XV750 cylinder failure, 1981 Virago

**tourist76** · 3rd June 2013, 22:29

Hi there, looking for some advice guys. My trusty 1981 xv750 virago is having the front cylinder failures when riding. Runs fine when stationery and for the first couple of miles on the road, then the front cylinder begins to cut out.

Whats been done to try & fix it:
Spark plugs changed (old ones were also fine)
Coil lead replaced
Coils swaped around
Tank clean n reseal
Taps/ petcock seal and diaphrams new
Hoeses check on fuel and vacoom
Fuel filters changed
Carbs cleaned and balanced
Problem occurs even when running in pri position so probably not a vacoom issue

**ducatilover** · 3rd June 2013, 23:35

Do a compression test

**cynna** · 4th June 2013, 00:41

my xv400 i had about 20 years ago used to do this. took it to two different bike shops - one said it was electical and the other said iy was the ypis (or what it was called). ended up trading it in - spent a lot of money and never got anywhere.

**unstuck** · 4th June 2013, 07:13

Like loverboy said, get a compression test done.

**pete376403** · 4th June 2013, 19:24

can the carbs be swapped?

**carburator** · 4th June 2013, 19:50

Originally Posted by tourist76

Hi there, looking for some advice guys. My trusty 1981 xv750 virago is having the front cylinder failures when riding. Runs fine when stationery and for the first couple of miles on the road, then the front cylinder begins to cut out.

Whats been done to try & fix it:
Spark plugs changed (old ones were also fine)
Coil lead replaced
Coils swaped around
Tank clean n reseal
Taps/ petcock seal and diaphrams new
Hoeses check on fuel and vacoom
Fuel filters changed
Carbs cleaned and balanced
Problem occurs even when running in pri position so probably not a vacoom issue

TCI issue... to run well they need FULL voltage..

**Warr** · 4th June 2013, 20:36

Had a similar issue with my XJ900. 80's vintage, but could be you are experiencing a CDI fault as I did.
My easiest advise would be, locate a replacement CDI unit.
The originals are a sealed unit and with time the solder connections inside start to corrode and go 'dry joint'
Because the XJ900 is an IL4 I was able to confirm that 1/2 my unit was faulty.
By swapping the sensor wires and the CDI > coil wires I could swap the fault from 1 pair of cylinders to the other pair.

I opened my CDI sealed unit by removing the epoxy resin and re-soldered the joints. Followed by cleaning the visible parts of the circuit board and resealing the unit.
Fortunately my efforts were rewarded and the fault cleared.

Another option I would recommend, much easier and one I would pursue today would be contact this Trademe seller to see if he can supply a CDI unit for your bike.

**tourist76** · 4th June 2013, 23:25

Forgot to mention compression test already done and all good. Will try the cdi check if i can switch the wires over to the other cylinder. Also will try Check the float level with the clear tube method.

Will keep this thread updated, thanks fellas.

**tourist76** · 5th June 2013, 23:00

Originally Posted by tourist76

Forgot to mention compression test already done and all good. Will try the cdi check if i can switch the wires over to the other cylinder. Also will try Check the float level with the clear tube method.

Will keep this thread updated, thanks fellas.

Ok, looks as though the cdi cant be flipped around between cylinders... Going to look for one to borrow so i can make sure, before i throw $250 at it.

**ducatilover** · 5th June 2013, 23:13

I'd agree with checking the cdi unit since you've taken all other logical steps

**Theantidote** · 10th June 2013, 21:21

have you had a look at viragotechforum ...http://viragotechforum.com/ some of the guys on there really know the xv inside out...and being yanks it's a bit polite...

but worth snooping around

**ducatilover** · 11th June 2013, 19:18

Could be worth checking the valve clearances too

**Grumph** · 12th June 2013, 13:12

The ignition pickup wiring is known to get faulty with age on those things.
Worth pulling the sidecover and examining the insulation.

**Theantidote** · 12th June 2013, 21:04

Originally Posted by Grumph

The ignition pickup wiring is known to get faulty with age on those things.
Worth pulling the sidecover and examining the insulation.

just read about this online and makes some sense...
i'm following this coz i to am having probs with a viagra that's started playing up....

**tourist76** · 14th June 2013, 07:29

Hey there, an update on recent checks which were done to try n identify why this 1981 xv 750 (virago) runs great first 2 km then cuts out, has a 5 min rest and ready to go again for another 2 km etc. etc.

Whats been done since the last post:
Carb floats checked using the clear tube method
CDI replaced
Wiring from the CDI to the left engine cover found to be exposed and contacting the metal where it comes out from behind the clutch cover.

Many thanks to all those submitting ideas, going through them slowly guys (have 3 kids that compete for time with the bike :-)
Many thanks to Jim Doherty in Lower Hutt for lending his advice and parts