Holes above the throttle plate

Hey Im new here. Bought an 1982 xj750j cheap. Ran ruff so I did the church of clean carb cleaning twice including soaking in chem dip for several days twice, carb cleaner and air compressor blow out ect... Wet set the floats ect.... !!!! Ear tuned the air screws, sunk the carbs at idle all match, at 2500-3-- rpm the #4 not longer matches the sink of the other 3. 3 holes run great. #4 runs but the plug is wet when pulled. I have 3 tan plugs and one wet. I was looking here to see what those 2 holes one each side of the throttle plate are. Something is a miss. Couldn't seem to type in the correct key words to find out. Im thinking there is still a clogged port in the body and think those holes are dumping fuel through??? Can any one point me in the right direction. Headed to Apple mountain in a few weeks for fun one way or another !! LOL Thanks in advance for any possible help.

 

Since the carbs were dipped I hope they were seperated from the rack and you replaced the throttle shaft seals. If not then that could be part of the problem.

 

what's a "throttle plate"?
I'm thinking, if you got one wet plug ,then its not getting a spark!
stu

 

He means the butterfly

 

+1 on the care of the throttle shaft seals.

The small holes are ineed fuel passages, but if there were a blockage you would not be getting any fuel through them.
The initial synch should be set with each throttle plate set so the first hole is just barely uncovered, but the second hole is not visible when looking at the throttle plate.
Your wet plug is more indicative of a mixture issue (too rich) than of a throttle plate synch problem, or not having spark on that plug (assuming that the wetness is fuel and not oil).
Did you put the air jets back into their correct places, or did you put them where the photo in the service manual shows?

Here is a thorough explination of what goes on inside of your carbs. http://www.xj4ever.com/inside your carbs.pdf

 

If the throttle seals were bad sucking air then it would run lean I would think and I did take the rack apart for the dip. But who knows what may have occurred in the past. Will check the seal while running with a mist to see if it has any effect of sucking it in. I will double check the jets but pretty sure its correct. Did a compression test and all is well there. Im thinking maybe the fuel mixture screw is buggered. But maybe it is just more sensitive then the other 3. Any air leak would result in a high lean uncontrollable idle but it idles fine and drops rpm quick after a quick snap of the throttle. Ive been wrenching since 71 but this ones got me saying HMMMMM LOL. Any yes I replaced the o rings on the fuel screws, just an fyi the proper o rings are not available that I found and the replacements are 1mm thicker so your 2 1/2 - 3 1/2 turns, turns into 2-3 out instead. And yes a throttle plate is also called the butterfly ty !

 

Almost forgot the fuel passages where so they go to, If one is blocked then may suck more through the other, and or if a air passage was blocked maybe the same effect. HMMMM

 

The proper o-rings are available from Chacal. I just got a set myself last week.

I'm going to say that this is most likely a spark problem based on the fact you know what you're talking about (though that does not preclude something being wrong in that carb (I used to be a maintainance tech and I still triple-check my work as I'm doing it and still sometimes find mistakes)).

I'd also be inclined to check the fuel level. If it's too high the carb will tend to run rich throughout the rev range of the engine.

Not for nothing, but have you checked valve clearances yet? It would be an oddball cause, but too much overlap might conspire with the other possible factors to cause a wet plug. Normally you'd expect the clearances to be tight, but recently one member found that a PO set the clearances a bit too loose on a few valves.

 

k-moe thanks for the link, Killer

 

K-moe that was next on the list, valve clearance. TY

 

Just an FYI--- YES THEY ARE.... Just contact Len at info@xj4ever.com , or click on the xj4ever banner at the top right of the page , or find member "Chacal" ..... all the same person.

 

Ok, you got that...... I replied before finishing reading the whole thread

 

one of those holes is the pilot screw opening and the other is the choke/enrichment opening. make sure the enrichment plungers are all the way down. you said it's running on all 4 but #4 comes out wet, then i have to ask are you sure it's running on all 4 ? rearrange the plugs, see what that does i can't think of any passage that could plug up and make it rich

 

I thank everyone for the wealth of help and knowledge. I can see the pilot and traced the enrichment. there are 3 holes in all the first near the body opening, the other 2 are one each side of the butterfly/ throttle plate. I'm starting to think the mixture screw may have been damaged, next trip to the garage ganna pull one I know all is well with the #4 to see if there are any noticeable differences. I know the bike had been run way too rich for a long time and the carbon on the top of the piston and on the spark plugs I pulled from the last rider were carboned up as well.

 

Polock yes running on all 4, all 4 pipes hot.

 

Pondering what I know what would make a synk be spot on at idle but not at 2500 rpm, 1,2,3 still spot on but 4 off

 

Weak spring on the synch platform for #4? Bent linkage? Stuck slide?

If you just let it idle and then cut the ignition will the plug still come out wet?

 

there's two different kinds of springs on the sync screws, i think the spring under the screw is made with thicker wire. i'll take a look in the morning.
i'd move that plug around 10 times before i'd take those carbs off, but i am just lazy

 

I will check the linkage and spring today. I got lazy last nite and watch the UFC instead. I think that may be the synk issue and could possible dump more fuel than the other three if it was opening slightly more than them. Moved the plug around not the issue, valve clearances are spot on. Leaning toward bad or over sensitive fuel screw as well. Checked jets and needles again for miss match but not the case. Eye sight as ya get older isnt to be trusted. Slides are spot on equal nothing stuck. Diaphragms checked again with bright light in the dark if that makes sense to anyone, no pin holes. Ive had carbs on and off bikes so many times over the years it only takes me 15 mins to pull the seat, tank, clamps, disconnect choke and throttle and remove carbs under the clutch cable with ease. Makes it easier after 10-15 times the rubber on the airbox lines is so soft and pliable. If ya loosen the 10mm bolts on the air box it slides back 1/2 inch or so to give ya the little bit of play to get them out easier. I replaced the intake rubbers and gaskets when I first pulled the carbs they were cracked and dry rotted, not all the way through but I wont have it on my bike even if I only paid 250 bucks for it. The guy I bought it from tried to teach his wife how to ride on it, what a moron. You don't teach someone how to ride their first bike on a 750. Of course she smoked the clutch so new clutch plates, bearing and basket also done before I even took it for its first ride. Basket was worn and notched and hanging up. Also found rubber in the first oil change so I pulled the motor and replaced the starter chain guide. You can do it from the bottom end only ya don't have to tear down the top end. Flip it over split the case and pull the tranny, not easy access but access enough to do the job.Wanted to put and over drive gear in for 5 but no one ever did it before. Hard to believe no one but me wanted more top end LOL. O ya almost forgot do the Hitchi carbs have the rubber seal built into the carb body for the choke / enrichment shut down, looked like just brass to metal carb body on mine, but have to double check that today.

 

on the sync linkage, the spring with the heavier coils goes next to the screw head. there is no rubber seal/ o-ring in the enrichment circuit anywhere unless you count the cap over the plunger shaft

 

Thanks Polock your the man the springs are in the correct place and linkage seems to be fine. I pulled the fuel screws and at first glance they all appear to be the same but theyr not. The one not working properly I think is not the correct fuel screw. The ones that are correct are tapered conical and the one not working correctly is not as tapered and more blunt, the taper is not as long and a slightly different shape.So as you turn it out it hits a point where the taper no longer restricts the fuel flow and allows it to dump. Walla!!!!! The ahaa moment ive been looking for. Had to get out a magnifying glass to do it. Anywhere I can buy a fuel screw. The search is on. Nothing on evilbay.

 

This also explains the odd synk. I can put a mic on it but I can see with a magnifying glass it is indeed just slightly shorter and different shape than the others and no its not damaged in anyway, plain old wrong fuel mixture screw. Id bet its from a 550 maybe? Just guessing.

 

Fine thread or course?

 

Fine thread HCP 8394

 

Dug, order the idle mix screw from Len Chacal

 

Thanks gentlemen parts ordered now on to the finer things in life, life the battery sensor lol

 

Len sells those also.

 

Are you getting the idea that Len HAS EVERYTHING you need..... Even when your local yamaha dealer will adamantly tell you things are permanently unavailable? Good, you're learning quick.

 

It's easier to just change the final drive, so there isn't demand for a overdrive 5th gear. I'm not even sure there is a stock Yamaha gear that will do the job and fit.

 

You want a low rpm cruiser? Get a different bike for that.

Don't worry about the higher rpms on your bike---- it's built that way. It can wind at 7k rpm all day and be ready to go as soon as you're done gassing up. You ain't hurting it one bit.

 

Not to mention that an overdrive will lower the top speed of the bike.

 

Thanks to Chacal my preferred site vendor new throttle shaft seals and pilot screws are all installed and ready to tune tomorrow. Parts came quickly and fit perfectly!!! Thanks to all for all your help, all I need now is a little luck and off to Apple mountain Friday !!!!! If I have to put the friggin thing on my truck and take it there I will. One way or the other the bike is going LOL.