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ViragoTechForum.com Tech Help Hitachi carb cleaning problem (SOLVED)

#1:  Hitachi carb cleaning problem (SOLVED) Author: IndianaJohn Post Posted: Thu Sep 02, 2010 7:09 pm

I'm currently cleaning the carbs on my 920 and things have been going okay until now. I'm trying to clean out the passages in the float bowls, but not getting anywhere. This is the hole at the bottom side of the bowl that apparently lets fuel flow into a "well" in the side of the bowl that has a thin brass tube fitting into it from the main carb body that looks like it pulls fuel out of the well. The problem is that I have tried flushing it out by blasting carb cleaner thru it, as well as blowing through it with 100 psi air, but no luck. I pulled the bowls off my 750 carbs hoping they would be better, but only one of them has that passage clear, and the other won't yield to either cleaner or air (same as the originals). So anybody else ran into this problem? If so, how did you fix it? Sure wish I had one of those ultrasonic cleaners right about now!

Last edited by IndianaJohn on Sun Sep 05, 2010 6:07 pm; edited 1 time in total

#2:  Re: Hitachi carb cleaning problem Author: eddiethetech Post Posted: Thu Sep 02, 2010 7:52 pm

First a warning. Don't use high pressure air unless you've completely disassembled the carbs, as you may damage delicate parts, such as the diaphragm in the upper chamber.
Remove the top cover and take out the slide & diaphragm assembly. Remove the jets and float valve. There's a brass tube down in the main jet passage that comes out the top with a series of holes around it. Once removed you can soak it in cleaner and use a fine wire to clear each hole. You also have a horizontal tube across the side of the body held in by a hex plug. Take out the plug a remove the tube. There's a couple passages under it that need to be clear. Generally, just take each carb apart, one at a time so the parts don't get mixed and approach cleaning that way. Use canned air or low pressure air to test for flow by feeling for a return as you spray into each passage. If this still doesn't help, repost and let's see where to go from there.

#3:   Author: IndianaJohn Post Posted: Thu Sep 02, 2010 8:14 pm

Thanks, but I've already gone thru all that. I've done many bike carbs over the years, mostly Hondas, but also a couple of Yamahas too. I'm just down to those passages in the float bowls, and I'm stumped on how to fix this problem. Never ran into anything like this before, but I've never worked on Hitachi bike carbs before either. Kehien and Mikuni, but not Hitachi. Looks there are tiny brass jets with even tinier openings down in the bottom of those passages, and they aren't removable..............

#4:   Author: 1986 XV700 Post Posted: Thu Sep 02, 2010 8:18 pm

To clean the small passages you can go to your local Lowes, or Home Depot and look in the welding section. Welding (torch) tip cleaners come in handy. Dont try to drill or use any sharp hard metal that could become a reamer and enlarge the hole.

I've use a single strand of #12 stranded building wire, not machine tool wire like used in cars, the strands are too thin to work.

Ditto Eddie's comments above. Also make sure the screen in the top end of the needle vale seat is clean they will catch debris and clog up.

#5:  Re: Hitachi carb cleaning problem Author: babysteps55 Post Posted: Fri Sep 03, 2010 12:17 am

When I cleaned a set of 920 carbs for a buddy I had a heck of a time as well. I ended up putting carb cleaner in a syringe and injecting the fluid in the appropriate place (feed to the slow jets on those) I then used my heat gun to heat up the metal around it and then when the carb cleaner started bubbling it drained through. I had to do this twice before the passage would remain clean. My buddy installed those carbs after trying 2 other sets and god knows what else ( plugs, coils,tci) . It now runs like a charm, even with what I consider a very whimpy spark.

#6:   Author: club_c Post Posted: Fri Sep 03, 2010 12:31 am

B or G string, electric guitar, you can buy individual strings for about $1 each at a music store. Fill the tube with carb cleaner and start working that string into the tube, it will eventually start to 'leak' into the bowl as you begin to clear the passage. Yes those ones are a brute, but take time to do it...

#7:   Author: deltatango Post Posted: Sun Sep 05, 2010 6:39 am

well, its not the right way because you right "ream the hole out" but ive done a few sets of carbs now with this problem and what I used was a sewing pin, once of the ones with a colored sphere of plastic on on end. When you slide the needle down, work the tip gently around and you will find the passage at the bottom, one you find the passage give the pin a gentle push, then flush and repeat. I got a bowl that had solid varnish in that passage up to the top, completely clean this way in less than a min.

#8:  Re: Hitachi carb cleaning problem Author: mark42 Post Posted: Sun Sep 05, 2010 5:54 pm

The passage is not all thet small. I used a small drill bit to clean mine out.
just use your fingers to turn the bit.

#9:   Author: IndianaJohn Post Posted: Sun Sep 05, 2010 6:04 pm

Well, I didn't have any guitar string and wasn't going to drive all the way into town for one, so I got to thinking about how bicycle cables use inner cables made of very thin stiff strands of wire, so I dug around in the barn and found an old length of cable. I pulled a strand out of the inner cable, then squirted some carb cleaner down into the top hole of the bowl passage and stuck the wire down in there and started twirling it between my fingers. After a few seconds, carb cleaner began to flow out into the bowl thru the bottom hole. In fact in one case I was able to see very fine particles flush out with the cleaner. I then sprayed cleaner thru from the top, and blew out with air a couple of times. So I guess this one is solved!
ViragoTechForum.com Tech Help Hitachi carb cleaning problem (SOLVED)


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