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Discussion Starter #1
So a recent introduction thread got me wondering about whether I had bad driving habits since I don't spend much time in the low RPM range, so I paid careful attention to my tach over the past couple days.

I can idle fine at 1k while warming up, and have plenty of smooth power above 3k, but if I spend any time cruising (not actively climbing gears or engine braking) in the 1k to 2.8k, my engine feels like it's anemic and stumbling. There's no way I could do a slow comfortable ride down a country lane at 2.5k.

Are my pilot jets possibly too rich and I'm choking out the engine when the throttle is closed? I would have thought that would cause idling issues, which I don't seem to have.
 

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You could be right, if the pilot gets clogged, it shuts the cylinder down below 2500 rpm. When one of mine clogged I had to crank the idle adjustment way up, since it ran on one cylinder below 2500..

What size pilots are you running?

If it's rich on the pilots, the plugs should be fairly black after a low speed run or just a bit of idling.
 

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Discussion Starter #3
I got the bike second-hand, with a fair amount of work done on it (tux mod), so it's possible the jets were changed. Never disassembled them, and hope not to ever have to!

I did increase the idle screw shortly after I got it to keep it from dropping below 1k and stalling when idling. Do the 750s have a separate idle circuit from the pilot? That would explain a lot.

I'll try to do a low RPM circuit around the neighborhood when the weather clears, then check the plugs.
 

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You don't need to dis-assemble the carbs to change the jets, though. That can be done with them in the bike.
 

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The pilot jet feeds the idle circuit, so 1000 to about 2800 rpm. The air screw also affects (only) the idle circuit, but I doubt that's the root of the problem.

Also check the petcock vacuum line to make sure it's dry.
 

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My bike runs well, but cruising below 3k RPM is out of the question for me. 4k-6k are ideal cruising RPM's. This is a high-revving engine that doesn't start making good power until about 4k RPM's. It's just the way the motor was designed. Whoever said you ought to spend time in the low rev range may have misinformed you, since this engine lugs like crazy at low revs.

Barring any issues with running, but if it idles solidly and revs to the top of the rev range smoothly, you are probably lugging it. I'd advise revving it out. I certainly do, almost never letting the revs go below 3k.
 

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My low speed shift point is 2300 rpm, it pulls away just fine from there. Plenty of low-end torque.
 

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On my spirited ride to work, I was shifting at 6K as I pulled away from a stop, settling into a 70 mph cruise at 5k rpm. Once I got into the city, I was shifting around 3.5k. I'm not afraid to dip down to 2300 through a school zone, if I know it only goes up to 30 mph on the other side.

My personal rule of thumb is keep the throttle at or below 1/4 until I'm past 3k. If I need more power than that, I should be downshifting anyways.

Low RPM itself won't destroy the engine or it'd blow up every time it idles. But putting a lot of load on the engine with a low RPM can cause issues because the oil pressure is also low. Higher RPM gives higher oil pressure, and more of a cushion against metal-on-metal contact.
 

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I tend to really wring it out if I have room. These engines like to spin. They are a very short stroke design, and don't have the torque of, say, a Harley Sportster. I have hit nearly 100 mph down a freeway on ramp, shifting at around 6000-6500 at full throttle. Remember this engine has a 9500 redline compared to about 5500 for a Sportster. The short stroke accounts for that. It has to spin to make power. It has more power at high RPM than at low RPM. Cruising down the highway at 75 mph in top gear at 6500 feels just about right. This is NOT a typical cruiser engine. Don't try to compare it to a Honda 750 Shadow.
 

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Remember this engine has a 9500 redline compared to about 5500 for a Sportster.
I've seen you mention 9500 redline twice now. Another guy mentioned doing 9500 rpm in 5th gear. Mine's clearly at 8500. Are there differences over different years? Or is that why you have a parts bike VN750 and just bought another one? >:):laugh:

And...how did someone get theirs up to 140 mph without a hill, tailwind and tow vehicle?
 

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You are correct, it is 8500 RPM. I haven't ridden a Vulcan 750 in almost 3 years. My bought new 2002 model had an engine failure at 108,000 miles. Broken cam chain. I put in a shed and bought an '06 Sportster 1200. But every time I went into the shed I would look at the Vulcan 750. I recently found a nice low mileage stock 1997 in great condition (I hope) for a good price on Craigslist and bought it. I rode it home, and it seemed to run ok. But the tires were completely shot. The tread was coming off the back tire. I parked it in the garage, got new tires for it, but haven't gotten around to putting them on yet. My '02 has about $1000 (when new) worth of genuine Kawasaki accessories on it I plan to put on the '97. I'm also going to do a full service on it, except the carbs. I'll wait until I see how it runs before I get into that mess. I'm also going to use the '02 as a parts bike for the '97, as it has a lot of good parts on it. I definitely didn't over rev the '02. It would not pull redline in top gear, which is a sure indication it is not under geared. These bikes have defective cam chain tensioners from the factory. My first set on the '02 lasted almost 17,000 miles, but I let the chain rattle for quite a while without realizing what it was. I then installed 2 new oem tensioners on it, and they began to fail around 10,000 miles. I finally gave up and installed a set of TOC manual tensioners on it. They are still available, and cost less than the stock ones. I never heard the cam chain noise again. But I may have damaged it early on. This engine has 4 cam chains. It was the upper rear one that broke.

There is no way a Vulcan 750 is going to go 140 mph. It starts to become unstable around 100 mph, and even if it had the power to go faster, it would probably develop a serious wobble. Cruisers just don't have the high speed stability sport bikes do.
 

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FREEBIRDS MC CENTRAL NY
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I intentionally brought mine to 9500 (was in a very bad mood and should not have been on a motorcycle that day). Yes redline is 8500

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