Lost idle

In short: the FJR no longer seems to idle at all when warm, and badly and just barely, when cold.

I recently had a machine shop replace a bad exhaust valve (one cylinder had lost a lot of compression). Checked the other valves too and machined things back to standards. Afterwards, I synced the throttle air intake ('unauthorized' first, then the regular TBS). While doing that, even fully closing the idle screw barely made the bike idle up to 1000RPM. The idle was more stable than before, but sometimes it stalled. Next, I gave the throttle cable a bit more slack using the topwise throttle cable freeplay adjust.

After all that, the bike accelerates nicer and runs smoother overall. But the (warm) idle seems to be completely gone. Even the fast (cold) idle has trouble keeping the bike running, and after the fast idle stops, the engine just revs down and dies. So starting and stopping requires constant very careful throttle and clutch use. Otherwise the engine just revs down and stops. No roughing, just dies down unless I twist the throttle in time. The idle screw seems to have no effect.

There was a TPS recall job done about ten years ago on this bike, so that should not be the issue. Given that things seem to have gotten worse after increased throttle cable slack, I am starting to wonder about the TPS though. But shouldn't that cause additional trouble?

I am suspecting the engine is either getting too much or too little air - but which? I guess I can open up all the TBS air screws and see what happens.

Suggestions?

Timing might be off one (or two) tooth.

Canadian FJR

My first thought was also a skipped tooth in the timing chain.

What is the warm idle speed set to? Are you able to set it to 1100 rpm with the idle adjuster? 2nd Gens are very sensitive to the warm idle speed setting. If you cannot get at least 1100 rpm at warm idle the bike will run crappy and stall. This was true on even brand new 2nd Gens when they would come from the factory with idles set to 1000 rpm.

Unlike the 1st Gens, which have an adjustable throttle stop to open the throttle butterfies slightly, the 2nd Gens have a small bypass air manifold to allow extra air into each of the throttle bores.

If you cannot get 1100 rpm from the idle adjuster, set the idle adjuster to mid range and then open all four air screws the same amount, a small amount at a time, to bring the idle up to 1100. Then re-do your sync bringing the highest and lowest to match the median cylinders.

Hopefully they got the valve clearances right after all that re-work. One might expect they had to use a lot of different shims.

Fred W said:

What is the warm idle speed set to? Are you able to set it to 1100 rpm with the idle adjuster? 2nd Gens are very sensitive to the warm idle speed setting.

Click to expand...

His is a Gen I... (At least I assume that the 2005 Euro model is the same as North America?)

Ooops. Thought it was a 2006.

Well. still want to set the idle to 1100, but the first gens do not seem as sensitive to the warm idle speed as 2nd Gens are.

I'd check for a vacuum leak...classic symptoms and since the head was off the TB's had to have been removed and reinstalled.

I earlier lost the idle after driving. The engine usually stays at two bars (after stopping it rises to three after a while).

But now I tried just starting and letting it run without going anywhere. When it got to three bars engine heat, I was more or less able to keep the bike idling at around ~900RPM by tuning the idle screw (to almost max; makes no difference after a certain point). Had to twist the throttle every 15-40s or so, to make sure it did not stall.

Idle should be set to 1100 or more. Try adjusting before anything else..

eflyguy said:

Idle should be set to 1100 or more. Try adjusting before anything else..

Click to expand...

That's the issue, I cannot get it that high...

Hmm, that was my issue. I opened each air screw 1.5 turns, then started bike, fit my rpm up... But still have idle air screw cranked fully up... 1300 rpm, and I'm running it.

Sorry, I missed that it wouldn't go higher...

Petri said:

I earlier lost the idle after driving. The engine usually stays at two bars (after stopping it rises to three after a while).
But now I tried just starting and letting it run without going anywhere. When it got to three bars engine heat, I was more or less able to keep the bike idling at around ~900RPM by tuning the idle screw (to almost max; makes no difference after a certain point). Had to twist the throttle every 15-40s or so, to make sure it did not stall.

Click to expand...

I'm still thinking the timing is off. This idle problem is EXACTLY what I had when my chain jumped one tooth on the crank sprocket. 900-950 max, idle screw adj'd all the way, stalling, etc. To me it's like deja vu all over again.

The plot thickens.

To open the air screws a bit more, I raised the tank, moved it backwards and propped the front of the tank up. The tank was near empty (>20 km into reserve). The engine was completely cold, no riding today.

To my surprise, the cold idle was better than I've ever heard it, for well over a minute. I sounded nice and stable. Then approaching two minutes it slowly descended into its regular too-low-rpm warm idle and ultimately stalled.

I am going to try the front-propped-up tank again once the bike cools down to see if it really makes a constant difference. I wonder how the tank orientation could matter though; I don't think I've got any kinked hoses underneath the tank or anything like that, either???


Well, after the cold idle switched off, I opened the TB air screws a bit more (extra full 360 degrees each, except #3) to get the idle up, but it didn't seem to make much if any difference. If anything, it forced me to screw the idle adjust knob all in, ie. close it completely.

I also checked the TPS; the max resistance was 5.13 kOhm so well within the 4-6 spec range.

I guess I'll have to check the timing, too. I wonder if there's any way to check using some measurement or tool? Without having to open valve cover etc...

On your 1st Gen the idle adjust is a variable throttle stop. By screwing it in (CW) you cause the throttle to be slightly more open at the stop. If you are fully CW (won't turn any further) then you are maxed out on the idle adjustment. CW adjustment should raise your idle.

Opening the four air screws (CCW) will also introduce more air, which will also raise the idle speed. Do not worry about opening #3. There is nothing magic about that air screw. As long as all 4 are vacuum balanced when you are done the bike will run smoothly.

To check valve timing requires you to remove the valve cover and the timing chain cover on the right side of the engine. The timing marks are under those covers. While it is possible the timing is off a tooth, I'd rule out the other easy stuff first.

Thanks everyone! I will try to remember to post a summary here when I get the idle working better. One way or another, I will...

Any updates?

Canadian FJR

As noted, OPEN (CCW) the base TB air screw.

As I re-call, stock, the air screw is about 3/4 a turn out from lightly seated.

That should give you more adjustment (with an idle and a throttle stop screw that NOW works)

Now, re-sync your TB's. You should be able to obtain 1,100 with turning that stop screw back out as designed..

As Fred posted, this is assuming the valve timing is CORRECT.