Driveline Lash?

[bramfrank]

So I keep reading that there is excessive driveline lash in the FJR.

All (almost all?) bikes have some last (play) in their power trains and the FJR is certainly no different. Mine has some, but I have learned how to deal with it so that shifts, both up and down are smooth and I have no significant issues in the twisties.

However I decided to look at my service manual after someone asked an electrical question and it struck me that, while Yamaha has a number of different values for shimming and torqueing the various bevel gears and such, there i no overall specification that I could find to make simple go, no-go measurment of the total free play in the drive system (or it could just be that I am blind - the STBE (Soon To Be Ex) says I'm selectively deaf, so it wouldn't be a stretch).

I also searched the forums and there is ample reference to lash issues and how to deal with it by adjusting throttle cables and such - but that's treating the symptom, not curing the disease. There are some measurements of free play provided by members (presumably in first) of 2.5" to 2.75", but that is experiential, not an official specification.

Does anyone have (or know where to find) an official number for just how much free rotation the rear wheel should have when in gear with the engine off?

Just curious.

 

[ionbeam]

I’ve looked through the FJR Technical Orientation Guide as well as the Gen I & Gen II FSM and there is no mention of total driveline lash. It specifies a middle gear lash of .004” to .008” and drive shaft lash of .010” to .018”.

For those that are newer to the Forum, back in the dark ages the cave men that original purchased the ‘new’ FJR arbitrarily set up a drive line lash test. This test is highly technical and requires a specialized tool: A ruler that measures in either metric or inches. Put your motorcycle in first gear and deploy the side stand. Roll the motorcycle forward until it will roll no more, put it down on the side stand. Place the ruler so that some major mark on it is aligned with the tip of the side stand. Now roll the bike backwards until it will roll no more. Read distance on the ruler My memory is slightly different than bramfrank's (he should very thankful for that!) I vaguely remember that almost all the readings were between 1.75” to 2.5” (4.44 cm to 6.35 cm) for ’03 to ’05 bikes, in any case you get the significant span range. My '04 started life with ~2.5 inches of play (63.5mm), after 34k miles it now has ~2.5 inches of play

Even though there still is no definitive value for total drive line lash, we can all take solace that we all are within a range of ‘typical’.

While .004” and .010” sounds like a really small lash values, they get multiplied by gear ratios as well as the diameter of the rear wheel.

There is more info in this lash thread.

 

[Constant Mesh]

Other components in the drivetrain also probably add to the "freewheeling" during throttle off-on transitions. The spring loaded cam system on the middle gear assembly probably rotates a bit during a power transition. The rubber? shock absorbers in the rear wheel hub also likely take a bit of the mechanical edge off. Even the clutch housing which mates to the crankshaft gear has a spring shock absorbing system built in. And of course you have the two 90 degree ring and pinion gear sets in the driveline.

The new Concours doesn't include this middle gear assembly. It just has the two transmission shafts without the extra middle gear shaft. It also includes the spring loaded cam system but it's configured with the transmission output shaft.

 

[temp357]

Yamaha has done a pretty good job of focusing all the magazines on the AE version so no one has really put any attention on it. (Other than the online forum) ...so as far as yamaha is concerned, what problem?

If I can find the article about the FZ1 in cycleworld, it describes to a tee the problem with the driveline on the Yamaha bikes. Apparently on Decel it cuts all fuel to the engine. Combine that with sloppy throttle cable and a progressive throttle pully, you have driveline lash.

"The engine occasionally stumbles right off idle, and it consistently responds with a big hesitation when the twistgrip is turned open from trailing throttle. It’s almost like the engine stops firing for a fraction of a second then abruptly springs back into life, a characteristic that’s annoying in traffic and upsets the chassis when you’re trying to be smooth through the twisties....Those injection quirks are caused by the lean air-fuel mixtures Yamaha employed to help the ’06 FZ1 meet the emissions requirements of all 50 states. The off-idle stumble is the result of leanness at small throttle openings, and the hesitation stems from the EFI completely shutting off the fuel delivery during trailing throttle and then restarting it once the throttle is reopened. "

The best cure is fixing the fuel mixture problem by installing a pciii with a custom fuel map and g2 throttle tube.

 

[ionbeam]

If I can find the article about the FZ1, it describes to a tee the problem with the driveline on the Yamaha bikes. Apparently on Decel it cuts all fuel to the engine. Combine that with sloppy throttle cable, you have driveline lash.
The best cure is fixing the fuel mixture problem but installing a pciii with a custom fuel map.

I see this as two separate issues.

Drive line lash is a mechanical factor; it is there on all FJRs. Even if there was no abrupt fuel issues, coming on and off the throttle will give a little driveline bump due to lash.

Separately there is the rude Acel/Decel fuel management that causes abrupt engine rpm changes. Even if there was no driveline lash this abrupt fuel management will give you a rough ride. If you do a search you will find that the Acel/Decel fuel management is recognized as a real problem and it has been pretty well documented.

Putting it all together leads to very rough throttle transitions, worse on some bikes than others.

 

[temp357]

If I can find the article about the FZ1, it describes to a tee the problem with the driveline on the Yamaha bikes. Apparently on Decel it cuts all fuel to the engine. Combine that with sloppy throttle cable, you have driveline lash.
The best cure is fixing the fuel mixture problem but installing a pciii with a custom fuel map.

I see this as two separate issues.

Drive line lash is a mechanical factor; it is there on all FJRs. Even if there was no abrupt fuel issues, coming on and off the throttle will give a little driveline bump due to lash.

Separately there is the rude Acel/Decel fuel management that causes abrupt engine rpm changes. Even if there was no driveline lash this abrupt fuel management will give you a rough ride. If you do a search you will find that the Acel/Decel fuel management is recognized as a real problem and it has been pretty well documented.

Putting it all together leads to very rough throttle transitions, worse on some bikes than others.

Agreed. I would say that most of what people perceive as driveline lash on the FJR, is not mechanical in nature.

 

[ELP_JC]

One related comment to the 'driveline lash': I NEVER abruptly open the throttle after decel. You obviously can't do that in the twisties, but it's very easy to do when slowing down on a straight then speeding up again, like when a driver brakes at the last minute making you think they didn't see you.

Anyway, when you close the throttle then open it abruptly, the sound of the 'slack' abruptly slowing down is horrible. I always use the same 'finesse' on off/on throttle transitions regardless where I am, so I'm always gentle to my drivetrain, and it's second nature in the twisties. Just like I always ride with the ball of my feet on the pegs, unless stretching out. Later gang.

JC

 

[v65]

One related comment to the 'driveline lash': I NEVER abruptly open the throttle after decel.

I accidently did this the other day. About 7k in first gear, the results were ahhh... exciting.

 

[CHRIS_D]

One related comment to the 'driveline lash': I NEVER abruptly open the throttle after decel. You obviously can't do that in the twisties, but it's very easy to do when slowing down on a straight then speeding up again, like when a driver brakes at the last minute making you think they didn't see you. Anyway, when you close the throttle then open it abruptly, the sound of the 'slack' abruptly slowing down is horrible. I always use the same 'finesse' on off/on throttle transitions regardless where I am, so I'm always gentle to my drivetrain, and it's second nature in the twisties. Just like I always ride with the ball of my feet on the pegs, unless stretching out. Later gang.

JC

This is the first bike I have owned with a drive shaft, so please bear with me. Yes I too have been trying to work on a smooth speed transitions, but for me it's been especially hard to remember when riding on the highway and needing to roll off/on to modulate your speed. I can't stand that noise!!! :dribble:

With that said, I was wondering has anyone experience this on their bike: When going a steady speed and rpm do you ever experience a feeling of "surging" (I guess it's the best word for it)? The RPM seems to be steady, so I don't think it's the engine causing this or the altitude surging issue.. When I roll on or off the throttle the bike responds as it should. It's almost like the feeling of the clutch slipping in and out. Is this "surging" feeling that I'm experiencing a symptom of driveline lash or is it another problem?

 

[FJRMGM]

the driveline "slop" is in the transmission in my '05 FJR - just take the rear wheel and drive assembly off and turn the front u-joint by hand and feel the "play" when you move the u-joint left/right - that won't be adjusted out.

 

[Bounce]

you don't mention what rpm you're at when this "surging" happens. 2500-3000 rpm with no/little load is a known situation of the EFI hunting between 2 different parts of its map.

 

[CHRIS_D]

you don't mention what rpm you're at when this "surging" happens. 2500-3000 rpm with no/little load is a known situation of the EFI hunting between 2 different parts of its map.

THANK YOU Bounce!!!! :clapping:

That's exactly around what RPM it's doing that at, and it's with little or no load. I will do a search, however is there any fix for that?

 

[ionbeam]

Bounce describes the classic FJR surge. Once the basics are in good shape (TBS for instance) you can try a no cost & easily reversed CO adjustment, referred to as the Barbarian Mod (named after the pioneer of the procedure for US bikes). THE CO bump helps many bikes run better and outright cures some. The best and final solution is a PCIII. This topic has to be one of the most heavily documented issues this side of NEPRT :lol: