New Guy 94 with Huge Fuel Leak

[JimMoore]

HI Guys,

 

I'm new here. I hope I'm putting this in the right spot. I'm resuscitating 94. I have rebuilt and installed the carbs. When I start the bike I get a massive fuel leak. it appears to be coming from a brownish fuel pipe that appears to go into the left-rear carb. I haven't looked closely yet, but I assume the pipe is cracked, or the o-ring is leaking. Do I have to pull that carb off the bank to fix this problem? If so, is there a HowTo of some sort around somewhere? If not, I'll try to do one when I fix this mess.

 

Thanks,

 

Jim Moore

[Mikey]

Hey Jim, if you go on over to V4dreams.com the gent there recently posted a carb rebuild in his shop blog section. Excellent write up full of pictures. I'm sure people around here will pitch in as well. Good luck, we love to hear about V4's being restored. 

[Marsman99]

Yes, you'll need to separate the carbs to get to the fuel joints (fuel manifold pipes).  It would have been good to check the o-rings when you had the carbs pulled.  I just went through this on my '94 and the o-rings on the joints were all dry and cracked.  Replaced them all using the Gasket Set B (16040-MZ5-600).  You need two of these gasket sets to do all six of the "joints" that connect the 4 carbs. There will be 12 o-rings total in these two sets (4 sets of 3), each set is obviously the o-rings for both ends of the pipes that connect two carbs. Of course, if the pipes are cracked you'll need to replace them too.  If one o-ring is leaking, the others are close behind, I'd replace them all...which means all four carbs must come apart.  Don't lose the thrust springs and throttle springs, so you can have the unfortunate experience of trying to get them back into place.  This whole thing is a bit of a puzzle to reassemble.  Find the manual pages, it helps.  I can provide them and some tips if you like.

[Terry]

Apparently if it is just an o-ring leak, these can swell up in contact with fuel and start sealing again. Hope that happens for you Jim.

[JimMoore]

thanks guys. that's all great advice. Mikey, that blog was just what I'm looking for. I'm a little more confident at this point. MM99 I'm trying to do this on the cheap, but I'll keep that in mind. Thanks. terry, I'd like to think that would work, but this was not a tiny leak. This was a "Hmmm, I wonder if I should call the fire department" leak.

[JimMoore]

Hi guys. It's leaking at the spot where the gas line goes into the right rear carb. Prolly a bad o-ring, maybe a cracked line. I think I may be able to pull that carb off without disturbing too much stuff. Anyone have any suggestions?

[Marsman99]

The right rear carb is the number 3 carb.  The right front carb is the number 4 carb.  The removal sequence is 4-3 and 1-2, if you are doing one side at a time leaving the rest attached as you go.  Or 4-3-2-1 if you plan to break the set down fully.  Thus, carb four must come off before carb three.  This really needs to be done on a bench, though not impossible to do on the bike, but doing any work over open intake ports is not wise.

 

As I said before, if one o-ring is bad, the others are close.  If you have the carbs separated on a bench, it makes no sense replacing just the offending o-ring.  Replacing them all is not expensive at this point, getting stranded and having to do it all over is.  Or, worse watching the bike go up in flames.

[JimMoore]

I'm sorry, I meant left-rear. It's leaking from where the gas pipe joins the left-rear. I appreciate your thoughts though. I gotta tell ya, I'm a little intimidated by this process. I guess you're saying there is no way to remove that carb (left-rear) without disassembling the entire thing? Man, that's sapping my will to live.

[Marsman99]

If it is the left rear, then it is the number 1 carb, which means you're in luck...sort of.  The number 1 and 4 carbs come off their respective sides first if breaking down a side only.  They sit on the outside of the mounting bolt scheme, so removing the two nuts retaining the 1 carb will allow you to separate it and slide it off the two bolts that hold the two rear carbs together.  The rear thrust spring and throttle adjust spring will fall out, so watch for them.  If you insist on replacing only the one o-ring, then this is when you may get lucky.  There's a snowballs chance that the fuel joint may only pop out of the number 1 carb.  If so, you've been blessed, replace your one o-ring (ignoring the others in the set you must buy together anyway), reassemble (enjoy getting the throttle spring back in), and wait for the next leak. ?  More than likely, the fuel and air joints will come loose from both the 1 and 3 carbs, which means you have perturbed them and increased the likelihood they will leak once reassembled.  However, if they do all come out, you now have access to them and can use the rest of the o-rings in the set you bought to do the job properly.  This is not a job that takes great mechanical skill, but it does take patience, being methodical and clean. 

[JimMoore]

My will to live is returning, slowly. The thrust spring, is that the tiny spring under the plate where the throttle adjust spring rests? If so, how is that attached to those two plates? It looks like it's just sitting there.

 

Also, if I pull that carb off (#1), I think I can detach the brown fuel line from the other side and replace that o-ring too. I that what you're saying?

[Marsman99]

No, the small spring you refer to is the throttle adjust spring.  There should be two on the linkage for carbs 1 and 3.  The upper spring stays with carb 1 and should not fall out since it is retained between two linkage plates on carb 1.  The lower spring will fall out once the two carbs are separated because the lower linkage plate holding it stays with carb 3.  When assembled, the spring is retained by a small raised dimple on the carb 3 lower plate and is compressed into place by the carb 1 lower linkage plate.  I've found it easiest to install this spring last using a small flat tool (I use a dentists mixing spatula) similar to a screwdriver, only flatter.  You essentially wedge it in place and use the tool as a shoehorn to get it over the dimple.  The first time is challenging.  I suggest backing the throttle adjust screw out to provide added clearance for the lower spring.  Accurately count how many turns so you can set it back to the correct position.  Also, make sure you're prepared to look for the spring when it pops out and lands somewhere in the area.  ?

 

The other spring is the thrust spring located between the carb 1 and 3 throttle butterfly shafts.  It is bigger and is easy to snap in place at the end of assembly.  I still can't see why it is needed as the shafts are retained in each carb, but hey, don't second guess Honda Engineering, they designed this wonderful machine.

 

Yes, that's what I'm saying.  And, you'll certainly have the opportunity to replace the o-rings on both ends because it is almost certain all thee joints (pipes) connecting the two carbs will come out of each carb when you get the carbs separated.  It makes no sense to me to not replace them all at this point.  You have the carbs on a bench, you have a kit of o-rings, and the joints are just sitting there pleading to be refreshed.?

 

You'll need to disconnect the linkage arm from the carb.  It is attached at carb 1 with a small cotter pin, holding in two flat washers and a plastic spherical washer.  Pay attention to their positions before undoing them.  The spherical washer goes into the spherical cavity on the linkage.  Light grease when installing.

 

BTW, assuming your carbs are all properly synced beforehand, it is very important to make sure you screw the throttle adjust screw back to it's original position after you back it off for spring clearance.  Otherwise, you'll need to sync the carbs.  It is argued that any disassembly of the carb linkages requires syncing of the carbs.   I tend to agree with this practice.  Syncing is a whole new discussion.

 

 

 

 

 

 

[JimMoore]

Hi Guys,

 

I got everything put back together and she's running like a champ! I was able to pull the left-rear carb, and I replaced the O-rings on each side of the fuel line. buttoned it back up and I'm good-to-go. I'm going to start two separate threads, one on pulling a single carb, and one on installing the carbs on the bike. IMO I've learned THE trick for carb installation. Thanks for the help.