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Should I buy some new Mikunis?

6982 Views 30 Replies 5 Participants Last post by  Hessian, 
H
Im almost at the end of my patience with this high idle on the GPZ.

I've stuffed the nice replacement carbs by breaking the pilot mixture screw and no one in rocky wants to repair it with a helicoil.

So I saw these last night


and Im waiting on a price, but I though $1100 or so. If thats the case, aside from the cash, I cant see a reason not to get them.

Can you guys see a reason not to get them?

Of course, if the problem persists after getting a new set, I'll do like the panadol ads say and see a doctor - which may be handy as I will be stabbing myself shortly thereafter.
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O
The only reason I can think of not buy those would be to buy these.


There's a set going on ebay.com (not .au) that ends in 20mins currently only US$315

http://cgi.ebay.com/ebaymotors/Keihin-35mm-FCR-Carbs-Ninja-CBR-YZF-_W0QQcmdZViewItemQQhashZitem414fccc57eQQitemZ280511694206QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_500wt_956

They're a bastard to tune apparently but once you do they are supposed to be better than just about anything.


'tiK.[hr]
Actually scrap that. They're only 35mm and I reckon you might want something larger for a 900.


'tiK.
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H
Dang I missed it, and its a 750/810 and the current ones are 34mm
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G
Thats not cool! Is the carb set with the damaged screw the set that is fitted to the bike?

Im thinking that you called it a replacement set, so you have two sets of carbs? Can you seperated the banks and make one good set of carbies out of the two sets that you have?
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H
I have

The set on the bike that has the odd high idle
Another set that looks to be in much better condition (albeit with a stuffed pilot mixture screw)
Another mystery set which look to be slightly larger - but FBS02 thought they looked very similar (but they are in really poor condition - even after a dunking in thinners)

Now all of them are a 4 bank on rails. Ideally, itd be great to pull one off the current bank and put it on the second set - I just dont know how to do it as such and I thought individual carbs shouldnt be mixed and matched with others.
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D
The individual carbs should all be more or less the same (maybe details around the throttle etc and different jetting) so you should be able to disassemble a set and reassemble some of the other ones into it.

The other thing is that if nobody else will do it for you then you may as well have a crack at the helicoiling yourself, the worst you can do is make the carb unusable and if its stuffed now then you won't have lost anything... do you have a pedestal drill? Its probably the easiest way of guarenteeing that you're drilling square and true. Also, theres a trick you can do with a pedestal drill where you get a tap handle with a center mark then use a dead center off a lathe to locate the tap so you don't end up cutting a bent thread.

I'm heading to the workshop this afternoon so I'll take a photo if I remember ;)

EDIT: I also forgot to mention, if you're going to blow $1k on the bike and you want to keep it for a while why not have a crack at fuel injecting it that would probably only be as much of a pain in the arse as the carbs have been so far and you don't have to fiddle with it all the time, you get more power/fuel economy and its a cool thing to do :)
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H
Yeah its a cool thing to do, but I really thing EFI is beyond my capabilities and its still an old bike. The GPZ750 turbos had fuel injection but I dont think adding a whole heap of electrical gremlins from that vintage of bike would be a good idea.

Arrgh
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D
Lol as opposed to carb gremlins right? :p

Seriously though, I've been trying to con somebody into doing a microsquirt install for years now, you should do it! ;)
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O
Yeah Luke, you should be conned.


'tiK.
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H
Ive had enough conning for one lifetime. I found an ex on facebook the other day and she now has a kid. Thankyou Jesus for getting me out of there.

The dudes at the yamaha dealership reckon I would need to get the carbs resealed if I took one off and put it back on. ALSO, they recommend a machinist to do the carb as they werent really keen to do it. One machinist has already said er no, cheers.

I think everyone wants to put it in the too hard basket. I can only use 34mm ones, right?

What would I need for fuel injection? A new system or rip something suitable off an old bike? Just entertain me.
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D
Well, you need three things that you don't have at the moment, an ECU, a set of injectors and a fuel pump... the other thing you're going to need is an intake manifold, which could be a bit of a pain, depending on how much equipment/time/friends with machinery you've got...

For injectors you can look at taking some off a vehicle with a similar engine layout and power output, you might think about the system out of a barina or astra? Or maybe most of the injectors out of an old commodore V6? I'm not sure how much the bike you're repairing would put out in its heyday.

For the fuel pump you can either get the fuel pump out of a newer FI bike or alternately look at cars again, the pumps for either aren't really very big but for the car one you'd probably have to do some surgery to disconnect the fuel level sensor etc... then you've got to patch it into your existing tank, or alternately run a line to it and run it remotely, which could be a problem because I think the modern fuel pumps use the fuel to cool them?

For the ECU I'd say go with a Megasquirt or Microsquirt, they're an open source design with a forum for support... I had a look at it a while ago and it looks like it would do the job, Tony (Eclipze) has said that it wouldn't do high enough rev high enough to be to do a CBR250, but I think there are a bunch of people who have them on modern sports bikes etc.

I think from memory that the Microsquirt (which is the tiny one that is waterproof and completely assembled/ready to go) is about $500 all told, with a small chunk of loom. Getting fuel injectors you'd have to talk to a wrecker about, getting a fuel pump much the same...

Its a shame you're not down here in melbourne, I'd love to give you a hand ;)

After you've done all of that you'd have to get it mapped, I think that there is software on the Microsquirt website to make the Microsquirt work with dynodynamics dynos and tuning link etc. so basically any retard could tune it for you if thats the case.
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H
Could I just purchase a fuel tank that already had a fuel pump in it? Im asking because I dont think it would fit through the holes in the bottom of the GPZ tank... how big is a fuel pump anyway?

From wiki

Type Air-cooled, 4-stroke, DOHC, 8-valve, in-line four
Displacement - (cc) 738 cc
Bore Stroke - (mm) 66 × 54 mm
Compression 10.5:1
Power - 92 hp 67.2 KW / 9000 rpm
Torque - 6.5 kg-m / 7000rpm
Starter Electric
Induction - 4x 34mm Mikuni
Ignition / Starting - CDI / electric
Fueltank - (L) 22
Transmission 5-speed
Gear ratios
1st 2.800
2nd 2.000
3rd 1.590
4th 1.333
5th 1.153
6th 1.035
Reduction ratio
1. 1.732
2. 3.062

Itd be pretty funny to do - yeah its 27yo. Yeah, thats fuel injection. Why YES, those injectors are from a bommodore :D Dont worry I'd rather be in melbourne too

Back on carbs, Im going to do a run down to gladstone (hour each way) on the weekend with some additive to the fuel like wynnes spitfire or something like that. Im also going to do the aerostart around the carbs again, just to check there isnt a leak in the rubber.[hr]
Oh and with the overbore kit, its 810cc and 10:25:1 I think
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D
Well, at a guess the injectors off an astra, a corolla or a lancer would do the job, the forum on the microsquirt website would probably give you a lot more information on whats been tested with the system they've got. From memory there is quite an extensive set of information on whats good to use for what. ;)

As far as fitting a fuel pump etc in there, you could put a different tank on if it didn't interfere with anything else, or you could just cut a biggere hole in your existing tank and mount a fuel pump to that if your tank is large enough.

If you want to go cutting holes in sheet metal then I can't recommend a fein multimaster highly enough, they're an awesome tool ;)
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H
Apparently, Kawasaki made a bike in 1999-2002 called a Zr7 which shared the same engine pretty much and the carbs will fit. Chucked it up on findapart.com.au - see how it goes
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R
Drew said:
Well, at a guess the injectors off an astra, a corolla or a lancer would do the job, the forum on the microsquirt website would probably give you a lot more information on whats been tested with the system they've got. From memory there is quite an extensive set of information on whats good to use for what. ;)

As far as fitting a fuel pump etc in there, you could put a different tank on if it didn't interfere with anything else, or you could just cut a biggere hole in your existing tank and mount a fuel pump to that if your tank is large enough.

If you want to go cutting holes in sheet metal then I can't recommend a fein multimaster highly enough, they're an awesome tool ;)
Click to expand...
Just use an angle grinder. Make sure there's some fuel in there, that way the metal filings will be caught in the fuel and you can just drain it afterwards, leaving no residue ;)
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D
richo said:
Drew said:
Well, at a guess the injectors off an astra, a corolla or a lancer would do the job, the forum on the microsquirt website would probably give you a lot more information on whats been tested with the system they've got. From memory there is quite an extensive set of information on whats good to use for what. ;)

As far as fitting a fuel pump etc in there, you could put a different tank on if it didn't interfere with anything else, or you could just cut a biggere hole in your existing tank and mount a fuel pump to that if your tank is large enough.

If you want to go cutting holes in sheet metal then I can't recommend a fein multimaster highly enough, they're an awesome tool ;)
Click to expand...
Just use an angle grinder. Make sure there's some fuel in there, that way the metal filings will be caught in the fuel and you can just drain it afterwards, leaving no residue ;)
Click to expand...
Ah yeah, I nearly forgot, the multimaster makes a cold cut meaning that you don't have to worry so much about explosions :p
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H
Wellll it turns out a bloke in SA has a set of those ZR7 carbs. On a review though, it reckons they are only 32mm, not 34.

The bike looks like this http://a.z.a.z.e.l.free.fr/kawasaki_zr7.jpg and has pretty much the same engine as the GPZ 738cc air cooled. The bike is from 1999.

Obviously there is going to be some jetting shenanigans going on, but is the 32-34 a big deal?
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O
Go for these mate. Keihin FCRs off a 92 ZXR750. The 39mm's were standard on those 750s. Ya can't go wrong Luke, as far as carbs go you can't beat these FCRs, especially for these at US$200. Keihin were commissioned to develop a true motorsport carb and this is what they came up with. They don't really have any genuine competition from what I've been able to determine (The Mikiunis are still really good, just not quite as good). They are still the carb of choice on late model chookies and even 750 & 900cc Monsters. The results reported from people who use them are only ever 'outstanding'. All parts are still well and truly available and in supply.

http://cgi.ebay.com/ebaymotors/Keihin-CR-Flatslide-Carburetors-ZX7R-ZX9R-91-93-94-ZX7-_W0QQcmdZViewItemQQhashZitem3cadaf5cd7QQitemZ260611988695QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_500wt_1182

And here's a view from the Ducatisi. There's mad support for them as well.

http://www.ducatitech.com/2v/fcr_faq.html


'tiK.
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H
I see. Unfortunately the guy doesnt seem to post overseas, so Im waiting on his reply to sort it all out. I've only heard good things about FCRs too[hr]
It makes mention there that I'll need to get a different airbox or an adaptor?
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O
Yes he does, I checked that. Click the list of excluded countries ('See exclusions' link). We're not in it. It's just poor fraudulent countries (seems to hate eastern Europeans).


'tiK.
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