to cut a groove in the screw head to get it off (after carefully covering the carb with a paper towel to keep metal shavings from falling into the carb). None of the other screws were going to come off without the same treatment and I was running out of day light (no garage), so I left them alone. Now that I know how to dissassemble everything, I can pull the carbs very quickly. So I will take the time to replace all of the float valves and o-rings.

I found a float adjusting tool on Ebay for $30. Seems like a worthwhile investment (going to have to pop for the valve bucket tool soon too).

Regarding the vent hose routing. Clymer and an owners manual I found on-line all show the hoses from the 2 vents routed up along the top of the carbs. I ended up separating carbs 1-2 and 3-4 to I could rotate the vent to face backwards (towards the rear wheel). They were facing down and there wasn't enough room to attach the hoses. I used zip ties to attach to the tie bar to keep the hose routing neat. it seemed to work well.

[racerrad8]

Hmm, I guess off come the carbs again over the long weekend. Maybe I will separate the carbs. It is easier to hold one at a time than the bank of 4.

I found a float adjusting tool on Ebay for $30. Seems like a worthwhile investment (going to have to pop for the valve bucket tool soon too).

The floats can also be checked by using a hose on the bottom of the bowl drain, open the drain screw and hold the hose up creating a "U". Document the level of the fuel below the bowl flange and you can the adjust the floats if required when you take the carbs back off.

The floats are easily adjust using a small pocket size screwdriver and bending the float tab carefully, a special float tool is not required.

If you are going to be going through the carbs, you should get the bolt & o-ring kit from David (slowoldguy)before starting so you will have S/S allen head screws and all of the required o-rings to prevent having to work on them again...

And when you are ready for the valve adjusting tool let me know, I have those in stock.

Randy - RPM