Automatic choke not engaging all the time on start-up

[simy]

So as most of you would be aware i've had ongoing issues with my TB42 petrol fouling plugs on start-up and running super rough for the last 8 months. Long story short i have replaced a crap load of things in the last 8 months and on friday i put new plugs in again (third time). When i used to start it, it would rev low and then foul a plug. It revved low last night on cold start and i managed to press the revs up before it fouled the plugs, it did it again this morning, luckily didn't foul the plugs

So now i am 100% sure it's the auto choke playing funny buggers. It doesn't do it all the time, i press the accelerator down halfway quickly before i start it to open the choke up.

How can this be fixed?

Once the engine is warm it runs perfectly fine, last night i kept the revs up at 1000rpm and then it took 5 minutes of driving to come normal. if i didn't keep the revs up manually at idle it would drop to 200rpm and almost stall.

[patch697]

Im not 100% convinced it is your auto choke playing up mate...

One thing you can try is tying the choke off so it doesn't engage (won't work at all) & just see if the problem continues... It will either rule it out or confirm your suspensions...

If you give it 2 or 3 pumps when cold starting & just trim the idea up with your hand throttle until its warm enough to keep its own idea speed, that should get you though without a choke for a while.... & consequently give you the info you need to track the issue as well...

[simy]

Any ideas mate? i am seriously at the end of my tether, I don't understand why it operates normally once it is warm. The only good thing to come out of this latest saga is that now i can pinpoint what is wrong a bit better now.

So basically all it's doing is not holding revs on startup until it is warm, but it only does this sometimes

[patch697]

Any ideas mate? i am seriously at the end of my tether, I don't understand why it operates normally once it is warm. The only good thing to come out of this latest saga is that now i can pinpoint what is wrong a bit better now.

So basically all it's doing is not holding revs on startup until it is warm, but it only does this sometimes

Its probably not something to big or hard to get sorted but try what I suggested above & get back with what you've learned... If not me, somene will be able to help...

They do run a very complex carb so isolating issues can sometimes be a little tricky... I know a few who said to hell with it a swapped the Nissan carb out for Holly 350's & down draft Webbers off XF Fords that has worked well.... I chose to stick with Mr Nissan's pile of shit carb & mines working well now but its taken me a while to nut the thing out too....... Just food for thought

[NP99]

Carbs are not my specialty, but have you dosed it up with carb cleaner?

[93patrol]

I used to have the same problem on my 96 model zx6r motorbike turns out it was the fuel I was using causing the problems the newer fuels aren't made for older carbied vehicles I think. I stopped using premium and ultimate unleaded and just ran basic unleaded and it stopped fouling plugs and stuffing my 4 carbies.

Hope this helps


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[NP99]

I used to have the same problem on my 96 model zx6r motorbike turns out it was the fuel I was using causing the problems the newer fuels aren't made for older carbied vehicles I think. I stopped using premium and ultimate unleaded and just ran basic unleaded and it stopped fouling plugs and stuffing my 4 carbies.

Hope this helps


Sent from my iPhone using Motorculture mobile app

Same deal with my Honda VTX cruiser

[threedogs]

What ever you do ,do it one thing at a time,
one disconnect choke completely and try as Patch suggests.
My last 4x4 was dual fuel and never needed to choke start it once in 450,000K
When you say fouling plugs, do you mean just wet? as that would indicate to me not firing,
and would point me towards your dizzy. Is there a rotor button mod and a special coil that you made need to
update?
Is the EGR all clean and not blocked with soot etc.

[simy]

What ever you do ,do it one thing at a time,
one disconnect choke completely and try as Patch suggests.
My last 4x4 was dual fuel and never needed to choke start it once in 450,000K
When you say fouling plugs, do you mean just wet? as that would indicate to me not firing,
and would point me towards your dizzy. Is there a rotor button mod and a special coil that you made need to
update?
Is the EGR all clean and not blocked with soot etc.

Brand new carby, new plugs, new leads, new coil, electronic ignition, all new vaccum hoses, new radiator, fuel filter, fuel tank taken off and cleaned (was filthy). Everything tuned professionally, timing, fuel flow, auto choke etc etc.

I can start it with no auto choke but being Canberra and -3 most morning i have to sit there for 5 minutes holding at idle as my manual idle control is broken.

Once it is warm it is fine. It's something to do with start-up, as i said above, it's like the Auto choke just doent kick in, but whether its a auto choke problem or not is the big question.


EDIT, with ignition on i open the throttle by pressing on accelerator quickly before starting to engage the auto choke. (incase people thought it may be this)