Hitachi Carbs

I recently purchased a 1982 XJ750 Maxim. The bike had sat for a while so I emptied the gas tank, flushed and check the petcock filter. At this point the bike would idle but any throtle action would stall out, although the choke would rev the engine. Then I removed the carbs, remove the main and pilot jets, cleaned them as well as the bowl. Put it back together with no improvement. Any suggestions?

 

Yes, lots.
Welcome.
Polish the slides & bores, (see clunk test) check diaphramms for perishing & pin holes, clean the emulsion tubes, clean out the enrichment channels, clean the beeny filters, check the flow from the petcock, check fuel levels in bowls & bench sync.

 

is the bike warmed up before trying to rev?

 

Wizard thanks for the advice it looks like the easy way won't work, I was hopeful that a minor clean up would do it. And to bluepotpie, the bike is warmed up, but won't rev. Thanks again to both of you, this is my first time messing with four carbs so I have my work cut out.

 

There are *NO* shortcuts with the carbs. If you don't clean them right, you'll be back again, and again, and again ...

 

dont forget about a good seal from the carbs to the intake & intake to engine. leaks cause some strange issues.

 

Looks like I'll be taking the carbs off and doing it right. Just to make sure that I'm removing them correctly, I have been leaving the rubber boots from the head to carb intact as well as the rubber boots to the air box. Is this the preferred method or is there an easier way? I've noticed some cracking starting on the engine boot, not all the way through but starting so I guess I should replace them while the carbs are off this time. Does anyone know where to purchase them? For ease of removing the carbs, do you guys recommend replacing the air filter box with pods or is that a bad idea. To confirm my jetting, the main is 120 and the pilot is 40. Thanks for your help.

 

Hey John - if they do not go all the way through, get RTV sealant, and seal them up. Try to remove those and you'll never want to touch an allen bolt again. lol.

Leave them, and seal them.

Don't go pods - can make for odd tuning and sometimes/usually needs rejetting carbs.

Those jets are right.

For taking off the carbs, disconnect your choke/throttle/fuel.
Pop the intake boots INTO the airbox, just the first half, so you have space. Make sure ALL your manifold clamps are nice and loose.
Hop on the bike and wiggle back and forth, up and down. Slide the carbs out to the left. Tada!

 

You may want to order new bowl gaskets, fuel supply o rings, throttle shaft seals, pilot screw o rings.... am I forgetting anything?

Maybe float valve needles if yours look rough.

 

The bolts on the manifold boots tend to break when you try to remove them. They are usually frozen/corroded into place. Unless you want to have to drill some holes and then tap them, do not attempt to remove the intake boots unless you *HAVE* to. As Bill said, use RTV instead.

You may want to apply some silicone lubricant to the airbox boots before shoving them into the airbox.

Don't do pods unless you know exactly what is involved and can do it successfully. If you have to ask the question, then you don't and doing so will be a very bad idea, probably leaving you very frustrated and selling the bike off for parts at a loss.

 

DANG! Those posts that hold the float pin connection are brittle. Is two out of four about average for a firt timer, or it could be two out of two seeing how I stop after breaking two, (one on each carb of course). Well my two left side carbs are junk unless you think JB Weld will work. Carbs anyone? (I'm expecting a good ribbing on this one.)

 

I would just get another set off of E-Bay and see if you can make one good set out of two. The float pins should not be frozen on there like that. Those carbs must be in rough shape for the pins to be stuck like that. Must have had water in the float bowls to rust the pins in place.

MN

 

MN, the pins were fine, but the actual float valve (10mm) nut was on there real good.

 

I see you used a wrench and when it broke loose it hit the posts and broke them off..

MN

 

JB Weld has been used sucessfully.
There were just two different threads on post repair, do a quick search.

 

If you need a couple replacement carb bodies shoot me a pm and I will take a look at what I have. I know I got at least 2 of each around. I can get pics of them also if you would like.

 

TheHound, I checked out the post threads, very impresive, a pressed fit, dove tail joint and my favorite tie wire, no that's "old skool". I'm glad I did the JB Weld fix before I saw those or I'd still be choosing between them. And Tumbelweed, you were right, there are no short cuts. I found out why my bike would only idle. One diaphram had a tear, two needed great force to lift the slides and the last one I had to use a plastic ball point pen to pry it up and almost broke the pen. It's been quite a learning experience and you guys have saved me so much time, Thanks. No my carbs are clean, the posts are repaired and I need to locate a diaphram but it's all good. Oh, did I mention there was a "wood" screw in one of the diaphram covers, at least the head matched the others. What do you expect for $100 bike.

 

XJ, not taking away from what you're doing, but check the resistance of your wires and coils. After my carb rebuild I had the same problem you originally started this topic on and it was because of a bad coil Idled perfect but had nothing with throttle input, stall and not stall, stall and not stall. Let us know if you need the correct resistance to look for, it's real clear in the manual if you have one and it's a 2 minute test with a multimeter. I'm expecing my new coils from Chacal tomorrow and will post the scenario. IMO you can't beat Chacal for the parts, search for him on this site and check out is catalog!

 

Chacal may well have a replacement piston. You cannot replace just the diaphragm, you have to replace the piston.

I suggest keeping an eye out for a spare rack of carbs ... you never know when you may need a part.

 

tumbleweed, after looking at the diaphram / slide combo I can see that they're meant as one unit and my bad one has a crack in the retainer ring as well. So how do I get in touch with Chacal ?

 

Forum index - Supporting vendor - there you will find his "catalogue"

You can PM him, just enter "Chacal" ... his name is Len.

 

that crack in the retainer ring should not be a problem, lots of them are that way and work fine