Author Topic: Starting issues  (Read 1263 times)

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Offline Sammy

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Starting issues
« on: May 03, 2017, 04:43:23 PM »
Hey, Sammy here

I'm having a hell of a time trying to get my bike to start up after the winter. Being foolish and naive I didn't put stabilizer in the fuel tank. I ended up removing the carbs and cleaning them with carb cleaner. I drained the old gas and put fresh gas in the tank. No luck. Checked for spark and compression got both of those. The only I can thing of is the carbs are way out of adjustment, or possibly the condenser went bad and there's not enough spark? Idk but when I throw a little bit of starter fluid in the air intake I get a little backfire popping sound in the exhaust pipes. Don't have a clue what that could mean.

Any help or suggestions would be greatly appreciated

Offline dankeller

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Re: Starting issues
« Reply #1 on: May 23, 2017, 06:47:09 PM »
Hi Sammy.  Did you get your bike running?

If not, assuming it was running fine before you put it up for the winter, my best guess would be that the carburetors got gummed up since you did not use a fuel stabilizer.  The trouble could be any of 100 things, but I would start first by properly cleaning the carburetors (taking out the main and pilot jets, the emulsion tubes, floats, float valves, and slides, soaking the bodies and jets in cleaner preferably over night, [don't get cleaner on the rubber diaphragm of the slides]and blowing out all the passages on the bodies and jets with compressed air).  Then assemble them carefully. Check your float heights.  To start, put your mixture screws out 1.5 turns (gently seat them first with fingers before turning them out).  I wouldn't mess with the carb sync screw or idle set screw yet (if you have, put them back to where they were).

Put the carbs back on the bike and tighten all the boots.  Clean or replace your air filter.  Fully charge your battery or replace if it does not hold above 12.5v (with nothing on).

Clean or replace your spark plugs with new dea8's (fouled plugs will make starting difficult).  While at it check your compression holding throttle wide open (should be 140psi or more).  Test the spark by holding the plug outside of the cylinder grounded tight against the engine, one at a time.  You should see a good fat spark.  Your condenser is likely fine.  Check your points, sand the surfaces and set the gaps, but consider replacing them (I've had points look good but not work).

Then give it a try.  Remember to fill turn your fuel valves to prime to fill the carbs.  I assume you didn't fiddle with the timing, if so, you will need to sort that out too.

There are other things to try after that.  But let us know how things turn out so far.

Dan Keller

Offline Sammy

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Re: Starting issues
« Reply #2 on: June 08, 2017, 09:32:15 PM »
After cleaning the carbs with no luck I got a compression tester and found 90 psi in the right chamber and 100 in the left chamber. Not good! I know that there is obviously some leakage past a valve, through a warped head, down past the rings, or there is a defective gasket somewhere. I'm not really sure where to start and haven't really opened up an engine before. Thanks for the help before I really didn't think it could be compression because my bike was fine before putting it away for the winter but it was. Is it necessary to detach the engine from the bike to work on in or can i leave it attached.

Thanks again,

 Sammy

Offline dankeller

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Re: Starting issues
« Reply #3 on: June 09, 2017, 01:59:27 AM »
Hi Sammy,

Are those compression numbers with holding the throttle wide open? If so they are way too low to start the bike.  If you didn't hold the throttle wide open that would also give you those readings but they would be wrong.  You need to hold the throttle wide open as you crank the engine to check compression.  On a cold engine you likely won't get up to 140psi, maybe more like 125-130psi, but that I would say would be okay to start the bike.

If your low readings were correct, the next step I would take is to open the cylinder head and torque all the 8 big head bolts, and then carefully check and set all the tappets.  Issues with both of these have separately given me low compression.  You can take off the cylinder head with the engine in the bike. You need to remove the tank, and the air scoop, then unscrew all the Allen bolts.  Check for warpage of the cylinder head and use this opportunity to put in a new cylinder head gasket, after carfully cleaning the mating surfaces. You would also want to check that the camshafts are aligned correctly with the timing marks (there is a procedure for this) to make sure they didn't jump a chain length or something.  Or you might see something obviously wrong in there.  For example I had an intake camshaft that was snapped in two, and so would not open the right intake valve resulting in low compression (if I remember correctly).

 Careful not to overtorque the Allen bolts when you put it back to get her or they can strip.

If that does not fix the compression, I don't know what I would do next.  Maybe someone else here can assist.  I think there is a test where you put oil in the cylinder to see if the compression increases, in which case you will know if the problem is the valves or the rings.

Beyond that I don't know.

Let me know what you find out.  Good luck.

Dan

Offline wilberforce

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Re: Starting issues
« Reply #4 on: June 09, 2017, 07:45:21 PM »
You can take off the cylinder head with the engine in the bike. You need to remove the tank, and the air scoop, then unscrew all the Allen bolts. 

Dan,

Are you certain about this.

I always thought that to get the cylinder-head off, the engine must come out of the frame.   I've always thought that and have had an XS since 1980.  Yes I know the rocker cover, etc, needs to come off the cam chain needs to be split but due to the length of the main studs, to get the head off, it's an engine out job.

I do stand to be corrected.

Where are Crouchy and Guy when you need them?
One of the Boys from the Wall.
XS500E - 1978 vintage
Aprillia Shiver 750 - 3,600 miles.
Moto Guzzi Breva V750ie - 2005 vintage - sold.

Offline dankeller

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Re: Starting issues
« Reply #5 on: June 10, 2017, 12:40:36 AM »
Good catch wilberforce. I meant the cylinder head cover.  You're probably right that to remove the cylinder head you need to remove the engine from the frame.  But I think Sammy should look under the cylinder head cover first before heading down the path of removing the engine.

Dan