No heat on #3 and #4

[xs1100newb]

Hello all,

I notice that the headers of cylinder 3 and 4 on my 1100F do not get as hot as cylinders 1 and 2.

Cylinder #3 gets hot, and if you ride it long enough it becomes too hot to touch, but this happens long after cylinders 1 and 2 are scalding.

Cylinder #4 gets hot, but only long after cylinder #3.

Both cylinders are getting a strong spark and the plugs are not oil fouled or anything like that. Also, I seem to remember that a while back these two cylinders worked okay, so I think the problem is intermittent.

Any ideas of where to look? Also, I did an equal job of cleaning each carburetor, but I suppose I might have to clean them again?


Also, could this intermittent firing of cylinders 3 and 4 cause a hiccup at high rpms?


Adam

[DGXSER]

First place I would look is your fuel. 3 and 4 share the fuel feed from (typically) the right side fo the tank. If that line is kinked or if your petcock or its filter is partly plugged, that could cause the problem. Place to start anyway.

[xs1100newb]

That is a great simple idea. I will switch where the two petcocks are connected and see what happens.


Anyone else have any other ideas? I am trying to think of the simple stuff that might be causing the problem before I tear into the carbs.


If the two cylinders eventually get hot, could it be a compression issue?

Adam

[Toolmaker Tim]

Cylinder Temps

I'm guessing, cause I haven't looked at the thread where you stripped the spark plug threads out, you got that fixed. Quickest way to check that is throw a compression tester on and check it. A lot of auto parts stores rent them cheap after a deposit. I doubt its a compression thing, but it doesn't hurt to check. What color are your plugs? They should be a tan color. White or grey isn't good. That would be a lean condition, which could be caused by a kinked fuel hose like DGXSer said.

[xs1100newb]

Yeah, the threads have been fixed.

Cylinders 1 and 2 are a great tan color. Cylinder 4 was black and dry and cylinder 3 was black and slightly wet.

But these colors only indicate the state the bike was in when it was owned by the PO. I have only ridden the bike about 2 miles since I got it running.

Maybe if I ignore the problem for now and ride it a little more the other cylinders will begin to fire.


Adam

[DGXSER]

Do yourself a huge favor and buy new plugs. Those fouled plugs will not fire correctly even if you have everything setup perfect.

[DAVINCI]

And after that, do a proper carb synch.

[xs1100newb]

Ok. I will replace the plugs.

In regards to the carb synch:
My understanding was that you only sync the carbs when you know everything else is perfect. In this case, how useful would a carb synch be if 2 out of the 4 cylinders are misfiring?

Adam

[DAVINCI]

The hope was that after you cure this misfire (maybe by changing the plugs?), you could properly synch the carbs. You did clean the carbs, and that probably affected the synch.

[DGXSER]

It is often surprising what a good synch can do. It will never hurt to synch, and it can help. Now, if your paying a shop to do it, then yes you would want to sort out any other gremlins you have first.

[xs1100newb]

Ok, I have to required mercury gauges to do the synch, so I will give it a try.


If this does not pan out then I will be forced to remove the carbs. I want to avoid that like the plague.


Adam

[cywelchjr]

Ok, I have to required mercury gauges to do the synch, so I will give it a try.


If this does not pan out then I will be forced to remove the carbs. I want to avoid that like the plague.


Adam

Replace the plugs with new first, these bikes will very often NOT clean up dirty plugs once fouled and will continue to run poorly if the plugs are fouled. Plugs are dirt cheap if you get the OEM plugs (slightly difficult to find but cheap, every auto parts store I've tried has them, just most don't KNOW they do) and easy insurance to making sure that isn't the problem with poor running (although sometimes a good high speed run will clear them, and get you a ticket at the same time ).

[DAVINCI]

One more time.

Synch AFTER you replace the plugs.

[CaptonZap]

The Champion plug number that is listed in the Clymers Manual has been superceded by a new Champion number.
I went to a NAPA store and got the oldest fart there, and asked him if he could look up the old number and see if it crossed to a new number. Sure 'nuf, same number on the plug, new stocking number. I can find out what it is tomorrow when it is light, if you can't find out. (I saved the box.) The ones I'm using are RN9YZ. CZ

[xs1100newb]

I think I am slightly confused.

I simply walked into the local auto parts store, where I live it is O'Reillys, and told them the motorcycle model and year. They brought out 4 NGK spark plugs.

Is this not oem?

Adam