Reminder to XJ newbies with pods: check your enrichment circuit and your air screws!

Hi folks, just a reminder for newbies to double check your enrichment circuits and your air screws, even if you think your problem is your pods.

I have been lurking here for two years, and very grateful for the wisdom available in this community.

I also wanted to share two problems I solved on my XJ750 Seca that has pods:

Problems I was experiencing:

My 1981 XJ750 Seca with 12k miles would be very hard to start cold, even at a pleasant ambient temp (80 degrees F, 25 Celcius). The bike would only reliably start I cracked open the throttle fairly aggressively - about 1/3 turn (that's a lot) - and let the engine zoom up to 3-4k rpm, and hold it there for 10-15 seconds for the bike to warm up. The bike starts just fine when it is already warmed up. Of course, I knew that this cold start procedure was wearing the engine (high revs with cold oil = bad). Because the PO put pods on it, I suspected that the pilot circuit was too lean, and it needed a larger pilot jet size.

My second problem is that once started and warm (often using starting fluid), the bike would idle at 1500rpm fine. Any lower, however, and it would slowly decrease and die. It would never idle around 1100rpm.

As for problem #1 (hard to start when cold), I though had already cleaned the carbs perfectly, and I was convinced that it needed a larger pilot jet. Of course, because I had never checked the valves, and that is so frequently recommended, I did that to be safe. I ended up making small adjustments (0.05mm), and it didn't change my cold start issue.

I pulled the carbs again, and then realized I never checked the enrichment circuits which are actually in the carb bowls. All four enrichment circuit tubes/wells were completely clogged up!

After clearing out the wells (using carb cleaner and a torch), the bike started up immediately with NO throttle and only a bit of choke (enrichment)! Perfect. The enrichment circuit is so clean now, it only needs a very small amount of the choke "plunger" to move in order to be effective. In fact, when the bike is warm, adding too much choke will kill it (this never happened in the past).

I never changed the pilot jet, and I don't expect I will need to do so.

As for problem #2 (idles around 1500rpm and no lower) - I finally bit the bullet and purchased a Gunson Colortune. I drilled out the factory plugs and was surprised that the air screws were NOT all at the same 2.0-2.5 turns setting. Two cylinders were definitely too rich (too orange), and I was able to use the Colortune to easily dial them into a strong blue color (and my plugs were black when I pulled them, and I should have known earlier to check them).

The bike idles perfectly now around 1100 rpm, and even lower if I choose. That Colortune was $50 well invested!

Note to those interested: I tried to listen to the idle and adjust the air screws by ear, but to no avail. I'm a musician, and I think I like to have good hearing, but I couldn't do it. The Gunson would go from orange to blue and orange, with only a very subtle change in the idle sound.

Many thanks again to everyone for the great information on this site. I hope that this helps any owners who are overthinking their pods. Check your enrichment circuits in the carb bowls! Check your air screws!

 

I pulled the carbs again, and then realized I never checked the enrichment circuits which are actually in the carb bowls. All four enrichment circuit tubes/wells were completely clogged up!...................Mine were the same, I missed them first time I stripped the carburettors. After that and shim adjustment it runs perfectly.

 

If you think the Colortune was good value , buy yourself a Morgan Carbtune to synch the carbs , then you will be really impressed , cheers