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Luke_Healey
Jedi Trainee
Offline
Help me tune my 1098
OK, I'm at my wit's end with getting my Sprite running like it should. I've been through and through this car. Tonight's activity was to swap out the dashpot pistons and suction chambers with another set of carbs I had bought off of ebay. These other carbs use the spring loaded needles. I believe they are AAC needles. My old dashpots used AN needles.
Anyway, I got them in, tuned the car to a good mixture using my colortune tool (about 16 flats out in my case) and drove around. The car runs absolutely the same as it did with the AN needles and dashpots. I'm disappointed that it didn't run better or worse. Also, my car gets hot, even though the whole radiator is heating up evenly (meaning it's probably not plugged up anywhere and flowing liquid.)
I got my timing light out when I got home and checked timing. To me, it seems spot on. I've got my idle at about 1000rpm or lowre now. I'll post a diagram showing where the v notch in the crank pulley hits the timing tab when timing off of cylinder #1:
Ignition gap at the breaker points is properly adjusted. The vacuum advance 'works' with suction of my mityvac. Moving my timing light pickup to all the plug wires, they're all firing on every hit. The engine isn't missing at all. The ignition coil and wires, cap, rotor, points, condenser are all new as of last summer.
Compression in the engine is a nice even 195psi per cylinder. The engine was rebuilt by the previous owner and bored .030 over. It doesn't knock and there is no sign of oil and coolant mixing after I've driven it well over 1000 miles. I've got a new 7 pound radiator cap on the radiator.
I'm trying to think of anything else.. The only goofy thing about the car that's not stock is the fuel pump. The previous owner bypassed the original SU pump and installed an electric pump that almost looks like a walbro fuel injection pump. HOwever, I measure fuel pressure at 4psi pretty constant up at the carbs, so it's obviously not a FI pump.
The carbs pass the 'spray carb cleaner on the throttle shafts' test. They don't leak air, at least not noticibly.
I don't know the condition of the float and needle adjustments in the bowls. I'm tempted to order some grose jets just for kicks since my last Sprite had em and ran like a raped ape.
This car gets pretty poor fuel economy at about 25mpg. That's with me driving it pretty hard. My other sprite was known to get 45-50mpg even when I was beating it.
So... If any of you pros have any possible places for me to focus my attention, I'd love to hear some theories :wink:
Obviously, my carb setup is not new, but I do finally have the jets centered and the carbs do adjust by the book, other than perhaps requiring to be turned out too many flats (16) to be set correctly. My distributor is original as well. I am thinking of going to electonic ignition eventually.
OK, I'm at my wit's end with getting my Sprite running like it should. I've been through and through this car. Tonight's activity was to swap out the dashpot pistons and suction chambers with another set of carbs I had bought off of ebay. These other carbs use the spring loaded needles. I believe they are AAC needles. My old dashpots used AN needles.
Anyway, I got them in, tuned the car to a good mixture using my colortune tool (about 16 flats out in my case) and drove around. The car runs absolutely the same as it did with the AN needles and dashpots. I'm disappointed that it didn't run better or worse. Also, my car gets hot, even though the whole radiator is heating up evenly (meaning it's probably not plugged up anywhere and flowing liquid.)
I got my timing light out when I got home and checked timing. To me, it seems spot on. I've got my idle at about 1000rpm or lowre now. I'll post a diagram showing where the v notch in the crank pulley hits the timing tab when timing off of cylinder #1:
Ignition gap at the breaker points is properly adjusted. The vacuum advance 'works' with suction of my mityvac. Moving my timing light pickup to all the plug wires, they're all firing on every hit. The engine isn't missing at all. The ignition coil and wires, cap, rotor, points, condenser are all new as of last summer.
Compression in the engine is a nice even 195psi per cylinder. The engine was rebuilt by the previous owner and bored .030 over. It doesn't knock and there is no sign of oil and coolant mixing after I've driven it well over 1000 miles. I've got a new 7 pound radiator cap on the radiator.
I'm trying to think of anything else.. The only goofy thing about the car that's not stock is the fuel pump. The previous owner bypassed the original SU pump and installed an electric pump that almost looks like a walbro fuel injection pump. HOwever, I measure fuel pressure at 4psi pretty constant up at the carbs, so it's obviously not a FI pump.
The carbs pass the 'spray carb cleaner on the throttle shafts' test. They don't leak air, at least not noticibly.
I don't know the condition of the float and needle adjustments in the bowls. I'm tempted to order some grose jets just for kicks since my last Sprite had em and ran like a raped ape.
This car gets pretty poor fuel economy at about 25mpg. That's with me driving it pretty hard. My other sprite was known to get 45-50mpg even when I was beating it.
So... If any of you pros have any possible places for me to focus my attention, I'd love to hear some theories :wink:
Obviously, my carb setup is not new, but I do finally have the jets centered and the carbs do adjust by the book, other than perhaps requiring to be turned out too many flats (16) to be set correctly. My distributor is original as well. I am thinking of going to electonic ignition eventually.
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