madkaw

Flywheel is stock 230mm cut down to 16# by Top End Other mods were that I drilled around the perimeter of the ring gear in order to use a hall effect sensor someday. I was planning for a future megasquirt to control spark. In both cases, the flywheel was balanced afterwards. The balancing after drilling the ring gear was NOT done by Top End. My symptoms are vibration in the 2700- 3100 range- regardless of what gear I am in. At highway speeds it will blur my rear view mirror. Under hard driving it is most pronounced on deceleration. The vibration is rhythmic and simulates a tire out of balance. There is a time coincidence between noticing this vibration and the drilling of the flywheel. At first I only noticed it in final gear at high speeds and thought it was driveline. Now I have determined that it is RPM related only. My damper was rebuilt at the time of the engine rebuild- 10k miles. What else could be happening or what else should I look at? Recommendations as far as balancing the flywheel with the clutch? Could it be input side of my t-5 tranny?

Makes good sense! I just experienced it on my 600 mile round trip to the Midwest Heritage Z show. So I left riding with my 65 pilot jets at just shy of 2.5 turns out. With my gearing set-up, my rpm at highway speed runs between 2700rpm-3100rpm, right in that transitional area with these carbs. Engine sounded smooth at highway speed and not much in the way of a bog during acceleration----but, idle seemed way rich. At the show I pulled a plug and it was sooty around the top of the threads, but the tip was tan. Soooo, I decide to turn in the pilots a full quarter turn to lean out the idle and make it easier to start. Seemed good putzing around the show, but the ride home was different. The engine sounded funky at highway speed/transition area.The bog was worse too. I thought something serious was wrong and pullled over to check things. Then I decided it must be the adjustment, so I turned the pilot back out a good 1/8 turn and it made a big difference. The engine sounded almost normal again at cruise. Your explanation... BASICALLY what this means is at one turn out, and a BIG JET, you have very little annular space in which to supply fuel, and you therefore allow FAR MORE FUEL to be added during TRANSITION AND OFF IDLE than at idle. This allows you great flexibility in tuning idle mixture, and gives you far less chance of transitional or tip-in bog from enleanment when opening the throttles off idle and before main transition. As you see, the larger you are going on the pilot jet, and the further closed you are getting the idle screw, the better your tip in transition is getting. This is my feeble attempt to try and explain the mechanics of what is happening and what the engineers at Mikuini had in mind. .... does answer my question. I knew Mikuni had a reason for the 1 turn rule.

Maybe more tuning could be translated into- more learning needing to be done:) I am a bit of a perfectionist - which might be a downfall on a 40 year old machine. In the end, the dyno will tell all. I will use the same dyno I used for my SU's , so it will be a direct comparison. I have found that I need more heat shielding for my air box. I need to segregate my header with some sheet metal so it doesn't rise up straight on to my airbox.

Thanks for the input Tony. As far as the starting issue, I think you are correct and I am/was running to rich. I turned in my pilots a 1/4 turn and it seemed to help. I am still dialing things in here and I have been a little paranoid about running things to lean. I have been reading numerous posts that these carbs like to run FAT on the mixture-even at cruise. I just finished a 300 mile cruise yesterday and my AFR's hovered in the 14.5 range most of the day, and I didn't calculate it accuretly, but I believe I got high 20's on the MPG at 75mph with a 3.90 rear. But at idle, it seemed way rich and was hard starting-and pulling the plugs seemed to verify that after put-puting around parking lots and pulling the plug. Is that kind of AFR at cruise concerning? It seems ideal and might lean slightly at an initial slight tip-in, but never past 15.5 or so. Where I am going with this is; I know what the Mikuni manual says about pilot jet selection and the 1 turn out- rule. It has been posted that the rule is BS, and it is fine to be 2+ turns out. What are the effects of violating the 1 turn rule? Is this where folks start running into the hesistation during transition when they go beyond this 1 turn? In efforts to FATTEN(close to 2 turns out) up my AFRs with the 65's, my idle got richer and harder to start, and my hesitation got worse in transition. Without naming anyone, they are running a rebello motor and they were told that cruise should be in the low 13's----really? I would think that would be closer to a WOT AFR. Still lots of tuning to do!

Damn, that car is tough looking!! Good luck at the track

Yes, I think a set of 68's and 70's are in order. A few more main jet sizes and I might be ready for the dyno! As far as starting, I have had some success with just a turn key start when hot-but no always. From what I have read in these forums and others, it seems these carbs prefer a rich setting, so maybe that is part of the issue.

The tuning continues; I have the car running pretty good, power feels decent and the wideband shows a nice 14+ at cruise. Still have a slight bobble that only happens at the hardest tip-in. I went ahead and rechecked my adjustment on my pilots(62.5's)and I was out over 2 turns. So I reinstalled the 65's , and dialed them in-but I am still over 1.5 turns . My useless wideband really didnt give me a good indication of any change. Infact my gauge seemed to get more erratic with the new pilot size. I did get the engine running smoothly and-- at first, it seemed to be a bit torquier at the low end. So I am giving these tid bits of info as background to what I did next. I decided to bolt on my vacuum log again to see if I noticed any difference. The most immediate thing I noticed when driving the car with the vacuum log installed was-- a stabilized AFR on my guage. I couldn't seem to get a stable reading when I first installed the 65's , but with the vacuum log the reading was very stable?? Also, the vacuum log also seemed to lean out my AFR. I don't believe I have any vacuum leaks, the car has a rock steady idle at 750rpm. One last thing, is there a secret for starting the engine after it's hot? I don't have any issues on initial start up, but after driving it and shutting it down, it is difficult to get started. It usually takes a second try. I've tried different things like -one pump of the gas pedal, or giving no gas at all. Maybe I am trying to run it too lean at idle? Current set-up 65 pilots-1.5+ turns 200-main air 160-main jets 40 acc. pumps-set on the highest setting Vacuum log is 3/8" lines to ALL runners, and 3/8" to the PCV, and 11/32 to the MC booster

You could get your damper rebuilt by the Damper Doc. My machinist didn't want to balance my engine with my stock damper the way it was. I think the cost was around a 100$, it looked good and the Damper Doc said the damper was good for 8k rpm and more HP than I could throw at it.

Jon, I have been chasing clunk issues for a while and with some success. Recently I had found that vmy gland nuts were bottoming out on the threads before putting adequate pressure on the shocks. This was more of a clunk or rattle when the car was put in a twisting motion over bumps. I am still fighting an issue and I think I know what it is--see if you would concur. I made my own RT mount from drawings offered on this site. I think my RT mount has shoved the diff to far back and there is hardly any clearance around the rear control arm inner brackets that mount to the chassis. I have heard that the moustache bar actually twists a bit under torque-is this true? If so I can about guarantee this is my clunk issue. Also, shouldn't the halfshafts be a true 90 degree angle from the diff or where? Putting a square against my rotor shows the diff being pushed back back a few degrees from 90. What I have done: checked tightness of bolts new rubber mount bushings moustache bar Rt mount Made a strap for over the tranny mount. Old mount had a lot of slop. Everything in the rear suspension has been replaced or rebuilt,ie; spindle bolts, urethane bushings

any pics?

I am always amazed of the amount of issues coming from their products. It almost seems like a vendor sells MSA on a product and MSA never actually tries it out on a car before they put it in there catalog. And like you imply Ray, you would rather pay more for a high quality product from a vendor that supposedly specializes in your make of car. Where is QC?

I'm running 17X 8.5 +4 Rota's RBR's. I'm planning on installing ZG flares and will want to fill them-especially the rear. Problem is that 245 is probably as big as I want to go opn a 8.5" wheel-unless some of you disagree. From what I can tell by pics, my 8.5" RBR's look different in design then the 9.5" RBR's. The curvature of the spokes is more pronounced on my wheels, where as the 9.5" spokes lay flatter. I thought when I originally got the wheels I got the RB's and not the RBR's, but the boxes said RBR. I wonder if anyone went for the stagger look with smaller front wheels and ran into this??. Do you regret not being able to rotate tires? My other option is to run spacers, which would be the cheapest way out, but maybe not prefered. The whole reason for this post is my rears rub with my 245's. It's not much at all, I bet 6mm would cure it, but not too many options to fix. I'm slightly hesitant on cutting my quarters, they are very nice, but wouldn't mind having 275's on the rear eventually. My fronts clear with 245's.Love to be able to change the offset on my wheel by machining, but worried about integrity of the wheel

Pete, Have you tried any of the coolant products like water wetter from Redline? Or maybe trying to return the coolant to a different place like the upper hose?

Interesting!

I'm reading thru your build-very nice-but was curious about your Nismo head gasket. I installed a Nismo on my build and it was .047/1.25mm thick I believe. My head is also a E-88

Gave it a little shine today-looks much better

Thanks for the video! My exhaust definetly sounds different then yours. I will posting up a video soon -well as soon as I get my video camera back-it's on loan, Back to Mikuni tuning-After driving around with the 180 main airs for a while I noticed a slight stumble that I didn't have with the 200's, so I threw the 200's back in. I'm staying with this set-up until the O2 sensor arrives. Hopefully next month I will get the car to the dyno or sometime after tuning with a WORKING wideband.

This R&D is fun, but with a wacky O2 sensor makes for a bit of a guessing game-I'll be getting one on order shortly. I can see what's going on at cruise, which is a very steady 14-15 AFR, so I think I have the pilot's nailed. My only concern was the transitional stage around 3000 when all my timing was coming in-I thought I picked up the sound of detonation, but my loud exhaust makes it tough. To be on the safe side I put the 180 main air jets back in to bring in more fuel in this transitional area-if I understand the relationship correctly. Since I can't see what AFR's are doing at WOT, I would rather have too much if anything. I pulled the plugs after about 200 miles or so of combined driving-drove it work, 50 miles one way highway- the plugs couldn't have looked any better except for the lack of color. Maybe not enough miles to put color on the plugs, but a very clean burn. Engine runs very strong and maybe I can still run more fuel to it at the top end. I believe I have it running better than when I was running the SU's as far as mixture. I am over the top happy with the sound of my Triples+Duals= sounds better than any V-8 I have owned

Sure would love to hear that in a video!!!!!!!!!!!!!!!!

The odd ball you have to have is the BWT-5 driveshaft-no other driveshaft works with that tranny. If I remember correctly, you have to have the diff flange that was mated to the driveshaft also, but it will swap out into any R200. That's the bad part about the BWT-5 -dedicated driveshaft, non-replacable U joints.

I'm looking for a driver's side front ZG flare. Would consider buying the complete front set if needed. e-mail me please s_finnerty1018@comcast.net

Thanks Leon

For anyone still following this; Beautiful day here in Bloomington Indiana-high 70's and not much humidity Current set up is; pilots are 62.5's at 1.5 turns out. The engine is happiest at this point. NO hesitation or bobbles and AFR's hovering around 14. The engine idles best here and restarts the easiest. The 65's semed too rich and made my wideband go crazy-whic is usually an indication that my mixture is taking big swings. Main jets are 155 and main air are 180. Since my O2 doesn't like big swings it is a bit more difficult to diagnose the main side. Plenty of power, but maybe more is available. Accelerator pumps; went back with the 40's and the engine likes it. There is no bobble when bipping the throttle or heavy tip-in. With the 47's the engine sounded like it was drowning in fuel. Back to more R&D

Can someone tell me how the main air jet and the main fuel jet interact with each other. When I was expressing to Todd about richening the main side he suggested sizing up the main jet and dropping back on the main air to the 180's(from 200's).

Thats what I'm feeling when I drive. My stumble, if you want to call it that, feels like the pumps are drowning the mixture. Now that I have had the carbs off and have witnessed first hand how much fuel the pumps put out, I can see this happening. Jets came in today, so tomorrow us R&D day! Jon, did you wind up leaving the plunger rod in te middle hole? I also considered moving it to the lowest setting, but it's easier to change the pump jet from on top.