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This is my situation...

4K views 23 replies 9 participants last post by  Dustin Burrows 
#1 ·
I came looking for help trying to diag and repair a problem with my Shadow Spirit 750.. I am a microelectronics tech by trade, and can fix everything, basically, but I've never worked on my bike like this.

I left gas in the thing all winter, in my garage, like a moron.
I just replaced plugs, full oil change, filter, new tires, coolant (though I plan to do a coolant flush, now that I have located the radiator cap.. ;)

Previous to, and after my tune up, my bike would run, but only on full choke, and fuel would pour out of my carb overflow tube.
I tried to educate myself...

Believe I am having problems with my carb, so I drained the tank, then the bowl on the carb (1.. I found the other one when I removed the gas tank and air box. I have since drained it, but I have not put the bike back together enough to see if it helped at all.)

I then ran seafoam into my carb, via funnel in the fuel intake, using my fuel pump to push it in there, left it 24hrs.
drained bowl, (1, remember) and flushed it all out with gasoline from the tank till I felt certain it was pure gas again, tried to start it... much white smoke at first.. then back to the same issues...

(I do recall dicking around with my idle adjustment at the end of the season last year, but I dont think it applies here)

I decided whatever it was, stuck float, fubar float... etc, wasnt going to rectify itself so easily..
I have been taking the tank off, (found the other carb drain nipple and screw... Ahhhh I wont forget that next time... ) the air box, the air filter, etc... I can now see two black plungers with a pin running down them. both are extended, both can be pushed up pretty easily... just like the guy's in this video
https://www.youtube.com/watch?v=oBZYice1KTs
These are my floats?

Do I need to go further to figure out what my issue is? Can someone help? I have pictures, but frankly I dont know what you'd need to see... I imagine itll be more of a "feel" thing.
Ive got some seafoam in there right now. Im about to go drain it out...

Note, I have aftermarket pipes, both plugs on my carb mix adjustments are gone, so I presume they were tuned with the pipes in mind previously, I have not fooled with them, though I plan to.
I need to figure out how many turns past seated I ought to start at, first.
I do not believe I have any exhaust or air intake leaks..

I would really, really appreciate some help here, I believe in a man trying to help himself first, but I'm not afraid to say I'm not sure what I'm doing, when the time comes.

P.S. Moderator, I apologize if this is not the place for this, I will rectify that if I can, if it is..

I really appreciate everybody's time, in advance, thank you....

Dustin
 
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#2 ·
The black things your referring to are the carb diaphragms with the main jet needle attached to them they are not your floats. the floats would be in behind the carb bowls on the bottom side of the carbs. Do a search here on the site for info on rebuilding carbs. You also need a manual for the bike, you don't give the year of your 750 but there might be on in the manual section of the Tech Sticky. Keep posting everyone here will help figure things out, also pictures help a lot.
 
#3 ·
#4 · (Edited)
Your A/F screws should be about 3 turns out from fully seated to start with. With your aftermarket pipes you'll probably end up backing them out a bit more to tune, but that's your starting point. And check your oil for gasoline contamination. Also mix up some gas with a double dose of seafoam and run it through.
 
#5 ·
Think of the carb float circuit just like the tank on your toilet. The water pressure fills the tank to a certain height and the float shuts it off so it doesn't over flow.
The fuel pump fills the bowls and the float shuts it of at the correct level. If it still runs over the needle and seat connected to the float is not sealing.
But you may have corrected that with the filling with Seafoam now. Does it still over flow after draining and pumping fuel back in?
If not then check the condition of your spark plugs ( dirty, or flooded ) and try to start it up.
 
#6 ·
...
I left gas in the thing all winter, in my garage, like a moron....
Although Honda recommends draining tank and carbs, leaving fuel in the tank over winter should not cause the problem. I have stored bikes this way for years. Best to fill the tank before storage and if stored for longer term: fill, add a fuel stabilizer, ride home and store. I find best results with E10 (ethanol will help with any moisture)

G.
 
#8 ·
Although Honda recommends draining tank and carbs, leaving fuel in the tank over winter should not cause the problem. I have stored bikes this way for years. Best to fill the tank before storage and if stored for longer term: fill, add a fuel stabilizer, ride home and store. I find best results with E10 (ethanol will help with any moisture)



G.


I have always filled my tank, added Seafoam and then just run the carbs dry before winter.
 
#7 ·
If you messed with the screws, that could be your problem. They won't run worth a crap if they aren't adjusted right. The carb for the front cylinder likes to be set a little leaner than the carb for the rear cylinder. My ACE was happy with 2-3/4 turns out for front carb and 3-1/4 turns out for the rear carb.


http://i997.photobucket.com/albums/af95/gnjturner/154.jpg
 
#9 ·
Horray! Knowledgeable help!

I have progressed in my absence.
I have my carb disassembled next to me. I only got that accomplished today, my previous post was the night before.

I did figure out those diaphragms were not floats, as I have them out, and both floats, the jets... everything pretty much. I left the choke assembly on there, and parts separated between front and back as I can see some differences. I bought a OEM gasket kit, and I am going to town right now.

I think I detected a stuck float as I opened the front carb up. I cannot be sure now if I dreamed it up or not. There was definitely some chudder in the float covers, sunk em into the ultrasonic cleaner at work. I've got the jets out now, front separate from back, as I understand there are some differences. I plan to clean all this as best I can and put it back together. I sincerely hope this fixes my issues.

The gentleman who asked me about fooling with the adjustments, I only played with the idle speed adjuster. The air/fuel mix ones were previously tuned, I presume when the previous owner put the aftermarket pipes on.
The front was at 4 1/4, rear was at 3 3/4. I'm about to replace those little gaskets, clean the ports and put em back on.
I dont have a compressor... Is that a problem for this job?
 
#10 ·
You don't need a compressor. If you have a can of carb cleaner with a straw on it, you can "prove" the cleanliness of all the jets and orifices by spraying through each one and see the amount of flow.
Wear eye protection.
Set your idle mixture screws at 3 turns to begin with and see if the throttle stop screw for idle speed is set to a little open, by looking at the butterfly plate against the carb throat.
 
#12 ·
One bit of advice,,,although a bit late,,,when turning the mix screws in to the closed position be careful not to put much pressure against the seat. If to much pressure is used damage can be done to the seats that can cause trouble.

This is true for auto carbs,,,but a carb is a carb.

Sent from my SM-S920L using Tapatalk
 
#13 ·
I was refering to a basic throttle stop adjustment so the throttle is at least open a little, so it probably can idle. If you look into each venturi you can see how closed the plate is. So turn the screw in until it is open maybe a thickness of copy paper at least. Then look at both of then in turn and try to get both carbs open the same amount. That is a basic syncronizing of the throttles. So they are working about the same amount to begin with. Just a starting point. If they are closed totally it can't idle.
 
#14 ·
Phantom- I had read that somewhere, and so was very careful to go slow, let them seat, and stop. ;) I'm really worried about adjusting these later, but I made note of the position they were tuned to when the aftermarket pipes were put on..
Swifty- I understand the venturi effect. But you seem to use that as a noun...
What I think youre telling me its that i need to set my idle adjustment to allow the throttle to keep the giant valves it is attached to open about the width of a piece of paper.. which I have PLENTY of time to do, because I cant go get the new washer for the pilot screw that I somehow lost.. Which pisses me off, because I'm methodical to the extreme, until tomorrow.
HA!

Intelligent search operands in Google has informed me that the giant hole the giant valves are in, is in fact, the venturi... noun.
So, I'm double sure I understand you.. I think. ;)
 
#15 ·
A few things...

A) I'm really concerned about trying to tune this thing, leaving the pilots at 3, and starting there, I had assumed I'd be putting them back how I found them, but understand now they may have worked themselves out again, being set with such low tension because of the pipes. is it possible my original issue was this? Remember I couldnt get it to run unless full choke, and it spewed gas out of the carb vent hose. I have been working with the idea i mush have a float valve stuck...? Maybe I just needed to adjust these?

B) I intend to mount this thing the way I toook it off, and with help from this:
http://www.vt750dc.com/HONDA_VT750DC.pdf

Do I need to go buy grease or somerthing? Can I just reassemble this thing like this? I think I was told to grease both air intake hoses at the clamps... That doesn't seem smart to me.
Anything I need to know about putting this together again? Tips?
Do you think I'll be able to figure out how to tune this thing enough to get it to start? Because I cant really do it till I can warm the thing up, right?
Can an inexperienced person do this without a tachometer?
 
#16 · (Edited)
Also, the side with the throttle is the rear carb, right?

Swifty, Incidentally, I never separated the carbs, I did not believe I needed to, nor did I remove the choke. I figured Id let those stay how they are, but I believe you are telling me if the cvalves both are in sync, and open barely, I'm golden... Is that correct?
 
#18 ·
The basic setting can always be changed after the engine warms up. Idle speed can be too high and then slowed down. Mixture screws can be too rich and adjusted to the best smooth idle afterward. Since you have cleaned the jets the original problem of fuel starvation may be fixed. No tach needed to get a good idle.
 
#19 ·
A trick I learned on the Valkyrie forum was to use alcohol when attaching rubber parts to plastic, it will make it slide easy and evaporates leaving no residue.
 
#20 ·
Well, I had a hell of a time getting that carb back in there .. And the hose clamps are nice and snug on the carb side, but I can grip them and spin them around on the engine side... It appears there is a spacer of some kind in there, I never took them off from there, so I'm a little concerned about that...

I've been manhandling my air box on again, then the air filter case. I think I can see my way to getting that done.
I might have the routing of these hoses a little off, my pictures were not as helpful as I imagined they would be.. But nothing impedes anything else thus far, and I got the throttle linkage back on without a hitch.

After all this, I can't tell you how I'm gonna feel just before I try it.. It's not gonna start right away, regardless, but you know what I mean. I'll be very impressed with myself. I'll still be a little impressed, if it doesn't, pending finding out why..
But if it blows up, I'm gonna cry like a little girl.


Tell you what though. Here is three cheers for trying your damnedest to help yourself... Which too few bother to try to do these days.
Anywho, I thank you all for your time, and your advice. it must be tiresome at times to educate noobs.. Thanks for doing it anyway. ;}

If anyone has a computer question, or has broken electronics in the midwest... I'll return the favor. ;)
 
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