No combustion on 2&3

Hey guys, Im new around here and so is my 86 XJ 700. I picked her up a few weeks ago and have been going about putting her back together. Heres my problem, cylinders 2 & 3 arnt firing . I am getting spark and have swapped coils and replaced plugs. Im no expert mechanic but those seem to be the obvious solution. Still no difference. I can turn her over and unplug 2 & 3 with no change to how she runs. Any ideas?

 

Sure. Get the valves in spec and do a compression test. Let's be sure 2 and 3 are capable of firing.

 

compression test is the next item on the list, I left the bike over at my buddys place because he has the garage space I need.
Ive never done valves before. I have an Idea but am not sure what is in spec. Also whats spec for compression ? Ill be checking it all tonight.

 

Valve clearance specs for aircooled XJs are:

.11mm ~ .15mm intake and .16mm ~ .20mm exhaust.

Valve clearance how to: http://xjbikes.com/Forums/viewtopic/t=14827.html
Part Deux, understanding the tool and alternatives to it: http://xjbikes.com/Forums/viewtopic/t=29209.html

You'll have to double-check your manual for compression specs on the 700, not sure if they're the same as for the 650/750s.

 

thanks fitz. Ill be diggin into this tonight and tomorrow.
the how tos will be a ton of helpas this is my first time doing bike related maintenance.

 

The first time is the scariest, Heath. You got this!

 

Well after being in a car accident ( no injuries minue my expedition ) I finally had a chance to do the valves ( halfway as I just took a break and am headed for dinner now )


Exhaust
1. 2. 3. 4.
.203 .178 .127 .127
Intake
.102 .127 .152 .152

I haven't pulled the shims out yet. Will be doing that this evening

 

You should use a set of metric feelers for your measurements (instead of converting US).

FYI-there is no way you measured that accurately (to three digits). I am willing to bet your #1 exhaust is in-spec as it is very uncommon to see a valve that is loose; just rounding error going from US to metric. Dont go swapping out that shim just yet; get a metric set and recheck.

 

Get metric feelers and tell us what you get in : .XXmm

Don't worry about a third digit. We won't care anyway, and it'll be a waste of your time.

In spec is in spec, and out of spec is out of spec. Fitz gave you the correct ranges.

DO get compression numbers, though, for us.

Dave

 

Those were the only gauges the local hardware shop had on hand. Both metric and standard. Ill swing by a parts store on my way home from work to get another.
I did do a compression test, twice. My xj is missing its center stand and not thinking I did the first with her leaning on the kick. Second one I did having someone hold her up for me. Here are my two results

Leaning

185. 155. 161. 165.

Standing

161. 165. 163. 165.

 

I think 185 is a fluke.
That's like Guinness Book compression for that Bike.

 

Always do a compression test with wide open throttle.

 

were those numbers wet or dry? if those were dry... that's some pretty good compression....

 

This is enough compression to fire all cylinders, I'd say.

 

Im not the most mechanically enclosed person so sorry for all the questions guys.

Jmilliken - what do you mean by wet/ dry? There was no fuel in the system if that's what you mean

Lostboy - I didn't give any throttle , just turned it over. Ill be sure to do that tonight

Rick - my buddy said that didn't seem right , that's the whole thing that lead me to standing the bike up. We did check it twice leanin because that was so far out .

Bear ( or is it bare?) with me gentlemen, as this is my first rodeo.

Another question, when I opened the valve cover while on the kick should an abundance of oil have spilled out ? I figured it was because it was leaning but just want to make sure .

 

Heath........NO need to keep apologizing. THIS is why we are here. We'll get you going, and you'll end up staying.

Compression seems high enough for now for what you did. If there were a blown cyl, it would have shown up, even if the numbers are not quite dead on. It would have shown a really really low number somewhere.

So,can you give us a little more detail on what your procedure was when you "swapped coils" ? Let's see if we can narrow anything down a little bit.

Also, did you pull the plugs and look for a free-air spark? Did you swap the coils again and watch for the free-air spark? Lets see if we can determine where the spark is getting lost. Compression, valves, and carbs are all things that need to be put to spec but if there's no spark to fire things off............................

Dave F

Dave F

 

when doing compression tests, to check the health of your rings, first do a "dry" test, then pour 2 tsp of marvel mystery oil or motor oil in the spark plug holes and then do a 2nd compression test.... you are looking for a uniform increase across the board as well

I just happened to do mine the other day (same bike) and was 130-135 dry and 165-170 wet across the board. If I had one at 130 dry and 135 wet, it would indicate bad rings.

And Dave is right, don't apologize. We all learn, and we're all here to help each other... even the best of us get stuck sometimes.... Just when Fitz tells you to check your valve shim clearances - check your valve shim clearances!

 

When you turn-over the Plant doing a Compression Test and have the Bike on the Side Stand, ... Oil will pool on the left side because it can't flow to the Scavenging Ports as it would if the Engine was level.

 

Ok so I took my time ,went through and did my valves , compression test brakes , and carbs. The carbs were 100% the issue. Those things were disgusting. Got it all squared away now just need to replace my clutch cable today , should be taking her out for a ride this evening. Thanks for all your help guys.

 

Good going. Be sure to lubricate that new clutch cable.