main needle jet and throttle plate question

So I spent at least 3 hours trying to get these damn throttle plates to be light proof and I just can't seem to get it perfect. Is it possible that the edges of the throttle plates could have worn away over time or have worn away from rubbing on the insides of the venturi tube, specifically near where the throttle shaft runs across the back of the throttle plate?

This is as close as i could get to light proof (i shined my flashlight through the back of the carb and took a picture of what light was coming through). Another question, is it possible to compensate for this air leak through adjustment of the mixture screw or is too much air for compensation to be possible? Any tricks as to getting the throttle plates seated perfectly light proof (besides lightly seating the throttle plate screws)


Also, I feel like this is normal but there's a small metal cylinder in the bottom of the vacuum piston pictured here


and it causes the main jet needle to sit slanted, is this normal? I feel like it straightens out whenever the needle is inside the emulsion tube but i figured i'd ask anyways. the needle pictured is brand new ordered from Len.

 

It's really hard to tell from the picture how much light is leaking. It's a bit out of focus and we don't know how bright the light is. Having said that, they do typically leak a bit of light near the shaft.

Not sure which carburetor you have, and I never really looked at the bottom of the Hitachis on my 650 but it's common for there to be a protrusion that kicks the needle over a bit. Yours clearly was manufactured there.

 

Yes, the "tilted needle" is correct. Have no idea why they were designed like that.

 

The throttle plates do not have to be perfectly sealed to work; yours are close enough. What little air gets past them will not cause any trouble, unless you have other vacuum leaks in the system (which should be fixed). If you really want perfectly sealing throttle paltes you will need to take great care in dressing the edges with crocus cloth until they seal perfectly, but it is really unnecessary.

 

your motor will stall long before the throttle plates get that far closed and the running sync will take care of any tiny differences between carbs butterflies

 

Exactly, for everything said above....

 

Woohoo! That takes a great weight off my shoulders To hear that about the throttle plates. sorry guys i should have known to put my bike and everything. Its an 82 650 maxim.

And yeah it is kinda funny that they made the needles sit slanted. But i guess i was right in assuming that it wont matter once its in the emulsion tube cause it'll straighten out. Cant wait to get my colortune plug kit and get this bitch runnin nice!

Thanks for the replies yall!

 

Oh yeah also. I got my reproduction yics tool in the mail today and opened the yics chamber to check out how the tool works and i stuck that puppy in and pulled it back out and noticed there was a bunch of black wet shit all over the tool. It wasnt hard or crusty like i would assume carbon build-up would be but wet and dark, dark black almost like oil. Anyone know why or how oil could reach the yics chamber like that or is it natural for moisture to accumulate in there and turn the carbon build up into a wet mush??

 

Well, it could be fuel vapors, oil vapors, water vapors, carbon/soot/etc...... It's been 32 yrs since that has been opened, you should expect something to have been sucked in by now ----

One of the guys that comes to the carb clinic usually brings his "YICS snake" that he made, and will clean the passages for whoever wishes. I've seen some clogged right shut.

Dave

 

Clean out that YICS chamber before you put the tool in is a good idea, think rifle bore .. an oily rag and a rod or some thing like that, make it shiny and that will make the whole process easier.

 

will do.

 

The hose from the shifter cover to the air box is a oil separater. A small amount of oil (almost a mist) is returned to the air box which mix with the air/fuel. There are four holes in the top of the yics port. Use a pick of some sort with a 1/4" 90*bend to clean them. Lastly, don't leave the tool in the port too long. Allow it to cool between adjustments. A hot engine will melt rubber washers fairly quickly.

Gary H.

 

That hose is a crankcase vent--- it allows for fumes and gasses that develop in the crankcase to be vented back to the airbox where they get sucked in and burned.

Dave

 

That's what i meant Dave.

Gary H.