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TR6 76 TR6 will not lean off

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loach1

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I've been trying for some time to get my TR6 running correctly. Let me try and explain the problem and hopefully you experts can give me some pointers!
It runs super rich - smoky and eye burning rich.
When I lift the air Pistons it wants to stall.
The timing needs to be advanced past the scale to get a smooth idle.
Vacuum is steady at about 15" at 1300rpm or so.
EGR and EVAP are present but I've capped off everything for now to simplify troubleshooting. The vac gauge is connected to the servo connection.
I pulled the carbs on Friday and fixed a stuck choke disk. Everything else looked as it should.
The engine runs best with the carb needles fully rich and struggles if I lean it off.
There's no sign of the timing cover having been removed recently, the chain is quiet.
Tappets are quiet.
It revs happily, drives OK but is too smoky to take for a run.
Plugs are new.
Fuel is fresh, filter is new.
Air filters are off.
Air by-pass screws are all the way in.
Carbs are balanced ok.
Anti-popping diaphragms are adjusted to stay closed for now.
Distributor hose is connected.

It seems like a carb issue but I'm stumped. I read that 90% of carb issues are caused by the ignition but I don't know what to check other than timing? I can't adjust that to the factory spec so I have used the vacuum gauge to set it to peak vacuum.

Thanks for any suggestions!!

David
 
David, all I got is floats too high or the adjustment has been backed out all the way and not being effective.


Wayne
 
When I adjust the needle height it does make a difference, but it stumbles and stalls if I lean them off. The lift test suggests too lean, but the tailpipe and my eyes say too rich. I have the usual 2-3 turns from atop to stop and everything operates quite smoothly. I should double-check the float heights.

I believe the carbs are original to the car, but I don't have proof. They have the requisite vacuum ports and extras for the emission controls that are on the engine, so I think they're right.

Thanks for the feedback so far!!
 
Lift the air valve is not really that good of an indicator.
If you lift the air valve over 1/8 of an inch and if you do not interpret the immediate response from the engine, you'll probably interpret what you observe as LEAN, regardless of the actual mixture.
Spark plugs of the same heat range as Champion RN12YC read after 300 miles will give you a better idea of mixture,'
With a stock engine and with both carbs' evacuation ports connected to the valve cover, a needle height in the middle of it's adjustment range should be very close to the sweet spot.
AND, one thing you do NOT ever want to cap off is the float chamber vent nipples on the carbs that are pointing towards the cockpit.
 
Are the needles and main jets an identical pair?
I would replace the float needles and seats with new and ....adjust the float levels as suggested above.[ I have found previously that although they seem to function correctly as tested off the car, they may be faulty]
 
I'm typing from my phone so forgive me if I miss anything....
I'm not sure if the jets and needles match - I'll google how they are identified and report back. I haven't plugged the float chamber vents, so I should be ok there.
The valve cover vent is connected and well sealed at each connection, but so is the valve cap so there is a high vacuum on the crankcase which seems odd to me but the cap looks right.
I have replaced one float valve with a grose jet. Why one? I don't recall, possibly feeling hard up when ordering lots of parts! I'll do the other just to be safe when I check float heights.
I'm stumped by the ignition timing needing to be so advanced - could this be caused by the rich mixture? I verified that the pulley TDC was the same as no.1 TDC. Ignition wires, cap and rotor are new too. It starts very readily so I think the spark is good enough.
 
Grose jet could be part of the problem....I tried them and they flooded my engine more than once.
Replace it with the original plunger style 'needle valve'.
I haven't read anyone having luck with Grose jets in a ZS carb with the possible exception of some real old ones.
I wouldn't attach too much significance to the marks on your damper.
There is only one jet available for your carb. It would be 0.10" in diameter with a ROUND hole and while there are other needles that will fit, the appropriate needle is B1AF
 
Fueled by some renewed enthusiasm thanks to you all, I had a quick tinker this evening. I wanted to keep it simple due to time so I plugged the crankcase vent ports in the carbs. This made it possible to get running with the carbs leaned off a bit so I took advantage of that and balanced the carbs, turned the distributor until I got 17-18" of vacuum (at a high 1300rpm), and it revved quite freely for a change.
I played around and found that 1-3/4 turns back from full rich was the point where it wouldn't smoke much at all and would idle reasonably well at 1100 or so. The vacuum gauge was surging just above 15". When I reconnected the crankcase breather it would stumble so I left it off for now.
My guess is that I have an intake leak, so I will make sure my sealing off is good and I'm thinking that the intake to head gasket might need attention? Is there a common leak point on this engine?
I'll dig deeper at the weekend but if you have any easy checks in the meantime, please let me know!
 
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