Okay, so I suck at tuning carbs. I have read all kinds of articles about it, including a well-written one by the (maybe?)designer of Nikki carbs, but I'm still having troubles. I have a side-draft Mikuni that I ripped off of my $80 parts car, and I have managed to get it to idle at about 800-900 and choke at about 1,700-2,500 depending on where the **** is. It has a number of problems though.

Problem 1: The throttle is EXTREMELY touchy. I have gotten used to it, but it's so sensitive that when I drive other cars it feels like I am giving tons of throttle before it will even rev

Problem 2: The engine bogs down and loses revs when you floor it from idle

Problem 3: The exhaust pours out white-ish smoke at high RPM's

Problem 4: There are 3 vacuum/fluid/air/whatever tubes coming out of the carb whose purposes elude me. One is on the top next to the choke cable mount and the other two are on the bottom, symmetrical to each other. I currently have all 3 plugged up

Problem 5: There are two adjustment screws which are flat and rather wide on the top on each side. I don't know what these do either, though somebody messed with them in my tech class and they leaked fuel breifly.

Now here's the catch: One of the two idle adjust screws is broken and the tip is lodged inside the carb. I think it is limiting the fuel going to one of the rotors, which is why I have to set the throttle high and set the other idle adjust screw very low to keep it idling properly. I figure this could explain some of the problems, but if anybody recognizes the symptoms an explanation would be appreciated.

I looked all over the internet for info about my carb but I couldn't seem to find anything, so I made a quick diagram of my carb in paint. Does anybody know what the mystery items are?

 

I'm not really sure if those are OMP lines now. They are two clear (at least the were at one point in time) tubes that travel from the bottom of the carb down to the lower front-right portion of the engine. Like I said, I know nothing about carbs. So far all of my knowledge of RX-7's and car mechanics in general has come from trial and error in my automotive class.

 

Those clear lines that run down the front cover just above the oil pan are omp lines.

 

Check this site out. It has an exploded diagram of the 40 and 44 PHH.

http://www.toysport.com/catalog/Mikuni%20Carburater.htm

 

Mikuni sux get rid of it and put a holley on it

 

^what he said^

 

First realize, I only deal with weber on an NA rotary IDA/IDF models only (down drafts) so it might be different for a side draft

Problem 1: The throttle is EXTREMELY touchy. I have gotten used to it, but it's so sensitive that when I drive other cars it feels like I am giving tons of throttle before it will even rev

put a heavier return spring on it


Problem 2: The engine bogs down and loses revs when you floor it from idle

look for the accelerator enrichment pump linkage, it should have several settings, set it so it puts a smaller "squirt" of fuel in when you tramp on it, (white gray smoke on punching it = rich) if that doesn't work go the other direction to add a little more.

Problem 3: The exhaust pours out white-ish smoke at high RPM's

OMP is set higher than required, (but safer) leave alone

Problem 4: There are 3 vacuum/fluid/air/whatever tubes coming out of the carb whose purposes elude me. One is on the top next to the choke cable mount and the other two are on the bottom, symmetrical to each other. I currently have all 3 plugged up

watch it one of them is probably a vent for your air correction tubes, and blocking it will not allow them to operate properlly. pull the caps YOU put on one at a time, adn check for vacume, or fuel leakage, at idle, if you have neither than test again at WOT, if neither leave unplugged (you may experience a slight vacumn at WOT if it si the air correction tubes)(also I might not be useing the common US terminology so sorry if words don't quite match)

Problem 5: There are two adjustment screws which are flat and rather wide on the top on each side. I don't know what these do either, though somebody messed with them in my tech class and they leaked fuel breifly.

maybe sight level screws ie: remove, set needle valve until it just seeps out of them at an idle and then close them (just a suggestion i don't know)

Now here's the catch: One of the two idle adjust screws is broken and the tip is lodged inside the carb. I think it is limiting the fuel going to one of the rotors, which is why I have to set the throttle high and set the other idle adjust screw very low to keep it idling properly. I figure this could explain some of the problems, but if anybody recognizes the symptoms an explanation would be appreciated.

I looked all over the internet for info about my carb but I couldn't seem to find anything, so I made a quick diagram of my carb in paint. Does anybody know what the mystery items are?

[/QUOTE]

 

Sorry to disagree with that. I really liked the mikuni when i had it on the stock engine. What sucks is I now have to go to a Holley 600 for the bridgeport.

I'll dig out the mikuni tomorrow and look to see what I did with the port nipples. The 2 passenger side ones under the carb I know are for the mop lines, I think the other ones are capped. You will not get it to idle right with a broken screw, so you need to order that part.

There is also a place in NY that has mikuni parts. I bought 2 rebuild kits and a photocopy manual from him off eBay. Can't think of his website offhand, may be able to find that later.

 

Mystery tubes b and c are capped, but I didn't run any vacuume advance, that may be a source for it.

Mystery tube a and mystery screws are not present on either one of the 44's I have, can't help you there.

I haven't found the NY web site yet, nor my manual, which should have the address. PM me if you need anything else.

Scott.