Modern Vespa

Went to check the oil level just now on my GT with 5,7XX miles and the oil smells like gasoline. Oil level shows as normal, and I performed an oil change about 1,200 miles ago, replacing the drain nut o-ring and torquing all parts in the process to spec.

Any ideas? Running Castrol 5W-30 full synth for four-stroke.

Does the engine get up to temperature quickly enough? Petrol in the oil was a problem for X9 500SL models, which required a different thermostat to be fitted. If the engine doesn't warm up quickly (or is only used for short journeys) then unburnt petrol can get blown back into the sump, and there's not enough heat for long enough for it to evaporate.

If not dealt with, the petrol can make the plastic gears (oil pump etc) go brittle, and eventually break up.

I've gone on several short trips running errands and such over the last few days, this after riding on many longer trips at Amerivespa last weekend. I checked the oil level last week, but did not take a sniff of the oil then.

GT seems to get up to temp OK as normal. It's been cooler than normal outside, so the bike has been running at the normal 1/4 on the temp guage this week.

I just remebered over-filling the tank last week but the evap hose is disconnected. Could that be related?

I doubt it. Can another GT200 owner confirm that 1/4 on the temp gauge is normal?

Mine usually runs at about half way. maybe a bit less.
The only time it goes higher is if I get stuck at a railroad crossing or a ridiculously long light. That's when the fans kick in.

+1

Mine also runs at just slightly less than half. At least with air temps above 20F

Under that temp it would stay at 1/4 unless I did longer drive.

mine usually runs just under 1/2 after it's warmed up. the only time it's gone higher was during the heat wave (ah, fond memories ) that we had a couple of weeks ago

OK, so the OP's bike may be running a bit colder than it should. I'd be taking the thermostat out and testing it. They are cheap enough to replace, anyway.

It is pretty normal for some fuel to get in the sump, usually evaporates as Jim said. On the X9 the oil level would rise. If your level is not going up then I doubt you have a problem. The other thing is that if you are not used to the smell of synthetic oil this can be what you are smelling. It does smell a little like gasoline once it heats up a few times. I know when I had my X9 500 and I read about this issue I was always sure I could smell gasoline but the level never changed, I imagined my problem and the more I smelt it, the more I was sure it was gasoline.

To be fair, it was never a problem on the X9 500 Evo, only the SL models.

So gas in the oil is no big deal? Or is it turning the plastic bits in the sump brittle? Or is it minimizing the lubricating effect of my oil, thus shortening the life of the motor?

A series of oil changes are needed to remove fuel content from the oil, correct?

Or, does used 5W-30 full synth simply smell like gas?

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usually not a big deal, a little gets in most egines, evaporates at temperature, as long as your level is not rising on the dip stick. If a lot of fuel is allowed to build up it could have those effects on your plastic bits and would minimize lubrication. One, oil and filter change would do and full synthetic does have a strange smell that is petrol like. If it was me i would just keep an eye on the level, make sure you warm it up to temparature once a week over several Kms. I have never heard of an issue with a thermostat on the Gt200 or fuel in sump, I doubt you have an issue. That little screen that you pull out and clean on your drain plug on the problemX9s would come out twisted and tortured looking from the petrol I think. Also if left too long they had issues with plastic bits on the oil pump... Jim may know the detail a little better but something like that.

Had the same problem. . .have you had a tip over of any kind?

No tip-overs, just over-filled when gassing up, twice now. Gas pump's auto shut-off didn't and gas was sitting in the filler neck.

So to try and get to the bottom of this situation, I completed and oil and filter change yesterday, tilting toe scoot to the side to try and get as much of the old oil out as possible. I also did a little tinkering with the evap system, re-routing hoses, installing dust filters, etc. since more than one person (and one Vespa mechanic) have suggested verbally (and off the record) to me that the evap system and fuel overflow could contribute to fuel in the oil. Sooo...

After buttoning everything up, letting it run to get oil to temp and such, I went for a ride in the ~83 degree heat here in CA. The ride consisted of about 5 miles at freeway speeds between 55-70 mph, all the while keeping my eye on the temp gauge. Only upon exiting the freeway sitting at a signal did the temp rise above 1/4 indicated, and it was to about 1/3 on the gauge.

Max from ScooterWest ordered me up a new thermostat which should arrive this week.

The new oil still smelled like gas after letting the scoot warm up, but I attributed this to some of the old oil remaining in the case from the oil change.

I should also note that it idles like silk, the fuel milage is around 70mpg and there seems to be no loss of power in my peppy little scoot, leading me away from thinking it is a stuck float or bad piston ring.

All sounding good - the new thermostat may very well help - let us know if the temp shows higher after the install.

The ScooterWest thermostat arrived 30 minutes ago. Since then I have drained the coolant, replaced old unit, refilled coolant and run the engine to operating temp. First time I can recall thst the temp gauge has read near half. Fan did not kick on, but no leaks and coolant is full. Will have a chance to road-test tomorrow.

So I've been on the bike for over three hours now riding in varied temps. Cooler outside temp makes for cooler temp gauge, warmer temps equal warmer gauge. Idling for a few minutes at rest stops yeilds even halfway on the gauge. What gives?

Where do you think it should be on the gauge?

[see below]

OK, so I blasted home from San Francisco down 280 today, about a 50 mile ride, as outside temps were between 85-90 and the engine temp gauge stayed at just under the half way mark the whole way, all the way into the driveway.

NightWing: I'm familiar with automotive thermostats - engine warms to operating temp and thermostat meters out water to keep the engine temp within an optimum range. I would expect that the scoot temp would hover around just below halfway, which is where it remains when left to warm up at idle. The thermostat's open/close cycle keeps the temp right there, but when riding, it cools WAY down, depending on ambient temps. Is there a "seep" bypass or some other route that the coolant takes in the cooling system, besides through the thermostat?

Is the purpose the scoot thermostat is simply to prevent overheating?

No thermostat prevents overheating. The purpose of a thermostat is to maintain ideal operating temperature by partially blocking the flow of coolant, and opening and closing to achieve that. It prevents the engine from overcooling, if you will.

So I wonder then how the GT'[s cooling system is set up, since mine gets cooler when riding and the ambient temp is cooler. Normally riding makes the engine hotter, no?

I am going to guess that the radiators on Vespas are pretty efficient. But, in traffic, with reduced or little airflow, they need the help of the cooling fans which kick on only if the temperature starts to creep up. Many owners report very little fan operation unless it is a bitchy hot day. From what I have read here, creeping up to the middle of the gauge is considered normal. I believe the 300GTS Super actually runs closer to the top of the gauge, and that concerned the new buyers of that model. It was discussed here for several days.

So that is what I experienced today, in hot weather. In cool weather, the temp gauge went low, at one point to between 1/4 and zero. Ambient temp was in the high 50's.

Here is the rundown:
I smelled gas in the oil. Jimc suggested it was running too cool and to check/change the thermostat, since running too cool might cause unburned gas to blow into the oil. I ran a complete oil/filter change and changed out the thermostat. The bike runs nicely with good power and really good fuel economy.

One of the following is the case:
1. Nothing is wrong. The synthetic oil just smells like gas and/or I am hypersensitive to smell and/or I am high - all possibilities, by the way.
2. Bike still runs cool and unburned gas is still getting into the oil with no/little ill effects on the machinery
3. Bad piston ring - typified by gas in oil, rising oil level (which I am not experiencing) poor fuel economy and loss of power (which I am also not experiencing)
4. Funked up carb - float, needle valve, jet, etc. - typified by poor fuel economy and loss of power (which I am not experiencing)