Jump to content

'84 VT500 Ascot....can't get it to idle on rear cylinder


Recommended Posts

 **I'm hoping that the mid-'80's Honda ignition system is similar enough that someone here might have some insight**

 

Working on an '84 VT500 Ascot. The bike sat for at least 14 years and  I've been through it from stem to stern. Carbs were professionally rebuilt. I have a pretty good carb guy and never have to go behind him. 

 I can't get the rear cylinder to idle. I suspected a plugged pilot jet circuit. The carbs were professionally rebuilt, but I did run the bike on an IV bottle for a while, so it's possible that there's trash in the slow jet.

 Front cylinder/pipe gets hot. Rear cylinder/pipe does not. I'm getting a fat purple spark that will jump a substantial gap. The outer plug WAS gas fouled today, but I've been messing with it and trying to get it to idle on both cylinders. Fresh plug made no difference.
 I poured SeaFoam into the carbs and let them sit for 4 hours. Drained it, added gas, no change. I tried to pull the mixture screw, but I can't get it out of the carb body. Wish it was magnetic. No change when turning the mixture screw on that cylinder.

 I suspect the slow jet because when I ride the bike there's a BIG rush of power just past 3,000 RPM, once it gets on the needle/main. That cylinder/pipe starts to get a little heat in it then. I'm only riding it on what's in the bowls until the new petcock gets here.

 Over the last two days I've pulled the carbs twice. Pulled the main jet, emulsion tube, pilot jet and mixture screw and cleaned all of them and all associated passages. Did a bench sync. Didn't really find anything, to be honest. I am very, very confident at this point that the carbs, jets, and passages are clean. 
  Still having the same problem. Checked choke operation. Checked fuel level in bowls using the clear tube method...both the same. Ran the bike with air box off and diaphragms/slides are working. If I put my hand over the rear carb, it wants to pick up and I get fuel on my hand. It just acts like it's not getting fuel to the slow circuit on that carb. Checked compression on that cylinder and got over 175 PSI. Fat purple/white spark.
  Double checked valve adjustment and operation on that cylinder. All good.  I'm stumped. 

 At this point I'm beginning to suspect the ignitor. Even though I am getting spark when grounding the plug to he head, I'm not sure that it's firing INSIDE the cylinder, or at the correct time. 
 Can I swap the two ignitor units and see if the problem  moves to the front cylinder? Is there a way to test the ignitor? Any other suggestions?

 Pics for attention....

21150194_10210285942011043_4368829928423
21106562_10210285946691160_7478879474020
21106610_10210285940250999_7668375202280
21192428_10210285939450979_4817466642124

Link to comment
Share on other sites

Got it guys! Third time's the charm!
I have to admit, it was a bit of a bonehead move on my part, but suggestions here to go ahead and swap pilot jets and confirm jet sizes set me on the right path.
Turns out I was cleaning the FRONT cylinder carb ev
ery time! It's easy to get them confused when you pull them, flip them around and turn them upside down on the bench.
Found trash in the pilot jet. On the CORRECT REAR carb! LOL.
Running like it's supposed to now!
New petcock should be here tomorrow and I can (hopefully) wrap it up for good!

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy.