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Carb damage? Won't take quick throttle

4916 Views 15 Replies 3 Participants Last post by  Noisy Neighbor
Being the genius auto mechanic that I am I tried something very common place on a automobile carburetor when there are running issues. I thought I may have a jet blockage so I tried to choke the carb at wide open throttle. Now the bike won't take anything but a very slow roll on the throttle. If I try to rev it, it just falls on its face. Running WAY too lean. If I pull the choke all the way out it works better. What did I damage? :eek:
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If you pulled the choke knob at high throttle all you did was dump a ton of fuel in the cylinders, the X doesn't choke it enriches the mix (many are to dumb to know what enricher means so they named it a choke).

Pull the plugs and clean them to start with then make sure the enricher cable is still seated in the carb body.
When I initially choked the carb I rev'd it up and shoved a rag in the throat of the carb. Pulling the choke(enricher) cable all the way out now makes it accept throttle much better as does covering most of the throat of the carb as if I was closing a choke flap on a automotive carb. It idles great. Could I have damaged a diaphragm or ????
Thats great as the bike isn't designed to run without a filter.

You will have to pull the top off the carb and see if it did any damage to the diaphragm.

You made alot of work out of a simple job to pull and clean a couple of jets and pilot screw.
I suspected diaphragm as soon as it happened. I should have read up a little before trying a old CAR trick knowing the bike carb wasn't the same. Just a dumb mistake by a impatient rider looking for a quick fix. Oh well, live and learn. Fortunately there are kind people willing to help those of us who make dumb mistakes.
OK, while I'm at it .... my carb is factory original, never tweaked. It has always had a slight flat spot right off idle and typically runs lean from what I have read many times before. If I'm going into the carb would you have a suggestion as to what I should do while I have it off? I live in central Florida so conditions are mostly hot with high humidity. My driving habits are pretty tame with the occasional need to romp on it. Primary goal is mileage.
Thanks for the continued help.
You don't need to take the carb all the way off the bike just take choke knob loose 17 mm nut on the back side and it slides out.

seat and tank off
loosen band clamp closest to carb then tug and wiggle it will come loose

You will need a "D" shaped tool to adjust the A/F and it needs to be open to around 2 1/4 from a lightly seated position.

carb top needs to come off to get to the slider and needle, take the retainer nut loose add 1 shim aprox .020 thick to needle point then put retainer back in place it is a cam lock so push down and turn till you feel it click in place then push on needle point and make sure it will push in a little (can't be solid)

For cleaning jets you pop the bottom screws out then with your finger hold up the float pull down on the bowl (acell pump rod spring holds it up) then swing to the side.
Main is in the hex tube (emulsion tube) and pilot is next to it just clean like you would on a car.

The philips head screws are metric so file a little of the driver point off to get a solid bite with it.
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Well, apparently the previous owner was into the carb right after he bought it. I pulled the upper section apart and the needle retainer has been clipped, SCAR mod. Now the question I have is, does the factory needle have more than one clip position? My needle has 5 which made me wonder, why shim when the clip can be moved? Leading me to believe that this is probably a re-jet kit since the bike already has V&H pipes on it.
Now what? lol
Aftermarket needle...A shim in there equals 1/2 clip position..

BTW...SCAR did not "invent" that mod...Guys have been adding shims to stock needles for decades...
Odds are you have a dynojet kit in there
Go ahead and clean the jets and then remove the shim and move the clip to the next position closer to the tip, then re adjust the A/F screw to 2 1/4 turns out from lightly seated.

About 80% of the kits need the clip on the 4th position
I only used SCAR as a reference, not to give credit where it wasn't due. I knew you guys that have been doing this for some time would know what I was talking about. I used SCAR because anybody else that is newer to carb mods would most likely have read about "SCAR" before and would have an idea as to what was going on here. Just trying to make things easier to follow for us rookies. :confused:

Got the carb back together and the bike runs great. Nice snappy throttle response off idle now and runs well in the mid range. Didn't get a long enough run to really get it up there but should be fine. Either cleaning fixed the throttle issue or something was stuck/jammed. Either way it looks like no damage to diaphragms was done. WHEW!
OK Charlie, here's what got me to try this failed initial action in the first place. You had suggested to myself and others to do a jet cleaning(not by stuffing a rag in the carb lol), on another thread, to straighten out vibration issues that we are having. Carb cleaned and tuned now but vibration is still there. There has always been a RPM range that gets the right harmonics going and vibrated, not terribly hard but a good fast buzz through the entire bike. Last time I headed out for a ride it seemed to be suddenly worse starting at lower RPMs and increasing intensity with engine speed. Not the usual sweet spot. Almost like a weight fell off somewhere or a crack. Using automotive terms, like a flexplate cracked making a normal little vibration much more intense. It goes away instantly when the clutch is disengaged so it has to be engine related. Any history of that? I just don't want to be buzzing, literally, down the road and have some disintegrate.
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And that comment wasn't directed at you personally, more of a "to everyone that reads it" type of thing...Scar did take the time to do the write-up and answer alot of questions when he was a regular here, but even he'll admit (maybe) that he wasn't the first to do that to mod a carb....Hell back before there were "jet kits" guys drilled out stock jets with wire drills to get the size they wanted, and added washers to the stock needle...
Certainly didn't take any offense to your comment Bill and appreciate your input. I took it as you intended. I know text conversations can be easily misconstrued so I don't read between the lines. I wait till someone really gets crappy with me before a attack. LOL
Being a former auto mechanic I know all about bench made carb mods. Plenty of racers and conservationists out there trying to get every BTU out of a ounce of gasoline.
Vibration yep got it too.

I have heavy mods to my fuel system and some nobody else has even done.

With a 215 main jet I run smooth as silk all the way up to the top

Now if I want a true power mode I toss in a 220 main and it gets it on and right now but at 68 mph (true per GPS) I start getting heavy vibration and it will do it also in the other gears at the same RPM.

Yesterday I set up for power mode again 220 main 4th clip and .036 in shims and took it for a romp on the interstate it flat got with it but vibration was real pain in the a$$ at 70 which is 5 over the speed limit.

Today I took out my .024 shim and left a .012 in and it would fall on its face with fast throttle I did 10 miles on the interstate and I could feel surging from the wind so I come home and swap to the .024 shim still just a slight surge in the 25 mph wind gust but the vibration moved from 68 to around 72.

I may go to the 225 main tomorrow after work and drop the needle to the proper position that I like (right on the bubble) when cold I get slight hesitation when full temp it is perfect.

Now with my heavy mods and running the 220 with vibration I am just entering the low end of the power band at 68 but at 75 I get 42 mpg with my mods to the carb.

So it all boils down to how much power do you want at true highway speed if you are like me when you roll on the throttle at 70 and the back rest punches you in the back hard it is perfect.
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Alrighty then. If playing with jets and needle settings might get smoothness back in the machine I guess I'll have to see exactly what jet is in my carb and start some testing. I'll leave the custom emulsion tubes for you(seen on other threads). As long as I can get good mileage and can still embarrass my friends Heritage I'll be fine. hehehe I love hearing his Squealing Eagle ..... behind me. :bleh:

Thanks for all the help and cool riding!
I should have mentioned you won't get rid of the vibration the best you can do is move it to a speed you don't normally run at.

With my 215 main in it moves to around 45-55 in 5th and I just run right through it to around 60 to work in a 55 zone.

I am thinking the 225 for me might move it up to around the true 80 range and I don't run there unless I am passing then right back to around 70.
Something obviously changed the bike and immediately after a fill up. I might just deal with it through this tank and see if the next fuel up fixes the severity of the vibration. Maybe it's just a crappy load of fuel? I never used this particular location before and it's a trashy looking place. Maybe those dirt bags are pulling something weird in their tanks. I threw in some SeaFoam just for the hell of it in case there are any water issues.
Before this happened my vibration was around 55. On local highway runs I either had to piss off traffic or run a little over the limit. Not being one to anger people in vehicles much larger than mine
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