ejdirin
XS650 Enthusiast
I fired up my project (1979 XS650 SF) the other day using a temporary fuel tank (ie, gatorade bottle) and I could see the fuel just pouring in. I burned 1/4 of the bottle in probably 8 minutes of idling. I installed POD filters and basically straight pipes with minimal baffles.
I took the carbs apart (1979 Mikuni). Everything looked clean, but to be safe, I took everything apart and soaked all the small parts (jets, starter plunger, float needle/seat, etc) in carb cleaner and blew compressed air through everything.
The main jets are #135. I have some #145's on the way. First I'm going to try to reassemble the carbs as close to stock as possible (float at 24mm, #135 MJ, #27.5 PJ, etc) and see how that goes, because most of what I've read says that the bike should run ok if the carbs are stock, regardless of the new filters/pipes. I'm also using a non-vacuum petcock.
My questions are: Should I use the #145 MJs? And, is there any reason to lower the jet needle?
Here is a comment from a doc I had on file:
"Bub pipes require jetting changes to the stock Mikuni carbs. We found that K&N R-135/2 air filters (they replace the airbox) are quieter and cheaper than the OEM-type K&N replacement filters. After fitting the Bub pipes and K&N filters, the main jets
should be replaced with No. 145 jets, the needle should be dropped to its lowest
position (remember, lower the needle not the clip), and the plastic caps removed
from the idle mixture screws. Adjust the mixture screws for fastest idle, keeping the
idle speed down to less than 1200 with the idle-speed screw. The idle-mixture screws
should be set so that turning them a quarter-turn in either direction will cause the
idle speed to fall slightly."
Will this work for me? I know a lot of this will be trial and error, but those jet needles are a pain to adjust. Thanks in advance, I'm a carb rookie
I took the carbs apart (1979 Mikuni). Everything looked clean, but to be safe, I took everything apart and soaked all the small parts (jets, starter plunger, float needle/seat, etc) in carb cleaner and blew compressed air through everything.
The main jets are #135. I have some #145's on the way. First I'm going to try to reassemble the carbs as close to stock as possible (float at 24mm, #135 MJ, #27.5 PJ, etc) and see how that goes, because most of what I've read says that the bike should run ok if the carbs are stock, regardless of the new filters/pipes. I'm also using a non-vacuum petcock.
My questions are: Should I use the #145 MJs? And, is there any reason to lower the jet needle?
Here is a comment from a doc I had on file:
"Bub pipes require jetting changes to the stock Mikuni carbs. We found that K&N R-135/2 air filters (they replace the airbox) are quieter and cheaper than the OEM-type K&N replacement filters. After fitting the Bub pipes and K&N filters, the main jets
should be replaced with No. 145 jets, the needle should be dropped to its lowest
position (remember, lower the needle not the clip), and the plastic caps removed
from the idle mixture screws. Adjust the mixture screws for fastest idle, keeping the
idle speed down to less than 1200 with the idle-speed screw. The idle-mixture screws
should be set so that turning them a quarter-turn in either direction will cause the
idle speed to fall slightly."
Will this work for me? I know a lot of this will be trial and error, but those jet needles are a pain to adjust. Thanks in advance, I'm a carb rookie