Loss of power/acceleration?????

jester 42 · Dec 28, 2013

On the road today.
Could not accelerate past 80 mph.
When I came close to 80 mph, the bike acted as if a govenor had kicked in.
If I down shifted; bike acted as if it was ready to accelerate, but when I hit around 80 mph again, I would lose power again.
If I maintained a constant speed below 75 mph; no problem.

No unusual noises.
No smoking; bike is very low mileage.
No problem starting or idling.
No problem shifting.
Bike is a 2005.
Has K & N filter.
Fuel is premium grade, and fresh
Never encountered this issue before.

No get up & go; acts as if it is fuel starved??????

Jester 42

adambweird · Dec 28, 2013

Might need to do the shotgun and/or pea shooter to the carbs and probably switch to regular unless youve had engine work done to raise the compression ratio.

VMAX1260 · Dec 28, 2013

check your fuel filter . . when you rev high with Neutural does it goes to redline ?

Fire-medic · Dec 28, 2013

Check the fuel pump output into a container, I think there is a figure for volume in a certain time in the shop manual. Beware of doing this anywhere close (within 30') of a pilot light appliance, like a furnace or water heater, or a space heater.

Can you run it close or to redline in 1st w/o it bogging-down?

A severely-restricted air filter could do something similar. Try cleaning it and re-oiling, 'less is more' when it comes to the re-oil.

jester 42 · Dec 28, 2013

The engine is completely stock.
I have always used premium fuel , and have never had any issue using premium.

The K & N filter is clean; virtually like new.

It will redline in 1st & 2nd gear without bogging down.
It will rev very high in neutral; no bogging down, but I didn't take it to redline, other than to just blip it quickly & back off.

It only bogs down when I to accelerate past 75 to 80 mph.
Acts as if gas has been cut off.
As soon as I back off, or downshift, it will accelerate again, and then bog down again.

Jester 42

MaxMidnight · Dec 29, 2013

Only guessing and clutching at straws but change fuel filter (if not done within living memory); balance carbs; check fuel tank breather is clear; check throttle slides diaphragms for a split.

alorio1 · Dec 29, 2013

I would guess that you have fuel starvation also.
I would check the vent off port located on top of the fuel tank and the tip over valve that connects to that port for obstructions . You should only be able to suck air thru this small plastic valve located close to the bottom of this vent off hose. You should be able to suck or blow thru the port on the tank. After checking the vent off circuit, you need to check the supply fuel port located on top of the tank and make sure this port is clear from obstructions. Inspect the fuel line leading to the fuel pump for pin holes and also the fuel filter for a crack or loose hose clamp that would allow the fuel pump to suck air. Even the slightest leak will cause inadequate fuel delivery to the carbs. Make sure the fuel filter is clean and non restricktive to fuel flow, change if in doubt. Check carb vent off lines for proper routing under the air box. If all these checks are ok, I would check the fuel pump for problems with-in the pump itself....here is a good write up on how to check the internals of fuel pump.

http://www.vmaxforum.net/showthread.php?t=8775

jfeagins · Dec 29, 2013

My vote is with your fuel pump. It, s a well known problem for one of it's internal tiny rubber valves to become dislodged and fuel pressure to suffer accordingly.

V4bandit · Dec 29, 2013

My bike did the same thing to me this past summer. If I was running hard with a buddy the bike would pull awesome to about 8 rpm and then shut off like a govn. I checked the fuel pump and changed the filter and no change in perf.

Turned out to be water in my fuel bowls. It would sit dormant till I opened her up then it would raise its ugly head. lol

customizedcreationz · Dec 29, 2013

As a fyi using premium will cost you power. If the bike doesn't knock on 87 octane, then using premium is doing nothing for you but wasting money.

Second fuel problems with high rpm starvation first thing is fuel filter like mentioned. Its cheap and easy to replace. The problem your explaining is definitley fuel starvation. At low rpm fuel demand is low. As you increase rpm demand increases. Hence the reason why you can accelerate through low rpm up to high rpm and then start to fall off.

Checking the filter, if you still have a problem check the fuel pressure and flow. If still an issue then you will have to look into the carbs. But usually carbs cause a problemat idle or if at high rpm it will happen all the time and not only under load while riding.

Check those things first and report back.

Todd

jester 42 · Dec 30, 2013

Input is much appreciated.
Will check back when problem is resolved.

Bike with issue is in foreground.
As you can plainly see; it's a poorly maintained old beater.

Truthfully, this is the first problem I have ever had with this bike.

Jester 42

tugla · Dec 31, 2013

what about ignition wires and caps. they all good also I assume. you haven't chg plug recently either eh?

fmcandrew · Dec 31, 2013

+1 for fuel starvation. I think the fuel requirements for hitting redline in neutral under no load is very different then hitting redline under load at 80mph...I think...

alorio1 · Dec 31, 2013

I wouldn't try and recreate symphoms you saw @ 80 MPH with engine not under load......I'm a firm believer that constant high rev's on an engine not under load does it harm.

RobCar · Dec 31, 2013

Did you buy a Harley and forgot you bought one? Happened to me once. ONCE!!!!

jester 42 · Dec 31, 2013

The spark plugs are fine.

I did NOT try to recreate the problem by running the bike up to high rpms in neutral.

If others want a Harley, good for them. Their dime.
I have no concern about what bike others ride.

Jester 42

Shorty · Jan 1, 2014

I had a car that was doing the same thing years ago. That turned out to be the coil starting to die. I don't know? Maybe that's what your bike's doing too?

jagco1 · Jan 2, 2014

My bike had the same problem when I was riding out of town last year. My freak-en gas hose was bent right at the carbs gas hose holder clamp. Almost closed. Bike would run slow at about 85 to 90 miles in hour until move the hose out of the silver clamp on the back of the carbs.

This may not be your problem in your case. But you can easy check this.

dustincooper696 · Apr 9, 2020

My 1990 is doing this. Did you guys ever figure out what the problem was.

Tales Feeler · Jul 12, 2020

My 2002 started doing same this summer (got 3000 miles since March this year)...

new air filter
new spark plugs

thought was a clutch = replaced clutch, same issue;

- replaced (actually) bad battery;
- replaced all 4x coils (were cracked) with good-shape stock ones;

bike started running well again but for ~2 weeks only

so I might've touched something else;

- replaced fuel filter;
- took out and checked the fuel pump = works well (provides enough pressure and clicks once or nothing
once bowls are full) = same (almost, a bit better) issue...

Any idea what the problem can be?

Loss of power/acceleration?????

Help Support VMAX Forum:

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Attachments

Well-Known Member

Well-Known Member

Well-Known Member

Active Member

Well-Known Member

Member

Well-Known Member

New Member

New Member

Similar threads

Join the conversation!

Join today and get all the highlights of this community direct to your inbox. It's FREE!