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Discussion Starter #1 (Edited)
Gentlemen,

I have recently purchased a 2003 VTX 1800S with 3400 miles on it; however, I now have up to 5200 miles on it and I was wondering why above 78 MPH it begins vibrating significantly more. I have accelerated from 0 to 80 and it is very smooth as it likes the hard accelerations; but, if crusing above 80 it just vibrates and acts like there is a "Harmonic" which comes and goes at a constant rate. If I try to accelerate from above 78MPH in 5th gear it sounds like I am lugging it down. Last Sunday I was on a country road cruising at 65 and decided to give it heck up to 120 and it performed well with little vibration. After only a few seconds I resumed normal cruising speed and at 80 it still vibrated significantly. All components on the motor are totally STOCK with no modifications.

Thanks everyone,

Margarita Machine
 

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A harmonic vibration is usually tire balance. Do a search on Dynabeads - work like a charm.
 

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Discussion Starter #4
2003 VTX 1800s Engine Vibration / Harmonic Repair

I stated I would try to provide some feedback as to the repair of my 2003 VTX 1800S so here are the details of the repair and test ride:

As the problem with my bike was difficult to diagnose I took a trip from Houston, TX. to Leakey, TX. on the first day of testing after the repairs were completed by the Race Team at Honda of Houston, (HHR). I traveled via. multiple back roads between US290 and I-10 to determine if everything was working properly. On the second day there I rode the Texas Famous "Three Sisters" in both directions. On the third day I returned to Houston, TX. to complete the evaluation of repairs. This ride was sufficient to test any motorcycle under an extensive variety of conditions as the total miles covered were 1016.

I averaged 29.81 MPG on the trip overall; however, if anyone is familiar with the Three Sisters, you don't go there to get a GOOD MPG rating. On the return trip, traveling at 80+ MPG for over the last three tanks of gas I averaged 33.64 MPG. That rating would have been better had we not ridden 337 from Leakey which is by no means FLAT for about the first 20 or 30 miles. On the last tank of gas from Flatonia, Tx. to Houston Tx. I got 34.30 MPG at approximately 81 MPH.

Overall I would have to say I am very satisfied with the Professionalism and courtesy I was shown by all the members of the team at Honda of Houston. They did multiple checks to verify the integrity of my bike, took significant steps to ensure that other problems which might have been related were completely eliminated, and went the extra mile to provide me with a bike worthy of a trip of over one thousand miles which I took after picking up the bike.

The following testing was done on the Dyno by Honda of Houston Racing, (HHR):
Ran bike at 5% load – no results noticed
Ran bike at 10% load – no results noticed
Ran bike at 15% load – noticed variable ignition irregularity @ approx. > 6K RPM; hence, the Air / Fuel ratios varied erratically from front exhaust pipe to rear


The following repair was done upon testing of multiple components by Honda of Houston Racing Team, (HHR), Shaun Martin, Race Team Manager & Naveen, Race Team Technician:

Check resistance of each spark plug wire and found an open / intermittent short in the Left Front Spark Plug Wire - Replaced

The following precautionary measures were taken by the dealership:

Apply the “Ground Fix” per Tapers Directions

Test of the Fuel Pressure Regulator –
within tolerance as per pg. 5-53. (50 psi @880 rpm)
Compression Test –
as per pg. 8-3.:
657kPa (6.7 kgf/cm2, 95 psi) @320 rpm
my results:
(Front 122 psi, Rear 120 psi)
With 34.30 MPG at approximately 81 MPH should I be worried? (yes I’m aware that it states a buildup of carbon but I’m working on that)

New Spark Plugs – installed

Dyno results, (Pre-Repair), CF: STD Smoothing 5:
Max Power = 84.11
Max Torque = 99.34

Dyno results, (Post-Repair), CF: STD Smoothing 5:
Max Power = 85.78
Max Torque = 101.28



Thanks again to all the folks at Honda of Houston Racing, (HHR), for ensuring that I have a highly reliable bike in which to enjoy.

Note: I did NOT see a T-Shirt that stated “I did the 3 Sisters, Both Ways, In 1 Day.”

:coffee::choppersm:choppersm:choppersm:cheers:
 

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MM we've got the same bike, make model and year. I regularly get 33 mpg. So what are you doing about a carbon build up? Good info about the plug wires.
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Discussion Starter #6 (Edited)
Mdolph,

I'm currently running the Chevron Techron® Concentrate Plus every few tanks, as per the directions on the 20oz bottle which = approximately 1 oz per gallon. I've just had the bike dynoed, ran it over 1000 miles @ which I got over 34MPG @ over 80 MPH, and am hopeing with the new plugs the deposits internally will eventually burn out. When I open a bottle I just add the Chevron stuff after each fill-up when I get home so hopefully it will have some positive efffect on the motor parts.

Thanks,
MM
 

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Thanks MM, I'll give that a try, I could use an additional gallon per mile or so. Out of curiosity, how much did all that maintenence work cost you?
 

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Nothing wrong with that MPG at that MPH.

Slow down to 55-60 (if you like) and it'll bump up.

I've gotten 'high 20's' @ 80+, loaded down + 'large' windshield. (PCIII equipped)
Recently got 39 mpg with same tune / no shield in the Ozarks puttering around @ 50 mph or less.

Been to all the places you've mentioned, (including H of H,,,)

Typically, when it's 'sister time' for me, we head out thru the Austin/Hill Country' area, stay in either Marble Falls and/or Kerrville.

Depart Kerrville for Leakey/sisters via some 'less traveled' roads past lost maples state park. There is a pretty nice antique MC museum just 'south' of lost maples. Lots of old rare bikes.

You are correct, not much 'flat stuff' around the sisters! Beautiful in the spring. Good ride, for sure.

Never had any wrenching done at H of H. (Or anywhere else)
(PCIII Dyno tune done by Johnny Cheese in Round Rock)
Parts are pretty high there (Just like any other Dealer)
Staff has always been helpful and courteous,,,

Welcome to the Cafe!
 

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Food for thought
While removing carbon build up The oil should be changed as that is where the carbon will end up.
I use a carbon remover made by HD, works very well. I do not remember what is is called. It has been a while since I needed any. I change the oil at 100 miles and did it twice. Some of the carbon was as large as my pinky nail.
Never use premium fuel. That is what caused the carbon build up.

just a thought

dd
 
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