R100/7 Vapours in Garage Doing my Head In

[theswedishthing]

Hello!

Would really appreciate some thoughts here:

My 1978 R100/7 has always been stored outside, under cover. The wife and I just moved to our very first house with a garage (YES!) and I can't store the bike IN the garage because it smells so much like gas it's giving us sore throats and making the entire house smell like gas.

A few notes: 1) I have a Monza-style gas cap rather than the OEM version, but otherwise all appears to be as it should. Has anyone else experienced this ungodly emanation of fuel vapours from their airhead? 2) When we first moved in a few weeks ago the tank was ⅓ full; after fuelling the tank full three days ago the smell is worse than ever. 3) there is no dripping fuel anywhere.

I'm a) ready to cry with frustration, and b) concerned if anyone lights a match my whole house is going up.

Does anyone have any thoughts on what it could be? Is the gas cap leaking? Are the petcocks/fuel hoses/carbs leaking and then it's evaporating? There are no drips anywhere.

Thanks in advance!!! I know it's my first post on here but I'm at my wits end trying to figure this out... Would really like to be able to put my garage to use. <:-S

[barryh]

The carb bowls are vented so there will be some evaporation as can be proved by removing the bowls after a few weeks storage to find the levels are low. The gas cap seems the more likely culprit. It will be vented as is the original but that supposedly incorporates a one way valve. If you bounce the bike on the front brake to slosh the fuel in the tank any emissions from the gas cap will be easily noticed.

All that said my bike lives in an integral garage without any noticeable fumes.

[Kurt in S.A.]

Do you turn your petcocks off when the bike is not in use? You should. Are the fuel lines internally cracked and letting gas ooze out? Replace as needed.

Kurt in S.A.

[jagarra]

In order to isolate it, you could lay some plastic on top of the tank covering the gas cap to see if that makes a difference in the fumes. I have an exhaust fan in my garage, so placing a small fan in the window and having it blow toward the outside could give you some relief in evacuating the fumes till you figure it out.

[Ken in Oklahoma]

My solution to your problem?

There are only two places for the gas to be in the motorcycle, the tank and the carbs. I suggest doing the following operations while the bike is still outside of the garage.

The tank is easy enough to remove, well except for those plastic nuts holding the back end of the tank. Pull the tank off the bike and store it outside of the garage. You could put that tank in a plastic tote if you like, or some such closable container. (I like the old Rubbermaid totes with the snap on lids, but they seem hard to find nowadays.) Or you could get one of those plastic lawn boxes that some people put their sprinklers, lawn tools, etc. into.

That will leave you with some residual gas in the fuel lines and the carbs. For that you can drop the carb bowls and get rid of that gas, perhaps putting it into the tank. I would expect that any residual gas in the fuel lines will drop out pretty well.

There is still that line between the two carbs which passes through the air cleaner housing. Get rid of that line and run another longer line back and around the 'clam shell' cover. It doesn't have to go through the filter housing.

If you or your wife are particularly sensitive to the odor of gas, you could put a window fan into the garage window, uh, if you have a window.

That's all the thoughts I could find in my fertile mind.

Ken

[Duane Ausherman]

To have those fumes, you have something way wrong. Fix it.

Otherwise, do wot Ken said.

[Zombie Master]

Could be a slow leak, probably at the seamed bottom of the tank.

[Seth]

I agree that it would be either the tank or carbs, but I'd start the other way around.
Take the tank off and leave it in the garage.
Leave the bike outside for a day.
Especially since you have a non-standard cap.
And I assume the bike runs well, so I'd think the carbs have less of a chance being the problem.

[theswedishthing]

Here's where I've gotten to so far:

1. Stored the entire bike outside for the night and the smell disappeared, so it's not our Mini or my wife's ninja.. (might do just the tank tomorrow).
2. Made sure the gaskets are present on the Monza gap - that said, I went to tighten it down on the tank today and got another TWO whole turns out of it.
3. Going to replace my fuel lines. I have the black braided ones and who knows how old they are.
4. Likely getting some weeping from the float bowls as they're relatively soiled on the outside; popped them off today and checked the gaskets and they could certainly use replacing. They are "aged".
5. The petcocks look clean, but will try tightening them into the tank a bit.
6. I always turn off the petcocks when it's parked, and always park it on the center stand. Probably going to start turning them off a bit earlier (i.e. As I'm coming up the street, Before I park and shut off the bike). Will also not store the bike with a full tank (although always thought that was best to prevent condensation/moisture).
7. I've bought some spray foam insulation and caulking to seal up some gaps that are definitely seeping air into the house from the garage.

Good call on it maybe being a tank seam leak. I guess the way to figure that out is take the tank off and have a look. Tomorrow.
We'll see where that takes me. Might look at a through the wall bathroom fan for the garage too.

Thanks a lot!

[SteveD]

Tank seams, pinholes around the petcocks and minute cracking under the tank bracket are the usual spots. When you remove the tank, it'll likely be obvious is that's the cause.