...to get some replies around here? I thought this was the best place to get help, but I've posted two threads now about tuning my Mikuni and nobody has anwered my question yet. I know rx7doctor or carl and probably quite a few more should now about Mikunis. What I need to know is if I should go with a smaller main fuel jet or go with a larger main air jet to lean out the mixture. Could somebody please help me. I have a meet to go to in less than a month and I need the car to run good for the 5 hour drive. Help would be greatly appreciated.

 

well honestly, alot of people DONT know about mikuni's. it's not a commonly used carb anymore. everyone here usually knows the nikki's, webers, and holleys. hell post about a holley and you hardly get any help. it's not you, and it's not the fact that people dont care. its just not common knowledge. sorry bro.

NOW, in general you cant just ask, what do i need to do to lean out the mix. if you drop the main jet size, your top end will be lean. if you get a bigger air bleed then your mid range will suffer as well. when does this problem start and why do you think it's rich? i may be able to help you out with general tuning knowledge here.

 

I know the feeling, I've had a lot of trouble getting help with my Mikuni. The thing still is a bundle of mysteries to me. If you want the manual, which has a ton of information, go to http://www.wolfcreekracing.com/. You can order it for $10. They also have parts and rebuild kits.

When it comes to tuning, that's definitely not my specialty. I'm letting AIM deal with that lol. They've got a dyno and a lot more experience anyway.

 

at least 5 people have helped me before so there's enough people that have experience with Mikunis. They just don't seem to ever read my posts any more.

I know my car is running rich because you can smell it in the exhaust and you can see the black spot covering my right taillight. It runs rich all the time as far as I know. People who drive behind me complain of the richness.

 

All 7's have the cologne factory going. Look, I have a Mikuni 44phh and I have gotten the following jet sizes verified over and over from different sources on both coasts and in between, so here goes:
Main Air Jet = 240
Main Jet = 200
Pilot Jet = 62.5
Pump Nozzle = 90 ( Special Order )

Also, Do you have the 24 page PHH Carburator Service Manual ?

I would like to know if there's anybody out there with parts and facility to rebuild a 44phh. I think I'd just send mine for a freshening if it were reasonable.

 

Your running a sidedraft and a RB exhaust, What did you think it was gonna smell like, Roses?

 

Sorry man, no Mikuni experience here. I will make one suggestion though, if you have not upgraded your ignition system yet, do that before you start leaning out your carb to ensure that you are burning as much of the fuel as possible. Good luck.

 

Wolf Creek Racing has parts and rebuild kits for Mikunis. I bet they have whatever you need. I have those jets in my car right now and it's just way too rich. It makes my taillight black within a week. And that's just driving 15 minutes a day. I found my manual and reread it. Ordered two different smaller sizes of main fuel jets and am waiting delivery. You can rebuild the carb yourself in an hour, maybe two. It all comes apart very easily and goes back together easily, but make sure you get it right when you put it back together. Whoever rebuilt mine before I got it put the butterfly valve shaft in backwards. I'd been driving for months with the accel. pump working the opposite way it's supposed to. You should just rebuild it yourself.

Wolf Creek Racing: http://www.wolfcreekracing.com/classified.htm
Go halfay down the page for Mikuni parts.

 

Quote from the Mikuni manual, p. 20

"D) If engine runs rough or hesitates, or if there is exhaust afterburn or dark exhaust smoke: Indication of a rich fuel mixture. Change to a smaller pilot jet, one size at a time, until knocking is apparent, then try one or two sizes larger to obtain best jetting."

The pilot system works from 0-20% throttle, which is most normal driving, other than hard acceleration. The main air and fuel jets regulate the mixture under power or acceleration.

Buy the book, it will help you understand how the carb works and how to tune it.

I have 2 Mikuni's I bought off eBay, the one for the 12a has a 52.5 pilot jet, the one for the 13b has a 57.5 pilot jet.

 

I guess I didn't read that page in the manual. Thanks for pointing that out Trochoid. I'll see what size pilot jets the carb came with and maybe order some new ones. I just wish you could rent jets to find the correct size then purchase that size. I probably shouldn't have rushed into buying hte smaller main jets. Oh well.

 

You can buy a Holley jet kit for $50 or so, Webers and Mikuni's, on the other hand, have no such thing that I know of. And jets aren't cheap for our carbs.

What we need is a traveling jet kit, so we can tune, then just replace the jets we use.

 

Werd. Main jets are $4 a piece from Wolf Creek Racing. And pump jets are $6 a piece. That's alot compared to the $50 Holley kit.