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Hello folks, it's been quite a while since I've been on here, I had a different name before but since then we've moved, new job, new lifestyle really so I've had to create a new account since my old email account is no more. Getting the new place setup and acclimated to a new environment etc has been challenging at times.

So naturally, my first post after coming back is going to be a problem right? Yes, of course it is.

So here it is, I cannot for the life of me get my girl running correctly. Here are some particulars:

2004 1300
  • clayton mod
  • decapped airbox w/ k&n
  • pair valve gone
  • Glenn's a/f screw
  • FP jetting (more on this below)
  • fuel, 1-week fresh / 87oct
So here is where it started - riding weather started about a month or so ago. Up until then, she sat in the garage for a little while, empty tank, empty float. Prior to getting her going, pulled the carb and gave it a solid once-over. Reassembled, 210 main, 60 slow, needle 4th down. For the last month (and last season), she was running positively beautifully. Strong, no decel popping, good pull all the way to the top end, no flat spots, no hesitation... only issue was mpg was pretty dismal. 30-32.

I decided that I just couldn't leave well enough alone, we have a saying where I work now - "if it ain't broke, fix it till it is" and I did it.

The only thing I did, was put in a 58 pilot and lower the needle one clip position. That's it. Here is what I'm dealing with:

Idle - perfect.
Crack throttle from idle to wot, strong pull and settled back to idle with no hanging or dips. Definite hesitation depending on how fast I crack it.

Roll on the throttle through the mid range circuit, I get stumbling, backfiring through the carb at 1/8-1/4 throttle big time. If I let off, goes right back to a good steady idle. If I roll the throttle very, very slowly i can get through without the backfiring etc. 1 out of 3 times.

I cannot for the life of me get this sorted out, in my head it has to be a fuel delivery or air/vacuum issue. Here is what I've done to this point:

  • checked vacuum lines, and all appears to be fine. I've done my best to flex the lines looking for cracks or disconnects
  • petcock, flowing as it should
  • electrical, (green/black wire etc) all is well
  • acc pump, strong squirt with each twist of the wrist
  • needle vacuum diaphragm, inspected thoroughly over a strong light, no cracks or holes
  • checked carb manifold boots, clamps are tight. I cannot "see" any cracks or splits there
  • I put the 60 slow back in, raised needle back to 4th slot, same issue.
  • looking at the needle/piston, when I roll out of the idle circuit into the mid range and she is stumbling/backfiring, you can see the piston jumping up and down /fluttering which is what had me thinking of a vacuum leak, but again, if I crack it from idle to wot it blows right past the issue.
I'm missing something somewhere here. I've done this a few times with my initial carb setup when I originally opened her up, but I either missed something this go around, or at her age I nudged something and created a problem that I can't find.

Any ideas?

And let's go ahead and assume that I'm very well aware of the fact I should have left her alone. :) Talk about poking a bear here...
 

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Discussion Starter #2
I forgot to add:

I very very rarely use the enrichment valve (choke) however if I do pull it, even slightly she dies right away which is confusing since that would almost insinuate a flooding issue - but I may wrong with that thought.
 

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Something come loose causing float needle not to close all the way.
We have had some weird carb issues this spring.
If nothing shows up do a complete tear down and clean.
looking at the needle/piston, when I roll out of the idle circuit into the mid range and she is stumbling/backfiring, you can see the piston jumping up and down /fluttering which is what had me thinking of a vacuum leak, but again, if I crack it from idle to wot it blows right past
Go back through some carb threads this year.
Piston jumping up/down>>>>

Had one recently with a Spike intake, foot placement on crash bars caused mayhem..
 

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Discussion Starter #8
That came to mind, I haven't removed the float, but I did check where the needle lightly seats, and I have just shy of 3/4" of an inch from the mating surface of the carb body and float bowl to the bottom of the float.

Not the most precise measurement, but being that they are not adjustable I'm thinking that it's where it needs to be.

Then again, I "thought" I was just gonna lower the needle a notch and change a slow jet, look where I'm at now. Durrrr
 

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Discussion Starter #9
Thanks Hans, double checking the float may prove to be worthwhile. This is very perplexing. I can tell you this without a shadow of a doubt... carb is clean. Doing a teardown and clean despite storing her dry was the first thing I did, along with two dirtbikes and two quads. That being said, I just blew some air through the passages for good measure, I'm about to put the tank back on for another try. I'll pull that float first... be back with you in a few.
 

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No joy. Float needle looks perfect, no scoring around tip, seat is 100% clear and clean. Made double sure float wasn't binding in float bowl prior to reassembly.

I'm fairly frustrated at this point, second guessing just about everything. In the hope that this may assist those who are taking time out of their day to help, I recorded a quick clip of what she is doing. I did not hold the throttle into the choking stage, but hopefully this might spur an idea based on your experience. I personally saw something that for whatever reason I didn't notice before, I'm going to do some searching on the subject. Willing to bet you'll notice it too.

 

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No smoke from carb, as to the other... I don't know. I had to walk away for a bit, I really thought I had found a solid suspect which were the intake manifold clamps. I noticed when putting the carb back on that it seemed like a lot of excess movement, and the clamps on the manifold boots were a tad loose. I've never messed with those before, but it was possible that when everything was bolted back into place it was putting just enough pressure on to create a vacuum leak. Not really though... although the issue is technically less now, it's still there. After letting her warm up via idle for a while it isn't as bad, but it's bad enough that merging onto I-5 mid 6% grade would be pretty iffy. Can't have her falling on her face with diesels on my rear.

I've re-checked every vacuum line in there, pulled the carb/manifold boot off and inspected it thoroughly. Tore the carb apart again and ultimately what I am left with is your suggestion, and the possibility of a failed gasket in the carb. They looked fine to me, but that's the tricky thing with gaskets. Most of the time, they always "look" fine. I didn't replace the float bowl gasket when I changed the slow jet, and it had been on there a while, about a year, so maybe i could be pulling some air from that area?

Spark plugs were a bit on the darker side of optimal, which was to be expected being that i thought she was a tad rich with the prior jetting, which was still way better than this scenario. Right now, I'm playing with the kids and getting ready to sit down for dinner. I've been going at this for way too long and I'm too frazzled (pissed off to be truthful) to think clearly at this point.
 

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Okay, so after dinner I'm playing with my son again, we are just being dorks and we are goofing around with Legos, and this one piece on one of his sets keeps falling off. He says, "yeah, it doesn't stay on very well anymore". That got me thinking... my vac hoses all looked fine. No cracks or splits mid-line or in the ends, but a few did come off of their connecting points rather easily. They weren't falling off, but it didn't take much to get them off either. So, in a "hell with it" kind of moment, I went back out and just got done replacing all of the vac lines with some leftover Tygon from my boat engine overhaul. The video is the end result. In this video, you can see the air filter/cover on whereas in the prior video it was not. You will have to trust me when I state that in the prior video, the only difference between on/off was the decibel level of the backfire. This is the same aforementioned jetting, 210 main, 58 slow, needle 3rd down.

 
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