I changed my plugs over the weekend trying to chase an issue I was having where the bike would stall with throttle, and now the bike won't even start. What could I have done during a plug change that would have caused me to be worse off than before I started?

Original Issue (2006) - Bike sat for many years after it started to display issues with throttle. It ran great otherwise, but I figured I needed to put the bike away until I could find time to clean the carbs. Well, life got busy, and I didn't expect it to take 7 years to finally tackle the project! The bike only has 5K miles on it... so it's practically a new 1999!

Cleaned the carbs (5/11/13) - This didn't fix the throttle issue. The problem seemed to be exactly as it was previously. However, I didn't pull out the Pilot Screw to clean, so I might still need to do this. I posted another thread in the F4 forum asking for help with this issue... https://cbrforum.com/forum/cbr-600f4...t-help-146777/

Changed the plugs (5/18/13) - Things seemed to be a lot better. The bike fired right up, and the throttle issue seemed to be 90% fixed. Previously, I would just touch the throttle in neutral at idle and the bike would stall. Now, as long as I was slow with the throttle, all was good... not perfect, but at least ridable. So, I let the bike idle for a few minutes and then decided to take it for a quick ride. I rolled out of the garage, popped it into 1st, slowly gave it throttle as I let out the clutch... and it died. I couldn't get it started again and eventually flooded it. I finally got it started after I let it sit for awhile and started it with the throttle open, but it ran extremely rough for only a few seconds and died again. I never got it started again.

Reinstalled the new plugs (5/20/13) - I was asked to pull the plugs and snap some pictures. When I re-installed the new plugs, the bike sounded like it was going to start, then it backfired, and that was it. I played around with it for a little while. I noticed that if I crank it with the choke on for a few seconds... and then follow that with cranking it with the choke off but throttle wide open, I get a few sputters like it wants to start. Finally this morning, I did get the bike running before I left for work using the choke, no-choke/open throttle method. It ran poorly, and I had to keep on the throttle to keep it going.

New plugs (in order of cylinder) Note, #4 already has some carbon on it, and #3 is cleaner than the others...




Old plugs (random order)...

 

Always check the obvious, Coil wires in the proper order??

 

I thought maybe I messed up the coil wire order when I saw in the Service Manual that the firing order is 1-2-4-3 (being that I have them wired 1-2-3-4), but it was pointed out to me that firing order is different from the wire labels. The length of wire provided leads me to believe I have the wires in the proper order, as it would be a stretch for wire #3 to reach plug #4.

I pulled out the carbs again last night just to be sure i didn't miss anything thing there. Everything still looked good to me, but I snapped some pics in case someone might see something I don't.

The float needle valves looked good, but I guess I don't know what a bad one looks like. The diaphragms also looked good... no splits or pinholes. I did notice a small amount of fuel on the back side of diaphragms, which I thought was strange. So, I paid extra attention to make sure they were seated properly when I reassembled them.

I put everything back together and attempted to start the bike. It started for about 2 seconds, and that was it... never got it started again.

Here are the pics...

 

Might pull the coils back out and check that the spark plugs are seating properly in them and the springs in the ends are not corroded.

 

Pulling the plugs a 3rd time was what I was also thinking for my next step. Since the non-starting issue started directly after the plug change (and not the carb cleaning), I've got to believe that the problem has to be directly related to that... especially now that I've pulled the carbs a second time, can't find any issues there, and I still can't get get the bike to start (fired right up and idled fine after I pulled the carbs the first time).

Based on this, I'm thinking that the next logical step is to reinstall the old plugs since the bike was at least running originally with those installed. Is it possible that one of the new plugs went bad... does that ever happen? I get spark from all the coils/plugs when I test against the frame, but I'm not sure that necessarily means that the plugs are performing the way they are supposed to. Is there a better way to test the plugs?

 

Update... It runs!!!

Thanks to a roundabout post by another member on my other thread, I noticed some pictures I took when I was disassembling the bike showed some conflicting information. It only took me about 5 minutes to switch the tubes around to the correct positions. It took a bit of cranking to get it to start, but it finally did. I tried it again this morning, and it started right up. I haven't gone for a ride yet, and I still need to sync the carbs, but I'm confident my biggest problem is behind me now. Everyone on this forum has been REALLY helpful, and I am VERY thankful for that!

Correct configuration...




My configuration...