I.O. Posted July 6, 2014 Share Posted July 6, 2014 Hello hoping someone can help me out on here. I have triple mikunis that upon acceleration will not let my car go above 60mph and also has a lot of stuttering and misfiring. Now I'm thinking bad fuel among tuning of the carbs. The fuel in tank is a few months old. So any help will be greatly appreciated. Also I didn't know how to share my ebay findings but there is a SK manifold and surge tank for sale for turbo carb set ups here 240Z 260z 280z Custom Surge Tank for Turbo HKS Cartech Greddy | eBay 240Z 260z 280z Triple SK Intake Manifold Triple Carburetors | eBay Quote Link to comment Share on other sites More sharing options...
Badler Posted July 6, 2014 Share Posted July 6, 2014 The ethanol in modern gas can cause a layer of water to separate out, or so I'm told. I use a fuel stabilized whenever I know I will let my Z sit for more than a month. If you want to play it really safe, you can drain the tank, or if there isn't much in there you can try diluting it with some fresh high-octane. As for Mikunis, I'm sorting through my own tuning issues at the moment. Finally broke down and bought an autometer wideband air fuel and the bung to install it. Going in tomorrow. I talked to Todd at Wolfcreek Racing who probably knows Mikunis better than anyone this side of Japan, he sent me a series of jets to tune with till I hit the sweet spot. At the end of the week I can let you have what I don't end up needing for a discount. Let me know if you are interested and I'll message you by the end of the week and let you know what I have available. Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 7, 2014 Share Posted July 7, 2014 Hello hoping someone can help me out on here. I have triple mikunis that upon acceleration will not let my car go above 60mph and also has a lot of stuttering and misfiring. Now I'm thinking bad fuel among tuning of the carbs. The fuel in tank is a few months old. So any help will be greatly appreciated. Also I didn't know how to share my ebay findings but there is a SK manifold and surge tank for sale for turbo carb set ups here 240Z 260z 280z Custom Surge Tank for Turbo HKS Cartech Greddy | eBay 240Z 260z 280z Triple SK Intake Manifold Triple Carburetors | eBay You need to update your signature with some description. There's hardly a way to answer your question with so little information provided. Engine specifics Carb setting specifics Ignition History Check out my thread triple Mikuni Help in the fuel delivery forum Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 7, 2014 Share Posted July 7, 2014 It's not an SK surge Box, it's a fabricated unit made here in the USA as a "semi replica" whatever that means. Quote Link to comment Share on other sites More sharing options...
I.O. Posted July 8, 2014 Author Share Posted July 8, 2014 Here is a vid showing the problems...need to film another as the battery died in middle of the film. Just click on link or copy and paste. http://perpetualroad.com/2014/07/08/mikuni-problems/ Quote Link to comment Share on other sites More sharing options...
Pasquale Posted July 9, 2014 Share Posted July 9, 2014 It's hard to tell for sure but it sounds like you may have a vacuum leak. Does anybody else hear hissing? Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 9, 2014 Share Posted July 9, 2014 Yep- that's the first thing I thought of with that high idle. Have you done a vacuum reading? Quote Link to comment Share on other sites More sharing options...
z240 Posted July 9, 2014 Share Posted July 9, 2014 (edited) He has the "starters" (Mikuni chokes) open when he re-starts near the end. They make a hell of a hiss/sucking sound. That's the hiss you hear, at least in that part. High idle is often also a symptom of poor sync, but vacuum leaks are more common. While I'm at it, using starter fluid or something combustable, to diagnose vacuum leaks is an old wive's tale, given my recent experience. I was playing vacuum log games with some new bits and wanted to know if they were sealed. So I grabbed a can of starter fluid and sprayed a bit around. No change in idle. Great, musta done a good job. Then for a lark (I mean 'reference point' clears throat...), I sprayed a good shot right in the barrel of one carb just to see what will happen, ie, what kind of a change am I'm expecting to hear. The damn crap made ZERO, nadda, ziltch change in idle, combustion sound, anything. Maybe if I was watching the AFR gauge. So be careful spreading that "tip".... I went back and looked at the vid again, the sucking starters/chokes are on at the start too. BTW, also noticed the engine is cold (scan of the gauges early on), all tuning should be done fully warmed. THEN you can fiddle with how it starts and runs cold. Edited July 9, 2014 by z240 Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 9, 2014 Share Posted July 9, 2014 Good catch- I didn't watch the complete video at first. Operating the throttle while starter valves/chokes are open is a no-no. You don't ever touch the gas because you will flood your engine. They are just there to start the motor in cold conditions. On CZCC I have a triple thread there that shows the manual that you might want to read. Hook up a choke cable to the starters so you can turn them off and on from inside the car simultaneously Quote Link to comment Share on other sites More sharing options...
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