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Thanks to everyone that advised me during my 2002 search.

I have bought a 72 2002 in pretty decent shape. But is obvious needs major tuning and carb adjustments. It has dual side draft Mikuni's. do not know anything else about the specs of the carbs. Searching forum didn't bring up info on rebuild/ tuning, ECT.. Of these carbs. Internet search only brought up Mikuni's for motorcycles.

Car has rough idle, shakes whole car, sputters with light acceleration after shifting to 2nd and 3rd. Smooths out and great acceleration if I press the peddle hard.

Plan on plugs, points ECT...

I will try to post pics of carbs, any advice appreciated . And what do you think the function of the long chrome tube attached to the valve cover is?

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post-45229-0-36823500-1375156297_thumb.j

post-45229-0-69418200-1375156334_thumb.j

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Wow, 72s are rarer than hens teeth these days good find. All the symptoms you describe scream of vacum leak, looking at pics probably leaks. Chrome tube looks like a homegrown vacum source, any chance this was originaly a tii, that unit towards the top of the last pic sure looks like a cold start valve? Get this thing right you better hold on, she will scream.

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Tube system seems to be to make vacuum for brake booster - I think. Also breather from valve cover is connected there - is that PCV (positive crankcase ventilation) then? Never seen such a setup. Normally with side drafts vacuum is taken from just one port and it's well enough.

 

Life might be easier if you replaced Mikunis with Webers. Not because there's something bad in them but because they are so rare. Finding parts and getting help for tuning etc. may be difficult.

 

  Tommy

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Thanks for the input.

Looked at the set up today, just received the 2002 last night, the chrome tube does have a line to the brake booster, it is the hose with a one way port valve, what some thought looked like a cold start valve and individual lines to each manifold port. Also to a PVC type " something " connected to the valve cover.

I did find on one of the carbs, it pays to have a second carb to reference from, a open vac. Port about 1/8 inch in size. I plugged it and started her up. Still rough idle and slight miss on steady throttle. But definitely a much smoother idle. All of the hoses on the " thing " are cracked. So I hope to replace the tomorrow .

And thanks to hanksjim1 for the PDF offer and link. I will send you my email.

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FYI, those Mikunis are very similar to the Solex sidedrafts that originally came on 2002ti's (40PHHs).  Don't know for a fact, but I've heard that Solex jets will fit Mikunis--someone on the board will be able to confirm this. 

 

Which 2002AD owner owned the car previously, as it's been through several owners since 1989...Looks like a nice one.

 

If you're not really hot for those sidedrafts, you could convert to a Weber downdraft (32/36) and sell the Mikunis--and make money on the deal.

 

cheers and welcome to the fraternity/sorority

 

mike

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I don't know why someone would interconnect the ports just to make vacuum for the brake booster?  Part of the jetting for this type of carburetor is based on "one throat per cylinder"  if you tie them all together like this you get cross talk between the throats especially at idle and instead of a pulsed signal at the idle jet you get more of a constant flow and the jetting needs to be completely different.  Get rid of the chrome tube and just plumb the brake booster into ONE of the runners (just like BMW designed it)  

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Just cap off the ports on the manifolds. Use one for the brake booster vacuum source.  The crankcase should not have a PCV on it, if you want to run the breather vent on the valve cover into the air filter box that is ok or just install a catch can and run the hose into it.  You really don't want oil vapor going into your carbs anyway. 

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Thanks Preyupy,

 

I will put that on my list of cleaning up the engine bay. I did however replace all of those old dry rotted hoses and plug an open vac tube. And to my amazement the engine no longer shakes or sputters on accleration. The shakeing was so bad that the whole car shook at idle.Now not totally smooth, but just a tad of a shake. I am going to try and clean the carbs and adjust them tomorrow. Hope to smooth it out even more and hope for smoother acceleration. Although that is much improved also.

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Buy a synchrometer.  Best $$60 you can throow at dual carb setups- then flow all 4 bores.  I've found bent throttle shafts

that way, and that will give you that 'slightly stumbly' idle you can't cure.

 

But I'm with Byron- toss the plumbing.  It's asking for trouble, and solving nothing.  And it'd mess up idle

metering in the carbs something fierce.

 

And yep, Datsun roadsters and 510s use those- they are good carbs, probably better than the Weber, on a 

daily.  But a lot less common, and more expensive to jet, etc because of it.

 

GGood find!

 

t

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I did find on one of the carbs, it pays to have a second carb to reference from, a open vac. Port about 1/8 inch in size.

 

 

 

Ooooh oooh, spare vacuum ports?  Sounds like similar to that on my Mikuni bike carbs!  These can be great for synching carbs without buying any tools.  On my bike, one of them is used for the vacuum operated petcock, and the othe rhas a factory cap over it.

 

Here's what you do for synching (and I think this is a more precise method than using the squirrel cage gauge that I have to use on my DCOEs):

Get a long piece of clear plastic tubing that can connect to the same vacuum port on both carbs at the same time.  Wrap the tube all the way down a yardstick, and back up the other side.  Tape it on the yardstick to hold it steady.  Fill the tube with some red ATF until it goes a little way up each side.  (red is easier to see, and ATF won't hurt engine if it gets accidentally sucked in).

Fire up engine, and watch whether ATF gets sucked either way differently.  Adjust synch screw until its balanced out on both sides of yard stick. 

From google:

diy_manometer.jpg

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Wow kfunk,

That will be interesting to try . I still am " messing around. " with the carbs. I adjusted the pilot jets today using a tach. I achieved a very nice idle. And nice performance , with no bogg down shifting gears. But this was on level ground, or going down hill. Turned around at bottom of hill and was very disappointed . The car stuttered some acceleration modestly in first and really bogged down into second and somewhat less in third gear.

However I think my trimming is set at 0 degree TDC. Strobed the flywheel pressed in ball at 1500rpmlt. I can not make sense of the markings on the harmonic balancer . There is a single Line then a double line and then a stamped T0 ( not TD ). My distributed is centrifical advance, at least it does not have vac advance.

Any tips on setting the timming ?

Walt

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