Help please!

[DirtyNasty]

With in the last day my XS11SF has started to idel low, sputter when I get going and backfire off and on. From the vantage point of looking at the bike head on the 2nd header pipe in from the right is cooler than the other three. I am giving her fresh oil, spark plugs, fuses, filters and a battery tomorrow morning. I pulled and cleaned the spark plugs this morning they are great according to the pics provided by this fantastic site. The battery has died three times in the last month. The weater is now cooling off to the temps of 40-60 degrees f. From what I have read through it could be the battery, or the plugs. Am I heading in the right direction? Still new to working on the bike as I've only had her for 9 months and been gone for about 5 of those off and on. Army takes a lot of my time. She is in mint condition, always been reliable and the PO said it was serviced right before I bought her. Any help would be greatly appreciated....oh and in reading the numerous posts, I found the tool box with full Yamaha tool kit never used! Learning more every day through you all and my clymer. Thanks in advance

[fredintoon]

With in the last day my XS11SF has started to idel low, sputter when I get going and backfire off and on. From the vantage point of looking at the bike head on the 2nd header pipe in from the right is cooler than the other three.

Hi Bill,
just one cylinder acting up is almost always a carb problem. (~2% chance it's a dead sparkplug or other ignition fault)
Here's a cylinder by cylinder breakdown of the most likely causes:-
A single cylinder acts up, it's carb has problems
1 & 2 or 3 & 4 act up, it's the fuel supply to that pair of carbs.
1 & 4 or 2 & 3 act up, it's the ignition.

[GLoweVA]

If it's only happening at idle, then it's probably the pilot circuit in that one carb.
Maybe just one little bit of debris fouling that jet.
Like most here have said, An XS11 owner WILL get proficient at removing and cleaning carbs. (it gets easier once you figure out how to mess with the airbox)
If it were me, I'd plan on a half day, one med(to big) can of carb cleaner and "get er done".

Not that you have to completely tear down the carbs, but at least pull the idle screw/needle and the main jet out and squirt, but that depends on what you see once you get in there. If it looks dirty, then go a little further.

Then again look at your spark plug connections. If that plug only fires sometimes that could cause you backfiring.
These bikes have a wasted spark system. (ie. it sparks once for the firing cycle and once more 180 out from that one)
so, if it doesn't fire when it's supposed to (ie at tdc on the firing stroke) but it does on the 'back' cycle, that could cause a backfire.

[DirtyNasty]

Thanks guys!

[Lonerider62]

From your desciption it sounds like #2 cylinder is not firing or at least not firing consistently. I'd take it out and get the bike to normal operating temp then re-check the temp of #2 exhaust again. If it's in fact much cooler than the other three then you should check to see if you have a wet plug. A wet plug would tell me it's not firing and if it's a new plug, the plug is not the reason. You could swap coils with the plug wires to see if the problem moves with the coil or stays the same, that would either point to the coil and wire or eliminate it as the culprit. I'm still not that familiar with the diferent model variations, but it may also be the wiring in the advance mechanism. The bottom line is that your are going to eliminate the cause one by one till you discover where the problem is coming from and it's usually easier to start with the most accesible stuff first unless you know of the most common failures.

[TopCatGr58]

Hey Dirty,

The others have already given great advice on the troubleshooting steps. It does sound like carb related, but can also be a lone plug cap/wire/plug as well. Do you have an Ohmmeter, you can check the plug caps to be sure that one doesn't have an immense amount of resistance vs. the OEM 5k ohms.

The battery dying also has me a little concerned. Is is a new battery? If so, then you'll want to use your multimeter to check your voltage, both at idle, and then at 2500+ rpm, should be ~14.5 or so volts, if still barely or less than 12, then it's not charging, and more diagnostics are needed, and low voltages can also contribute to poor/weak sparks. Good luck! Keep up posted IN THIS SAME THREAD, and we'll do our best to steer you in the right direction.

T.C.

[fredintoon]

Hi again Bill,
if only one cylinder is acting up, here's a Q & D way to check if it's carb or spark.
Swap the plugs & wires (1 & 4 or 2 & 3) If the problem moves with the swap, it's ignition; if it don't, it ain't.

[DirtyNasty]

arrrrgh

Ok plugs looked weathered so I changed em out....still acting up. Since I had her warmed up I went ahead and changed the oil, topped off the tank and added 2 ounces of seafoam ran the bike a bit and let her sit for the night today she is still popping and kicking, so I will swap the wires from 2 and 3 to see if in fact it is the harness. I really don't want to take this girl apart as I am mechanically declined. Never had anyone around to show me things like this growing up as a military brat. I pick up quick though. I just cant fork out the $200 some odd bucks to have a shop do it. I hear it's easy....soooo I may just try and knock her out this weekend. Now forgive me because I havent had the time to research this question yet but how do I do a compression test? Thanks again for all the help! I am learning more and more everyday on this site!

Bill

[GLoweVA]

Compression test

First, you got to get a compression tester. (maybe borrow one from a friend, or the local auto parts store might lend you one)
They are a little pricey, but once you got one, you'll never have to borrow another one.

It's basically a gauge with a release valve on it that will screw into the hole where the spark plugs go.
(make sure the part that screws in isn't too long. It'll make contact with the piston)
(they make adapters and such, compare it to the plug you pull out and see how deep it might go in)

This is how I'd do it.
1. pull all the plugs
2 screw in tester to cylinder 1
3 hold throttle wide open (tank petcocks to off, so you don't suck in a bunch of fuel to the cylinders)
4 use starter to crank engine enough until pressure on gauge doesn't change anymore. (that's how much compression the cylinder holds)
5 release pressure from tester and remove.
6 repeat for other 3 remaining cylinders.

The numbers should all be about the same (about 10-20% from the average)
Low numbers mean the cylinder isn't tight enough. (spec in the manual says about 120 psi it think)(it depends on a lot of factors like heat, elevation, engine age, timing outta wack, etc.)
The bottom line is they should be about the same. If one is way lower than the rest, that's your problem child/cylinder.

[skids]

I would only add that before removing the plugs, you should clean the sand out of the recess area of the plug locations. You don't want to suck in some sand/dirt/debris while cranking.

[petejw]

also have the engine at operating temperature
otherwise youll get inaccurate readings.

[BA80]

When I first got my XS and was going through the same learning process you are DN, everything and everyone pointed me to the carbs. I removed cleaned and re-adjusted them repeatedly to no avail.

The problem ended up being the pickup coils (the distributor) under the left engine cover. It can be deceptive and seem very much like a carburetor problem.

Worth a check and much easier than pulling the carbs if it is the problem.

Here's a thread that will help you check the wires and repair them if necessary.

http://www.xs11.com/forum/showthread.php?t=121

http://www.xs11.com/forum/showthread.php?t=543

JAT

[DGXSER]

For the compression check, I will add that if you come up with very low readings or one really low reading, as in below 120, then add a teaspoon or two of oil to that cylinder through the spark plug hole, wait a few minutes to let the oil spread, and rerun the compression check.

If the compression increases with the oil, your issue is in the piston rings, if no change, then it is valve related.

I have seen these engines have one bent valve and cause alot of problems in that cylinder obviously.