So I didn't want to hijack MM900RR’s thread but I am having an issue similar to him as my #2 cylinder was running about 100-150 deg cooler than the rest. I did some initial tests on the coils and everything seemed to check out (at the time) then pulled the carbs again and did a deeeeep clean ultrasonically. Put it back together, sync’d them nice and tidy like then started the idle drop procedure. Everything went well until I got to the #2 carb. No amount of adjustment would change the idle at all. So I took the temp at the header and just like before still running cooler than the rest.

After chattin’ with MM900RR I decided to take another look at the coils. So when I got home from work I pulled both coils and proceeded to break them down as far as I could and test each piece alone. The in groups as I put them back together. Started with the left coil (2&3) and no surprise the numbers checked out. Then I tore (not literally) into the right one (1&4). Checking the primary side first thing, bam, matched with the left coil. Checked the secondary side, and checked again, and again, and again. NOTHING, numbers will not appear no matter how I connect the probes! So I tear it down like the left one, started with the secondary side of the coil and bam, matched just like the left one. Then I check plug wires, bam, numbers match. Then on to the boots, #1 checks out. Hook up number #4 and nothing! Tried another MM as well as different probes still nothing. So I peek closer at the plug side and see a perfect slot for a flat head. Stuck one in there and cracked it open. Tipped it over on the table and had a spring, barbell looking ‘resistor’, and the retainer screw fall out. See pic below (if it attaches). Checked the boot again still no continuity. Opened the other boots and only the resistor and screw came out. The springs are snuggly retained inside the boot. Further inspection of the spring that fell out, I found some discoloration at one end (circled in the pic).

Now here is where my logic gets defied! I used care taking the coils off the bike and didn’t have any issues with the #4 cylinder. Now, where the spring seats in the boot, it is almost rock hard so I cannot see it getting damaged by removing it off the bike. Now I got to get a new boot before I can finish troubleshooting my #2 issue.

Let the new new saga begin!




*edit* - Reread this post and realized I may have not clear enough in expressing what was in my head versus what I wrote out. Basically I can’t understand atm how #2 checks out electrically but #4 doesn’t when I was having an issue in the #2 circuit not the #4.

 

Well got another set of coils to boots coming so hope I get everything else figured out by then.

 

Well I cut open the bad boot to see if I could figure out why it became non-conductive. The best I could figure is the spring is seated and held in the boot cup by the plastic/resin when placed in the mold injection. At some point it must have gotten hot enough to unseat itself enough from the plastic/resin in the cup, breaking the continuity of the boot. With my luck I can completely see that this could have happened (during the Carb Sync) right before being removed . Hence not having a number 4 issue before removal and then not having continuity after removal. I have included some pictures to reference with my thought process on this.


Boot Cutaway




Boot Cup




Boot Cup Close-up

 

Ok got the coils today and did a once over on them just like I did on my set. I started with the 1-4 coil first and guess what. Never mind don’t guess, it checked out with the same problem as my set did. Coil and #1 side checked out good but the #4 boot also had zero continuity! Opened it up, just the screw and resistor slide out. For a moment I thought maybe the resistor or screw wasn’t making proper contact inside. But I gave the boot a little shake by my ear, heard it rattle, then gave it a little tap on the side and out slid the spring. I know luck is luck but it would be really nice to have more good than bad. I finished testing the other coil and components, all good.

So To get a good 1/4 coil set I took my #1 boot stuck it on the eBay #4 wire and BAM!, had 48.4k ohms. Switched out the coil pack with mine and still pulled 48.3k ohms on the secondary side.

So I’m off the put them on the bike and see what happens.

 

So I am still working through my number two circuit issue and this struck me as odd. Hoping maybe a misprint in the diagram or clarification as the order in which these parts are drawn seem incorrect to me.




Looking at Item 1 (o-ring) in Item 6 set screw (Pilot), shows it is placed second after the small washer. Pretty sure when I pulled them out for cleaning the o-ring was on top of the washer on top of the spring and that’s how I put them back in. Seems to me that would be proper as the washer then protects the o -ring from the spring during adjustments and such.

 

Correct. It should go, o-ring, washer, spring then F/A mixture screw.

 

Thanks for the confirmation!

 

So this question is off topic from it’s intent but does tie into this thread as a possible source to this issue or potential future issue(s).

How important is the heat shield A &B in the picture below? My bike has not had it since I got it.

 

So I’m still chasing down a final answer/cause to my issue. Seems like I get one thing corrected (or functioning better) a different issue pops up.

I took the carbs back off, opened them up removing everything I could without splitting them down. Re-inspected and blew out all passages, ports, and surfaces I could see. Every passage had the relative same resistance (or lack of) as it’s equal counterpart carb. Leaving me to believe that it’s clear as clear can be visually and audibly. Once reassembled I looked at the butterfly valves and noticed the #2 carb was visibly out it alignment with the others.

Checking the #2 butterfly position with a feeler gauge I found out that when seated (at rest) it completely closed off the circuit while the others where left in a more open position than they should be. First, I now know that I need to sync my carbs with a proper sync tool (vacuum gauge set) and not my DIY tool that doesn’t provide a specific readout. Secondly, this makes it understandable why at idle the #2 circuit would not get any hotter than 200-225 deg. So I re-bench sync them and put back on the bike.

Now at idle there is a little lop to it and the number 2 circuit is still running cooler than the others but is heating up beyond the previous 200-225 deg range. The #2 pilot screw still does not change the idle speed at all. When riding there is a small hesitation in acceleration (first 1/3 throttle) but runs great beyond that. I wouldn’t think that a bench level sync would throw off and idle or cause that much of a hesitation.

Anyone have any thoughts beyond what I’ve mentioned so far as to a possible cause perplexing me?

 

The bench sync is the 1st step. You also need to perform a proper vacuum sync with the bike running and a set if sync gauges or tubes.
You will be amazed at the difference that makes.