1988 Honda shadow- bike cuts out after i give it throttle, please help.

[Jdawson01]

so i have a 1988 Honda shadow VT800. up until recently the bike has run like a champ.
It starts up with no issues and idle's just fine.. but as soon as i give it gas and it hits above 1500 RMP's the bike dies.
which i leave the choke on and give it gas it goes to above 2k-2500 RPM's then dies..
It was sitting for about 2 months before i started it back it, and when i did start it, i put fresh gas in it as well as gas cleaner so i dont think it has to do with bad gas. Any suggestions???

[Moppie]

Does it miss and stutter, or just die?

I don't know a lot about bikes, but an engine is an engine.

I would be checking the ignition system, is it getting spark?

And the carbs, are they supplying enough fuel?

Also, what condition is the fuel filter in?

[Jdawson01]

fuel filter, good condition. gets fuel, gets spark, and runs perfectly until i open the throttle. new carbs, only about 1 year old.

[MagicRat]

My guess is the carb(s) have dirt or gum in the float bowl thats obstructing the fuel flow. Depending on the design, the idle circuit is just fine, but the main jet is partially or completely blocked.

I suggest remove the carb(s), remove the float bowl, clean up the insides and jets with spray-can carb cleaner and carefully blow out the passages with some compressed air.

BTW when you stored it, were the carb float bowls full?Long term storage should be done with drained float bowls. If the bowls are full, the gas can evaporate over time, leaving gummy residue that loves to clog up carbs.
Sometimes it helps to shut off the gas and run the engine until it stalls, or drain the float bowls. There should be a little screw or valve on the bowl for this purpose.

[Jdawson01]

i actually left gas in it stored, so that may be the issue. would it be possible to run carb cleaner through the gas? or do you think i have to remove the carbs directly and clean them out?

[speediva]

I'm late to the party on this, but I think it would depend on how long the gas sat in the tank as to whether a full cleaning or just a gas additive would be necessary.

Did you ever get it running?

[jeffcoslacker]

Your floats stuck high during storage, which cuts the fuel almost off entirely because that pins the float tips up. So it's just getting a trickle through, just enough to idle. It will run up higher rpms with choke on because the choke is enrichening the mix, but only again until it starves out.

This is typical when you let the gas sit in them. It evaporates out of the carbs so slowly, the floats never drop, and then get "glued" in place by evap residues. When the floats get stuck down, fuel will come out the spill tubes, and it'll run rich as hell.

One trick I've found works much of the time is to shut off the petcock, run the motor until it stalls, so the carbs are empty. Pull the fuel line off the tank, and spray carb cleaner straight into the fuel line until it fills the carbs and backs up outta the line. Watch you eyes, and protect your paint.

Go do something for about 15 mins to half an hour. Come back, hook up the fuel line to the tank, turn the petcock on, and fire it up. It will be running on all carb cleaner initially, so it may sound rough and take some throttle feathering to keep it running. Keep flogging it, it'll smooth out as the fuel gets down to it and starts replacing the cleaner. Keep trying to open it up and get the revs as high as you can, within reason.

If you're lucky, this will unstick the floats and tips, as well as flush out the jets, and it'll run like a champ. If not, try it again. If still no go, you've got carb work to do. Good luck!

[jeffcoslacker]

PS if you have a vacuum operated petcock (it'll have a vacuum line run to it) make sure the hose isn't split or pulled off on either end. That'll make em act like this too. If it sucks air, the petcock will not fully open.