Front left cylinder at 90 degrees when the others are at 220+

I have a 84 VF700F with 14K miles. Champion plugs gapped at .035
I just got a little non contact thermometer for $10 from harbor freight and I wanted to see which cylinder heated up first. Well I have tested it on all the cylinders and the front left is cold. I pulled the plug and it was black and I tested to see if it was getting spark and it was. Now I am out of ideas. I did have to take the carbs off a while back to clean them. Could I have not cleaned this one right or synchronized it properly? Any ideas from the experts?
Thanks in advance.

David

 

What manner of "black" is the plug from #1 cylinder?

Dry fuzzy black?

Wet oily black?

Wet stinks like gasoline black?


JMO, Champion plugs are for lawn equipment. NJK mo better.



Rex

 

Dry fuzzy black. I didn't smell it. I should have but I have already put it back for today.

Champion plugs are OK in my book.

 

Symptom of overly rich fuel/air mixture. Causes weak spark and misfiring.

Possibly an improperly adjusted idle mixture screw or faulty choke (enrichener).
Also check that the slide is not sticking in the carb body.


Rex

 

It could be a situation where the plug is not firing under compression, but then it should be wet. I agree get those champions out & put in NGK's, you may also want to check compression on the cold cylinder just for peice of mind.

 

I checked it again today. Its black and wet with no gas smell. I synced the carbs too. It was sort of easy. I used a hose to listen to the vacuum sound out of each of them until the all matched sounds. I will have to check again later to see if that cylinder is still cold. But at least now they all sound the same and I get better idle and starting off. I think this bike would have been easier with a good old fashion holly 4 barrel. But that is another thread when I do that.

 

I will do a compression check too. That should tell me something more.

 

What could be the cause of this? What would fix it?

There was ticking sound when I was syncing the carbs. Is there something to that?

 

A dead/non firing cylinder can cause a ticking noise, the trick is to determine whether the tick is at engine speed or twice engine speed. Engine speed indicates ugly things like rod bearing, piston slap, or just a dead cylinder, etc.; twice engine speed indicates cam & or valve train noise which could be an actual mechanical failure or an adjustment issue or just normal V4 top end noise. As far as the plug possibly not firing under compression that is usually caused by a defective plug.

Note: Being a pre gear drive cam model it could be chain noise

 

If the cylinder is dead that would solve the mystery of why the previous owner got rid of this bike with only 14k miles on it. I noticed that when I would lay into the throttle the bike seemed to jump in power like the #1 was working again. I will do a compression check before I make up my mind that its bad. I also have the old insurance and registration information for the old owner. Maybe still lives there? Do you think that I should write him a letter asking him about the bike? I hope that it isn't a dead cylinder like the rings or valves. I was just starting to like this bike.

 

Any other ideas? What is proper compression that I should be looking for?

 

Buy a shop manual. Either Honda or Haynes or Clymer. If you can, get one of each. Lots of good info....specs, maintenance procedures, repair procedures,trouble shooting, etc.


Rex

 

Clymer sucks it doesn't have a routing diagram for the carbs.

 

David - I agree that you should run a compression test. Anything in the 180-200psi is typical. Don't get worried if it's 160psi or something, that won't cause a completely dead cylinder. You are looking for a situation where three cylinders are, say, 185psi and one is 50psi.

Are you sure your carbs got sync'd closely? I've had several V4's with carbs that acted screwy. They did the same thing you mention - one header tube did not heat up like the others. I would completely rule out the carbs before digging into the engine. I think you would know if a cylinder was dead because it would run with a really big miss.

Let us know what you find out.

 

T-Bone - cams revolve at half crank speed, not twice. Two crank revolutions = one camshaft revolution.

If I was hearing clicking / clacking from the top end of an early VF, I'd be removing the valve cover to look at the cams, since the top end oiling prob is a known issue with them.

+1 on what Jamie said regarding compression and carbs.

 

You can easily confirm this observation by taking the bike out for a quick run and then IMMEDIATELY checking the header pipe temps with your non contact thermometer.

If the readings indicate that #1 cylinder is, in fact, pulling it's load beyond idle, then you need to look into the idle circuit and/or enrichener as the cause of the rich condition at idle.


Rex

 

Sorry, thinking about the stuff I normally work on:redface:

 

Update its the number 2 cylinder.

 

Update. I was going to do a compression test had the tester and everything. When I started the bike I had the choke on and was warming it up. I ran the thermometer over the bad cylinder and what do you know it was warming up. It got to 220+ the same time the other ones were. I thought I fixed it. But later when I turned the choke off it started cooling down. That makes me think that the carburetor isn't doing its job. I think that one or more of the jets is clogged with something and then I was reading a manual for the 1000 f and it said that the valve seat for the floats has a filter. And that could even be clogged too if my 700 has one. I makes sense since its the last carb in the fuel line all the junk could get pushed down there to collect. But I am going to pull the carbs and the float bowls and see what I can see in there. If anyone agrees let me know since this is just a guess. If anyone has a different idea let me know as well. Thanks for your help I hope this is the last time I have to pull it for a while.

David

 

Ok I took the carbs off the bike and I was messing around with the float bowls on all of them. I started with the first one and the seat valve filter wasn't clogged at all. However, the slow jet was and it still had varnish in the bowl like from when I cleaned it the first time. Cleaned out the hole with a splinter off a wire wheel. It fit in there and got the jet to clear. I did it on all the carbs and cleaned the bowls too. The slow jets were all clogged so it was good thing that I got in there. I had a heck of a time getting the carbs back on and I needed help. But the cylinder is working as well as the others. I am glad that I had this group for help. I don't think that I could have done it with out all of your help. The idol is a bit rough (like a harley's) but it doesn't mean anything yet.