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Thread: Yaw Power
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rotarynews
Moderator
Too Many Rotary Websites
Posts: 206
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posted December 04, 2001 05:45 PM |
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Yaw Power
Well, I took some of your suggestions, and am sending my carb off to Paul Yaw.. Yaw Power to get the stock carby reworked, and tuned for the REPU.
It is kinda nice, since the carb is off of an 83 RX-7, he should have no problem pushing the HP up a bit... and hopefully this one won't flood like that m*****f*****ing holly!
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repuguru
Redlining
Posts: 319
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posted December 04, 2001 10:31 PM |
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I am loving mine!!
Patience is a virtue. Good things come to those who wait... Thats what I can say about my Paul Yaw Carb. It took a little time to get it. But I absolutely love it.
He set up the Nikki carb I sent with his "Street" modifications. He knows how to move alot of air through the Nikki without hogging out the venturies. Says he can make it flow about 450cfm. Now thats not setting the world on fire like a big Holley or a Weber 51, but for a daily driven street ported truck, I feel I have the absolute best combination of both worlds I have tried yet. He can explain velocity way better than I can, but I can verify that low end drivability is maintained while giving great power increases on top.
Next he milled a 74' 13b manifold upper base to accept the smaller outer throttle body of the Nikki. This looks like it was done in Hiroshima! He then put it on his flow bench. This to clean and reshape stagnant areas down each port runner and to plug and shape any imperfections and holes he deemed worthy. It is top notch the way the whole assembly came back.
I have been tuning the primary venturies over the course of a couple of weeks. Sorta going for the gas mileage on bottom. Started with a his 56' jet went to a 55',I have his 57 jet size in right now. I am going to try a 58 for a week or two just to see if there is any difference. I think I like the 57'.(S.E. U.S., street ported 13b)
I haven't even touched the secondary jets and the motor already pulls hard up top. Thats when the fun really starts.
Yaw does great work. He does great work for alot of people. So you must deal with his schedule. It took about 3 or 4 months to get my Carb/Manifold back. He may not return every call or Email you send during that waiting period, but he none the less feels your pain. He knows it is "you" that boxed up "your" stuff and sent it to "that" address in Arizona and that it is "you" that haven't heard a damn word since.
He honors his word. You'll get a good product. Please mention the REPUGuru. My dad is wanting a PY Nikki for his 1st Gen 12a RX7 , maybe Paul will cut me a break for referals.
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Jeff20B
Moderator
Posts: 661
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posted December 05, 2001 01:31 AM |
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Hmm, I have a '79-'80 12A intake manifold and two Nikki carbs from various years (I'm not sure). Maybe I should find out which carb is the '83 version and have him perform his magic on it. Maybe I'll have him mod my 13B intake manifold for a Nikki since I don't have any running 12As at this time, otherwise I'd send him my '79-'80 manifold.Aybe I should send him both my manifolds "just because". I guess I haven't given it much thought.
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'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7
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Jeff20B
Moderator
Posts: 661
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posted December 05, 2001 01:36 AM |
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Speaking of carb stuff, I installed a Racing Beat dellorto carb on my friend's REPU today. It's interesting trying to find out how much gas pedal travel there should be for this carb. We've been fingering it out pretty well though.
I also got my carb back (it is stock). I wonder how well my engine will run with this carb.
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'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7
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repuguru
Redlining
Posts: 319
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posted December 05, 2001 08:00 AM |
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Pedal travel
I had that to do also with my Nikki. The Hitachi had a different butterfly rotator on its throttle body and cable attachment point.(If that is the term I am looking for). Since this is the case the REPU cable was too short. I couldn't adjust enough slack in too it to keep from rolling the Nikki butterflies past center.
Solution?? I had to limit lower travel on the gas pedal. You already have an upper adjustment. But below the pivot there is no adjustment. I just welded a 10mm nut to the lower arm of the gas pedal. Now it can be limited with the adjustable bolt. I adjusted till I had full movement of the carb and locked it down.
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Jeff20B
Moderator
Posts: 661
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posted December 05, 2001 05:01 PM |
 Edited By: Jeff20B on 5 Dec 2001 17:05 |
Interesting fix. My REPU has a piece of sheetmetal that the previous owner glued to the paperboard material on the sound deadener on the firewall. The adjusting screw contacts the sheet metal and prevent the pedal from traveling too far. But the strange thing is the Hitachi carb that came with the engine I got has a metal N or S, more like a non slanting Z tab/bracket (yeah, that's it) bolted to the stock cable hole. The Z tab has its own cable hole which places it at least 1 inch further away from the butterfly actuator than stock. This strangely enough was perfect. The threaded end of the cable is basicaly centered in the Z tab so I even have plenty of adjustment, though it isn't really needed. When my pedal is floored, the butterflies are 100% open (perfect 90º perpendicular with the bottom of the carb). I can't explain how it turned out so perfect.
My friend's REPU, on the other hand, is seriously out of adjustment. It was originaly modded to fit an RB Holley kit. Then My REPU's engine went in it. Fortunately a stock carb has a butterfly stopper which prevents it from being over-opened. Then the guy reinstalled a Holley briefly, then installed a different engine with a dellorto. This carb used to alway over-open which had the effect of actually closing the butterflies a bit. Not good! What I was trying to do yesterday was figure out a way to limit pedal travel so when it's floored, the butterflies are opened 100% but not more. I don't think we'll need to weld a nut on the pedal arm because he found a piece of sheet metal and adjusted the screw to near 100% perfect last night. All it needs is a few more turns in the correct direction and it will be perfect. I'm trying to figure out how many spacers the OMP needs (if any at all). I also need to adjust the throttle cable tab/bracket because it is way scewed. This was done because the carb would never idle well and always got loaded up at low RPM. They over adjusted the cable to try to make up for it (and the misadjusted pedal). That was back when the ignition was trashed. Now with DLIDFIS the ignition is rock solid so we'll see if it still has that funky idle.
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'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7
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repuguru
Redlining
Posts: 319
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posted January 08, 2002 12:36 PM |
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Air Box
What do you guys run for air boxes on your Nikki's and Hitachi carbs?
Stock air box?
The Racing Beat "frisbees"?
Any of you guys holding one of those Rotary Engineering venturi air box?
I have tried them all and have come to the conclusion that the stock 74' air box works best.
The damn noise those open ones made is what finally drew me back to a stock unit. But I also never liked the idea of hot air from under the hood being used for induction. I mean most of that comes from heat rising from the header. And then I find out the combined dimensions of the four venturis is about that of a 2 inch water pipe? Hmmm... Does that open box really matter? That was it I was putting back the stocker. With a air snorkle going to cool air.
I am thinking of making my own cold air box. A sealed box with the R.E. venturi. And believe it or not I want to keep my heat riser tube working. But thats another project
What do ya'll think? And why?
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rotarynews
Moderator
Too Many Rotary Websites
Posts: 206
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posted January 11, 2002 01:55 PM |
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Got the carb back -- WOW
Wow, this carb is clean! I mean, really really really clean. The work that Paul Yaw is great, appearance wise. I should have the carb, fuel regulator, and pressure gauge on the truck soon, let's see if it does better than that horrible Holly.
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repuguru
Redlining
Posts: 319
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posted January 11, 2002 04:24 PM |
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I month!!!!!
Did he really do your carb in one month Dan? Damn, I guess being the web master of RotaryNews.com carries clout.
Do you still have the A motor in it? What jet combinations did he send? What did he start you at for a baseline jet set up?
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rotarynews
Moderator
Too Many Rotary Websites
Posts: 206
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posted January 11, 2002 04:28 PM |
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Less than a month
Actually, I sent it in around the 22nd, and got it back around the 2nd.. 2 weeks. But I've been working on my FD, and been to Detroit in the mean time. I also kinda neglected this site, so...
Anyhow, I'll get the jetting #up here soon.. and, yes, I still have the 12a in there.
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