fuel in the air cleaner

[johnson0023]

I am new to cycling and XS11's so please be kind.
I have a 1978 Yamaha XS11 and I have questions. I took a short ride on the new bike and discovered a few issues. What would cause gas to leak from the air box under the seat and after about 15 minutes riding around town my bike looses all power and dies.

I am guessing a bad float for the excess gas but the power loss is beyond my shadetree mentality. I am comfortable working on my old cars but I am less than a novice with the "NEW" bike. I got a Clymer manual with the bike but there is not much for troubleshooting information in the manual. I have read many tech tips and most of the posts with replies but did not see much info on my specific issue. I have a syncroniser but don't really know how to use it. I understand #3 is set and 1+2 are matched then 3+4 are mached then both sides to each other.
Thanks in advance.
Gaylord

[ross]

welcome new member...

hey there johnson0023....welcome to the family...best i can tell you is to do a search with the upper tabs and search for fuel leak or air box...there are many threads that deal with just the issues you are having...float levels/heights are critical, carbs must be clean...tank must be clean....petcocks must be clean....see where this is heading....also look in both the carb sections off the home page to get some ideas of what needs to be done to repair the problem....if someone here can't answer your questions, i would be very surprised....most all the answers to your questions are here but for the asking.....if you want, search my handle and check out the lastest postings.....have been going thru the carbs myself and trust me, cleanliness is truly next to godliness....hehehe...anywho, welcome aboard and don't ever be afraid to ask a question about anything....ross

p.s. also the xs family really likes photos to describe what the problem is...helps us id what bike you have....if you could put what type of bike you have in your signature, that will help greatly...

[wa407mpp]

Sounds to me like you have one or more float valves stuck open and the bowls are over flowing into the carb. throats and causing the spark plugs to foul out, this would also explain the loose of power before it quit. How long has it been setting? Also you will have to remove the carbs., to clean the float bowl valves so you should go ahead and give the all the carbs. a good going through. You should buy a good repair manual if you don't already have one.

[TopCatGr58]

Hey there Johnson,

As has been mentioned, aside from searching the thread posts, if you'll scroll down from the MAIN FORUM PAGE to the tech tips, you'll find lots of info on maintanence, repairs, etc., please take the time to read thru ALL of them! Also, in the MISC forum is a thread on what to look for in a neglected XS11, and it will give you lots of ideas of what to do to get your machine back into running safe condition.

You'll want to check your OIL and make sure that it hasn't gotten contaminated with fuel from the leaking carbs, cause they can also leak when the bike isn't running, flow UP into the intake boots, into the head, past open valves, into combustion chamber, and past rings down into the case/oil! Will burn up bearings very fast if it is contaminated!

The carbs are a big part of getting these machines to their peak performance, and the fuel system will require lots of attention from the petcocks and tank, as well as the carbs. The older 11's used brass floats and they can develop leaks, but it's more likely just leaking float needle seat...are all metal. A search for VITON FLOAT NEEDLE will reveal recent thread about converting to the rubber tipped ones on the older carbs, easier to get to seal!

DO NOT SOAK the carbs in a bucket of cleaner, you'll ruin the butterfly shaft seals! It's info like this that is in the tech tips. Also care should be taken when doing the cam chain tensioner adjustment, otherwise it won't be right and damage to the valves can occur due to slipping chain!

So...please READ the tech tips before doing anything on the bike!
T.C.

[wa407mpp]

first.

I should have said, the first thing you want to do is drain some gas out of both petcocks into a small glass jar and see whats coming out of your tank, if you have rust or dirt in your tank you will need to fix that problem first, then do the carbs,or you will have to do the carbs. twice.

[tarzan]

hey there

Thais is a great site with a lot of good guys.I'm new here too.I 've had two of these xs11,s.Both of them '80 Specials.
Anyway on my old one and the one I have now,they both had carb problems when I got them.I dont know if you have an vacuum operated fuel regulator(octupus),but both of mine have.If that goes bad it can cause youre problem.You will have to do a search,but there is information about this on here.I don't know if that will help but good luck.

[egsols]

welcome to the site.

Like was was said before....

Check oil to make sure no gas in it.

Choke all the way off?

Check for clean fuel

pull plugs to see if any are fouled, this will tell you which cylinders are running rich

syncing works great but doesn't help if carbs are not 100% clean with free and properly adjusted floats.

I believe the 78's carbs are vented into the air box so also check the vent lines to ensure they are not plugged, which can cause fuel to push back to the airbox.

I have always found it best to start with the simple things first and cross them off one by one.

[johnson0023]

Thanks everyone for the great advice. I have been reading all I can on this site. Wow what a wealth of information. Lots of very good tips.
I have found info I wouldn't have even thought about.
How do you check the mid oil level and the final drive level if you don't have the tool for proper measurement. Like the manual shows. Looks like a small dip stick.

I plan on changing all the lube/oil/filter out this weekend.

[AlanB]

Hi Johnson,

If you do a search, you will find drawings to make a dipstick for middle and rear oil levels. Easy way is to drain 'em both and refill with the correct amount, as listed in your manual, then make your own dipstick!

If you have bought the bike recently, change ALL of the fluids NOW!.... brake fluids, engine, middle and rear oils........ Fresh fuel is also nice!

AlanB

[Axel]

dipstick

You can still get that dipstick from Yamaha .

[CarolynS]

WELCOME!

This place is awesome!
As I learned, the search feature is a huge help. All you need to know is here and if there's something that you aren't clear on, just ask! Everyone here is so helpful and would never be less than kind.
I want to mention that I noticed the funds are low. For all of us that are new especially, we should all consider donating to the site to keep it going. I can't imagine if I tried to log on and it was gone! I made it my home page and it matters!
Send some pics of the bike. I'm going to do mine asap-as soon as I figure it out.
I'm removing my carbs tomorrow and cleaning them. Then I'm hoping the bike will run, not just turn over. Good luck with yours, wish me luck with mine.