Very General

[rgouette]

A real general problem fellas, forgive me.

Bike: 1981 Yamaha Maxim 650.

Problem: turning over but will not start.

History: Carbs were just cleaned by a very good bike guy: not a total rebuild, just a good cleaning.(I hear they really needed it too)
So, I put them back on yesterday, and set petcock to 'PRIME' for a few minutes, I cannot get the bike to start.
I have spark, but I have not verified yet that there is indeed gas in the carbs...?

Boots are orinigal I believe, but I don't see any gaping cracks...

thx in advance!
Rich

[Gummiente]

Well, if you're sure there is proper spark then the next step is to check for proper fuel delivery. I'm not familiar with the carbs on your bike but there should be a drain screw on each of the float bowls, try cracking them open a bit to see if gas flows out. If it does, then the problem is internal with the carbs. If not, then chances are the petcock and/or fuel lines are clogged and need cleaning as well. You could also have a tank of bad gas - especially if the bike has been sitting for a few months. Drain some of the gas into a container and pour a SMALL amount onto a smooth concrete surface... if the gas beads up then it is contaminated with water and you'll have to drain and flush the tank, petcock and fuel lines. If it just soaks into the concrete then the fuel quality is probably okay.

Assuming the battery is fully charged and you're getting a strong spark on all cylinders then it's unlikely the problem is ignition related. Are the plugs wet when you remove them? That's usually a sign of no spark, although it can also mean contaminated fuel. Sometimes a plug will show spark when you ground it against the engine but will fail under combustion pressure inside the cylinder, but that's pretty rare.

[poppygene]

This will let you know if there's any gas in the carbs: On the bottom of each carb there is a nipple with a drain screw right next to it. Leave the petcock on Prime for now, attach a piece of tubing (I prefer clear tubing) to the nipple and open the drain screw. If you don't get anything out the tube, your petcock may be clogged up or faulty. You can disconnect the fuel line from the carb and turn the petcock to Prime to see if there's any fuel flow. Most petcocks have a fine wire-mesh screen that sometimes clogs up resulting in no fuel to the carbs.

Hope this helps.

Edit: Ahhh... I see Gummiente beat me to it! Looks like we think alike!

[Gummiente]

Edit: Ahhh... I see Gummiente beat me to it! Looks like we think alike!

I know, it scares me too!

[rgouette]

All good stuff, thanks fellas.

I can say additionally, that:

1) the gas only is 1 day old(now)
2) there is spark at the plug
3) Battery is new

I will certainly check the petcock flow, and fuel in th ebowl, in that order.
Thanks much.

Oh, and then I'll get the Haynes manual: I've been delaying it , but I guess I really need it. Unless you find another service manual to be far superior?

Cheers!
Rich

[poppygene]

Edit: Ahhh... I see Gummiente beat me to it! Looks like we think alike!

I know, it scares me too!

Hey, Mike...
I remember telling my wife once, "Hey! Great minds think alike!"
She quickly informed me, "Yeah, but mediocre ones do, too."

She has a way of putting me in my place...

[rgouette]

Ok gents: so I'm getting fuel to the carbs.
Spark, etc
What it does (after having sat for a few hours) is :
I'll turn the key ON, turn to RUN, & it fires right up, revs fairly high, then shuts right off, not to start again, until I apparently let it sit for some time.

atrrghghg

Rich

[rgouette]

Ok, new revelation.
I just spoke to the guy who did th ecarb cleaning, & he said it's possible that he placed the jets in reversed, thus causing a initial surge of power, then they flood.
sounds good to me?

Rich

[poppygene]

Rich, is this with the choke on or off?

[rgouette]

Choke off.