General engine question (motorcycle)

[AKcharger]

Hi Guys...OK I took on this project for my brother, an '84 nighthawk that's been sitting for about 4 years after being vandalized. As soon as I got it I was able to get it running, although poorly. I figured carbs, so sent bike off to a motorcycle repair shop while I did the body panels. Got it all done but still runs bad, so sent it to another shop who said the #2 cylinder has zero compression...but I'm not so sure.

So here's where I need help, what do these clues tell us?

1) With starter fluid I can start it and after about 15 seconds it will idle fine but if I advance the throttle it will cough and die...BUT if I shoot starter fluid in the air box while increasing the throttle it revs right up (with an occasional pop)

2) at Idle I shot the exhaust pipes with a laser temp thing there was no wind of sunlight:
    - #1 was 118°  
    - #2 was 124° (the  "dead" cylinder)
    - #3 was 93°
    - #4 was 87°

3)  The I shot starter fluid in the air box and revved it for about a minute
    - #1 was 154°  
    - #2 was 147° (the  "dead" cylinder)
    - #3 was 108°
    - #4 was 106°

4) So Obviously #3/4 aren't firing...Bad coil? that's what I was thinking but the left coil runs #1 and #4 and the right coil runs #2 and #3


I ain't ready to quit and dump it craigslist...what do you guys think

[skip68]

Sounds like the carbs need to be torn down and cleaned.  Take out the jets and clean them good and use a small wire to poke through all the holes.   Did you check for spark?   Have you pulled the plugs and felt compression with your finger?    Was it running when parked?   

[AKcharger]

- Ran great when parked
- the one place "Supposedly" rebuilt the carbs but it runs EXACTLY the same
- Nope haven't done a compression test..might do that tomorrow

[skip68]

Sure sounds like carbs to me.   I just had this problem with the 600cc buggy I've been building.   I went through them and now it purrs. 
As long as you have spark and compression the only obvious thing is carbs cleaned and synchronized.   It's possible that it needs valves adjusted.  You can do it yourself, just do a search.   

[skip68]

   let's get this old boy running.   Those are great bikes.   

[AKcharger]

I didn't get a chance to play with it this week, but stand by!

[Patronus]

I'm putting $100 on the pilot jet

[AKcharger]

Ok so plan was to re do the compression test and if good check spark...and if good pull carbs...sound solid?

[skip68]

   I agree.   When you pull the carbs, be sure to pull them all together.   Keep them hooked to each other.   Remove them from the rubber boots on the carb side leaving the boots on the motor.   Before you pull the carbs, check to verify that the carbs are getting gas.  Each one should have a drain screw on the bottom of the bowls, open them and see if gas comes out. I'm saying this because it's possible that they aren't getting gas.    When pulling the carbs do it with a rocking motion as you pull off.   If they were just off it should be easy.