Topic: VT500 Seized Engine?

[ggrant]

I recently came into possesion of a vt500. I got the bike running recently and have been trying to get her road worthy.
I went away this weekend and came back to a small puddle of gas on the ground. I forgot the petcock in the on position. Afterwards i tried to start the bike. When i did i heard a large clunk and then the bike wouldnt turn over.  I tried pushing the bike in 3-4-even 5th gear and i couldnt get it to budge. Have i seized the engine? How is this possible?

[scottly]

You may have one or both cylinders full of gas, hydro-statically locking the motor. Try removing the spark plugs and see if the motor can turn. Be aware that if this is the case, gas will squirt out of the plug holes when the motor turns, so you might want to put rags over the holes.

[Old Scrambler]

If the cylinders are full, and the motor turned a half or more of a revolution when you tried to start it, you may have bent or broken a valve

If the pistons are clear of fuel, try rocking the bike BACKWARDS while in gear.  You may have partially engaged the starter and its stuck................or broken. The starter-gear shaft is known to stick from abuse and wear.

[MoMo]

Check the oil level for overfill and smell of gas.  Crankcase (as stated above) is probably filled with gas.   Drain oil/gas, refill oil and give it a whirl...Larry

[grcamna2]

bump

[ggrant]

I drained the oil last night and it reeked of gasoline. (ding ding ding) . I was able to get a wrench on the crank bolt and rock her back and forth. She now rotates completely. 
Now, as for the carbs overflowing. I know for certain that both of the float pins move freely, what could be causing the overflow?

[strynboen]

side stand can do it...cbx 1000 does it often. fill the silenders vith fuel.i alvays use the senter stand ...and close for fuel

[grcamna2]

I think that after you change the oil & oil filter it'd be a very good thing to check to see if your fuel tank/tanks are clogged w/ "stuff"  ...,you may have to completely flush them out until you're sure there is no more rust or dirt,water,etc. in them..,you may have to re-line the inside of the tank/tanks if it's real rusty.

First thing to do is drain the carb. bowls & catch what fuel comes out of them in a white colored plastic spray can cap..,that'll give you a hint as to what's in the fuel tanks.... I'm not sure that this is your problem,but I know that if it is, it'll cause your carb. float valves to stick(from small particles & chunks of rust) which'll overflow the carbs.
 The other thing that'd be good is to remove the carbs & go through them,check the condition of the float valves/needles & seats & clean/blow those carbs passages out real good.Does your model VT500 have an electric fuel pump(if you do,the fuel pump needs flushing out along w/ replacing your inline Honda fuel filter also) & a sub(under seat type)fuel tank ?,you know,a main top fuel tank & a small frame mounted tank ? Those small frame mounted tanks can Really get lots of rust/water,etc. in them over time.The other thing that would be good is to see if your fuel valve/petcock is sealing well when you turn it to the "off" postion;it makes a lot of a difference especially if it only has one (upper) top fuel tank & it is a gravity feed only system.

                Let us know what you find in those carb bowls 

[Old Scrambler]

Your lucky so far..............Yes, a lot of early '80s models are prone to fill the cylinders with fuel if the bike is left on the side-stand for an extended few hours. Even with the petcock turned 'off' it can be a problem if the petcock is dirty. I bought a well used VT500 and gave it a small amount of love (cleaned the fuel system) and was very surprised at how well it performed. After a few thousand miles I sold it for good money because I could claim its reliability. You have found its weakness. The sometimes result is a bent valve or broken cam-tower. That can be expensive.

Suggestion...........when all is OK, do a compression test..........or at least turn the motor over with the kill-switch on 'OFF' and listen for any strange sounds.

[grcamna2]

How's the VT500 doing ggrant ?

[ggrant]

Sorry i have been delayed as for waiting on parts in the mail.

@grcamna2 - the tank is clear/clean/gas is new. Im almost positive the floats arent sticking. I will pull the carbs off (again! haha) and check the float height and ensure they arent sticking before i fill with new oil.

Are you guys saying that this could happen just from leaving the petcock in the on pos? Or by leaving it on the side stand? A combination of the two?

[scottly]

Are you guys saying that this could happen just from leaving the petcock in the on pos? Or by leaving it on the side stand? A combination of the two?

Your VT500 should have a vacuum-operated petcock, like on my FT500. This style petcock should not allow fuel to flow if the motor is not running, even if the petcock is left turned on. This system uses a diaphragm operated valve, plumbed to the intake between the carb and the motor. Here's a couple of pics of my FT valve:   

[ggrant]

Someone may have replaced it at some point then.  Its definitely not vacuum operated now.

[grcamna2]

How's she coming along ggrant ?