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New-to-me 150 St. Tropez dies at idle when cold

 
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selftaught
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Joined: 26 Dec 2019
Posts: 5

na

PostPosted: Wed Jan 01, 2020 9:35 pm    Post subject: New-to-me 150 St. Tropez dies at idle when cold Reply with quote

Hello ModernBuddy, this is my first post here after reading for several weeks and soaking up lots of great info from helpful folks.

The other day I bought a 150 that was single-owner, seemingly garage-kept for all its 3700 miles. It starts and runs great.

I'm waiting on an oil filter in the mail but between now and then everything seems good except that in the couple days I've had it, each morning has been cold (45-60 degrees) and the bike won't stay alive at idle unless I ride it and get it fully warmed up.

Once warmed up and back home, it'll idle pretty well (though I feel like I do hear an occasional 'miss' in there).

Today, after riding to get warmed up, then idling fine, and then turning off for ten minutes, it exhibited the same behavior of dying at idle after being restarted. No loud noises or funny smells, just quietly died.

Has anyone else experienced this? I'm hesitant to check carb jets if this is something that seafoam might eventually help with (not betting on it in my experience of motorcycles and mopeds I've owned over the years, but it doesn't cost much to run). I'm not afraid of carb work by any stretch, just don't wanna chase anything there if that's a wrong direction.

This is the only Buddy I've ridden but it seems to run fine under throttle once warm. Riding cold at a constant 20 mph or so I do notice a little surging for the first couple minutes, but it smooths out.

What you think?
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tenders
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Joined: 03 Dec 2018
Posts: 164

Buddy International 50 Italia

PostPosted: Thu Jan 02, 2020 11:45 am    Post subject: Reply with quote

If I were you as a matter of establishing a baseline I would skip the Seafoam, go through the carb completely, cleaning and checking everything, and then set the valve clearances.
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selftaught
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Joined: 26 Dec 2019
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na

PostPosted: Thu Jan 02, 2020 2:13 pm    Post subject: Reply with quote

[quote="tenders"]If I were you as a matter of establishing a baseline I would skip the Seafoam, go through the carb completely, cleaning and checking everything, and then set the valve clearances.[/quote]

Thanks! I've been looking for an excuse to buy an ultrasonic cleaner for some small outboard motor carbs and jets anyhow that have stacked up, and read/watched more about valve clearances after my original post.

I see recommended clearances for the valve lash of .08 mm / .003 in and will probably go with it:

http://www.modernbuddy.com/forum/topic22184.html


I'll report back in a few days.
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selftaught
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Joined: 26 Dec 2019
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na

PostPosted: Fri Jan 03, 2020 4:49 pm    Post subject: Reply with quote

Well I haven't had time to look at the carb, but this morning I checked valve clearances while the motor was cold. One was already right, the other was one feeler gauge off, so I adjusted it.

The previous owner had put in an 'R'-type NGK plug so I swapped it out with what's called for specifically by the manual. The previous plug was more or less gapped right, but between the valve adjustment and new plug the scooter started up stronger/faster than it has and idled great. Didn't die at all in 10 minutes of idling.

Temps are about 60 degrees today, rainy, and after the first 5 minutes or so of idling I did notice a slight surging up and down from time to time. I have no idea if this is normal for this scooter but I'm not worried. Would welcome feedback on it.

If the rain lets up I'll ride and see if anything is perceptibly different with how it feels.
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tenders
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Joined: 03 Dec 2018
Posts: 164

Buddy International 50 Italia

PostPosted: Fri Jan 03, 2020 5:16 pm    Post subject: Reply with quote

Sounds like progress. Personally I don’t worry about what happens when a carbureted engine is idled over a long period of time from a cold start. There is never a reason for the engine to have to do that.
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selftaught
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Joined: 26 Dec 2019
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na

PostPosted: Fri Jan 03, 2020 6:31 pm    Post subject: Reply with quote

Thanks Tenders for all the help so far.
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