UTC

Hooked
'06 GTS 250; '18 GTS 300; '21 Liberty 150
Joined: UTC
Posts: 114
Location: Oregon
 
Hooked
'06 GTS 250; '18 GTS 300; '21 Liberty 150
Joined: UTC
Posts: 114
Location: Oregon
UTC quote
Just purchased a new-to-me 2018 GTS 2k miles, and will start when cold but after running, stop (as if for gas, errand, etc.) hit the starter button: nothing or you get a super brief start attempt not long enough to start the bike, then nothing.

Figured first time it happened it might be the battery, cheap to replace so I did so, same behavior.

If you hold the starter button for 5 seconds or more seems like the starter finally really engages most of the time but the whole thing is flaky. I'm wondering if I have dirty contacts on the starter button on the handlebar (which presumably controls a relay for the starter). I may try to disassemble and see if I can remove / clean that mechanism or failing that order a replacement switch.

My '06 GTS has other weird issues occasionally but starting the bike warm or cold never an issue so far. It's good to always have a challenge

Otherwise love the bike, I'm sure this will get sorted, part of the delight of owning such a machine


FWIW
⬆️    About 1 month elapsed    ⬇️
@dimhpe avatar
UTC

Lurker
HPE' 19 Yacht Club
Joined: UTC
Posts: 1
Location: Athens / GR
 
Lurker
@dimhpe avatar
HPE' 19 Yacht Club
Joined: UTC
Posts: 1
Location: Athens / GR
UTC quote
Hi there.
I had the same issue 3 weeks ago.
I went to the dealer, they changed the starter relay but it kept doing this until the engineer realised that I had the ''bad habit'' to touch the throttle grip when attempting to start it up and he said : ''Don't do this. When ECU detects that the grip is slightly open, it won't let it start.''.
And so it was.
When I do the start-up I only use the left grip/lever by pressing the start button on the right hand side, not touching the throttle grip at all. And that's it!
Forgot to mention that all the necessary checks made by the engineer upon arrival of the bike, such as the electrical system, wiring, spark plug and also did a re-mapping as this action covered by the warranty as well. No problem ever since and now on.
Hope you find it helpful
⬆️    About 2 months elapsed    ⬇️
@pammieellen avatar
UTC

Hooked
2020 GTS 300 HPE
Joined: UTC
Posts: 145
Location: San Diego, CA
 
Hooked
@pammieellen avatar
2020 GTS 300 HPE
Joined: UTC
Posts: 145
Location: San Diego, CA
UTC quote
Hot Start Problem
I've had this a few times on my GTS 2020 HPE. I had my first service done at dealer and mentioned it. They updated/reloaded the software-- it fixed the problem at first but now it's happening again. I'll try not to touch the throttle. on another forum I saw a TSB on it. Copied it. I will address it at next service since under warranty. It always eventually starts but it's a bummer, for sure.
⬆️    About 2 months elapsed    ⬇️
OP
@mayorofnow avatar
UTC

Molto Verboso
2020 GTS 300 HPE
Joined: UTC
Posts: 1350
Location: 🤷‍♂️
 
Molto Verboso
@mayorofnow avatar
2020 GTS 300 HPE
Joined: UTC
Posts: 1350
Location: 🤷‍♂️
UTC quote
Hopefully got this taken care of today, and got an explanation of what's going wrong.

There's a cam that operates the valve that lets exhaust out of your engine. When an engine is hot, there's higher pressure in the cylinder, which makes the engine harder to start. The more that valve opens, the more pressure can be released, and the easier the engine is to start.

There's a rod called a decompressor that sits inside the edge of an exhaust cam. There's a round side and a flat side. The round side is .44mm taller than the flat side. That extra .44mm nudges the exhaust open a bit more (alleviating the pressure that can keep the engine from starting). The rod is weighted. As the engine revolves, centrifugal force flips over the rod: exposing its flat side, and eliminating the nudge so the engine can run at full power.

Here's a handy video demonstration:

As parts are manufactured, they're sorted into batches (A and B). Some of the decompressors in batch B are only nudging the exhaust valve by .2mm. Cylinder pressure needs to be <110PSI for the fuel to ignite in a stopped engine. Pressure with the defective decompressors can exceed 135PSI.

While I was looking for photos to include in this post, I also found a service bulletin from Piaggio that discusses this problem. Crazy that I'm the guy whose problem got published by the NHTSA.
@touring300 avatar
UTC

Ossessionato
GTS 300ie Touring 2013 - Signora D'argento
Joined: UTC
Posts: 2092
Location: Lancaster, U.K.
 
Ossessionato
@touring300 avatar
GTS 300ie Touring 2013 - Signora D'argento
Joined: UTC
Posts: 2092
Location: Lancaster, U.K.
UTC quote
Pleased to hear you have (hopefully) found the crux of the problem.

So from what you have discovered, Piaggio do not know which batches of the 300 HPE's have been fitted with the defective decompressors. Therefore, instead of issuing a product recall showing the VIN numbers of the scooters affected, they have decided to issue dealerships with a general 'Technical Communication' to dealerships for for customers who report having difficult hot engine starts?
OP
@mayorofnow avatar
UTC

Molto Verboso
2020 GTS 300 HPE
Joined: UTC
Posts: 1350
Location: 🤷‍♂️
 
Molto Verboso
@mayorofnow avatar
2020 GTS 300 HPE
Joined: UTC
Posts: 1350
Location: 🤷‍♂️
UTC quote
5 hundredths of a millimeter is a pretty tight tolerance. I don't understand what measurements go into the batching, but an A decompressor with an A camshaft is supposed to give you the .45mm lift. (Similarly, a B decompressor mated with a B camshaft.)

The solution to this issue seems to be to give everyone decompressors from the taller batch.

The NHTSA requires recalls for defects that impact safety. There's no safety impact for occasionally taking an extra minute to start up. It's probably not worth Piaggio's expense to prophylactically replace an engine part for a non-safety defect; people who are impacted will probably notice during the warranty period and complain to their mechanics.

When I reported this last fall, neither my mechanic nor Piaggio had heard of the issue, nor had any idea what was going on. Yesterday, the mechanic said this has become a common issue - he's already replaced plenty of decompressors.
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