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I've searched and read on the forum about my issue, which is my GT200 will slow down and hover around 60-65 mph top speed after about 30-40 miles of riding at 70-75 mph. If I pull over, or even ride slowly, it seems to get better and then will be fine for another 30-40 miles at high speed.

I've recently had the belt and rollers changed, and all's good there.

I do still have the evap system attached, and I notice when unscrewing the gas cap definite pressure after a long, hard ride.

So, I'm thinking of disconnecting the evap hose off the carb (and putting a sponge filer over the car).

What are thoughts on then cutting the line on the evap that goes to the canister vs. just drilling a small hole in the gas cap to deal with the pressure issue? Pros vs cons appreciated.

Obviously, if you can think of another cause, let me know.

Thanks,

Eric
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Another option is to just drill a small hole in the gas gap.
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Does drilling the home in the gas cap cause any problems long term?
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I can't say because here in the UK we don't have the EVAP system. This solution has been proposed before for this problem and it's easier than removing the EVAP system. Obviously you'd only want a small hole otherwise you'll have petrol leaking from the cap if the bike fell over.
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I wouldn't drill a hole in the gas cap. Get rid of the evap system. That may help. If you look in the Wiki section you'll find a tutorial on how to DIY. Have you ever changed out the gas and vacuum lines? They are probably rotted by now and will leave you stranded, sooner rather than later. If their spongy your not going to get enough gas flow at higher sppeeds. They need to be done anyway so do them and see if it helps. The clamps are a one time use so get some of these. MotorSport Scooters have some line that you can use. I've changed mine out twice on my 8 1/2yr old bike. Once before and once when it failed. Here's what mine did when i removed them. They looked fine but crumbled when we got them out. Good luck
Forum member supplied image with no explanatory text
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I haven't Judy. I did ask my mechanic to check the lines at my last service, though, and he felt they were fine.

It needs to warm up before I di any work, though. I will double check lines myself as well as disconnect the evap system fully.

I just wondered if the hole in the fuel camp might be easier and safe.
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You might want to contact the people on these threads that drilled a hole.
This thread or this one etc. You could also look up "gas cap vent" on google and find that a lot of bikes have a small hole close to the cap. In California they don't like petrol fumes going out into the air so they fit the EVAP system. When it works it's fine, when it doesn't you tend to get the problem you're having. You can either clear the block in the EVAP system, remove the EVAP system or drill a tiny hole in your gas cap. The risk of having a hole in your gas cap is that when the bikes on it's side then fuel could dribble out and might cause a fire risk - if you have a tiny hole then fuel won't dribble out. Obviously it's best to keep your bike upright.
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Ah, the bike should be upright, gotcha. LOL. I think I'll start by drilling a tiny hole. Seems easier than anything else.
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You can take a needle and push it into the space inside the O in gasoline. It doesn't have to be very big.
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That is super easy. Thanks!
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If it were my scooter, I'd delete the Evap system rather than drill holes. It's a more elegant solution.
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Oh, I don't know...a tiny pin prick in the middle of the O is fairly elegant. Occam would approve compared to all that fancy rvap system work.

Too cold to ride, but already did the pin prick bit. Before doing it, I had significant pressure build up from a 10 minute ride home on a 50 degree day at 40 mph.
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at high speed it's pumping a lot of gas. If the venting system is not operating properly (and I'm not convinced the Evap system ever does for long) a vacuum can develope which will suppress top speed. The correct solution is to remove the part that has gone bad (silly charcoal evap canister). The easy solution is to drill a tiny hole that lets the pressure disapate. If you open your tank and it goes "swoosh" you've got a pressure problem.
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I definitely had a pressure problem...the swoosh was a pretty constant companion. I'll probably disconnect the evap system when it's warmer, but a small pin prick in the gas cap was a quick fix and I am sure will make rides better in the meanwhile.

Thanks everyone!


Eric
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That definitely worked. 1.5 hour ride and no slow down.
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Did you notice any other changes when the speed slowed?
I have had a similar issue with Rocket. It slows after running fast for several miles. When it slows, the temperature goes up, not far but between half and three quarters. And when I come to a stop, the check engine light goes on for a few seconds.
Did you have any of these symptoms?
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No...I didn't have either the temp increase nor the check engine light.

All I had was the slow down that went away after slowing down or stopping.

Looking back, there was a bit of that feel you gat when it's starved for gas when at high speeds, too, and that's gone as well.
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