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Q: '83 gas cap

Started by jasonm., June 05, 2005, 09:54:48 PM

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jasonm.

I have always had a smell from gas from my '83 when stopped in warm weather. It is not the carbs leaking. Because the smell goes away when my nose is on either side of the tank sniffing . It is strong right at the cap. I don't remember my '82 doing this. The rubber gasket is fine. No gas leaks after filling up.  I do have a tank bag. But it is not covering the keyhole. Where I suspect it vents. When I have drained the tank I can hear the vent drawing air in. But are fumes suppose to be able to get out on these old bikes enough to be noticeable. The '83 gas caps are different from the '82. Anyone with an '83 notice the same?
looks aren't important, if she lets you play by your rules

Lucky

Hmm, Why would it be different...? i have an 82 on mine so can't help you with a comparison.  sounds like it's time to take it apart & see what you can see..

How was Britjam?
1982/3 XZ550 Touring Vison, Gold on Black

jasonm.

'82 cap is plastic, '83 is metal. plus being behind the fairing may make this more noticable...no matter what the cause. I don't know if there is a check valve to let air in and not let fumes out? It's done this since the day I bought it.
looks aren't important, if she lets you play by your rules

Lucky

huh! good trivia, 83 cap is metal...
1982/3 XZ550 Touring Vison, Gold on Black

ProfessorRex

What about the warm fuel recirculating into the tank.  Warm fuel is certainly more likely to put out fumes, especialy on warm days, and the recirculated fuel is not present on 82's
Hey honey, uh, I got another vision... HONEY??? Oh yea, thats right she moved out...

Walt_M.

I have never noticed a gas smell in the fuel cap area on my '83. It's kind of hard to tell now with my raging petcock leak but I never noticed anything when it was new. And, I never knew the '82s fuel cap was plastic!
Whale oil beef hooked!

jasonm.

Here is the thing. I do not have to ride it. Just put the bike in the sun and wait 10 minutes for the tank to warm up. I feel stupid now. Not trying the '82 cap before I sold that bike. I have 2 '82 caps. But they both are missing an internal gasket. So they do leak gas when it just sloshes around. I am debating on chancing, taking the '83 cap apart??? Bye the time you read this...it will probably be apart. Hope the gasket does not fail.
looks aren't important, if she lets you play by your rules

jasonm.

Well, I took it apart. The gasket is complex but more important. It has a gasket material that is not common...from the looks of it. Seems to have a rubber like coating over the regular paper. Standard paper gasket...it is not. I cleaned the gasket and all surfaces. The design is simple. Maybe too simple. A ball on one vent hole, the other hole has a filter. These holes are next to each other and the gases  could realistically vent through either hole. I suspect one is for air in, the other for fumes(venting) out. But the ball does not fit tight, up/down. But fits left/right in it's hole. It does float. It appears to be the proper size. Similar in idea to the accel pump ball.
looks aren't important, if she lets you play by your rules

jasonm.

My memory is sometimes poor. I just went thru some notes I have. Only on long rides have I smelled fumes. Cleaning up the gas cap and gasket seems to have helped. No fumes to my nose when stopped. It was 80+ degrees today. But it was only a 20 minute ride. In the past, I have had some fuel out the overflow after a hi-speed or bumpy ride. Maybe that's what I have been smelling from time to time when stopped? The floats are correctly set.
looks aren't important, if she lets you play by your rules

Lucky

Quote from: jasonm. on June 07, 2005, 07:33:21 PM
In the past, I have had some fuel out the overflow after a hi-speed or bumpy ride. Maybe that's what I have been smelling from time to time when stopped? The floats are correctly set.

I wouldn't be surprised.  When i first rebuilt my 82 carbs, not having touched Vision carbs before thet, I had fuel pouring out the overflows when the bike was on the side stand.  i pulled the carb tops & rechecked the float level, which i had set correctly, then did the clear tube fuel level test & found it to be correct also.

it took me a couple of hours of looking, measuring & double checking to decide to actually measure the length of the overflow tubes in the carbs.  what i found was that one tube was nearly 3mm shorter than the other.  I couldn't fathom that Yamaha had installed the tube either too deep or the tube was manufactured too short.  someone, at whatever plant that little tube was made at, was asleep at the wheel.  you figure even with tolerance checks that the shorter tube would be obvious sitting there with hunderds of others in the box at the plant...

I lowered that particular float by 3mm & never had that problem again.

I've mentioned this before, but measure the tube lengths when you have the carb apart & measure them. compair them against each oter. iff you find you have a short one, lower that float the same amount lower that the tube is.

when rebuilding these carbs I allways check the tube length & adjust the float lower by the same amount.  i've found 8 more carbs with this problem
1982/3 XZ550 Touring Vison, Gold on Black

ArrrGeee


Jason,
I've had the same problem since I've had this particular bike but the lock
on the gas cap has been broken since I bought it and I figured that the
seal never quite sealed perfectly because someone had damaged the lock
to get it open. Last year I picked up a lock set including a good cap.
The gas smell went away after that. at one point I had opened up the old one
to check the vent in the cap ( I probably posted about it back then.)
I found the ball arrangment that you are talking about but there were pieces
missing inside the cap so I lived with it till I finally found a replacement.
I believe the vent ball should be loaded with a spring to keep it sealed
from gas venting out but let air in as the tank empties.
mine had no such spring. I have not taken the new one apart but you
can probably hit the hardware store to find a spring to do the job.

-Ron