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Carbs?

2K views 18 replies 10 participants last post by  JD13 
#1 ·
Blew the motor in my 2003 America. Bought a 2008 w/ 19K miles. Put it in myself. Turned the key then took it for a ride. Ran great for about a mile. Fouled out plugs, I guess the carbs. Brought it to a local MC shop. For $572 he "adjusted and cleaned carbs" Told me it would run crappy for about 200 miles because of "a lot of build up on the pistons" Rode it home about 9 miles crapped out again. I'm thinking of doing the carb myself. New jets...etc. Any suggestions?
 
#2 ·
first check the fuel filter, then the tank vent. if that's ok pull the bowls. i have a t100 but i helped a friend with an america with pods. the bowls could be removed and jets pulled without removing carbs and blow through passages with carb cleaner. maybe you'l get lucky. use a new #2 phillips screw driver bit like the ones you use in a drill for the bowl screws.
 
#3 ·
Just to add to the previous post. Check filters on both ends of the fuel flow. Check /clean the petcock screens and the "hidden" filter in the T pipe between the carbs.
If you drop the carb bowls (recommended) you may want to replace the soft screws with SS hex ones (something like https://newbonneville.com/shop/carburetor-screw-kit/ ).
Troubleshooting with the fuel cap on but not latched helps get things going if you have a tank venting issue.
 
#4 ·
Anyone telling you it will run crappy... buildup.. is an idiot not a mechanic. Go after him for the money he stole from you. A carbon buildup on the piston raises compression and can cause detonation during under the right (wrong) conditions otherwise higher compression results in higher power output - that's why engineers work their asses off to achieve it and we want it.

If it has run right at any point don't change the jets, they are the right size. Were they new plugs? Did you see them before your first ride? Fouled by gas or oil fouled. You need new (or at least clean) plugs to diagnose the problem.

Intermittent fuel problems means crap moving around. Any half-assed cleaning job should get rid of loose crap. A hard deposit in the wrong place causes a consistent malfunction which you don't have.

I couldn't stand the idea of the hidden screen in the tee that was hard to service. I eliminated it, perforated the petcock screen and added a clear exterior filter where I could see it and carry a spare.
 
#5 ·
To see if you have a fuel flow problem, open the fuel bowl drains to see if you have consistent flow out both sides. If the flow comes out well, you don't have a filter issue. One issue is that dirty carbs don't usually cause a rich fuel condition. They cause a lean condition because of the dirt blocking fuel flow unless the needle valves aren't closing but that would cause flooding and fuel coming out of the carb bodies through the carb vents. You have some questions to ask.

I agree with Since65 about the mechanic who "fixed your carbs". He's blowing smoke somewhere and robbed you of your good earned cash.

Some questions you need to address.
1. Did your new engine come with carbs or were they from the old engine?
2. You said you blew the old engine, what was the failure mechanism? Trying to determine if the problem from the first engine isn't causing a condition with the 2nd.
3. When you said the plugs were fouled, did you see the condition? I would expect both to be black with carbon. If you didn't see that both were black....????
4. What would cause both cylinders to run so rich.
5. Plugged filter or inlet (any squirrels make their home in it?).
6. Choke seized and left on would affect both cylinders. What was the choke condition?
7. Someone played with the jets and installed oversize ones. What size of pilots and mains do you have in the bike?
8. Your ignition system might be failing. If both plugs are bad, you could have a problem with the throttle position sensor (disconnect it by unplugging the sensor. This doesn't affect performance and will reduce popping on decel. If you do decide to disconnect this, make sure you unplug it. Don't remove it from the carbs).
9. If you have a problem with only one plug fouling then it is either localized to that carb or you have one ignition coil issue or an ecm acting up. The way to determine if it is a coil/spark plug wire verses the ecm is to switch the 3 wires between coils (2 primary wires and 1 spark plug lead). If problem switches sides, you have a bad coil or spark plug wire. If it doesn't switch sides, your ECM is starting to go.

These are some of the questions you need to resolve before chasing this problem. Don't go back to that mechanic.
 
#6 ·
" Told me it would run crappy for about 200 miles because of "a lot of build up on the pistons" - WHAT?!?!?!?! BWAHAHAHAHAHA!!!!
THATS THE FUNIEST THING IVE HEARD IN MY LIFE!!!!!
BWAHAHAHAHAHAHA!!!!!!!!!!!!!!!!!!!!


Ohhh, OK, Im better now.


Sorry man, but you've been had. $572? Yikes....
 
#7 ·
Thanks everyone. I did order new jets, it's the least expensive thing I've done. I'll take everyone's advice and get working on it ASAP. I've had a couple of guys tell me it could be the ignition coils. Even my car mechanic thought the coils should be checked.
I'm going to have the most expensive America, in America.
 
#9 ·
I'm slowing figuring out what's not wrong w/ this America. I'm still need to rule out the ECM and choke. What's the best way to determine if the choke valve is good? The last time I had it running it actually seemed like there was no difference from being choked to when I released it. Thanks
 
#10 ·
Hey, hope you got this fixed. You know you can rule out (or in) the coils with a $15 multi meter - just set the meter to Ohms (not M Ohms, just Ohms, and touch the positive and negative terminals on each coil. The specs are detailed in the Haynes manual and a 2008 EFI should be 1.3 to 1.9 Ohms.

Let us know what you found to be the culprit.
 
#11 ·
For buildup on pistons just run Seafoam in your gas. One ounce per gallon. Do this forever, or as long as you own the bike, whichever comes first.
 
#12 · (Edited)
"For buildup on pistons just run Seafoam in your gas. One ounce per gallon. Do this forever, or as long as you own the bike, whichever comes first."

Why doesn't the factory provide a Sea Foam injector ? Darn those college educated Mechanical Engineers ! Always forgetting something. ;-/
 
#13 ·
There is a Sea Foam injector. It's called a Carburator.
 
#14 ·
Why would anyone want to remove buildup of carbon from their pistons (unless the engine is suffering from detonation).

Carbon on top of the piston raises the compression ratio - which is desirable.
Carbon on top of the piston insulates it, keeps the piston cooler, keeping more heat in the combustion area producing more expansion, power, instead of transferring the heat to the oil in the crankcase.
The buildup reaches an equilibrium state of thickness. A clean piston top runs at a low enough temperature to encourage carbon to stick on it, as the thickness builds up, the surface is more insulated from the piston, runs hotter and eventually reaches a temperature that is kept burned off.

The rest of the piston? There's no room for buildup on the sides, fuel and additives don't contact the bottom. That leaves the ring groves. Yes they can carbon up to the extent that the rings stick and don't expand and contract correctly and can plug the oil ring. I've only seen this on very high-mileage, poorly maintained, smoking, sludged up car engines.
 
#15 ·
Thank you all for the input. This f-ing bike drove me crazy. It was the ECU. There was nothing indicating it was a problem w/ the original engine. But when I put the 2008 ECU on my 2008 engine it ran great. So I'm going to try and figure out if the output is different between the 2003 790cc ECU and the 2008 865cc ECU. Big question for me now is, was this the problem all along. First mechanic told me my compression in one of the cylinders was down to 70%. I'm hoping to figure that out soon. One thing I know for certain is, I'll never waste my money on a mc mechanic again. Got it going just in time for the Conn. winter. jp
 
#18 ·
Sounds like it was your ecu/cdi the whole time . When the cdi fails( I believe the ecu is for the fuel injection models) it generally causes one cylander to fail to fire. That would be the one that is down 70% compression. My money is that there isn't anything wrong with the original motor.
 
#16 ·
Glad you were able to resolve the problem.
Hopefully spring comes early for you. Maybe the original motor can be the winter project :nerd:
 
#17 ·
An igniter unit from the first Hinckley carb twin produced will work on the last carb twin manufactured, the only real differences between the 2003 and 2008 igniter units were the ignition advance maps and the implementation of the EVAP system.

Of course it would need to be a 360° or 270° igniter, as an igniter unit from one engine type can't be swapped with the other.
 
#19 ·
On a side note. Since you have an America you should spend some time over on bonnevilleamerica.com . I am not trying to take anything away from this forum, there is a lot of great info on it but bonnevilleamerica.com is specifically geared toward the Americas and Speedmasters and the guys over there are very knowledgeable. There are a few issues such as bad cdi units that tend to be more specific to the America/Speedy. When my cdi was going bad I knew that was what was wrong from having read about other guys issues with them over there.
 
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