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Discussion Starter · #1 ·
I have a problem where my bike tops out at 95 mph indicated. I check the butterfly at the carb and it fully opens. I can redline in the lower gears but it may be getting there slowly (can't remember how it used to feel, too many bikes). I was thinking that it uses roughly the same amount of fuel at redline in any gear so my next thought was the air filters which were cleaned last year.

I rebuilt the carbs 2 years ago and the bike has not sat since. Throttle is a bit sticky but I believe that is a separate issue. Signs are pointing towards main jet clog and I'd also like to check the petcock filters. I checked the vacuum to the petcock and it holds air well. The other carb vacuum appears to be connected to what I believe yo be the thermostat. This hasn't changed at all though so I don't believe that could be an issue. I'm also running somewhat lean based on the plugs, even with the af screws out an extra 3/4 turns while trying to start due to a separate fixed issue yesterday.

I'm gonna try running some Lucas injector cleaner through my next few tanks and see if that helps at all although I don't put much faith in those except for maybe a "maintenance" preventative cleaner. I also have some amsoil additive which is potent stuff. I'm leaning towards clogged petcock since it's lean in both cylinders but t doesn't change whether on regular or reserve and I'd find it odd that a clean tank would clog both when only one is used mostly. Any insight would be helpful, even if just for better understanding of the bike
 

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Right side carb vacuum goes to the air valve under the seat if not modified.

Restriction in the air intake? But I lean a lot more toward fuel delivery instead.

Fuel lines running uphill? They need to be level or downward to the carbs.

You can apply vacuum to the petcock and watch the fuel flow from both outlets.

Wonder if the slides are lifting all the way at full throttle?
 

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Just curious, How often do you have a chance to hit redline in top gear? I have had the bike 3 years and haven’t done that, even if I wanted to I don’t think I have enough open road in this area and if I do there’s always those pesky State troopers out there.
 

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Discussion Starter · #4 ·
I am leaning towards a fueling issue as well. I don't think I've let gas get over 2 months old in the bike since the rebuild and 1 month or less is the norm. I find it odd that I can hit redline in 1-3 but not in 4 or 5 since my understanding of carbs would indicate that even in the lower gears, you're running at roughly the max fuel delivery of the system.

I checked my fuel line routing and they're running down but the one I thought could maybe be pinched but that didn't solve it. Drained the carbs and the fuel looks normal without any particles in it. Petcock filters look as if I just cleaned them even though I didn't. I double checked the plugs at wot in first (no good place to do it in higher in the time I had) and the rear is running seemingly a bit lean and the front very. Discovered a carb boot to the front wasn't on all the way so that is my prime suspect at the moment and would make sense for the lack of power as well as the lean front cylinder condition.

Won't have time to remedy until later today and I've also got a bear of a hydraulic clutch to attempt to bleed. Hoping to take my st1100 to the Austin motogp races but my trusty vulcan is my main backup touring bike. Ordered a fuel light connector for my vfr750 as a backup backup. As you can tell my goal is to not fly to Austin and do it on a bike. On top of that I've got two track days this weekend and the weather up in north jersey is just begging me to ride
 

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Discussion Starter · #5 ·
Just curious, How often do you have a chance to hit redline in top gear? I have had the bike 3 years and haven’t done that, even if I wanted to I don’t think I have enough open road in this area and if I do there’s always those pesky State troopers out there.
I've done it on a handful of occasions but not often. My vulcan is mostly a commuter for me since I'm up to 9 bikes and it is my second slowest (4th if you count the two non running projects but we're talking theory here). If this fix bumps the power up enough for me it may give me the incentive to get around to replacing the front end components on my sv and sell it to buy an aprilia v4. Slowly working my way towards only having 4 cylinders and mostly Vs. I don't think I could ever part with the vulcan. After 17k miles of twisties, 2 up, and longer trips, it's just too good of a value bike for me to consider parting with it.
 

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I've done it on a handful of occasions but not often. My vulcan is mostly a commuter for me since I'm up to 9 bikes and it is my second slowest (4th if you count the two non running projects but we're talking theory here). If this fix bumps the power up enough for me it may give me the incentive to get around to replacing the front end components on my sv and sell it to buy an aprilia v4. Slowly working my way towards only having 4 cylinders and mostly Vs. I don't think I could ever part with the vulcan. After 17k miles of twisties, 2 up, and longer trips, it's just too good of a value bike for me to consider parting with it.
gotcha, I don’t have a full stable, in fact I don’t even have a stable so I’m a solo bike guy for now lol, but back to your original post, I guess 95 is somewhat short of what this bike SHOULD do. I have come close to 90 without going WOT knowing full well the bike has more to offer.
 

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Discussion Starter · #8 ·
gotcha, I don’t have a full stable, in fact I don’t even have a stable so I’m a solo bike guy for now lol, but back to your original post, I guess 95 is somewhat short of what this bike SHOULD do. I have come close to 90 without going WOT knowing full well the bike has more to offer.
I have hit 120 indicated if I remember correctly. That's how I lost one of my heat shields lol. The more I dig the more I find. Went to adjust my throttle cables and discovered the return is on its last legs. That can't be replaced without pulling the carbs, right?
 

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Discussion Starter · #9 ·
I've had trouble with clogged jets and corny gas around the 30 day point.
For now I'm praying it was just the air leak. I know losing a full cylinder can make getting to 65 a chore so hoping a carb boot off caused my 25 mph discrepancy. I may have to pull the carbs regardless to replace my throttle return but at least lubing it stopped it from binding. Hoping that can hold off till the weather gets colder but not quite winter. The vulcan is still my winter work horse
 

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I have hit 120 indicated if I remember correctly. That's how I lost one of my heat shields lol. The more I dig the more I find. Went to adjust my throttle cables and discovered the return is on its last legs. That can't be replaced without pulling the carbs, right?
Should be able to replace the cable with carbs in place, that's one of the first things they want you to remove for carb removal, but I just left them connected.

I've seen 115 with the speedometer corrected by the oversized tire, pretty much maxed out on wind resistance. Didn't get a look at the tach, things were happening pretty fast.

A dose of seafoam cleared one clogged jet for me.
 

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Discussion Starter · #11 ·
Should be able to replace the cable with carbs in place, that's one of the first things they want you to remove for carb removal, but I just left them connected.

I've seen 115 with the speedometer corrected by the oversized tire, pretty much maxed out on wind resistance. Didn't get a look at the tach, things were happening pretty fast.

A dose of seafoam cleared one clogged jet for me.
I can report back tomorrow morning on the speed issue. I'll see if it'll go above 7k in 4th and that should tell me if I'm somewhat good. I'll have to adjust the af screws again though but I'll pull the plugs at work to check them. God bless kawasaki for including a spark plug wrench with the tool kit. I am gonna run my Lucas injector cleaner for the next few tanks just to be safe. I typically like to run one every few tanks on each of my carbed bikes. In other good news, my st1100 appears to be running properly. I still need to test it out but the vulcan is getting tested on my commute tomorrow and maybe the ST after work or Wednesday. Either way, my road trip is happening
 

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I know mine will go above redline, third or fourth gear. It should keep climbing if you let it.

I always adjust the air screws for the leanest, fastest idle, if it doesn't pop on decel I leave it there. If it pops, I add 1/4 turns until it doesn't pop. That's all bikes with a carb, two stroke, four stroke, etc.

You said you're riding to Austin... Texas?
 

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Discussion Starter · #13 ·
I know mine will go above redline, third or fourth gear. It should keep climbing if you let it.

I always adjust the air screws for the leanest, fastest idle, if it doesn't pop on decel I leave it there. If it pops, I add 1/4 turns until it doesn't pop. That's all bikes with a carb, two stroke, four stroke, etc.

You said you're riding to Austin... Texas?
I definitely need to mess the the af screws. It's running way better but still a bit off and the idle is lower than before. I'll start by resetting them to where they were before but will read my plugs again at lunch. Regardless, between that and finally lubing the cables it feels like a new bike. Funny how you just get used to things the way they are.

I wasn't able to get a good high speed run due to traffic since I left 5 minutes late but I strongly suspect I've got near enough to my full power that I wouldn't look any further. Yeah I'm planning to head to Austin for the motogp race on the 3rd and take a week to make it back up to NJ.

I finally managed to bleed my hydraulic clutch yesterday as well so I have multiple wins (touring bike seemingly good, vulcan stator wire properly fixed not the hack job I had to do 2.5 hours from home, sticky throttle, and fueling issues seemingly good with minor adjustments left).
 

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I've managed is 109 MPH by GPS. It might have had a bit left in her, but I was rapidly running out of road.
That was last year on a colder day with a tailwind.
This year my record is 104 MPH by GPS. I had about 50 lbs of luggage at the time, so weight and aerodynamics were a factor.

The last bit to redline in 4th is always slow in coming, with next to no acceleration when switching to 5th.
If you search the forums, there's a dyno run posted somewhere for a stock bike, showing the torque falling off pretty fast above 8k.
I once graphed the torque curves against the gear ratios, and the gears are spaced just right to hold it right to redline.
Shift any lower or higher than 8500 and you lose out on acceleration.

I run my idle screws just into popping on decel. Preference really.
It's kind of an audible brake indicator.
 
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