Unstable throttle between 1.500 & 4.000 rpm

[Onraad]

Hi everyone

Just bought a 2011 ST with about 50k km on the odo.

Did a short test ride before buying it and everything seemed ok.

Last weekend I made a first real tour and noticed some hiccups between 1.500 and 4.000 rpm at constant speed. Seems very hard to get it long at constant non-highway speeds.

Otherwise the bike accelerates just fine and is perfectly smooth when going over 4.000 rpm.

What could it be?


Any thoughts?


Thanks already!

Arno

 

[Dogdaze]

Hello and welcome Arno. Where are you based? Was the bike exposed to the elements a lot, visually speaking (as you just bought it)? It sounds like a coil stick or two are on the way out. When was the last service done, have the valves been done at the 40k service?

 

[Onraad]

Thanks for your swift responses. I’m living in Belgium

Visually it looks like it was well taken care of and was parked in a garage. Bought it from a dealer (generic multi brand dealer) which claimed the bike was serviced properly and was delivered with a service at 50k.

Any way to check the coil sticks for good functioning?

Post about recall seems to address 2012 and 2013 bikes, mine was produced 2011.

For your information: don’t know if it’s related or if it’s unusual in any way. When cold (night outside) starting in the morning, it fires up right away but I have to wait like a minute or so before touching the throttle or it stalls. After that minute, idle sets at stable rpm and all goes well.

 

[Dogdaze]

I would still contact Yamaha Belgium and initiate a possible 'complaint', this then allows you to start a conversation if need be at a later stage, keep a copy of the US recall notice. There is a thread about checking the coils for continuity and correct function, if all fails then there is YouTube.
Do you at least get a 30 or 90 day used warranty from the place you bought it? I would not trust a dealer to complete a major service unless they can verify by letting you having the specs of the valve check.
If you do have a limited time warranty then take it back to them, as coil sticks run about 90 € each.

 

[Onraad]

Thanks for the advice. I’ll get in touch with Yamaha about this.

Yes we do get warranty buying second hand bikes (1 year) but I’m not eager going through the haste (settling under warranty can take a lot of time). However, I’ll contact the seller to ask for a thorough check and replacement if necessary.

Keep you guys posted about this.

 

[ballisticexchris]

I would not trust a dealer to complete a major service unless they can verify by letting you having the specs of the valve check.

Please help me understand? I always get the before/after clearance specs and shim sizes used as part of my work performed check list. I also get back original shims, gaskets and all other replaced parts. Never heard of a independent mechanic or dealership who would withhold that stuff.

 

[Don in Lodi]

My last valve check was done 'go/no go'. He didn't write anything down.

 

[Onraad]

Went to the dealer today.

He gave me a bottle of Forte Moto Power I and asked to give that a try first.

If that doesn’t help, he promised to check on the bike again and sort it out.

Fingers crossed.

 

[OldRider]

My last valve check was done 'go/no go'. He didn't write anything down.

I have a piece of scratch paper I write the numbers on, but I've never gave it to a customer and I've never had a customer ask for it. They often do ask if the valves were tight or loose.

 

[Onraad]

Hi everybody

As promised, hereby update on this matter. The dealer took the bike back in for service.
Problem seemed to be an obstructed fuel line, and bad sync of TPS.

Dealer sorted it out, resynced TPS and put on new fuel mapping and everything’s fine now.

Smooth in all gears and throughout the whole rpm range.


Thanks for your help guys and best regards!


Arno

 

[Nikolajsen]

 

[Checkswrecks]

Problem seemed to be an obstructed fuel line, and bad sync of TPS.

Dealer sorted it out, resynced TPS and put on new fuel mapping and everything’s fine now.

Smooth in all gears and throughout the whole rpm range.

Arno

Thanks for sharing this! These bikes are definitely tender when it comes to TBS.