No guts at 60 MPH - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 45 (permalink) Old 07-24-2016, 07:57 PM Thread Starter
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Unhappy No guts at 60 MPH

What a great day to ride today in western Washington state! Finally sunny and clear with tons of bikes on the road. I took a couple of new routes and had a ball. I put a bit over 80 miles on it and would have done twice that much but once the speedometer said 60 mph the bike would then slow down. Since the speedo said 60 it was actually going, what, 55-ish or so and turning 4000 RPMs. No amount of throttle could get it above that and it would pull a nose-dive in its haste to slow down. Below that speed and RPM the thing was just fine and fun. But try to keep it there and above was a no-go. Luckily most of the routes I took were for slower speeds with lots of twists and curves but for those straightaways I was getting passed by dead pigeons. Any thoughts?????

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post #2 of 45 (permalink) Old 07-24-2016, 08:27 PM
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first, check the carb bowl vent line.. make sure its terminated in dead air (either right side ear if still stock, or up under the tank if you have ear shaved). also, if stock, cut the end of the vent line that goes into the ear at a 45 degree angle and stuff it back in. sometimes it gets shoved in to far, and can be obstructed. the 45 prevents that.

otherwise, check to make sure you have good fuel flow from the tank.

it sounds like its starving for fuel at higher engine loading

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post #3 of 45 (permalink) Old 07-24-2016, 08:27 PM
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Carb vent line fall out or got bottomed out in the ear? (We reccomended cutting the end at a 45 degree angle to prevent this)

Could you rev it near redline redline in the lower gears? Throttle cable might need adjusting.



Edit....LOL, looks like we posted the same answers at the same time....

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post #4 of 45 (permalink) Old 07-24-2016, 08:34 PM
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Quote:
Originally Posted by Chris and Shim View Post
What a great day to ride today in western Washington state! Finally sunny and clear with tons of bikes on the road. I took a couple of new routes and had a ball. I put a bit over 80 miles on it and would have done twice that much but once the speedometer said 60 mph the bike would then slow down. Since the speedo said 60 it was actually going, what, 55-ish or so and turning 4000 RPMs. No amount of throttle could get it above that and it would pull a nose-dive in its haste to slow down. Below that speed and RPM the thing was just fine and fun. But try to keep it there and above was a no-go. Luckily most of the routes I took were for slower speeds with lots of twists and curves but for those straightaways I was getting passed by dead pigeons. Any thoughts?????
Check the easy things like air filters and add some Seafoam in the fuel. Maybe a back blow on the carbs. Any restrictions in air or fuel could limit the bike. As I said, if this is something relatively new, it could be the easy things rather than a major problem. Think back to the last time you filled the tank. Could you have gotten a bad load?

and always remember, "Ride until you rot!"
**Really not sure if the Big "C" is back right now
but having to face the fact that this is a lifetime routine
going forward. Five operations done and it still continues.

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post #5 of 45 (permalink) Old 07-24-2016, 09:40 PM Thread Starter
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1) The carb bowl vent hose has been long-time trimmed to 45 degrees and is in its correct place in the right ear. That was an easy thing to check. 2) No, in lower gears it will rev to around 4000 rpms and then you can feel a noticeable drop off in power but it WOULD rev beyond 4K. (Not sure how much past 4K, though). 3) Air filters are fine. 4) I put SeaFoam in the tank religiously. 5) While its possible the last gas fill-up (today at the same Shell station I always go to) was a "bad load" as you say, for some reason I tend to not think its this so much. Note, I also tend to doubt the gas cap air vent line is clogged either but I'll go blow some compressed air through it later today. It didn't feel like a POOG situation. Could the MCCTs be turned in too far?

TOC MCCTs
Saddlebags, hard mounted
Fork mounted tool bag (now hard mounted)
Relocated rear turn signals
LED turn signals, brake lights and running lights
LED license plate frame
Engine Guard and Highway pegs
National Cycles Low Boy Heavy Duty windshield
Home made lowers (nice)
Custom seat (made by a local guy)
Iridium plugs (DPR7EIX-9)
Shenko 230 Tour Master tires at 11,123 miles
Splines lubed at 11,123 miles
Luggage rack
Light bar with LED lights
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post #6 of 45 (permalink) Old 07-24-2016, 11:58 PM
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Check your spark plug wires and coils. I had this problem and it was the spark plug wires. Takes 2 minutes and an ohm meter
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post #7 of 45 (permalink) Old 07-25-2016, 12:06 AM Thread Starter
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Ok, I have read up on throttle adjustment in the manual. It says if there is too much "play" the carbs may not open up completely even at full throttle. For not enough "play" it says the throttle will be hard to control. Now I am interpreting the 2 to 3 mm of play that the manual states should be present as meaning that there should be 2 to 3 mm of "slop". Well, mine does not have what I would refer to as "slop" at all. If I am correct then mine doesn't have enough play in it. Yet, that being said, it seems to be responding in the manner defined in the manual as a problem deriving from too much play. I am confused. I now bow to others with superior experience in this matter as to how to proceed. (Assuming that my issue has anything to do with throttle adjustment in the first place....)

TOC MCCTs
Saddlebags, hard mounted
Fork mounted tool bag (now hard mounted)
Relocated rear turn signals
LED turn signals, brake lights and running lights
LED license plate frame
Engine Guard and Highway pegs
National Cycles Low Boy Heavy Duty windshield
Home made lowers (nice)
Custom seat (made by a local guy)
Iridium plugs (DPR7EIX-9)
Shenko 230 Tour Master tires at 11,123 miles
Splines lubed at 11,123 miles
Luggage rack
Light bar with LED lights
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post #8 of 45 (permalink) Old 07-25-2016, 12:13 AM Thread Starter
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To Rakillia: I really dislike electrical problems. My electrical understanding level is one step above my beagle's understanding. I have a meter that has 5 settings for ohms: 2000k, 200k, 20k, 2000, and 200. Pray tell does this help you in explaining to me how to perform such an electrical check of my wires and coils?

TOC MCCTs
Saddlebags, hard mounted
Fork mounted tool bag (now hard mounted)
Relocated rear turn signals
LED turn signals, brake lights and running lights
LED license plate frame
Engine Guard and Highway pegs
National Cycles Low Boy Heavy Duty windshield
Home made lowers (nice)
Custom seat (made by a local guy)
Iridium plugs (DPR7EIX-9)
Shenko 230 Tour Master tires at 11,123 miles
Splines lubed at 11,123 miles
Luggage rack
Light bar with LED lights
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post #9 of 45 (permalink) Old 07-25-2016, 12:27 AM
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Quote:
Originally Posted by Chris and Shim View Post
To Rakillia: I really dislike electrical problems. My electrical understanding level is one step above my beagle's understanding. I have a meter that has 5 settings for ohms: 2000k, 200k, 20k, 2000, and 200. Pray tell does this help you in explaining to me how to perform such an electrical check of my wires and coils?
It should be in the manual. At least the number you should be looking for. Just take both spark plug wires off 1 cylinder. Stick the meter in both ends. Your measuring the resistance of the coils and the wires all at the same time. Should be around 20k ohms but you'll have to look it up. If the number you get is much higher or lower, then you have to take the wires off the coils and measure individually to see where the problem is. Its something I usually check early just because its so easy to do and rule out. Would cause the rpm wall you're describing.

Last edited by Rakillia; 07-25-2016 at 12:29 AM.
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post #10 of 45 (permalink) Old 07-25-2016, 12:58 PM
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My guess is weak fuel delivery. Might try some seafoam for one tank full.

Otherwise, I'd look at flow out of the petcock, then would have to look at the carbs for dirt, float level, etc.. Did you try opening the gas cap at any time? (vent clogging) Could be a partially clogged main jet(s).

Wouldn't hurt to lift test the slides to check the diaphragms. Should be a woosh sound with the slide dropping somewhat slow, versus slamming down quickly.

It takes far more fuel to ride 35 mph than to rev 10,000 rpm in neutral. So rev testing doesn't cover everything about the fuel delivery.

Afterthought, make sure an air filter hasn't come apart and clogged the intake.

(some of this post was written before the others and you answered certain questions, didn't have time to post it yesterday)

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