I would like to start off with a big thank you for all of the information I have been able to search.

I didn't want to muck up other people's problems with my thread, so I figured I would start my own.

I have a 2003 SuperHawk and have spent the last three months chasing down issues left by an inept "motorcycle shop".
I have since gotten the cam timing set back properly, shimmed my valves back to spec, confirmed I have good compression, taken my carbs apart to clean them and set everything up according to the sticky, and made my own peak voltage adapter to test my ignition system in it's entirety.

However, I still can't go full throttle unless the bike is sitting still. I have quadruple checked my vacuum lines, electrical connections, and become an expert at removing my carbs. I have pulled the fuel petcock to make sure the diaphragm is good and the filter is not clogged. There is no rust in my tank and the fuel flows good when vacuum is applied to the proper nipple at the back of the petcock. The breather lines to the tank are free of obstructions.

I am no motorcycle mechanic, but I have had 5 years of automotive technology schooling, electronics schooling, and at least 16 years of applying said vocations. This was supposed to the one toy that I paid to play on. I was never supposed to work on it, but the shops local to me are terrible and have cost me $1500 and countless hours of my own time.

Is there a way to ensure good fuel flow while under load? If I had a dyno it would be easy, but the only thing I can think of leaves me less than confident while riding.

Please feel free to ask whatever questions you need in order for me to better explain what I've done. Any help will be greatly appreciated.

 

The petcock is open and closed (controlled) by a vacuum diaphragm.

Even if you were somehow loosing vacuum under load, the float bowls would still be full from when you were idling and full vac was applied. Have you checked fuel flow to the carbs while running?

Let carbs fill, kill bike. pull fuel lines from petcock, replace with fuels lines that run in to a clear container. start bike... see if you have fuel flow.

Other then that, start at the beginning, assume nothing.. nothing you have "fixed' replaced, changed or adjusted.

Pretend you have never seen the bike before and no noting about it at all, or even the design. What I mean is, do not relie on what you "think" you know about carbs parts or set up.. Find a resource, picture, manual section for everything thing you touch and confirm what you are doing, seeing, checking is as per the resource document.

 

Thanks for the response.

I'm currently working on a suitable container.

I was given a Honda Service manual when I bought the bike. It has been my main resource aside from this board.

I haven't messed with carbs since I was a teenager. I try not to ASSume anything with them. lol

I just took it out again and unscrewed the tank cap to see if maybe there was an obstruction in the tank's ventilation. It did seem to run better. I was able to nurse the throttle to about 90%. I had checked the hoses and ASSumed that was the only place left for an obstruction. When I flipped the tank to remove the petcock some gas ran out the ventilation upon flipping it back over.

Another odd thing about this issue is that it runs better at full throttle the faster I go.

My first assumption would be that it's leaning out under heavier load, which would imply it's too rich to begin with. However, the plugs look good and there's no smoke from the exhaust.

 

A possible source is the sidestand switch, which half a dozen or so people having worn or damaged ones that makes the bike cut out, stutter under riding conditions, but run fine stationary... Other than that, I'd look into the carb tuning like you yourself suggested...

 

I checked the side stand switch. It checks out good.

I'm hoping it is something simple that I repeatedly overlooked.

I found a motorcycle shop a few towns over that has a dyno. This gent sounds like he may actually know what he's doing. My wife thought he was a dick, so that makes me happy. Typically, when a business owner has been in business for many years, has that long of a list of repeat customers, and isn't afraid of sounding like an ******* while being completely correct, he usually does a good job.

He's also not a local yokel. He's got a bit of a reputation across the pond where he's from.

Here's to hoping I have an excellent running Hawk again.
<-----fingers crossed

 

You should double check that the springs and diaphagms are placed correctly. That is an easy thing to think is right when its not. I think that would cause what you describe.

Also, take off the tank, sit in on a trash can (or sim) and suck on the vac line. Fuel should gush from the 2 outlets. This will help you figure if fuel is flowing properly to the carbs.

Could be a clogged line to the carbs.

Dont do any of this with a real full tank. Even a perfect bike can get vapor lock from over filling up the neck.

 

My two cents for what it's worth.. often when a motor won't work under load it comes down to spark, either contamination (Ie. oil getting into the head), bad gas or bad plugs.. from there coil and pickups. My thought is week spark (coil) although I was told that very rarely happens on these bikes.
Start simple..
New gas ( I prefer a higher octane when testing )
Plugs.
Run motor in dark and look for arcing, to see if there are any cracks in wires or coil.

Switches!
I just had a neutral switch fail and since I do all my testing in the garage on the side stand this plagued me for days before I realized the switch only went bad at high temperature causing intermittent contact and the motor to kick buck and backfire.

Tweety suggested side stand switch.. don’t test it just ground the wire to the frame (bypass) and see if that fixes it.

One last thought.. if the intake timing was out by one tooth.. it would run but lack power.. I had this happen too..

Good luck

 

Oh yeah. Drain your gas and put it in your car. Start with new gas. Bad gas can do this too. Rend just reminded me.

 

Thanks for the replies, guys. I did all of those before getting it to the dyno. I even went so far as to replace the coils and boots with new factory replacements.

It has been confirmed that it's running lean. I'll know more later.

 

Update. There is no signal voltage coming to my throttle position sensor when reading the yellow/black (+) and green/black (-). I have excellent continuity between the ignition control module and the throttle position sensor.

This would lead me to believe the ICM is bad. Any other thoughts?

 

Could be - there was a recent case of a guy who tried everything - then he swapped in a known working module and he was back up and running.