carb leaks

I cleaned out my carbs as instructed by Rick's FAQ, then broke the rack and cleaned the synch springs, etc, reassmbled, bench synched, put the carbs back on the bike, turned the key, pushed the starter button, and...the bike roared to life! I danced a jig. It's the first time this thing has started in many years.

But of course, there are some problems: There's no idle. If I stop throttling, the engine dies. But I couldn't tinker with the idle settings too much, because the carbs were leaking gas. The leaking stopped if I stop the engine, and of course goes indefinitely on prime setting. While on the bike I couldn't figure out where the leak(s) is/are, so I took the carbs back off the bike.

Are there any problem areas for leaks on the hitachis? And any suggestions how to set up a system to find the leaks while the carbs are off the bike?

 

Sounds like a stuck carb float to me -- where's it leaking from is the first thing to find. If it's a stuck float, it'll be getting into the airbox then running down the drain tube to the ground. If that's the case - you've probably got gas in your oil now too (crankcase breather tube). If you've got pod filters, it'll be coming out of one of those (makes it easy to figure out which one).

Take the bowls off and check the assembly of the floats.

 

Pretty sure it's not the float needles. I've put a lot of love in all moving carb parts these past couple weeks. They fall right out when I pull the pin out of the floats in the bowls. And there wasn't any gas in the airbox. My current theory is the transfer pipes (="fuel rail tubes"?) - I think I damaged the o-rings on them pushing the carbs back together.

 

Duct tape a funnel to the top of clear tube 2 feet long.
You will see where your carbs leak on a table. Or bench.
This is part of the float level test. Look it up here.

Also run a thin wire thru 4 jets per carb: Pilot jet in float bowl, Pilot emulsion tube and side vent, Idle jet next to Main jet, chase with carb cleaner, re-assemble.

Good luck !

 

Altus, anybody else - now my floats might be stuck. put my carbs back on the bike, the old leaks are taken care of, bike was dry under the carbs, unlike before. It was the old o-rings on the fuel rails. But now there's fuel pouring out the overflow tube in the airbox when I prime the carbs.

Maybe I don't understand what causes a stuck float. I thought it meant that the float needles were stuck in place, not letting the floats move around. The needles are fine, they move freely in the valve. Are there other things that can cause floats to stick? I've already pulled them apart and cleaned them thoroughly.

So my other thought is, maybe the level is set way high. Possible?

 

Well, I've found that if the rubber tip of the float needle is dry rotted and hard (brittle), they won't seal the opening where the fuel enters the bowl. If this valve doesn't stop the flow of fuel, then there's only one place for the overflow to go.


Short version......

Check the tips of the float needles. If they are soft and pliable, then check the float levels. If they are hard and brittle, replace with new float needles and seats.

 

After you pull the rack of carbs invert them (bowls up). Remove the bowls.

Look carefully at the floats. They should not contact the carb body. They should be supported by the hinge pin and the tang on the back of the needle valve. Make sure the tang isn't resting on the base of the seat (the nut the needle passes through).

If everything looks good grab an extra length of fuel line and put it on the inlet. Blow on the line (with mouth, no compressed air). You should be able to hear air leaking out the valve(s) that is the issue.

I'd be tempted to replace all the needles and seats unless I knew they were fairly new.

Also, while you have the float bowls off make sure the drain screws are unstuck. You have a decent chance of needing new ones which you can order from chacal along with the needles and seats.

 

Good info, thanks guys. Guess I'll take the things off again. I replaced the drain screws with Chacal's yesterday. Actually snapped the extractor bit on the last one, it was stuck really badly. Was thinking, is it also possible I just put one or more float set in upside down?

 

Hmm. Checked the needles - they're downright supple, like a woman's...anyway, they really seem to be in good shape. Seats, too. I'm gonna see about new ones anyway.

What I don't understand is how the carbs can only leak while priming. When it's running, the bike doesn't seem to have a problem. Maybe it's reduced because some of the fuel is being sent into the engine instead of the airbox. Or is it normal for the hitachi carbs to overflow if let them sit on prime for a few minutes? I guess I should have asked that to begin with.

 

Might even be eliminated. If you have a needle letting a bit of fuel in and the engine is using it faster than the leak then you don't see the problem. I had one doing exactly that, didn't find it until I tried to set float levels.

Nope, fuel valve is a safety. Should be able to leave on PRI without spilling fuel.

 

Got some new valves coming in the mail. Rigged up a funnel and line to feed fuel into the carbs, off the bike on my workbench, and narrowed down the carb that was overflowing. Can't find anything visibly wrong with the seat or needle, but I don't see what else could be causing the problem.

What about the gas I've probably leaked into the crankcase? How much damage can that cause? Does changing the oil get rid of it, or are more drastic measures required?

 

Change the oil and filter, all that's required.