Fuel Spray - fuel overheating. Prevention must start NOW !!

ge217
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ge217 9/7/2021 5:18am
9/7/2021 5:18am
Never have I had fuel spray out the cap from boiling over.
BikePilot
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BikePilot 9/7/2021 5:26am
9/7/2021 5:26am
BikePilot wrote:
Why not vent the tank to the atmosphere like a two stroke so it doesn’t build up pressure? I realize boiling fuel may still cause issues...
Why not vent the tank to the atmosphere like a two stroke so it doesn’t build up pressure? I realize boiling fuel may still cause issues with running well, but no fires or fuel in the eyes/mouth or crotch.
gs317 wrote:
they do vent to atmosphere as far as im aware, but a 4 stroke also builds to a higher temp than 2 strokes and can heat...
they do vent to atmosphere as far as im aware, but a 4 stroke also builds to a higher temp than 2 strokes and can heat their own tanks faster. Then the rate at which the fuel absorbs heat and starts to boil and build pressure is at a faster rate than the small tube venting to atmosphere can handle. Eventually its enough pressure to blow the tube off altogether. Having a large diameter, keeping the fuel cooler and making the tube a mechanical connector instead of just a slip on piece would help prevent this.
Got it, thanks doe the insight. Seems like an easy fix!
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Johnny Depp
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Johnny Depp 9/7/2021 6:27am
9/7/2021 6:27am
Most gas cap venting today is primarily designed with safety in mind 1st. Gas escaping from an upside down bike.
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mxtech1
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mxtech1 9/7/2021 8:04am
9/7/2021 8:04am
Bruce372 wrote:
Good lord, it's not the design of the motorcycles, it's extreme use and conditions lol. If it was a problem with design, half the field would...
Good lord, it's not the design of the motorcycles, it's extreme use and conditions lol.

If it was a problem with design, half the field would have had the same issue.
The design is engineered and tested to say the 90th percentile use customer. Racing for 30+ minutes at professional speed, with race gas, and in 100+ degree ambient is called a corner condition.

Design engineers at the OEMs would be aware of the failures that are occurring, but it's not a large enough failure rate to drive a design change down to the production parts. It's more likely that they will make some modifications to the gas cap and vent design for race team use only.

So yes, it is the design, but it comes down to cost and what's "good enough" for 90%+ of the general use case.
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Johnny Depp
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Johnny Depp 9/7/2021 8:08am
9/7/2021 8:08am
Aftermarket 3d printing opportunity in 3,2,1..
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gs317
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gs317 9/7/2021 11:42am
9/7/2021 11:42am
Bruce372 wrote:
Good lord, it's not the design of the motorcycles, it's extreme use and conditions lol. If it was a problem with design, half the field would...
Good lord, it's not the design of the motorcycles, it's extreme use and conditions lol.

If it was a problem with design, half the field would have had the same issue.
mxtech1 wrote:
The design is engineered and tested to say the 90th percentile use customer. Racing for 30+ minutes at professional speed, with race gas, and in 100+...
The design is engineered and tested to say the 90th percentile use customer. Racing for 30+ minutes at professional speed, with race gas, and in 100+ degree ambient is called a corner condition.

Design engineers at the OEMs would be aware of the failures that are occurring, but it's not a large enough failure rate to drive a design change down to the production parts. It's more likely that they will make some modifications to the gas cap and vent design for race team use only.

So yes, it is the design, but it comes down to cost and what's "good enough" for 90%+ of the general use case.
This guy gets it. This is the same reason you see factory bikes have oil coolers and fans on radiators and stock bikes don't. They need special modification to handle the higher volatility of the fuel, more heat from a higher HP motor, longer usage at the extreme end of the RPM range, etc. Pump gas wont boil out of your stock bike because its much more stable and how often do you go wide open for 30 minutes on 100 degree days with your stock motor?
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Johnny Depp
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Johnny Depp 9/7/2021 11:54am
9/7/2021 11:54am
You are so wrong, regular bikes and hard Enduro lock up from vapor lock all the time due to poor set up. You must get rid of the backflow preventer’s and EPABS under the gas cap
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dkurtd
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dkurtd 9/7/2021 7:15pm
9/7/2021 7:15pm Edited Date/Time 9/7/2021 7:29pm
Bruce372 wrote:
Good lord, it's not the design of the motorcycles, it's extreme use and conditions lol. If it was a problem with design, half the field would...
Good lord, it's not the design of the motorcycles, it's extreme use and conditions lol.

If it was a problem with design, half the field would have had the same issue.
mxtech1 wrote:
The design is engineered and tested to say the 90th percentile use customer. Racing for 30+ minutes at professional speed, with race gas, and in 100+...
The design is engineered and tested to say the 90th percentile use customer. Racing for 30+ minutes at professional speed, with race gas, and in 100+ degree ambient is called a corner condition.

Design engineers at the OEMs would be aware of the failures that are occurring, but it's not a large enough failure rate to drive a design change down to the production parts. It's more likely that they will make some modifications to the gas cap and vent design for race team use only.

So yes, it is the design, but it comes down to cost and what's "good enough" for 90%+ of the general use case.
gs317 wrote:
This guy gets it. This is the same reason you see factory bikes have oil coolers and fans on radiators and stock bikes don't. They need...
This guy gets it. This is the same reason you see factory bikes have oil coolers and fans on radiators and stock bikes don't. They need special modification to handle the higher volatility of the fuel, more heat from a higher HP motor, longer usage at the extreme end of the RPM range, etc. Pump gas wont boil out of your stock bike because its much more stable and how often do you go wide open for 30 minutes on 100 degree days with your stock motor?
Pump gas could absolutely boil, it's not so much stability but the RVP number. Winter fuel (pump gas) from a very cold area could have an RVP up to 15, the VP race fuel that boiled this past weekend had an RVP of 11.01. Now granted the distillation curve would play a big part but you can't say pump gas won't boil because it can and in the right circumstance could boil quicker than VP MR Pro 6.
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Johnny Ringo
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Johnny Ringo 9/7/2021 7:26pm
9/7/2021 7:26pm
I think fixing this is on the AMA’s list right after getting timing and scoring dialed in. They’re so close to figuring it out
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dkurtd
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dkurtd 9/7/2021 7:39pm
9/7/2021 7:39pm
Johnny Ringo wrote:
I think fixing this is on the AMA’s list right after getting timing and scoring dialed in. They’re so close to figuring it out
I thought they already fixed it when VP created a regular MR Pro-6 and a high temp MR Pro-6.
yota
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yota 9/7/2021 7:51pm
9/7/2021 7:51pm
2 strokes. problem solved.
Timo
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Timo 9/8/2021 7:26am
9/8/2021 7:26am
I've had my gas at a rolling boil before, took a video of it because it looked like water boiling in a pot. Pump 91 octane in, 98° weather, single track in New Mexico. My Yamaha gas cap must be pretty good though because it didn't blow off, and even if it had I wouldn't have been sprayed with the gas because the seat is in the way.

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