carbs, in a deeper hole than i thought

hello all, first and forwmost forgive me if its hard to follow, i'm not a mechanic, nor am i experienced,
i posted awhile back about an xj750 maxim that idled at 3000rpm, the adjustment knob between carb 2 & 3 failed to help, as did checking and oiling the throttle and choke cables. so after reading for several days on this and other sites, i took the carb back off. In attempting to locate the problem, i found that the screws on the bottom of the bowl (one for each bowl) are totally stripped, the carburator is spottlessly clean, it passes the cluck test perfectly. what really bothers me is that there are 4 brass screws one for each barrel after the butterfly valve, 3 of 4 were covered with a type of silicone, or sealer, the 4th was not, 1 & 2 seemed perfect, 3 was badly stripped, i was able to remove it after a slow tedious hour or so, and 4, the uncovered one spun, but never changed in depth, i figured out that threads were shot, and after removal was serprised to find the threads on the screw were fine, but the ones on the carb, had been drilled and rethreaded (unsuccessfully) could these two screws (on carb 1 & 3) be the reason it idles so high?

if you have any suggestions or opinions, please drop a line,
Also if anybody would care to educate me on the proper terms that may help me more accuratly describe what i see, (good diagrams are hard to find!)

thankyou
Aaron, where in SD we have MORE snow

Ps i can borrow a camera to take some pics if needed.

 

Aaron those pics would sure help.
Without a proper description I am not sure which screws we are talking about.
I am wondering if youre talking about the small mixture screws on the top of the carb?!
Those screws that are stuck in the bottom of the float bowl sound like the drain screws!? They typically get stuck!

 

Sounds like you should start surfing ebay for a carb set. Your's sound rather mucked up!

 

Sounds like arron is talking about the "mixture screws" at the top of the carbs.

That could be why your idling at ~3k.

A replacment for number 3 shouldnt be that hard a project.
....number 4 may be a whole other story. We need chacal or Rick in here to answer that question
(...Paging Dr Chacal and Nurse Rickerstein to the carb ICU, STAT!!)

 

New threads shouldn't be that hard to fix. A good epoxy repair is probably all you need, but if nothing else you could always sleeve it. Both pretty common and minor operations. Any decent machine shop should be able to do it for you. Of course you could get a whole new set, but then you would be throwing away three decent bodies. You could always find a #4 carb body off a junk set, and swap parts to the new body. Chacal has new screws for sale, and he does have a pretty quick turn around. Look in his parts post in the for sale forum for more info. As far as high idle, it could be a number of things, stuck linkages, vacuum leaks, idle screws, jets in wrong. One of the first things I would verify is that the air jets (the ones under the slide diaphram) are in correctly. The main air jet should be in the "middle" of the body, and the pilot closest to the butterfly or engine. I say this because the Haynes manual in the "how to" pictures shows them in the wrong positions. The parts diagram shows them correctly.

 

Taubman, I should have a good used carb body (bare) available for you, send me a PM with the details of what kind of bike you have. Also, by #4 you mean the far right side carb, correct? (brake lever side of the bike).

I also do have the replacement bowl drain screw.

 

ok i hope this shows up, this is a picture of my carb as it would sit if it were on the bike, the 2 screws on the left (clutch side) were fine, i made a modded flathead so it fit perfect and they came right out, the third was stripped, but came out without damaging the carb barrel, the fourth screw was fine but the barrel was ruined and rethreaded by the PO. the screw no longer fits the threads.

but removing the carb am i going to have to adjust the floats in the bowl or anything else? i just want to figure out an extra step ahead if i can.

thanks
Aaron

 

didn't seem to work, well its the 4th of 7 pic in my gallery i guess.

or this hopefully.
my photo gallery in xjbikes

 

Okay, the far right (as you're sitting on the bike) carb is the #4 carb, I'll send you a PM with the info...........

 

No, no, NO. The jets are positioned correctly in the picture. The LABELS are backwards.

 

Maybe we have different revisions or something. The one I have clearly shows the big hole closest to the engine. Wouldn't surprise me too much to learn they did a revision at some point, and only got it half right. The book I have is pretty old.

 

Here's the Correct placement of the Air Jets.



The Air Jets are OPPOSITE Fuel Jets.

The BIG Opening is PILOT Air
The SMALL Opening is MAIN Air

Spray Carb Cleaner in the Main Air Jet and you should see it come out of the Carb near the Bottomm of the Emulsion Tube.
The spray into the Pilot Air hole should come out the Pilot Jet.

 

Mine shows that as well, and that is correct. The problem is that the Haynes manual says the big hole is the Main air jet, when in fact it's the Pilot air jet.

Again, the jets are correct. The labels are backwards.

 

where on the carb is that picture? i looked around and can't seem to find anything that matches, inthe 6/7 photo in my gallery there is a set of three openings 2 of which have brass screws in them but the third is oblong. s that the same thing? these openings would be ont he back of the carb, on the airbox end.

thanks
Aaron

 

That's underneath the carb hat. To get there, you would undo the four screws, and remove the spring and diaphragm.

 

Unless you have Mikuni's and then these two Air Jets are external, down on the Intake side of the Carb.

Some Hitachi's are so virgin that these Air Jets are located beneath a cover that screws into the third hole in the photo.

The Fastener holding the cover plate in place is a Special Fastener that remains with the plate.

Unscrew the Special Fastener nd eyeball the two Air Jets and make sure that they are in the correct place.
Shoot a shot of Carb Cleaner in them.

The (Big) Pilot AIR Jet has a passage to the Pilot FUEL Jet and the Pilot Mixture Screw.

The (Small) Main AIR Jet has a passage that goes down through the Carb Body and exits in the lower center of the Emulsion Tube Bore.