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Surging, Lurching, and/or uneven RPMs at constant speeds


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First off I'd like to say thank you to the FJ09 and tracer community, I've been lurking on these forums for a long time.

Original owner of a 2016 FJ-09 with approx. 20k miles. I'm having a surging at constant speed problem that other people have experienced on this forum. When trying to stay at a constant speed whether low or high speed the bike will lurch/surge back and forth. Most people attribute this to the fueling of the FJ/FZ's engine with people recommending either a Kev's O2 mod, or an ECU flash.

So far I've replaced the spark plugs and sync'd throttle bodies, installed Kev's O2 mod, adjusted the APS sensor and adjusted the throttle cables.

There's a few cardinal sins I've broke leading up to this making me think this might actually be something a lot worse, a bad main output bearing (bearing behind front sprocket inside the gearbox).

I now know that Yamaha's factory recommended chain tension is too tight and should be around 1". When I bought the bike new I was pretty bad with the chain maintenance, I would use Maxima Chain Wax and just cake it up every 500 miles and only clean and adjust it every 2000 or so. I started to notice uneven chain tension and a weird clicking through the pegs around 12k miles and thats when I switched over to Maxima chain guard and would clean and adjust the chain to factory tension every 400 or so miles like the manual says. I noticed surging around 16k miles and blamed it on the old worn out chain.

Where I think I went wrong was replacing the chain and sprocket with "oem style" steel sprockets and a "heavy duty"  (1300cc rated) DID 525ZVMX  chain from a website that sells only aftermarket chains and sprockets. 

When I put on the chain and sprockets I tightened the chain to factory tension and everything seemed to be fine for the first couple rides. Looking back I think the surging was still there but I was focused on getting out and riding. I kept the chain cleaned and tensioned and noticed the surging was back.


Hi! Due to the garage putting to much tension on the chain, causing failure, they now have to change the sprockets and the chain. Also the bearing on

This Is the post that made me the most paranoid FJ-09 owner. I haven't seen anyone with this extreme of an issue with an FJ-09 but that doesn't mean they aren't out there. I'm truely afraid my main output bearing(s) is/are shot. I even remember days with my original chain thinking to myself "I'll tighten it to factory tension and hopefully It will even itself out." 

Other puzzle pieces: bike went down on its right side at about 50 mph on the highway (plastics, handle bars, side cases replaced by dealer), clutch is very slightly starting to slip,  I have CPR8EA-9 spark plugs installed (one step too hot) all the dealer had and they said they would work fine. Chain/sprockets have developed a whining noise ever since I replaced them. 

I'm planning on either going back to a stock chain or a 520 conversion. I'm also planning on taking this to a shop to get it possibly diagnosed.

I know I have abused this bike but I love it and want to keep using it, If that means having the main output bearings replaced or replacing the whole engine altogether so be it.

Is it possible to diagnose a bad output bearing without removing the engine and splitting the cases?

Any other helpful tips, info, or guidance is much appreciated.


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@rongerb - I cant help with the output bearing but I am running over the my local Yamaha shop this morning and can ask my mechanic about your issue. (this is one of the few extremely competent dealers/service departments that I trust completely).

Is the output bearing leaking or even slightly weeping oil?

You mention several times that you adjusted the original and replacement chain to factory tension, have you since loosened that adjustment?  Factory specs are .5" and "real world" recommendations are 1-1.25".

After your crash on the highway you got a whine from the chain/sprockets, did anything get bent out of alignment?  Have you verified the chain alignment, other than using the swingarm tick marks?

You also mention that the clutch is slipping (after only 20k miles??) it must be ridden very hard, when you notice the surging is your rpm also fluctuating (clutch slipping)?


***2015 Candy Red FJ-09***

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@betoney Thanks for the quick reply. No, the bearing is not leaking and yes I run at about 1" now.

And the whine coming from the sprockets started when i changed sprockets, my hypothesis was possibly the sound of the rubber damper on the after market front sprocket, it could also be the sound of the beefier chain rubbing against the chain guides on the swing-arm maybe?

And after the crash the bike was assessed by my insurance company and repaired by the dealer i bought the bike from. The front forks needed to be reset to make the handlebars true but I'm not 100% sure a tire and chain alignment was performed I can only hope they did it. And no I actually have only used the factory ticks to adjust the chain myself. I've seen the method where you use the strings to see if your tires are in line, I can do that myself. Whats the best way to make sure your chain is straight?

As for the clutch this is something I've noticed recently and I have/haven't been pretty hard on the bike. 80% of the miles are highway commuting miles, where the other 20% is spirited back road riding. I'm definitely not a wheelie person, the  highest I ever get a is a 2" power wheelie, but there has been a couple times where I've slipped the clutch to get a quick launch. And Yes the rpms fluctuate when it surges, but it's a very sudden surge, slipping clutches I've experienced in the past seem to just not put the power down at higher rpms rather than surge. Honestly I'd love to swap out the stock clutch for the XSR slipper clutch. 


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