Throttle Racing and Stalling

[TenereRetiredSoldier]

I own a 2013 YST with 17000+ miles. Last week I started out on a 1500 mile ride and in the first 100 miles experienced several stalls at stop lights, then the engine raced when stopped in neutral or with the clutch in. I road to a Yamaha dealer in TN and we could not immediately repeat the problems, so we assumed a small particle in an injector...off I went on my trip...not so fast. After about 75 miles, the stalling started again, followed by the engine racing past 5000RPM. I even had an experience sitting on the side of the road where the engine raced to 3000RPM, then back to 1000, then back up beyond 5000RPM...I was touching the throttle and I hit the kill switch so it did not over rev. I got the bike back to the TN Yamaha shop and as I came into the parking lot the RMP would not go below 3000. Feathering the throttle thru stop signs and the parking lot, then got off the bike and watched the dealership guys look very puzzled. In a week, they have repeated the problems and spoken to Yamaha USA, but no idea what is happening. The bike is still under an extended warranty, but right now I'm paying for several hours of work until they find something that Yamaha will cover. I'll settle for something that will fix this racing-stalling throttle. ANY IDEAS!!!!

 

[terrysig]

Yes Yamaha knows about it. It has been reported on here many times. Its an issue with the throttle position sensor (TPS) and/or accelerator position sensor (APS).

The TPS failed on mine at 40+K and is the exact behavior you describe. Search this site and you'll find much more information.

BTW my raced when cold and died when hot. That gave it away as the TPS.

If the dealer doesn't know what you are talking about move on. It's not just the ST that can have this issue.

 

[stutrump]

It was the ACccelerator Position Sensor on mine (APS)..not the Throttle Position Sensor. It seems that both can be problomatic

 

[2daMax]

A bad plug coil does that also. Usually the right most coil corrodes from water getting into the wells.

 

[TenereRetiredSoldier]

An update for those following my original post and the great responses I received. After a month of working with a local Yamaha dealer and Yamaha USA Customer Relations, I've learned that the throttle issue is my to pay for even with a dealer maintenance plan and Y.E.S. At least that is what my dealer is saying. On two separate dates after I related what I had learned from my Forum friends, I was told YUSA to the dealer to do a Throttle Body Sync and run a shock treatment of Ring Free for carbon buildup...$500 later in labor charges, the dealer then said it was the software in the Tip Over Sensor...so why was that not a warranty claim? I went back to YUSA and was told they had no discussion with the dealer about Tip Over Sensor software, but if that was the problem, YUSA said a lot of the work would be justified in a claim. So I asked the dealer to get on the same page with YUSA. NOW the dealer says that even though they called me on two separate days to tell me it was the Tip Over Sensor, now their story is that its carbon buildup and I needed to pay. After more dialog, the dealer said they would contact YUSA and file a claim. But it sure looks like I'll eat this one. After more than a dozen bikes over 50 years, this has been a Big lesson for me that I will remember and pass on! Thanks Forum for your assistance.

 

[WJBertrand]

Was the problem ever concisely identified and more importantly fixed? Sounds like the root cause is still unknown.

 

[TenereRetiredSoldier]

Like you said, is it really fixed??? I'm not convinced. I guess I find out when I make my next long ride.

Another update. Well the dealer is now working with Yamaha USA to see if any of this is warranty work. I'm confused because after 5 weeks at the dealer, the dealer telling me twice it was Tip Over Sensor software that they worked out with YUSA, but now they say what fixed it is what they did...ring free to clean out any carbon and a throttle body sync = $500. To me they did a bunch of stuff, were not speaking with YUSA, and just want me to pay the bill. So I guess I'm now just waiting for YUSA to decide what they say is warranty work.