1989 xv535 rear cylinder misfire at 5000rpm (UK)

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sideshowgaz
Posts: 3
Joined: Wed Jun 09, 2021 3:32 pm
Location: Preston
What Virago you Own:

1989 xv535 rear cylinder misfire at 5000rpm (UK)

Post by sideshowgaz » Wed Jun 09, 2021 3:51 pm

Hi all

I am hoping someone one here might be able to help me diagnose an issue with my bike. It misfires badly at about 5000rpm and above, and it appears to only be affecting the rear cylinder. After a few miles, the misfire gets worse and eventually runs pretty much on only 1 cylinder. Removing the plugs shows black soot on the rear, and the nice brown on the front. Also, the rear exhaust pipe has a lot of black soot in the end compared to the front.

I have an aftermarket black widow exhaust, which is sold as plug and go. When I had it MOT'd the mechanic balanced the fuel mix. I have replaced the spark plugs (gapped) and the coil pack. It has a new battery and has also had a new regulator/rectifier. Both tanks have been cleaned out with tank cleaner and it has a new fuel filter. I also stripped, cleaned and refurbished the carbs. that being said, that was last year, before it was stored for the year

When I got the bike it was in a basket and had been stripped and standing for 5 years. The previous owner is my father so I know it has not had any crazy mods in the last 15 years, but it also means it is harder for me to identify if 1 fix/change has caused this issue.

I know if fails at about 5000rpm because I have a digital speedo and tach, but I have disconnected it just in case it was drawing power.

I am hoping that because it is quite a specific issue which I couldn't find here on the forum, that someone who knows a lot more about this than me might be able to help out? I only passed my test last year, so I am by no means an expert.

Any help would be greatly appreciated.

baldchicken
Posts: 37
Joined: Wed Jan 01, 2020 5:40 pm
Location: Salem OR
What Virago you Own: '97 535

Re: 1989 xv535 rear cylinder misfire at 5000rpm (UK)

Post by baldchicken » Thu Jun 10, 2021 12:24 pm

I am wondering if it is the TCI....

I recently read this article (Below), and it states that a defective TCI could cause such issues.

https://www.viragohelp.com/virago-ignition-systems/

"TCI Symptoms can be pretty strange. I had 920 which would start easily but would begin to run badly when it was half warmed up. Then things would straighten out and the bike would run just fine (until one day it didn’t, and I went ahead and replaced the TCI.)"

"An occasional ignition problem which defies intuition, involves the tachometer on the Virago. The tachometer takes its signal from the TCI wire to the #1 coil on early models or from the same circuit inside the TCI on later ones. Once in a while a tach will develop a short, and this plays hell with the signal. As a result the back cylinder starts to misfire. Doesn’t happen often, but keep it in mind if this is your symptom and everything else checks out. The quick test is to disconnect the tach and see if that corrects the problem."


Hope that this helps.

sideshowgaz
Posts: 3
Joined: Wed Jun 09, 2021 3:32 pm
Location: Preston
What Virago you Own:

Re: 1989 xv535 rear cylinder misfire at 5000rpm (UK)

Post by sideshowgaz » Thu Jun 10, 2021 12:43 pm

Cheers for the reply baldchicken. I sincerely hope it is not the TCI, because they are way over £200, that being said, if that is what it needs then fair enough. I'd like to know if there was any way of testing for sure before shelling out. I'll happily test the sidestand switch disable though as that should be easy enough to do.

I'm planning on checking the float levels in the carbs this weekend as I believe that can be done on the bike, and if no joy, then the carbs are coming off for a strip down and inspection. Fingers crossed

baldchicken
Posts: 37
Joined: Wed Jan 01, 2020 5:40 pm
Location: Salem OR
What Virago you Own: '97 535

Re: 1989 xv535 rear cylinder misfire at 5000rpm (UK)

Post by baldchicken » Thu Jun 10, 2021 1:49 pm

We are in the same boat my friend...

My bike is doing some crazy stuff... like it will run for half a mile (almost on the dot), and then start to sputter out. I am working on replacing the cheap stuff (carb rebuild, test coils, replace gaskets, etc.).

The last resort will be the TCI, which the way my luck goes, that will be the issue.

sideshowgaz
Posts: 3
Joined: Wed Jun 09, 2021 3:32 pm
Location: Preston
What Virago you Own:

Re: 1989 xv535 rear cylinder misfire at 5000rpm (UK)

Post by sideshowgaz » Thu Jun 10, 2021 2:07 pm

You are not having to charge the battery each time are you? I had a faulty rectifier, so when the battery lost voltage the bike would run like a pig. Recharged and fine again each time for a short while

I replaced the rectifier with a cheap faulty one and ended up getting a decent one from a yamaha parts supplier, but also had ro replace the battery as it had drained too many times

baldchicken
Posts: 37
Joined: Wed Jan 01, 2020 5:40 pm
Location: Salem OR
What Virago you Own: '97 535

Re: 1989 xv535 rear cylinder misfire at 5000rpm (UK)

Post by baldchicken » Thu Jun 10, 2021 4:10 pm

For charging the battery, nope.

I went for a ride with my daughter, got half a mile and it died... I pulled it over, tapped the carbs and nothing fixed it. Waiting about 20 minutes, then it started right back up running great. Then on the way home (half a mile) it died just as I was coasting up to my driveway.

So I initially thought that it was the coils, as I heard rumors that they can go bad, and show similar symptoms when they start to heat up. Also heard rumors that there could be a faulty gas cap (venting properly).

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