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 Post subject: Stock G161Z running crap? Here's a checklist.
PostPosted: Fri Jun 27, 2014 10:09 am 
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Joined: Sun Aug 24, 2008 7:12 pm
Posts: 1938
Location: Windsor Gardens
Car(s): TX G180W+T, TE G180W, TG G180Z, Piazza 4ZC1T +more
This assumes your car runs a G161Z with a stock cam, Nikki carby, and standard points ignition. I suggest being systematic and working through this checklist in order, even if you've looked at a few things already. Sometimes if a car has several problems and you fix one, it aggravates another. There's also several other things worth checking, but this will usually fix your problem.

Before starting this, I recommend replacing the following, unless they've been recently replaced:

Breaker points in the distributor
Condenser on the outside of the distributor
Spark plugs (use correct spec and gap)
Ignition leads (good leads like Top Gun are worth the money)
Fuel filter
Fuel - ie, if the fuel is more than a year old, consider replenishing it with fresher fuel
Any old and cracking fuel lines - just for safety's sake!

Okay, so here's my process.

1. Set points gap! 0.4-0.5mm. Ensure there's no crap on the terminals inside the dizzy cap or the rotor arm. Ensure spark plugs are clean, not fouled.

2. Disconnect and block vac advance, start car, on idle set timing to 10deg BTDC using a timing light.

3. Rev the engine a little bit, you should see the timing advance around 16-20 degrees by 3500rpm. This is centrifugal advance.

4. Connect vac advance to one of the fittings on the base of the carby. On idle, timing will usually be about the same, but slight throttle will instantly advance the timing. Hard throttle will not change timing (ie same as with no vac advance).

5. Check spark strength by turning off the car, disconnecting a spark plug lead and exposing the terminal. Set it up about 5-10mm from a decent earth. If you have to hold it when the car's on, make sure you're wearing thick rubber gloves or holding it with a whole bunch of cloth. Start the car, you should see a good blue spark capable of jumping 8mm. It might be worth trying to rev it a bit to see if it starts missing or dying at revs.

- It's now pretty safe to assume the ignition is good... Unless the coil is on its last legs (uncommon, usually they work or don't) or wiring is loose or shonky -

6. Check the fuel pump for flow (see your Gregories manual)

7. Check the float level in the carby is correct.

8. Turn the idle mixture screw in all the way (but NOT tight) and then out four full turns (note: not half turns! full turns!) then start the car. Make sure it's idling on the idle circuit not the primary, by adjusting the idle level screw and listening for a reaction. Now, adjust the idle mixture screw until you find the sweet spot where revs climb slightly. Then, go back (so the revs drop) to half a turn beyond where it makes no difference. This is making it just a smidge rich so it idles properly. Set idle level and ensure accelerator cable doesn't have too much slack - but you should be able to lean on the cable bracket without it changing your idle. Check the accelerator pump is squirting fuel upon sudden acceleration. Ensure both primary and secondary both open freely - note that secondary is vac activated beyond a certain throttle position on a Nikki.

9. Run some carby cleaner through, being sure to open both throttles while you do so.

10. Run some fuel system cleaner (the sort you put in your fuel tank).

11. Check fuel pressure at the carby if you're still having issues.

If that doesn't fix it, it might be worth double checking the cam timing is correct and/or trying another fuel pump, then another carby. If it's still running like a bucket, I'd be compression testing the motor.

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