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Discussion Starter · #1 · (Edited)
Hey guys been lurking these forums for a while, first time posting.

So i bought a 07 vt750dc with 17k miles, k&n air filter, and open cobra pipes. Got a good deal on it and I really like the ride but she needs a little work. And I could use a little advise.

When I purchased the bike it hadn't been ridden in 2 years and had accumulated a good amount of garage dust. I put a new battery in her, drained the tank, and she fired right up but wasn't running quite right - Not very smooth, down on power and wanted to bog down at high speeds.
I decided to tear into the carbs, which are new to me as I have only ridden fuel injected sport bikes until now. The bike was last ridden in Ohio and I live in colorado at 6k feet. After pulling the plugs I appeared to be running a tad rich but not too terribly. I'm assuming the open pipes compensated for the altitude change?
Once inside the carbs I noticed I had one float level that needed to be adjusted. I changed out the float needles, gaskets and replaced the old vaccum crossover lines. I changed the jetting to:
Pilot jets #40
Main jets #115
Air mix at 2.5 turns out
Air filter is a new k&n

The bike runs great around town and has power everywhere in the rev range , no problems pulling from 50 mph in 5th gear. Happy with how she rides.

Problems begin trying to pull up hills. I was out today for the first time in the mountains and had a serious problem gaining /maintaining speed above 65mph. I was on the infamous i-70 of colorado which has an unspoken speed limit of 75 and opens up to 4 lanes at times where the speed limit is seemingly as fast as you can go lol. I started up a section of a steep 5 mile incline initially crusing in 5th . I Quickly started losing speed with wide open throttle. Not a problem I thought and bumped it down into 4th.. still losing speed.i found myself having to run it in 3rd WOT just to maintain 63mph! I was able to merge to the right and ride the slow lane but I tried a couple times to kick it into 4th to gain more speed and there was just no power there.

What's the next step? Fuel petcock is flowing well and the shut off works. Fuel filter and fuel pump are all I can think of as far as a fuel flow problem? Vent tube is clear, Not sure if I'm way off with my jetting or if I should adjust my air fuel further out. I'm popping/gurgling like a mother on decel but I figure that's just the cobra pipes?

Any help is appreciated ! Thanks for taking the time to read all this

Edit for more information: I'm getting 35mpg right now so it's hard to believe I'd be running lean? And when I was having the bogging issues it was 50degrees outside not sure if this affects carberated bikes air/fuel mixture bc of the change of density? Gosh I'm prolly overthinking this all
 

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1983 Honda vt750 Shadow
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Not sure how steep that hill is or the wind in the area or your size or if you have a windshield.
But that model has under 50 HP, so it may be working as hard as it can up a long grade.
Other guys may have more info.
If the plugs are still black under that type riding it may be way too rich as you mention.
35 MPG is a bit low also. Unless you are full throttle a lot.
Maybe a carb sync would help get maximum performance.
Some guys open the air box for the "Bean box mod". Maybe that would help your altitude mixture.
 
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Discussion Starter · #3 ·
Not sure how steep that hill is or the wind in the area or your size or if you have a windshield.
But that model has under 50 HP, so it may be working as hard as it can up a long grade.
Other guys may have more info.
If the plugs are still black under that type riding it may be way too rich as you mention.
35 MPG is a bit low also. Unless you are full throttle a lot.
Maybe a carb sync would help get maximum performance.
Some guys open the air box for the "Bean box mod". Maybe that would help your altitude mixture.

Thanks for the reply man! ya it was pretty windy, no windscreen but I'm 6' 1 250 with gear i gotta wonder if you're right about running low on power . I gotta pull my plugs again today and see how they're lookin I suspect I'm running rich. And I'll look into that bean box mod I appreciate the info
 

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1983 Honda vt750 Shadow
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Pump up the tire pressure for less rolling resistance too. 35-38#

You might look up 4 degree timing mod also.
I have no experience with it, but a lot of guys have done it on the 750s.
 

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Discussion Starter · #5 ·
Update to close out this thread. The problem turned out to be my fuel pump was beginning to fail. After replacing my brown fuel filter to rule out the cheap fix; I found a youtube video on how to test flow and it tested less than adequate. Odd because my plugs showed a rich running condition rather than lean which has me scratching my head a little (not oil fouling)... but after testing out the new pump I can pull up very steep hills all the way through 4th gear. 5th gear isn't going to rocket me through any hills but most importantly does not lose speed. Next step for me is modding the airbox. Happy riding everybody
 

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2002, Shadow Spirit 1100
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Update to close out this thread. The problem turned out to be my fuel pump was beginning to fail. After replacing my brown fuel filter to rule out the cheap fix; I found a youtube video on how to test flow and it tested less than adequate. Odd because my plugs showed a rich running condition rather than lean which has me scratching my head a little (not oil fouling)... but after testing out the new pump I can pull up very steep hills all the way through 4th gear. 5th gear isn't going to rocket me through any hills but most importantly does not lose speed. Next step for me is modding the airbox. Happy riding everybody
Thanks for the repair update.
 
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