stalling over 80! - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 36 (permalink) Old 04-26-2013, 05:07 PM Thread Starter
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stalling over 80!

Hey everyone, i'll keep this as simple as possible! I own an 88 vulcan that I have done the earshave mod with filters and jets as per the earshave manual haha! When I bought the bike it had a custom made exhaust that is literally straight piped front to back, and the rear cylinder exhaust cuts over to the right side and exits with the front cylinder exhaust (i call them shot gun pipes)! Now i've messed with jetting before on other bikes and not had much trouble, but this one is throwing me for a loop!
The bike runs great at idle, and even rev's full on without a load! When riding, if I get on it from a stop it feels almost like it's running lean uptop, past about 5k, and the exhaust sounds flat! If i'm cruising 80, and gun it, it barely accelerates, sounds flat, and actually starts to stall it feels like! (maybe the plugs are too lean and it's dieing down?) once it starts to spit and sputter if i let out and coast and then just cruise low throttle, it'll be just fine again! But it WILL NOT go over 80/85 before it stutters!
Now I have not blocked off the reedvalves (coastered). They are just running open for now. Would plugging them/coastering them change anything or are they purely emissions (like a valve cover breather on a car?)
I have read where a few people are running closer to 150-155 mains with more open exhaust, this is my next move! The flat exhaust makes me think lean, but i guess i'm looking for a second opinion! I'm at about 50 above sea level (savannah georgia)!
Any and all help is appreciated, any other questions about the bike, please ask! It's gorgeous bike, fully customized top to bottom and I hate that it doesn't run 100%!
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post #2 of 36 (permalink) Old 04-26-2013, 05:43 PM
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Quote:
Originally Posted by low750r View Post
Hey everyone, i'll keep this as simple as possible! I own an 88 vulcan that I have done the earshave mod with filters and jets as per the earshave manual haha! When I bought the bike it had a custom made exhaust that is literally straight piped front to back, and the rear cylinder exhaust cuts over to the right side and exits with the front cylinder exhaust (i call them shot gun pipes)! Now i've messed with jetting before on other bikes and not had much trouble, but this one is throwing me for a loop!
The bike runs great at idle, and even rev's full on without a load! When riding, if I get on it from a stop it feels almost like it's running lean uptop, past about 5k, and the exhaust sounds flat! If i'm cruising 80, and gun it, it barely accelerates, sounds flat, and actually starts to stall it feels like! (maybe the plugs are too lean and it's dieing down?) once it starts to spit and sputter if i let out and coast and then just cruise low throttle, it'll be just fine again! But it WILL NOT go over 80/85 before it stutters!
Now I have not blocked off the reedvalves (coastered). They are just running open for now. Would plugging them/coastering them change anything or are they purely emissions (like a valve cover breather on a car?)
I have read where a few people are running closer to 150-155 mains with more open exhaust, this is my next move! The flat exhaust makes me think lean, but i guess i'm looking for a second opinion! I'm at about 50 above sea level (savannah georgia)!
Any and all help is appreciated, any other questions about the bike, please ask! It's gorgeous bike, fully customized top to bottom and I hate that it doesn't run 100%!
What are yor sparkplugs showing you? You could be running lean because of too much air, you could be running rich because of the jets, and in any case you don't have enough backpressure imo

JM2001

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post #3 of 36 (permalink) Old 04-26-2013, 05:49 PM
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What air filters are you useing? Try running it with out the air filters. For a better than good performance you will need the K&N pod air filter. RC-2340.

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post #4 of 36 (permalink) Old 04-26-2013, 06:04 PM Thread Starter
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I have not pulled the plugs yet, just moved to savannah and barely got it running and riding before the move, so I havne't had much of a chance! I will try to do that this week!

If I pull the air filters won't that just make it MORE lean (i suppose for testing purposes this could work) I am using Emgo's! I had them on my cb750 and wanted to put filters on the vulcan for a test ride!

Speaking of, as far as back pressure, the cb750 (inline 4 aircooled) is running stock exhaust with NO baffling, same as what would be considered on the vulcan, AND pod filters with no troubles with jetting! I've never really seen lack of backpressure cause THIS much of a stutter!

AND.....in doing more googling, I found this site http://jr_allas.tripod.com/documents/Ear_Removal.htm
he says he's using 162 mains at about the save altitude as I am! what are your thoughts?! I'd seen the 150 ish suggestion on other posts, but 162 is HUGE! but he checked his plugs and everything, AND with stock ish exhaust! ????I dunno lol
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post #5 of 36 (permalink) Old 04-26-2013, 07:17 PM
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The K&N and emgo are made a little diff. If it runs good with out filters it will run good with the K&N filter.

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post #6 of 36 (permalink) Old 04-26-2013, 08:38 PM
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with K&N filters I ran 148 mains and stock low speed jets. I ran a set of pipes like you are talking about and it actually lost power.The fuel screws were turned out 3 turns on mine.I tuned mine with no air filters and then put the K&N filters on.

I put Jardine rumblers on it and it got back some of the low end I had lost with the open pipes.

Just had a thought ,Have you checked the float levels on your carbs? you may be starving for fuel at High RPM.And how about your fuel flow from the petcock to the carbs.One more thing to check is the fuel vent hoses on the float bowls.the ones that were T-d together and a hose went into the back of the air filter housing.They need to be hooked together and up out of the airflow or it will cause fuel not to flow because of negative pressure in the carb bowls.

Mine screamed on the top end with the open pipes but lost some on the bottom.Your problem sounds like it is a lack of fuel at high rpm, not an exhaust problem'

There's a few more things to think about for you.hope it helps.




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post #7 of 36 (permalink) Old 04-26-2013, 09:06 PM Thread Starter
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Originally Posted by denny6006 View Post
with K&N filters I ran 148 mains and stock low speed jets. I ran a set of pipes like you are talking about and it actually lost power.The fuel screws were turned out 3 turns on mine.I tuned mine with no air filters and then put the K&N filters on.

I put Jardine rumblers on it and it got back some of the low end I had lost with the open pipes.

Just had a thought ,Have you checked the float levels on your carbs? you may be starving for fuel at High RPM.And how about your fuel flow from the petcock to the carbs.One more thing to check is the fuel vent hoses on the float bowls.the ones that were T-d together and a hose went into the back of the air filter housing.They need to be hooked together and up out of the airflow or it will cause fuel not to flow because of negative pressure in the carb bowls.

Mine screamed on the top end with the open pipes but lost some on the bottom.Your problem sounds like it is a lack of fuel at high rpm, not an exhaust problem'

There's a few more things to think about for you.hope it helps.
I have gone completely through the carburetors, seals/o-rings and ultrasonic cleaned everything! I set the floats according to the manual, tilting the carb to the 45 degree angle and have the float set in the middle of the two marks! It really FEELS like it's starving for fuel on the top end! I'm not real sure where the vent hose ended up, i'll check that, i could see how air flowing into the hose might keep fuel from filling the bowls! If I do a WOT pull from a stop it pulls very strong in the low end, and the higher I go the flatter the exhaust sounds, so that's why I figured main jet is too lean! But I wondered about flow from the tank too, though I did rebuild the petcock and made sure that fuel flowed from both lines in even and full amount, so I doubt it's that?! But thanks for the reply....
You ended up with 148's?! Did you see that link I posted in my last reply, that guy said he was using 162's! that seems WAY rich haha! I'll probably buy some 150's and see how that works and go from there!

I used my cb jet kit as a fuel percentage check, stock jet vs. dynojet stage 3 (pods and open exhaust) was a 30% increase in main and something like 12% in the pilot! using those numbers, the main for a vulcan should be roughly 165 and 42 pilot! Any thoughts?
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post #8 of 36 (permalink) Old 04-26-2013, 09:46 PM
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Quote:
Originally Posted by low750r View Post
I have gone completely through the carburetors, seals/o-rings and ultrasonic cleaned everything! I set the floats according to the manual, tilting the carb to the 45 degree angle and have the float set in the middle of the two marks! It really FEELS like it's starving for fuel on the top end! I'm not real sure where the vent hose ended up, i'll check that, i could see how air flowing into the hose might keep fuel from filling the bowls! If I do a WOT pull from a stop it pulls very strong in the low end, and the higher I go the flatter the exhaust sounds, so that's why I figured main jet is too lean! But I wondered about flow from the tank too, though I did rebuild the petcock and made sure that fuel flowed from both lines in even and full amount, so I doubt it's that?! But thanks for the reply....
You ended up with 148's?! Did you see that link I posted in my last reply, that guy said he was using 162's! that seems WAY rich haha! I'll probably buy some 150's and see how that works and go from there!

I used my cb jet kit as a fuel percentage check, stock jet vs. dynojet stage 3 (pods and open exhaust) was a 30% increase in main and something like 12% in the pilot! using those numbers, the main for a vulcan should be roughly 165 and 42 pilot! Any thoughts?
I think it'a kind of a crap shoot on the jetting ,i had a jet kit and just monkeyed around till I got it right.150 and s few trial runs with a plug check and definitely check the vent hose issue.These bikes all perform differently and jetting will wary with them.




If you see it on my bike I did it
VROC#30324
92 vn750(sold)
Current ride 05 1500 Classic FI
lovin' the new scoot



Quote:
"When all is said and done,usually more is said than done" UNK
Click on one x and drag to the other to read between them.

Psalm 40:1...
XI waited patiently for the Lord; and he turned unto me, and heard my cry. X
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post #9 of 36 (permalink) Old 04-26-2013, 09:54 PM
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I would definetly scrap the emgo filters. I learned that first hand. And Ron also helped me with that. But that is just my opinion.

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post #10 of 36 (permalink) Old 04-26-2013, 10:16 PM Thread Starter
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Originally Posted by denny6006 View Post
I think it'a kind of a crap shoot on the jetting ,i had a jet kit and just monkeyed around till I got it right.150 and s few trial runs with a plug check and definitely check the vent hose issue.These bikes all perform differently and jetting will wary with them.
Yeah, I'm seeing that! Think i'll start around 150 and see what happens, and i'll post back with my findings both in jets and the vent tube! Thanks!

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I would definetly scrap the emgo filters. I learned that first hand. And Ron also helped me with that. But that is just my opinion.
I have heard that a lot with this bike! I've had these on my cb for 3 years (with maintenance of course) and they have been great, honestly! I figured they would work just as well on the vn also, but maybe not? I'll definitely pull them off next time I go riding and see if it performs any different! Thanks!~
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