Idle Air Bleed Screws Carbon Build-up

[MartyO]

I’ve been plagued with my idle going low when the bike is between cold and full warm. This showed up when I had around 50,000 miles on the bike. It is also hard to start and idle sometimes on a very warm day after it’s been sitting a short time and still hot. I had it into my good mechanic at 50,000 miles and he found sooty fuel injectors. After around $350.00 it worked a little better but not fixed completely. My mechanic told me to use better gas and use fuel injector cleaner every 5,000 miles. Also my idle adjustment screw is full in tight and the hot idle is around 900 to 1,000 RPM.

I just had the bike in for valve adjustment and throttle body sync at 100,000 miles. I also asked them to raise the idle. When the mechanic took it for a test drive he found my idle dilemma. The light bulb went on for him. He has found that high mileage FJR’s develop carbon build up on the throttle body sync air bleed screws that cause idle problems. He removed and cleaned the air bleed screws, installed new O-rings and synced the throttle bodies. I have a new bike at 100,000 miles and it’s awesome. I now have lots of idle adjustment on the idle adjustment screw cable and the bike performs like new.

My mechanic is Al (27 years’ experience) at North County House of Motorcycles in Vista, CA. I guess he didn’t know about this issue when I was in at 50,000 miles but he fixed it now.

Happy feejering to all,

 

[ULEWZ]

He has found that high mileage FJR’s develop carbon build up on the throttle body sync air bleed screws that cause idle problems. He removed and cleaned the air bleed screws, installed new O-rings and synced the throttle bodies. I have a new bike at 100,000 miles and it’s awesome.

Good to know, thanks.

 

[SkooterG]

Good info to know. I had uneven idle on my old 226,000 mile FJR. It would 'hunt' and constantly go up and down a little bit. Other than a minor annoyance, it was never a problem - wouldn't stall or anything like that. Never did figure out the problem. Never would have thought to check the air bleed screws. My current FJR has 71k miles and idles fine, but will know what to look for if it starts acting up.

I edited the title of your Post to make it more accurate as to the problem.

 

[MartyO]

Thanks Skoot.................

 

[3dogs]

After around $350.00 it worked a little better but not fixed completely. My mechanic told me to use better gas and use fuel injector cleaner every 5,000 miles. Also my idle adjustment screw is full in tight and the hot idle is around 900 to 1,000 RPM.

What work was perfromed for $350?? From what you describe cleaning the air screws and syncing the TBs fixed the idle problem. Seems like the $350 charge was ********--wish I could charge customers $350 to take out 4 (easily accessible) screws, wipe them off with a rag and reinstall. Did your mechanic turn all the idle air screws out 1 turn, before syncing??? This seams pretty basic... He should have know to to solve this issue without costing you this much cash.

I have 85k on my 05, have never "cleaned" the idle air bypass screws-- but do sync the TBs every 5 to 10k miles. Also I don't synce at idle alone--but at 4000rpm where most ridig is done.

 

[Fred W]

The way I read it the big money spent was on the fuel injector cleaning.

I'd bet that you could have fixed the entire low idle problem just by opening up each of the 4 air screws by 1/2 a turn and then re-syncing.

That probably happened by default when the mechanic took the screws out and wiped them off.

 

[3dogs]

The way I read it the big money spent was on the fuel injector cleaning.

I'd bet that you could have fixed the entire low idle problem just by opening up each of the 4 air screws by 1/2 a turn and then re-syncing.

That probably happened by default when the mechanic took the screws out and wiped them off.

I agree, I always start with the air screws 1 turn out, sync at 4000 rpm using the throttle balance screws, go back and sync using the air screws. Cleaning fuel injectors is somewhat over-rated as the fuel used today does not tend to cause the same types of injector clogging problems as it did 15+ years ago. Sounds like the tech/dealer wanted to sell an injector cleaning--same **** happends in the automotive world.

 

[Constant Mesh]

Can those o-rings be excessively worn from too much syncing? What provides the friction to keep the air screw from turning after a sync?

The parts diagram shows four parts in an air screw set.

Needle valve air screw

Spring

Flat washer?

O-ring

I must admit I sync much too often because it's easy and I notice a reduction in vibration from my efforts. However, trying to reduce engine vibration is an elusive quest. You think you've made it smoother and two days later the harshness has returned.

Instead of the two bolts at the front of the fuel tank I need a quick release latch.

I just can't seem to accept that the FJR engine has an inherent inline 4 roughness that can't be tweaked out no matter how many times I turn those air screws or adjust the butterflies. I know mine is synced better than 99% of the FJR population and I'm still somewhat disappointed with its harshness in the upper half of the rpm range. With the engine hard bolted to the frame the handlebars and footpegs don't lie.

 

[carlson_mn]

I'm sure this is obvious to all of you, but - are we talking about the 3 screws in between the throttle bodies that are tweaked when performing a sync?

 

[SkooterG]

I'm sure this is obvious to all of you, but - are we talking about the 3 screws in between the throttle bodies that are tweaked when performing a sync?

Yeah, but there are FOUR screws - one for each throttlebody.

 

[dcarver]

Take a step back and look at the bigger 'carbon footprint' on FJR's -

1. My low compression due to carbon build up between valve and seat

2. Throttle body air screws

3. ??? (I seen to recall more, but have CRSS)

 

[carlson_mn]

I'm sure this is obvious to all of you, but - are we talking about the 3 screws in between the throttle bodies that are tweaked when performing a sync?

Yeah, but there are FOUR screws - one for each throttlebody.

Hmmm ... I've been doing my TB syncs like I sync'd my carb'd bikes. There's an adjuster screw that syncs cyl. 1/2 2/3 and 3/4. I believe it syncs the butterfly valves. I'll have to take a better look at the FJR. Either way my TB syncs have always gone well with my method

 

[Fred W]

I'm sure this is obvious to all of you, but - are we talking about the 3 screws in between the throttle bodies that are tweaked when performing a sync?

Yeah, but there are FOUR screws - one for each throttlebody.

Hmmm ... I've been doing my TB syncs like I sync'd my carb'd bikes. There's an adjuster screw that syncs cyl. 1/2 2/3 and 3/4. I believe it syncs the butterfly valves. I'll have to take a better look at the FJR. Either way my TB syncs have always gone well with my method

No, no, no... This discussion has been centered around the 4 slotted brass air screws in the throttle bodies. These are where the "authorized" TBS is done.

The 3 linkage adjustments that you have been adjusting are the ones that are "factory adjusted" and we aren't supposed to be adjusting. These are the ones that you adjust for the Unauthorized TBS.

Here's a link to where I detailed one of the methods for adjusting all of this, both authorized and unauthorized. The Air Bypass screws shown in that link are the ones that were suggested to be removed and cleaned in this thread.

 

[carlson_mn]

Thanks Fred! ... I never bothered reading into the Unauthorized TB sync 'cause I thought I was doing it the right way all along! A little ironic. I'll check out your link. My bike has always held a very good sync, maybe cause I haven't touched the 'authorized' screws?! I check it every 10k miles, always needed just small adjustments.

 

[3dogs]

Here is another, slightly more detailed, unauthorized sync procedure (5th post down) that is basically the same as above.

 

[Toolman]

I have to wonder if running at higher RPM helps prevent the carbon issue? I have 157K on my '03 and have not had any issues?

 

[RadioHowie]

He has found that high mileage FJR’s develop carbon build up on the throttle body sync air bleed screws that cause idle problems.

I got a real problem with that assessment.....not trying to start an argument, or to disparage a mechanic you trust, but how could the air bleed screws develop a carbon build up on them when they are SO far upstream of the combustion chamber? There isn't ANY combustion going on anywhere near the screws.

Unless you've got a severe combustion reversion problem with your FJR, carbon isn't gonna build up on the air screws. If it IS carbon, then you've got intake valves that aren't closing all the way and combustion is blowing back up the intake tract. Carboned-up bleed screws are then the least of your problems.

(picture borrowed from broodwhich's excellent TBS post)

 

[wfooshee]

Maybe oil grunge is "carbon" in his mind. We've all complained at one time or another about the state of our throttle plates the first time we take the airbox off.

 

[RadioHowie]

Maybe oil grunge is "carbon" in his mind. We've all complained at one time or another about the state of our throttle plates the first time we take the airbox off.

Or AIS spooge.....