My father was a Holden tech when XU-1s were new and he could do it with a stethoscope. He was the go to guy for them at the dealers he worked at. He taught me how to do it but you had to have excellent hearing which most mechanics do not have after a several years of being in the trade. We are both too old and senile to even think about trying that now. Air flow meters were just too expensive to buy back in the day, even most Holden dealerships never had them. Also, you have to remember, that the carbs weren’t that old back then. Keep up the great work.
If I can I add, I would have checked all 3 needles to make sure they were the same taper and set at the right height in the piston. I would also be checking the needle for wear, as the the needle can contact the main jet when it is not centered correctly and I would check the main jet for wear and ovality also. That main jet is easily removed for inspection and the O-rings were prone to getting hard and leaking. Also, keep in mind, that once the idle mixture is set correct at idle, it is still the needle/jet size and air valve spring that determines the air/fuel ratios throughout the rest of the rev range. Thanks for taking the time to create and post the video, It took me back over 40 yrs to my XU-1 days.🙂
yep, you are correct. In the background I did do a few checks that never made it to the edit table. One of my very first attempts at filming what I do. If I was to do this again today, it would be very different & cover a bit more of the finer points. Thanks for your comments.
Love the video. Always thought that carbs ran without oil, I'm sure thats GMH recommendation, but over the years I have had conflicting information. Some yes and some no. You have been the only one to explain why to use oil - thanks. BTW what oil should be used? Also I dont think all XU1's have the mixture pin you mention. Mine doesn't. Keep up the great work.
Thanks for your comment. If you have a flat spot, then use machine oil & see if that improves. If a small flat spot is still there then mix a couple of drops of engine oil to the damper until the flat spot is gone. Your right not all CD's have the pin but just insert a small screwdriver under the piston and lift it a few mils to achieve the same thing.
Your totally wrong on putting oil in the dash pots, they came dry from the factory, and you want them too open fully from the word go. Factory idle was 900 rpm, can't rember the timing advane at idle.
I was waiting for someone to question the oil in the dashpot. You are correct in that from factory they came out dry but there is a very good reason why the oil should be there in the first place. Admittedly not all engines require the oil. Generally high performance vehicle may get away without oil & some don't. The oil used can be from very fine machine oil to blends of heavier oil depending on the needs of the engine. The oil prevents the piston from raising to quickly, preventing flat spots. It works like an accelerator pump. The throttle opens suddenly, the air flow increases but fuel being heavier lags behind. Stopping the piston raising straight away allows time for the extra fuel to enter to create a richer mixture momentarily. So in essence you have control over the accelerator pump by changing the oil viscosity used in the piston damper.
@@mbsoldschool I remember back in the day that literally no one could tune these set ups properly, even Holden dealers. Looks like you've shone a light on why. That dreaded flat spot!
My father was a Holden tech when XU-1s were new and he could do it with a stethoscope. He was the go to guy for them at the dealers he worked at. He taught me how to do it but you had to have excellent hearing which most mechanics do not have after a several years of being in the trade. We are both too old and senile to even think about trying that now. Air flow meters were just too expensive to buy back in the day, even most Holden dealerships never had them. Also, you have to remember, that the carbs weren’t that old back then. Keep up the great work.
If I can I add, I would have checked all 3 needles to make sure they were the same taper and set at the right height in the piston. I would also be checking the needle for wear, as the the needle can contact the main jet when it is not centered correctly and I would check the main jet for wear and ovality also. That main jet is easily removed for inspection and the O-rings were prone to getting hard and leaking. Also, keep in mind, that once the idle mixture is set correct at idle, it is still the needle/jet size and air valve spring that determines the air/fuel ratios throughout the rest of the rev range. Thanks for taking the time to create and post the video, It took me back over 40 yrs to my XU-1 days.🙂
yep, you are correct. In the background I did do a few checks that never made it to the edit table. One of my very first attempts at filming what I do. If I was to do this again today, it would be very different & cover a bit more of the finer points. Thanks for your comments.
I wish I new this 30 years ago. Great work
Great video mate
Thank-you. Pretty much one of my first video attempts from 20yrs ago.
Love the video. Always thought that carbs ran without oil, I'm sure thats GMH recommendation, but over the years I have had conflicting information. Some yes and some no. You have been the only one to explain why to use oil - thanks. BTW what oil should be used? Also I dont think all XU1's have the mixture pin you mention. Mine doesn't. Keep up the great work.
Thanks for your comment. If you have a flat spot, then use machine oil & see if that improves. If a small flat spot is still there then mix a couple of drops of engine oil to the damper until the flat spot is gone. Your right not all CD's have the pin but just insert a small screwdriver under the piston and lift it a few mils to achieve the same thing.
Your right they came with no oil in the dash pots from.the factory, it's a XU1 you want them too open fast.😊
Yep, no oil in dampeners as stipulated by GMH service manual.
Your totally wrong on putting oil in the dash pots, they came dry from the factory, and you want them too open fully from the word go. Factory idle was 900 rpm, can't rember the timing advane at idle.
I was waiting for someone to question the oil in the dashpot. You are correct in that from factory they came out dry but there is a very good reason why the oil should be there in the first place. Admittedly not all engines require the oil. Generally high performance vehicle may get away without oil & some don't. The oil used can be from very fine machine oil to blends of heavier oil depending on the needs of the engine. The oil prevents the piston from raising to quickly, preventing flat spots. It works like an accelerator pump. The throttle opens suddenly, the air flow increases but fuel being heavier lags behind. Stopping the piston raising straight away allows time for the extra fuel to enter to create a richer mixture momentarily. So in essence you have control over the accelerator pump by changing the oil viscosity used in the piston damper.
@@mbsoldschool I remember back in the day that literally no one could tune these set ups properly, even Holden dealers. Looks like you've shone a light on why. That dreaded flat spot!
@@WascallyWabbitt You had to teach yourself. They weren't a bad carby, once you got your head around them.