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How to diagnose a twin tech system

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frustratedfrank

Member
I have a Bourget with a 2003 twin cam in the frame that is fuel injected. I have had the bike for a while and has run very well until it didn’t. The engine just was rebuilt with all kinds of new parts to make it more reliable. No go faster parts. The problems I’m having now is it won’t stay running. It has a twin tech Ecm running the fuel injection system. I have contacted the manufacturer and they tell me that the system is to old and I should buy a new one from them. I have no idea if the Ecm is the problem or a sensor. I cannot justify buying a new Ecm without knowing what the problem is. Does anyone know how I can diagnose this Ecm.I'm not interested in learning any of twin tech secrets I just want to fix my bike.
 
So is this a problem that started after the new parts were installed or 1000's of miles later.
How many miles on the fuel filter?
Being the bike is 22 years old I would start with a new fuel filter, you can have good fuel pressure but very low volume causing stalling when a filter is plugged. Can also cause back fire on deceleration do to extremely lean condition.
Is the air filter clean?
Next check for vacuum leaks. A can of carb cleaner with the straw spraying short bursts around the intake seals.
 
This all started with the bike running rough. Then the meltdown happened. The engine was completely rebuilt top to bottom. I have installed new intake manifold seals fuel injectors, fuel pump, filter and pressure regulator. The air cleaner is a k&n and is clean. The running issue even happens with the air cleaner off. I have double checked for leaks around the intake seals and have found no leaks. When I did take the bike for a short ride it seemed like it had an accelerator pump problem even though it’s fuel injected. One it stopped sputtering it took off like a rocket. When I let off the throttle it stalled. The bike fired back up and repeated the issue. So now it’s back on the lift waiting to see what its fate will be. Sold for parts or thrown out! I am going to test the crank position sensor and engine temperature sensor as well to see if maybe that’s a problem. I do know that the problem is definitely not mechanical it’s somewhere in the electrical system.
 
That’s exactly what I’ve been doing. As I’ve said before every time I reach out to the manufacturer they just want me to buy a new system and tell me mine is outdated. I’m not buying a replacement Ecm cuz I don’t know if it’s the problem or if a sensor. I do know for a fact it’s not a mechanical problem. Well there is only 2 more sensors to test or replace so I guess I’ll find out the hard way. Thank you guys for your help and advice.
 
Have you looked into checking for codes using the odometer readout? I think it can be done unless it is too old for that technology, someone here may remember the procedure, or Google it .
 
I have an aftermarket Ecm in a custom bike. I purchased a Bourget that someone built very poorly but it did run very well. Everything else was a problem. I have done a lot of work to the bike to make it safe and dependable never having to do anything with the engine other than oil changes and basic maintenance. The bike ran great until the heads failed by bent valves. Prior to the engine failure the bike did start to run different. At that time the mechanical end of it was fine and I took it to different shops and was told they couldn’t scan the Ecm cuz it is a twin tech. So after a complete engine rebuild it will not run correctly and I know it is not mechanical it’s definitely electrical. The system is not connected to the speedometer so there is no way for me to get codes out of the system. I will try a couple of more things before I remove the entire system.hopefully I’ll figure it out first
 
The Bourget, as the OP knows, is a "boutique" custom chopper, akin to Big Dog, American Iron Horse and others that were popular early 2000s custom bike boom; remember Orange County Chopper?:rolleyes: HD Twin Cam motors were used but S&S was a more often used power plant. Many parts were proprietary so repairs can be a major headache today-particularly electrical systems as the OP is finding out. The OP needs to start a search for a "grey beard" mechanic, someone that was around back in the day; someone that can troubleshoot the electrical system from top to bottom; that's the only way to get the bike running properly again. Very unlikely that the OP will find someone qualified at a dealership. Any independent that might be qualified will be very difficult to find; those older guys are rare. My advice to the OP is to search high and low for a tech qualified to troubleshoot and repair the electrical system; get the bike running and sell it as fast as he can.;)
 
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