Ignition advancer flat spot.
 

Hello all. My first post here.
About ten months ago I had a +4 ignition advancer installed, Adjusted the TPS, removed the PAIR and synced the carbs. It was all good, ran great, noticed the increase in HP. Then about two months ago while riding down the freeway it started stuttering from 4K to 5K. Below 4 is great and above 5 is great but in that range it seems as if it's not getting fuel continuously. So I took it to the shop. They said I needed a new converter unit. They wanted $600 so I ordered the part my self an installed it. Same problem. I did a little research on the net and I found, on these forums, this post https://www.superhawkforum.com/forum...86&postcount=5
Any of you had a similar problem?

Just have to ask, but...
 

So, right, yes - the problem arose after a couple months, but I just have to ask...
You sure you got a good aftermarket ignition advance? Here's a link to my post I made about getting a bad one that I wrote about last May: https://www.superhawkforum.com/forum...ad.php?t=14246
I had a flat spot all the way across the power band though. Take a look at the pics and see if you remember seeing a backwards 4 or a right triangle or not, before having had the ignition advance installed.
Other than that, with time going along and things being alright, I'd say something a long the lines of an air leak has come about.
I had a very severe flat spot in the area that your referring to in the power band when I had my bad advance in, and had put stock needles in, with DynoJet jets in (195/185). So when the stock Honda jets came in, that aggresive flat spot went away.
These are just notes to throw out there. I know your problem came up out of nowhere. But this has been my experience when I had a bad flat spot come about after some fiddling and a bad ignition advance.

Thanks for your reply!!
I'm not sure about the marking on the advancer. A bunch of SH riders had a get together to do some mods on our bikes and the organizer was the one who did all the tech work.
What leaking air would cause such an issue. I'll check everything of course.
So you're flat spot went away after putting in the stock jets, replaced the advancer or both?

The question on the air leak is a good one. And I have yet to research in the forums here for the most common area for an air leak to appear on our aircraft. ...I'm suffering from a probable intake leak myself; as I can't get the carbs to remain synchronized when pulling the RPM's out of idle, and the RPM's "float back down" when closing the throttle (Minimal/poor engine braking).
But I'm sure the most common area for an intake leak would be the front and/or rear carburetor boots (The points where the carb's mate to the intake portion of the heads.). Next would be where the carbs mate to the airbox.
My problem with my flat spot arose because I was using stock needles with DynoJet jets. This was my only way of getting by with things while I fiddled my way back to stock settings in the carbs. (I purchased my VTR with a DynoJet kit installed and it did not come with the stock parts.) Anyhoo'... This all was while I had the aftermarket ignition advance installed (EDIT: No, I had a stock ignition advance in there - sorry). The condition of my severe flat spot in the 4-5krpm range was based strictly on the fact that stock needles and DynoJet jets were used in conjunction with each other.
So in answering your question "So you're flat spot went away after putting in the stock jets, replaced the advancer or both?", my flat spot in the mid' range, that had appeared was because of the carb' part incompatibility and went away after going all the way back to stock parts in the carbs. But because of all variables being considered (And not to confuse anyone - more importantly, myself), I bring up the topic of carbs, because they are influenced on gasoline and air intake. The funny thing about this all is, is that your flat spot revolves around a performance coincidence that I had in the same rev' range - but based on different conditions. Anyway, things returned to a more normal state across all of the power band when I had a stock ignition advance installed. ...The 4+ degree ignition advance that was replaced by the very courteous people at Factory Pro has since been installed, and I have had no problems.
Another note on the side is the installation paperwork that came with my VTR from the previous owner - the hardware tech' that installed the DynoJet kit (I think it was 195/185 and on the 5th clip) and the 4+ ignition advance took the bike for a test drive after he installed both of these; and put in his notes that the bike "seemed flat" all the way across the board (Rev' range/powerband).
My point with throwing all of this out there, is to hopefully get some ideas jogging about a probable cause, or area of interest to dig into, to get a fix going. Hopefully I haven't done to much confusing damage. Maybe someone has some input they'd like to share. I'm sorry this isn't so well checked for proper grammar etc, but I gotta cruz'...
...Maybe one of the vacuum diaphragms wasn't seated properly in one of the carbs and it finally got tugged loose and has caused a minor air leak that makes this condition sympathetic to the 4-5krpm range.

Thanks again for the reply. You have definitely given me some ideas. I'll keep you informed my findings.