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Discussion Starter · #1 ·
Let me start by saying I appreciate any help you can offer. Let me also say that I am letting the bike run through it's full cycle before starting as well. Unfortunately my high/fast idle is still there and will not go away. In fact I have not felt comfortable ridding it so it has been sitting all year.

My Mods:

Cobra Drags
Power Commander
TRE3
Extreme Intakes

The Beginning:

Last year around the end of September I was out with a group of friends. We stopped to wait for another rider to meet up with us so we shut down the bikes and hung out for awhile. Upon starting my bike it backfired very hard and seemed to come out of the left side (Clutch Side) intake which happens to be the rear cylinder. I gave it another crank and it started right up idiling at 1500 - 2000rpms. Bike appeared to have power under load just idled like crazy. It has done this every since.

What I have done:

- I reviewed the forum up and down looking for information. I have removed the TRE. This did not help.
- I unplugged the power commander this did not help either.
- I have looked for cracks on the air box unplugged hoses and other leaks, but have found nothing.
- New plugs are installed
- I Ohmed out the coil packs and they match each other and appear to match specs I found.
- I ohmed out the injectors as well and they match.

Key Notes:

- When idling the rear cylinder appears to miss or is out of sync. You can hear it and feel it the front cylinder has a nice solid bump, bump, bump. The rear has a bump bump, bump, bump bump, bump pattern going.
- The coil pack plug does get very black and the rear cylinder appears to be running very rich.
- The front cylinder appears to heat up much faster than the rear. I can feel the difference by hand have not used any other tools.

With that being said... HELP !

I was doing some more reading and it looks like my next steps would be the fuel filter and possible the IAC on top of the air box? Should I buy a new coil? I am not sure what to do here. Lots of things going on so money is really tight (New Kid, House, wife laid off). I would love to put a few miles on it this year but not like this.

So guys and gals where do I start now?
 
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The back fire would seem to me to indicate what to look for. It either cause a vacuum leak of some sort, or damaged something else. Try spraying carb cleaner, or starting fluid litely around the intake manifold while the engine is running. If the RPMs pick up you have an air leak somewhere. It's also possible to have a problem with the throttle position sensor from the voilent shock to the throttle caused by the backfire. It could also affect the sync of the throttle body. You can find check proceedures in the manual.
 

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I was also about to mention your throttle bodies may be out of sync. Mine has idled at 1200 since I've owned it, with and without mods. I think mine needs a sync.
 

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Discussion Starter · #4 ·
Sync

Pegasus/Grampi,

Thanks for the replies. I have not had the TB's sync'd yet but will look at doing this next. If the TB's are out of sync would it cause the idle to be erratic as well? Sometimes it idles at 1200 - 1500 and other times it is more like 1500 2000. Sometimes it also seems normal.

The thing that bothers me is I can see the high idle with the TB's out of sync but why would one cylinder be so rich and why would it cause a miss? Increased fuel yes but a miss and a rich condition?

At this point I am trying everything just trying to get my head around it !!

Thanks Again !!
 

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If your throtles out of sync, the way i understand it is at the time when one is closed the other one is lightly opened, causing more air to enter one cylinder. Which would cause more vibration and higher idle. Correct me if i am wrong!!!
Edit: I would take it apart so i can see the throttle plates, and move the gas lever and see if they move the same and if they close the same way.
 

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Discussion Starter · #7 ·
Vibration

Slavic,

I am going to give it a visual tomorrow and she how she plays. You mentioned vibration which is something else I notice when I am idling, a very rough idle more vibration than normal.

On that note what does everyone use for a syncronizer? I was looking at picking up a TwinMax. They appear to have a good following.

http://www.aerostich.com/twinmax-synchronizer.html

Thanks Again !!
 

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Slavic,

I am going to give it a visual tomorrow and she how she plays. You mentioned vibration which is something else I notice when I am idling, a very rough idle more vibration than normal.

On that note what does everyone use for a syncronizer? I was looking at picking up a TwinMax. They appear to have a good following.

http://www.aerostich.com/twinmax-synchronizer.html

Thanks Again !!
I dont see how this will help you, since you have to put them in different pipes to check each cylinder individually. The stock pipes are 2-1-2. So i dont think it will help you much. However if you have aftermarket 2into2 than it might help you, but i understand its to adjust your air to fuel, and i dont think its your problem at the moment. Maybe some one who have more knowledge in this area will step in.
Once you get it apart let us know how it looks, probably from hard backfire it knoked something out of place.
 

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I dont see how this will help you, since you have to put them in different pipes to check each cylinder individually. The stock pipes are 2-1-2. So i dont think it will help you much. However if you have aftermarket 2into2 than it might help you, but i understand its to adjust your air to fuel, and i dont think its your problem at the moment. Maybe some one who have more knowledge in this area will step in.
Once you get it apart let us know how it looks, probably from hard backfire it knoked something out of place.
It's not an exhaust probe. It monitors engine vacuum.
 

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The backfire may have damaged the ISC, or Idle Speed Control. It's mounted on top of the air box on the right hand side.

Also keep in mind the both outside filter boxes dump into a common shared air box under the tank. If it backfires it should come out both sides, but you may have just heard it more on the clutch side.

Most of the guys that I know that sync their own carbs and such use a water tube instead of vacuum gauges. It's much easier to compare the height of two water columns side by side than it is to compare two vacuum gauges that tend to fluctuate a lot at low rpms. There's several articles on the internet on how to build them and what fluids to use in them. You just need a couple $$ worth of clear plastic tubing and a backing board to mount it on, along with the proper connectors to hook it to the throttle bodies.
 

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Discussion Starter · #11 ·
Thanks

Zoom this is the unit directly on top with the three hoses going to it? Should I start by syncing the carbs or should I look at replacing the ISC?

I supose I should just sync the carbs first and consider it good maintenance. I will look for the info on how to put one together. Do you have any links to messages on the forum of others that have built them and used them? If this does not help with the issue I will look at the ISC.

Thanks again for the info !!!

The backfire may have damaged the ISC, or Idle Speed Control. It's mounted on top of the air box on the right hand side.

Also keep in mind the both outside filter boxes dump into a common shared air box under the tank. If it backfires it should come out both sides, but you may have just heard it more on the clutch side.

Most of the guys that I know that sync their own carbs and such use a water tube instead of vacuum gauges. It's much easier to compare the height of two water columns side by side than it is to compare two vacuum gauges that tend to fluctuate a lot at low rpms. There's several articles on the internet on how to build them and what fluids to use in them. You just need a couple $$ worth of clear plastic tubing and a backing board to mount it on, along with the proper connectors to hook it to the throttle bodies.
 
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