85 vf500 running on 3 cylinders HELP

I picked up an 85 vf500 a couple weeks back. It has 44,000 miles on it and hasn't be registered since 2000 although it looks as if it was recently riden. When I got it the idle jets were clogged so I replaced the carbs. Now the bike starts right up and idles but only runs on 3 cylinders. I've got spark on all 4 and when I open the drain on the carb gas comes out so I'm assuming its a compression problem. I also get a ticking noise out of one cylinder I'm thinking its valve slap. So I'm going to check the valves tonight. My question is what else could cause this problem? Does the valve adjustment being off sound like it could cause this?

 

Are you sure the carb is delivering the fuel? With it sitting that long I would not be surprised at all if the idle circuit is plugged. That happens after just a couple of weeks. A good carb cleaning would be in order for sure. A compression test is not a bad idea and is pretty easy to do.

Let us know what you find out.

 

ticking sound? please explan.

 

I've already relpaced the carbs with ones that came straight off of a running bike.

The ticking noise is hard to explain its like a tick tick tick tick lol kinda a tapping noise sounds like valve slap to me.

Gonna do a compression test when I get off work

 

Check around the exhaust pipe of the cylinder that is ticking. Sometimes an exhaust leak will make a ticking sound where the pipe meets the engine. If this also seems to be the same cylinder that is not firing the problem could be much worse.

 

yea exhaust leaks will sometimes make that sound, but the only thing that would make it have " cylinder not firing problem" as in spark knock witch ive never heard a bike do at idle, but the plug wire might be cut and could be arcing off the closes metal object, i dont want to send you on a wild goose chase but if your compression turns out good then thats what its going to be.

Oh i just thouht of something check your muffler bearings

 

I know you said that you have spark, but try replacing the plug. I had that problem with my 1000R when I first got it. It was running on 2 cylinders. It had spark, but I noticed it was very weak. I put in a fresh set of plugs and it hasn't been a problem since.

 

ok let me give a little more info. I've already replaced the plugs and wires and verified that there is legitimate spark on all cylinders.

Tonight I adjusted the valves the ones on the cylinder that wasn't firing weren't too far off 2 were loose 1 was tight. The rear head tho is another story. I pulled the valve cover off and notice that one tappet is missing so I pulled the sump to see if it was in there and it was not but I found plastic bits in the sump.

What could these plastic pieces be? I took the guides off of the chains and the plastic is intact on those I can also see the tops of the guides that run from the crank up so those aren't broken either. The only other thing I can think of is what they call the cam chain slipper in the manual its the guide that goes from the top of the motor down. I'm guessing that that may be the cause of the plastic in the sump it also might be the cause of the ticking. My question is are there any other plastic parts I can check with out pulling the motor?

Also I know the head gaskets and gasket kits are nla but can I get the side cover gaskets still as well as the alternator cover gasket and sump gasket?

 

ok let me give a little more info. I've already replaced the plugs and wires and verified that there is legitimate spark on all cylinders.

Tonight I adjusted the valves the ones on the cylinder that wasn't firing weren't too far off 2 were loose 1 was tight. The rear head tho is another story. I pulled the valve cover off and notice that one tappet is missing so I pulled the sump to see if it was in there and it was not but I found plastic bits in the sump.

What could these plastic pieces be? I took the guides off of the chains and the plastic is intact on those I can also see the tops of the guides that run from the crank up so those aren't broken either. The only other thing I can think of is what they call the cam chain slipper in the manual its the guide that goes from the top of the motor down. I'm guessing that that may be the cause of the plastic in the sump it also might be the cause of the ticking. My question is are there any other plastic parts I can check with out pulling the motor?

Also I know the head gaskets and gasket kits are nla but can I get the side cover gaskets still as well as the alternator cover gasket and sump gasket?

 

did a compression test has 150 on all 4. Gotta wait for the tappet to come in to the dealer on monday so progress is on hold until then

 

It sounds like the internal engine parts are not your problem then. Check out the carbs and let us know how it works out.

 

UPDATE:

Got the tappet and finished the valve adjustment. Started the bike. It purrs like a kitten and fires right up on all 4. I rode it and its waaaay down on power so I need to sync the carbs and set the mixture and the bike should be good to go

 

ok got the bike sorted. I pulled the carbs and on one the idle and main jets were plugged solid on another the main jet was plugged. I cleaned the carbs and put it all back together and now it runns a thousand times better

 

Glad to hear that you've got it straightened out. It's a bonus that they were all simple fixes as opposed to being something major / mechanical.

 

I always like to run some Gumout in the first tank of the season. Keep those jets clean.

 

Yes, that's not a bad idea. When passages are really plugged that doesn't help much though. There's no replacing a good winterizing process!!!