Jeff20B

iTrader: (13)

On bad83's advice, I was looking around the web for a set of Mikuni #200 jets for my boost prepped Nikki, and stumbled on this kit which contains from 100 on up to 200 with lots of in between sizes for only $8.99 for a 24 pack with 2 of each size. Seems too good to be true.

Or is it just a set of 5? I'm confused. Follow the link to see what I'm talking about re confusion about a 24 pack vs a 5 pack.

Motor Factory Mikuni Main Jets #200 Pack Of 5. Brass, Slot Head Fit Mikuni from K and G Cycles!


If their numbers are metric and correspond/cross over/match our Nikki sizes, this would be a Nikki tuner's dream come true. No more messing around with clunky Holley air bleeds and their SAE sizing then having to do the math to find out what size, in metric, it is close to in order to know where you are. Uhg, I'll let old farts like Sterling and Yaw do it the hard way. I'd rather keep it simple and metric, you know?

So please check out that link and let me know if I read it wrong or made any other mistakes. I just simply can't believe such a complete set of jets are available for such a cheap price.

Oh and does anyone know whether these will actually thread into our carbs? bad83, are you out there?

bart_heemskerk

All jet treads in the nikki is metric M5.
Same as the jets found in japanese motor cycle carbs. (mikuni, keihin)
And also in cheap chinese mopeds scooters.

Cookboy

iTrader: (10)

I just ordered. Then revisited. I think it's 5 200's. Seems they sell them by 5 of every size. But I'll find out for sure when they arrive. Edit This seems to be the tuner pack. $95.00 https://www.kandgcycles.com/MTF-Muku...Main-Jets.html Edit again. The same kit description is with every jet size. Poor catalogue assembly, I think.
So, to good to be true? Yes. But still good.

Smokeyfb33

iTrader: (8)

"Replacement jets are sold in packs of 5 Kit includes tray with part numbers of individual jets for easy identification for re-ordering"

Not very hard to understand.


Either buy the full kit for 99. Or buy replacement sizes in a 5 pack for 8.99.


Save the time and trouble and hit up a moto repair shop. Just ask for large mikuni round jets.

Should be about $5 each at a shop.

Jeff20B

iTrader: (13)

Ah, thanks for adding a little clarity. 95 bucks makes a lot more sense for what you get. Their website is a bit "clunky".

And thanks Bart. It's good to know they will fit. And the price works out to be quite a bit less each than Mazdatrix. Compare with the 7.88 per jet from Mazdatrix. Eep! That could get expensive in a hurry if you need to tune, like I do.

Jeff20B

iTrader: (13)

Just an update.

Stay away from Mikuni jets for your Nikki!!!

Turns out Mikuni sizes their jets way differently than anyone else and they use a .075mm thread pitch. That could be disasterous! Nikki uses a .08mm thread pitch. You have been warned!

Here is a drilled orifice size crossover chart if you're needing to tune your Mikuni carb.


Just to clarify, the Dynojet brand jets are sized in actual metric. The other brands are sized for flow. Dynojet and Keihin have a more useable .08mm thread pitch. Use this info at your own risk!

Jeff20B

iTrader: (13)

Speaking of expensive jets from Mazdatrix, I found another supplier who sells
more inbetween sizes for around half the price. Note: these have to be the DGV
73801 jets like what Mazdatrix sells to work in a Nikki. No other weber parts
crossover.

Here is a link to where I found out about this supplier. Nikki carb jets sources? [Archive] - Improved Touring Racing Forums

And a direct link to the supplier's webpage. MAIN JETS <br><font color="red">73801</font>

Jeff20B

iTrader: (13)

Here is something else that will help.

In my quest for inbetween sizes to get a Nikki tuned 100%, I started looking for 122 in a size and thread pitch that would fit and not interfere with anything. Wouldn't you know it, the lowly Weber jets were the answer. Not from Mazdatrix, but from piercemanifolds. But then what if I needed a size they don't list? I found another webpage that has some other sizes. Together we have virtually the entire range from 80 to 240 including inbetween sizes like 107, 117, 127, 137 etc.

For 85, 95, 147, click Weber by Number | Carbs Unlimited
copy and past into search bar
73801.085
73801.095
73801.147

For 107, click Weber 32/36 DGV DGEV DGAV Parts Page scroll down to "DGEV Calibrated Parts" find "Main Jets", use drop down menu to find 107

For 117, 122, 127, 137, click MAIN JETS <br><font color="red">73801</font> and choose from the drop down menu.

Virtually every other size is mirrored across both websites.

Jeff20B

iTrader: (13)

For thread completeness sake, here is the part index at piercemanifolds.

Product Index

Scroll down to the 73801 section and you'll see just about every jet size imaginable from 40 to 250. This is, in my opinion, the best most complete source for jets if you're not interested in drilling your own. They even have in between sizes that are hard ot get elsewhere.

If, however, you are interested in drilling your own, here is where to get tiny metric drill bits and a pin vice to hold them.

Drill Bits and Pin Vises

Scroll down to "Metric 15 Piece Drill Bit Set 0.30 to 1.0mm" and the one below it "Metric 15 Piece Drill Bit Set 1.05 to 2.00mm" and then scroll up to look for the pin vice(s) they recommend.

rotaryjunkee

Im liking what im seeing, parts for fine tuning.
Great job jeff

Sent from my samsung gs4 using RX7Club app

Jeff20B

iTrader: (13)

I've got another update for everyone.

Looks like I found a source for perfect jets for our Nikkis. They are Hitachi jets for motorcycle carbs that look like some I've taken out of my 76-78 Hitachi 13B carbs.

They come in plenty of in between sizes for your hogged out primary venturis. I've been needing some 122s that my cheap set of micro drill bits just didn't cover.
HITACHI main jet 4H7-14984-40-00 4X7-14984-41-00

Just a note about actual sizes vs stamped sizes; they might a be a little off like Nikki jets are.

Here is something else that could prove very useful if you choose to mod your secondary air bleeds to accept Nikki jets like I did. You can get 40 and 41 Hitachi jets! They're called pilot jets.
HITACHI Pilot Jet 4H7-14984-40-00 4X7-14984-41-00

I assume they're .40mm and .41mm. These would be great to get and drill out to 60 or 70 or whatever for your secondary air bleeds to help get rid of that pesky secondary hiccup or delay that you get with some boosted Nikkis. Just make the air bleeds smaller so they start to work faster as soon as you mash the pedal!

One more interesting jet I discovered is a Mikuni that looks a lot like the primary short slow air bleeds in our Nikkis. It looks to have all the correct measurements and thread pitch! And the important part is it comes in useable sizes smaller than the totally unusable 150 to 190 size all stock Nikkis come with which have proven useless on any Nikki that had its choke flap removed. Or any venturi size larger than stock 20mm (and even then, 118 still benefits stock 20mm carbs). Get yourself a pair of 110s (approx 1.18mm according to the comparison chart above) and see how it idles for you! Or just get a set of 70s and drill them out to whatever you want (118!).
GENUINE MIKUNI AIR JET B42/55

By the way I found some aftermarket Mikuni style B42/55 in size #50 elsewhere on the internets but they only had 6 and I ordered all of them. I think that's the smallest they come in. I'm going to see how they do in the secondary side where the nickel plated 60s normally reside. Reason: I've been experiencing a siphon effect if I floor it briefly with some solder filled 170s where it literally empties the bowls faster than they can refill at 2.5psi so it appears you need a tiny .6mm or so orifice hole to break the siphon. The only problem is that it causes the secondary delay to come back or get slightly longer. Why? Too much air.

So I ordered a set of #40 Hitachi pilot jets and some #50 aftermarket Mikuni style slow air bleed/jets or whatever they are, and will see if I can a) prevent the siphon effect and b) reduce or eliminate the delay. Oh and c) to see if they are even going to fit correctly, right thread pitch etc.

Jeff20B

iTrader: (13)

I have an update. The Mikuni B42/55 fit really well in the primary side of the carb. They go in really deep in the secondary side. I think they'll work. I'll test run them soon.

Since these fit so well in the primary side, I think I'll get a bunch of small ones and drill them out to 118 or so for all the hogged out Nikki I'm going to do. I think this is the perfect solution to our lack of good slow short air bleeds for these carbs.

rotaryjunkee

Im following this thread, would like to see how those jets work, i havent switched to fi yet and still got the yaw nikki, give us some good news jeff

Jeff20B

iTrader: (13)

Cool! I always feel let down whenever a forum member gives up on the Nikki and goes to fail injection. I just don't see a point in spending like 2k on something that I couldn't make run very well. I tried four different EFI swaps and they all left something to be desired. And this is coming from me, a guy who actually enjoys wiring! Maybe that's part of it. I know what wiring can do, its limits etc. Maybe that's why I don't trust them to run my engine. Injector clips, sensors, resistances that affect the way the fuel table makes the engine run etc. I want as few wires in the engine bay as possible. I do my direct fire ignition upgrade, and I'm done in there. Well, if I do an electric fan, there's a couple wires for that, but you get my point.

Another problem with EFI: if you get even one tiny air bubble in your fuel system while in boost, you'll pop the engine. Ever mentally keep track of how many blown up FC and FD engines there are? Makes one start to think the rotary isn't reliable. No, it's all the poorly set up FCs and FDs that are unreliable, that perpetuate the stereotype. Which, sadly, is the vast majority. At least with a carb you have two "surge tanks" (float bowls) right there.

Carbs also have a venturi effect which removes heat from the incoming air charge. Like natural intercooling. The intake manifold can get pretty cool (cold) at times.

I still haven't gotten around to purchasing an intercooler for my setup. It just doesn't seem to need one at my current boost levels of whatever it spikes to on an S5 wastegate with a full 3" exhaust. Like 7psi or more? I'm usually looking at the wideband so I never see the boost gauge. I always get 92 octane and have never heard any marbles rolling around in a coffee can noises. I'll raise the boost with a manual boost controller soon. The NXS from eBay and a couple of brass fittings to make it fit better. I'll go for 10psi first.

Getting back on topic, Like I said these B42/55 air bleed jet things will fit the secondary side but seem to fit the primary side slightly better due to the way the holes are machined/threaded. For those of you experiencing a slight secondary delay, you can swap out the stock nickel plated 60s and swap in a set of these 50s for ten numbers less air. It should help. If you need smaller like I did, you'll have to look for blanks that you can drill yourself (I'm still looking) or a set of solder filled stock 170s and a set of quality micro drillbits. Like these. 3d Printer Bits Nozzles Extruder Cleaner Tools Micro CNC Drill | 20 pack Toy Making Carbide Micro Drill Bits .10mm .15 .20 .. 1.0mm .5 increments This one has all the sizes from .10mm to 1.00mm. They seem sturdy enough to go through brass. Better get the little pin vice they sell to hold on to the 1/8" shank. I could only find the "tool" as they call it on eBay. http://www.ebay.com/itm/4-Stainless-Steel-Micro-Drill-Bit-Hand-held-Tool-4-chuck-1-8-and-smaller-/221793885831?pt=LH_DefaultDomain_0&hash=item33a3f21e87
As for the primary side, if Mikuni sizes these B42/55 air jets the same way as their fuel jets in the list above, you will want to get a set of 110 so it will have a 1.18mm hole. I suggest 1.18 because it works on all venturi sizes up to 25mm. After 25mm you need to go smaller. I've had good luck with 1.05mm on my biggest Nikki at 25.6, but I also had one set of rare 42 long slow bleeds which helped a little. All other carbs have had to use the stock 46s and believe me I tried everything and nothing else worked. So leave the stock 46s alone and don't go bigger than 25mm. A stock ported 12A doesn't need anything that big anyway. You can get away with 24.5mm like wankel=awesome did. My carb at 24.7mm drives better than the bigger ones with only slightly less total power when all four bbls are open in boost. Well you know what they say, just crank up the boost for more power. They say you can make 300HP on a stockport 12A with stock 20mm venturis, so there's that too. So do yourself a favor and follow wankel=awesome's advice and your Nikki experience will be awesome. Not time consuming, head scratching, bizarre, regretful, or any other negative adjective you can think of in a short length of time while I'm typing this sentence. Just do 24.5mm.

Where was I? Oh yeah if 110 turns out to actually be 110, you can drill it out to 118 or just leave it. Shouldn't hurt anything. Just pay attention to your idle and if the mixture screw is all the way in or all the way out, that means you need to bring it back within its range, and I've found 118 does just that.

One more thing. Just be aware that anything which contains solder in a car environment (moisture) can potentially experience what's called solder bloom. This is when little crystals grow and can block the hole. My tiny .35mm hole could fill in probably after a year of use. Maybe. Anyway I hope to find a couple of brass blanks by then so the holes will stay open. I'm also not worried about them getting blocked by dirt because the stock nickel plated 60s don't unless your air filter is terrible. They're protected under the air horn with a small chamber for dirt to fall out of suspension before it gets back there. Same for the primary side.

Jeff20B

iTrader: (13)

Update time.

These arrived: HITACHI main jet 4H7-14984-40-00 4X7-14984-41-00

And they're perfect!

These are the perfect substitute for our Nikki jets. Period. Hitachi, same as Nikki. Perfection!