Issue with #2 Cylinder Again

[MarkD]

Hi again all, I thought I had success my success with #2 cold cylinder.But---bike still not running right. I've boiled #2 (PineSol), and cleaned all passages with cleaner and compressed air. They (I believe) are all clear. I've had carbs off and soaked and completely cleaned more than the usual 3X. Plug seemed wet when pulled. Compression is 150 lbs. in all cylinders. I switched plug wires #3 with #2, and #2 cylinder is still cold. It makes sense that # 2 carb is faulty, but after all my cleaning, it seems difficult to think it is plugged somewhere, but it must be?? There is fuel in the float bowl each time I remove the carb rack and look over #2 carb. I also inspected carb boot manifolds, and they're fine, I replaced them a few years ago. Getting very frustrated here. I've also replaced #2 spark plug to see if that was the culprit. No joy. Any thoughts? Thanks.

[Radioguylogs]

I know it was 0 degrees here in Presque Isle this morning, but what happens if you ride the bike? Does #2 warm up at higher RPM above idle?

[MarkD]

No riding up here in Michigan right now. I'm trying to put her to bed for the winter, but want to make sure she's all set for the spring. I fog the cylinders, add Strartron, etc., but have been fighting these carb issues since early November.

[bikerphil]

Maybe try a different pilot jet in that carb. It may be defective.

[cajun31]

Maybe try a different pilot jet in that carb. It may be defective.

I second that. The reason being I have been down this road and did all that you have done and still nothing. I bought a new pilot jet and problem solved.

[cajun31]

A bit more explanation as to why we say replace that pilot jet. This video from Andy's Motorcycle Obsession is one of the best explanations of how our carburetors work. Yamaha XS1100 Cafe Racer Project - Ep 17 - Carbs and Pod Filters Explained. You have stated that you have moved the spark plug wire from 2 to 3 etc... with #2 still cold on idle. Mike asked the question of whether you have ridden the bike to see if it stays cold. The reason being that as you increase the rpms the main jet comes into greater play. Andy explains that a bit in the video. I trust that you have cleaned those carbs as well as anybody could. These bikes run on a wasted spark system meaning that every time the coil fires it is firing in 2 cylinders simultaneously. Only one of the two is in the compression stroke so one of the two sparks is wasted. Doesn't hurt anything. The only thing left is at idle no fuel is being delivered through the pilot circuit which begins at the pilot jet. If not the pilot jet then it means you still have something blocking the pilot circuit. Andy semi draws the tunnel that the pilot jet serves and talks about being able to adjust that circuit via the pilot needle screw. Two turns out from fully seated should get something firing if the pilot jet is good. If I were working on those carbs I would take the pilot jet out of 3 and put it in 2 and vice versa and see if the problem follows the original number 2 pilot jet. If 2 remains cold then you still have a blocked pilot circuit and more cleaning is required. If that is the case invest in the gallon can of Berryman's and give that carb body a thorough soak.

[oldyam80sg]

Sometimes putting in a new jet will solve issues you have. I bought spares from Yamaha and have done that.

[MarkD]

Thanks, guys. I do have extra Mikuni jets in my parts, so I will get a new pilot jet installed, and check to make sure circuit is clear (again). Got family coming for Christmas, so will wait a few days. Thanks again, please stay tuned, and if anyone else has had issues like mine, I'm interested in hearing about your fix.

[thumperjsa]

I just had a problem with my #2 cylinder not getting hot. Well, it would heat up once I revved the bike to about 3K RPM. Cleaned the heck out of it. I still didn't fix it. I replaced the pilot jets, and in the process, it went up to 45s. Running like a champ since. The pilot jet hole is tiny, and it is easy to block that passage. I bought new ones from the Amazon Mikuni store. It costs less than $20 for 4 Mikuni branded. Thanks to bikerphil for the carb assist.

[MarkD]

Thanks, Thumper, I think that's my next move. I'm hoping it's not throttle plate seals, so this is my plan, to replace the pilot jet.After the gang leaves later in the week, I'll get them on the bench.

[cajun31]

Thanks, Thumper, I think that's my next move. I'm hoping it's not throttle plate seals, so this is my plan, to replace the pilot jet.After the gang leaves later in the week, I'll get them on the bench.

The butterfly shaft seals would cause problems but it would not prevent combustion. Having leaks on those seals or any vacuum leak for that matter effects your ability to finely tune the carbs in and synchronizing them.