Author Topic: Rev limiter or TCI?  (Read 148 times)

SonnyT

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Rev limiter or TCI?
« on: September 22, 2020, 03:16:09 PM »
Started my bike up and while still on enrichener, tach dropped to 0 and one cylinder quit firing. Lasted about 10 seconds then went back to normal. Did it two more times then ran normally. Did not check which cylinder was misfiring. From reading past posts I understand that when it is a rev limiter problem it does not affect the tach. Does that mean it is probably the TCI? I hope someone can clarify this for me.

jefferson

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Re: Rev limiter or TCI?
« Reply #1 on: September 22, 2020, 09:25:50 PM »
It would be real simple to remove the rev limiter wire from the plug and see what happens. Might get lucky.

briandneville

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Re: Rev limiter or TCI?
« Reply #2 on: September 25, 2020, 10:17:23 AM »
I experienced similar symptoms with a backup TCI that I installed to see if it worked.  I had my bike running and fully warmed up with a TCI that I know to be good (for now at least) and swapped in the backup.  The bike started fine and ran fine for about 10 seconds, then the tach went to 0 and the engine sounded like it was running on one cylinder.  I revved it a bit and let it idle for about a minute, then turned it off and started it up again, which it did but still on one cylinder.  So I put the good TCI back in and the engine ran normally.  I then put the backup TCI back in and it worked fine.  Sounds like your problem.

From a long conversation I had with Fiat Dr (who I bought my Vision from), I believe the tach runs from the TCI and I have heard from multiple sources that a symptom of a failing TCI is the tach going to 0 or bouncing around (I experienced this once about two weeks ago with my 'good' TCI, which is why I'm asking on another post about aftermarket TCI units).  Since the tach is electronic, it going to 0 while the engine is turning would indicate an electrical problem.  Fixing a broken TCI seems like a lost cause though there appear to be some people who have tried this.  Used units are easy to get, but who knows if they will work.

I've been told that riding a Vision anywhere w/o a spare TCI in the tail hatch is unwise.   Seems like you should find one and try it out.  Maybe your problem will be gone, or maybe it'll be gone anyway, with the current TCI.   40 year old electronics can't last forever.

Since the rev limiter grounds the spark to the rear cylinder (I have read this, I don't know this), it doesn't seem like it would affect the tach, so it doesn't seem that the rev limiter is the problem, but as Jefferson pointed out, it's an easy thing to eliminate from the equation and worthwhile regardless.

Hope this is helpful
How did it come to this?

SonnyT

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Re: Rev limiter or TCI?
« Reply #3 on: September 28, 2020, 09:44:40 PM »
Thanks for the response. It has done this only once. Rode it four times after and it ran fine. Removed yellow/black wire at TCI and it still runs fine (three rides). I do have a spare TCI so if it starts doing it again I'll replace it and see what happens.
Thanks