OK, this just doesn't make sense!

[markjs]

I have an old '81 beater XS1100. It's fully dressed, and it used to get 15MPG and blow a lot of black smoke. I pulled the carbs and cleaned all the passages with carb cleaner and very high pressure compressed air. I set the float heights correctly and got a new air cleaner.

Now it gets 20-25MPG! What the hell do I have to do to squeeze a measly 30MPG out of the damn thing?!?

[randy]

Stupid question:

How's the compression? If it's truly been 'beat up', 25MPg may be all she wrote.

[markjs]

120-130ish

[DiverRay]

Did you use a carb stix or vacuum gauge to sync the carbs? If not, you may pick up about 5 more MPG, and a LOT of fun. Also check the valves, you may have one slightly loose, or worse, tight. The tire pressure will also make a difference. I would keep a "dresser" at the high end, 37 to 40 PSI on my Dunlop 491 tires. 120 to 130 IS down a little. I would not expect over 34 mpg with everything set and new plugs.

[markjs]

I've said it before and I'll say it again. Carb synching is one of the most overrated procedures in motorcycle maintenence. I bench synch my carbs and on the couple of occasions I have taken them to the local shop to get it done professionally, they always tell me I was within a **** hair and the difference is inperceptable. Also the carbs being in synch down to the most minute measurement only really effects the bike at idle, the wider open the throttle the less it matters. All the same I don't have the money to do this and I'd bet at the most I'd get perhaps 2mpg improvement.

The Valves, well, if I can't afford to do the carb synch, there is no way I can afford valve shims. They aren't available locally and they can be expensive. But that is a valid point. I should do it, because if anything they might be tight because the bike makes ZERO engine click or rattle.

Still all things considered with the carbs all clean and back in spec and the plugs are good I just can't figure why I get 20-25. I get 20mg, really, and only 25mpg when I drive like a grandma. Even if the valves need adjustment it should do better. The carbs are super close to in synch, and I do not intend to ever waste money paying someone to do that again since my bench synchs are so good. I may perhaps get a synch tool someday, but even still I doubt that is much of a factor.

All the same, do you know where to get a valve shim set and a synch tool on the cheap?

[John]

Look up!

Look at the sticky thread that is posted at the top of the discussion forum. (Two threads above this one) It has something to do with shims.

[trbig]

They aren't available locally and they can be expensive.

Unless you live in a very small town, these are available at most bike shops.. especially any that do repairs. There are even cars that use these shims, so it's not like it's just something someone is keeping around for just old XS Yamahas. this is of course if you are worried about any down time. Just remember that there are 29.5mm shims out there also that you really can't tell the difference on looking at them... they just won't quite fit into the shim bucket.

If it can be down for a week...talk to John and use the shim library that's been created.


Tod

[81xsproject]

You don't have to spend a bunch of $$ to get a synchronizer. You can make one for under $5 and it will be better than the ones you buy. Google manometer or actually look in the tech tips for the vinyl tubing creations. We have heard your opinion of vacuum synching before, yes... and here you are again asking for advice and then throwing it overboard. Good luck with your mileage.

Also, please keep in mind that the aim of this site is 'family oriented.' Please keep language appropriate. thanXS

[wa407mpp]

sync. set

Markjs, I have a sync. set if you want to try them some time, send me a pm , and we can meet down at Jim's or something.

[Ken Talbot]

Re: OK, this just doesn't make sense!

Originally posted by markjs
...it used to get 15MPG ..... I set the float heights correctly...Now it gets 20-25MPG! What the hell do I have to do to squeeze a measly 30MPG out of the damn thing?!?

Lower the floats by 2mm from whatever thay're now at, and check it all again. This will lower the level of fuel in the float bowls, and it will lean out the air/fuel ratio. After that, try lowering the metering pins, whiuch will also effectively lean out the mixture. Keep checking the plug colour so you don't go too far.

[markjs]

when you say metering pins you mean air screws?

I hate having to pull the carbs again but I must admit a friend gave me a tip that helps a lot. He suggested using WD40 on the boots for easy installation and it works like a charm. and it also dries up after a short while so it doesn't leave it compromised.

[Ken Talbot]

Sorry, Markjs, I should have called it the needle, the one that rides up and down in the main jet as the carb slides lift and fall.

[RUSH]

Make sure your brakes are not binding.

[markjs]

Originally posted by Ken Talbot
Sorry, Markjs, I should have called it the needle, the one that rides up and down in the main jet as the carb slides lift and fall.

How does one adjust that? I didn't see any way when I had them apart. Not sure I will need too though, the plugs were pretty black and so I raised the floats to about 1 1/8th of an inch and the plugs are begginning to get brown, but I have not ridden enough to actually check the milage. The bike has so many problems and I have so little money.

Thing is though I have decided that my little Kawasaki 750 will net a bigger price and I like the XSEleven better, in spite of it being older and more beat. I have been focusing on selling the Kaw but if anyone in the PNW is interested in a restoration project I might be tempted to sell this XS. I only know one bike has to go and I need a car.

[RUSH]

so what do you want? an easy answer to the bike problem or justification to by a car? If you are taking the ferry daily, work on the bike.
If you are sure the bike wheels are spinning freely then you need to keep at the carbs. Maybe the jets have been replaced with bigger ones? Maybe the timing is off? Bring it to my house and we'll have a go at it.