1981 Maxim 550 spark+fuel but no run?

I just bought an 81 550 maxim yesterday. It cranked over fine so I brought it home figuring the carbs need cleaned. I tried to start it off of starting fluid and nothing happens. Even tried removing the spark plugs and spraying starting fluid directly in each cylinder.
I then did a compression test
#1 120
#2 110
#3 60 ???
#4 130

So compression seems low especially on #3. It seems to me though that there is enough compression to at least get it to run rough.
Any ideas?

 

If your sure spark is strong, and your still not firing with fuel, have you made sure your air filter is not plugged?

These XJs are finicky. Have you cleaned the carbs? I cleaned mine 2 times, and still didnt have much luck. A local small engine guy stopped over while working on mine and was convinced my carbs were still plugged. The jets and visable passages were clean, but he tells me that there are hidden passages that are not able to be cleaned well without ultrasonic cleaning.

Are your plugs wet? Black? White?

As for compression. Have you checked valve clearances? The valves one these bikes are supposed to be routinely checked. 5k miles i believe.

Air+Starter fluid+ Spark, on a bench syncd motor, should at least fire up. Check your choke cable to make sure that it still attached and pulling the choke up on the carbs.

Lastly, have you checked for vacuum leaks? The head-carb joints and the carb-intake boots can dry rot and start leaking bad enough to cause issues.



Lemme know,

-Kaya

 

Hidden passages......Balogney. You can clean them all by hand, but a dip will help to open some of the passages that are plugged/dried shut. It can take time, but time, patience, and perseverence can turn a nasty set of carbs into a show set of carbs.

Dave F

 

I have not cleaned the carbs yet. I usually buy old Ho
nda's and I have always been able to get other bikes to run on starting fluid only. I figure what's the point of cleaning the carbs if the motor is toast?

 

Well, then check the valve clearances and see if there's a reason #3 is so low.

Did you do a "wet" test, to see if it jumped up?

 

If your air jets are plugged its not gonna start either way. I suppose If you take the carbs off and shoot starting fluid in it, it should fire.


-Kaya

 

Well I will try cleaning the carbs. I have never adjusted valve clearances before but I will attempt to do that as well.

 

Valve clearances: http://xjbikes.com/Forums/viewtopic/t=14827.html

Part Deux: http://xjbikes.com/Forums/viewtopic/t=29209.html

Get the valves in spec and re-run the compression test.

If you're serious about getting this bike up and running right you're going to need a manual.

 

I learned from these guys,,,carbs on and off 4 or 5 times,,,carbs must be right and valves must be right...be thorough in cleaning carbs and adjusting the floats...or it will never run right.

 

Above all, DO NOT fall into the so-common trap/thought of "what's a quicker/easier/cheaper shortcut to do this?" If you follow along, methodically, as we present things to you, you WILL BE doing the 'quicker/easier/cheaper' way. If you decide to do as some others have done and try the "well I already did X', or "I figured I didn't really need to do Y", after we tell you that X or Y NEEDs to be done a certain way, then you're going to take the longer/harder/more exensive way because after all is said and done, you have done everything you said and it still won't be done until you find out that what said should have been done.

We'll get you there, just come along for the ride!

Dave F