Stumble at 3k rpm after new exhaust with rejet - Page 2 - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #11 of 12 (permalink) Old 09-23-2019, 12:18 PM
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Originally Posted by MSattler View Post
So playing around with the hesitation when slamming on the throttle, I have found that using choke stops this, and it has a smooth transition. However, it pops on deceleration with the choke pulled. The exhaust is turning a nice blue as well. Doesn't the choke add more fuel, and restrict the airflow? That means it is making it even more rich than the 42/142...
It's not a conventional choke with a butterfly that restricts airflow, but an enriching circuit. It still adds fuel to the mix.

Your description sounds like it's lean (choke helps .. bluing pipes and pop on decel). What color are the plugs?

Could be just a bad transition from the pilots to the mains, playing with the shims might cure that. Like maybe it's a bit too lean, so add a shim? Not sure where you're at with shims now. Or, it's just too lean on the pilot altogether.

Any chance the jets have just gotten dirty? 42/142 should be plenty rich.

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post #12 of 12 (permalink) Old 09-23-2019, 01:23 PM Thread Starter
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Originally Posted by Spockster View Post
It's not a conventional choke with a butterfly that restricts airflow, but an enriching circuit. It still adds fuel to the mix.

Your description sounds like it's lean (choke helps .. bluing pipes and pop on decel). What color are the plugs?

Could be just a bad transition from the pilots to the mains, playing with the shims might cure that. Like maybe it's a bit too lean, so add a shim? Not sure where you're at with shims now. Or, it's just too lean on the pilot altogether.

Any chance the jets have just gotten dirty? 42/142 should be plenty rich.


Well... Iíve been running a full bottle of either sea foam, chevron concentrated, or Lucas fuel cleaner every other tank... so something couldíve gotten shaken loose! I can try adding another shim on the needle. I have one now. I have to fix that damn pawl spring again... for the third time... so I can pull the tank again during that time. Again, I have the advanced timing, ear shave and Vance and Hines. Sometimes the bike is mean and peppy, sounding better than most sportsters. Other times, itís sluggish. It could be debris that is clogging the jets. I was running 91 octane all summer, until I saw here that it should be 89. Never ethanol though.


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