[Jason Pittenger]

Actually, since posting this a few days ago I actually notice the clacking to be way more noticeable when the motor is cold AND the temperature is cold, like low 50's or even high 40's. So the problem is that after 18 year and nearly 25,000 miles, the automatic cam chain tensioners (ACCT's) are starting to go. So I will replace my ACCT's with MCCT's (manual cam chain tensioners). You can get them on ebay for pretty cheap, but I went with the MCCTs from TOC MFG.

I was going to say when mine started to go, it would clatter on a "cold" start even when the temperature was in the 60s or 70s and would go away as the engine warmed up.

BTW, if you like the exhaust pops on upshift, I tuned my ignition to run -10 degrees during deceleration. It reliably pops on decel now! People behind me say they can see it in the pipes at night.

 

[Jason Pittenger]

How did you do that? Is there a way to adjust timing on these bikes after all?

I'm still chasing my decel pops. The little 'blat' I get when upshifting sounds pretty cool, but the decel popping on my bike has always been outrageous. I've done everything mentioned here for addressing that but am intrigued to hear of a timing option. My coast enrichers are fine, my EGR system is gone and plugged up tight and I've addressed all the exhaust leaks I've found. The only way I've been able to get rid of decel pops is having the idle set higher than 1100. But then I'm basically not decelerating either which, needless to say, can be scary when trying to slow down. 😁

I put an aftermarket ignition controller on my bike. I then ran some extra vacuum hoses to T the two vacuum ports together into a MAP sensor. The controller senses engine vacuum and adjusts based on load. Long story short, if you put the hoses and MAP sensor on like I did in the first link, the module is otherwise plug-in-play. I even left my factory controller installed in case something went wrong, but 1.5 years in I've had no issues with the new module. The rest of that "diary" is me waxing on about my discoveries along the way.

Here's the process for the extra vacuum hoses.

Linking Vacuum Ports On Both Carbs

For reasons outlined in another thread, I have linked the two vacuum ports together. https://www.vn750.com/threads/ignitech-sparker-tcip4.106338/post-1293974 I noticed some rev hang. Pinching off the linking hose causes the RPMs to rise slightly. I backed out the idle screws from 2.5 to 3...

www.vn750.com

And here's my "diary" on the process of tuning the ignition.

Ignition Advance and Vacuum advance using an Ignitech...

UPDATE 5/3/2022: Stock timing with 8,700 RPM rev limiter now available for download! This provides a much cheaper option to replace the OEM ignitor. It also helps with hot-starts by driving the ignition coils harder during cranking. EDIT: For the sake of those reading this many years in the...

www.vn750.com

Overall, the change gave me a slight bump in MPG (2-4 more), which was the motivation for the project. Not fuel savings, but increased range on a tank. But the additional benefits are well worth it in my opinion. I bumped the idle timing from 5 to 7 degrees. This allowed me to close the idle a bit more to maintain 1100 RPM, giving more deceleration than before. With the settings I'm running, I pull the ignition timing back to 10 degrees after top dead center (which causes popping) BUT it also further reduces the residual power during deceleration causing an even faster RPM drop. The engine overall feels a lot more responsive. I set up a 2nd ignition table for when I'm running on choke. This controller can change timing tables with an external switch. It runs significantly retarded ignition timing in this mode, causing it to idle at 1500 on choke, as well as rev down almost as quickly as the original bike off choke. It makes it MUCH more predictable to ride on choke.

 

[Jason Pittenger]

Ya, it's not for everyone. I can always go MUCH more than 10 degrees after top dead center to get the decel performance without the pops. It doesn't pop after 25 or so degrees after top dead center. I think it lets me go to 99 after? It's almost like a spark cut on decel then.

I forgot another benefit, I can connect a laptop to the serial port and sync the carbs by reading the vacuum. I just pinch one carb hose or the other to get a reading from each carb.

Also, it adds timing if the RPM drops below 1100 and subtracts if it rised above 1100. It stabilizes the idle RPM so I never have to touch the idle adjustments knob as it warms up.