B
bostonmish
Guest
I was addressing a leaky carb and used the occasion to check the jetting and other settings as well as the PO's relatively recent rebuild.
I discovered less than stellar previous work:
- Missalligned throttle plate
- Poorly peened throttle shaft screws
- Incorrectly set float
- Plugged overflow tube
- Incorrectly set Jet Needle
The carb itself was full of new components (O-rings, Jet Needle, throttle shaft, diaphragm, etc.), but the assembly was careless.
I wonder if this is the fate of EVERY PO out there - to be perpetually derided for the sins they left behind. Seems to be such a common occurance, ...but I digress into philosophy. Sorry.
The most important event that took place and one I want to share with others involves the Jet Needles in my carb.
The clip was set one notch too low (position 3, instead of 2). It just so happens that my motor is a dual plugged R90 which could be set leaner than stock on account of its more robust ignition. Instead, as purchased, it was set too rich.
The stock Jet Needle position for this motor is the 2nd notch. To go leaner, one would go up to notch number 1 (although that is a lot of leaning out all at once) or, preferably, would go more granular with smaller midrange jets (like from 2.68 to 2.66, etc.)
The PO, at the time of the carb rebuild went completely the other way. He went down by a notch, to position #3 which enrichens the mixture way beyond even the stock (single plug) settings. Why did he do this? I think it was mistake. I think he misread the manuals (he gave me copies, including the Tom CutterÔÇÖs dual plug opus) and intended to go leaner, but went the other way.
It seems that I have found at least one cause for the bike being such a P. I. G. pig on gas. Add to that the incorrect float height (too much gas in the bowl) and there you are.
But the story gets better. When putting the carb back together, I decided to take Robert FleischerÔÇÖs advice and actually measure the protruding needle, just for reference. Set on the second notch, its visible portion measured 40mm. Fine. I finished the carb (right side) and put it back on the bike. Buttoned everything up.
Now, the left side needed a needle adjustment. My assumption was that it was also still in #3 position. However, when I removed the slide and measured the needle, to my surprise I discovered it too was measuring 40mm.
One of several possibilities was on hand:
a. The PO set the left side Jet Needle on notch #2 and right side to #3 by mistake or
b. The needle was NOT seated correctly in one of the slides, causing one to sit higher or
c. Perhaps I made a mistake myself and set the left side to #3 and the right was still at #3 from the POÔÇÖs work.
It turned out to be (c.) !
Had I not gone the extra step and measured the Jet Needle height in the right carb, I would have reset the left side to notch #2 (the right would have remained at #3, although I would not have known it, thinking I had correctly set it at #2) and rode off to a future of never being able to properly tune the motor.
Hope this is not too boring for the casual browser. For all you Jet Needle changers out there, however, take note. ItÔÇÖs gotta be belt and suspenders with those needles!
--
Michael Stoic
I discovered less than stellar previous work:
- Missalligned throttle plate
- Poorly peened throttle shaft screws
- Incorrectly set float
- Plugged overflow tube
- Incorrectly set Jet Needle
The carb itself was full of new components (O-rings, Jet Needle, throttle shaft, diaphragm, etc.), but the assembly was careless.
I wonder if this is the fate of EVERY PO out there - to be perpetually derided for the sins they left behind. Seems to be such a common occurance, ...but I digress into philosophy. Sorry.
The most important event that took place and one I want to share with others involves the Jet Needles in my carb.
The clip was set one notch too low (position 3, instead of 2). It just so happens that my motor is a dual plugged R90 which could be set leaner than stock on account of its more robust ignition. Instead, as purchased, it was set too rich.
The stock Jet Needle position for this motor is the 2nd notch. To go leaner, one would go up to notch number 1 (although that is a lot of leaning out all at once) or, preferably, would go more granular with smaller midrange jets (like from 2.68 to 2.66, etc.)
The PO, at the time of the carb rebuild went completely the other way. He went down by a notch, to position #3 which enrichens the mixture way beyond even the stock (single plug) settings. Why did he do this? I think it was mistake. I think he misread the manuals (he gave me copies, including the Tom CutterÔÇÖs dual plug opus) and intended to go leaner, but went the other way.
It seems that I have found at least one cause for the bike being such a P. I. G. pig on gas. Add to that the incorrect float height (too much gas in the bowl) and there you are.
But the story gets better. When putting the carb back together, I decided to take Robert FleischerÔÇÖs advice and actually measure the protruding needle, just for reference. Set on the second notch, its visible portion measured 40mm. Fine. I finished the carb (right side) and put it back on the bike. Buttoned everything up.
Now, the left side needed a needle adjustment. My assumption was that it was also still in #3 position. However, when I removed the slide and measured the needle, to my surprise I discovered it too was measuring 40mm.
One of several possibilities was on hand:
a. The PO set the left side Jet Needle on notch #2 and right side to #3 by mistake or
b. The needle was NOT seated correctly in one of the slides, causing one to sit higher or
c. Perhaps I made a mistake myself and set the left side to #3 and the right was still at #3 from the POÔÇÖs work.
It turned out to be (c.) !
Had I not gone the extra step and measured the Jet Needle height in the right carb, I would have reset the left side to notch #2 (the right would have remained at #3, although I would not have known it, thinking I had correctly set it at #2) and rode off to a future of never being able to properly tune the motor.
Hope this is not too boring for the casual browser. For all you Jet Needle changers out there, however, take note. ItÔÇÖs gotta be belt and suspenders with those needles!
--
Michael Stoic