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virago only fires on one cylinder

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virago only fires on one cylinder

trxstunter
I have a 1982 yamaha virago xv750j   It doesn't fire on the front cylinder.  I have tested the stator, pick-up coils, ignition coils and lead wires,  I checked and cleaned all my connections and put in new plugs.  The dealer will not test the CDI box,  and I don't know if the CDI would do that.  Any help would be greatly appreciated.  Oh I did find a nick in one of the wires going to the front cylinders pick-up coil, right near the coil,  I don't see where it could have been hitting but I fixed that with electrical tape for now  but it tests good before and after the fix.  I would sure appreciate any help.  Thanks.
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Re: virago only fires on one cylinder

jlathem
You may want to have someone check the synchronization of the two carbs. If they are out it could cause one or the other to act like it didn’t fire.
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Re: virago only fires on one cylinder

david roupell
In reply to this post by trxstunter
Sounds like a fuel prob to me.  Remove front splug and turn engine over with tissue in it's place, if it's dry after you'll know.

I'd be inclined to change that wire too.
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Re: virago only fires on one cylinder

bhaas488
In reply to this post by jlathem
I have the same problem. I was told it is the timing. Did you get your to run?
Please email me if you know what the problem is?  Brad Haas
haas@sktc.net
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Re: virago only fires on one cylinder

GreenHorn1
In reply to this post by trxstunter
I have the exact same problem with 1 thing different-- the front cylinder kicks in when I really give it the throttle and you can REALLY feel the difference--it takes off like a rocket--i've had the carbs cleaned out by a professional shop and balanced, 2 new plugs all new hoses brand new battery wiring seems ok from what I see--hmmmmm....
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Re: virago only fires on one cylinder

yamaguzzi
you might want to go over the vacuum lines anything that carries air  and the intake boots,,with wd40  to see if you cause any change to the rpm. that would be the location of part ,if not, the whole of the problem,,good luck,,keep us informed yg
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Re: virago only fires on one cylinder

woodburner
In reply to this post by trxstunter
I had this problem on july the 30th and rode the bile home on one cylinder 130 miles.  It made for an interesting trip!  Tryed everything and finally replaced the cdi module and that cured the problem.  Good Luck
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Re: virago only fires on one cylinder

Number_67
I have a 1982 XV920 with the same problem. No fire in the front cylinder, but after the bike warms up the front  starts to fire intermittently. I checked the coil resistance, coil wire and cap: all within specs. If I pull the coil wire and put in a plug I get a thin purple spark across the gap.

The joint at the right muffler leaks a fine gas vapor and the pipes blow a fine white smoke which smells like gas. My petcock diaphragm is shot so I have to pinch off the fuel line when I shut off the engine. I think I'll rebuild the carbs next. Anyone know where I can find the beginning adjustments? Also, besides the float level, what could cause too much fuel in the cylinder?

Thanks
George
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Re: virago only fires on one cylinder

Geoffrey Gogan
In reply to this post by trxstunter
I just posted a reply to a similar prob at 10:26, Sun night, Feb 8.  It had to do with potential vapor lock from a clogged breather tube from that carb back through the frame.  
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Re: virago only fires on one cylinder

slugears
In reply to this post by trxstunter
hello mate i had a similar problem.i found out that a pick up coil wire insulation had worn away in the casing and was earthing out,causing miss firing,get a voltimeter and unplug the conection and check the pins that go into the cdi unit to the engine casing and see if you get a reading.
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Re: virago only fires on one cylinder

Number_67
In reply to this post by Number_67
I found that the front carb was my problem. Sometimes the bike would fire and sometimes I really had to crank the throttle to get the front cylinder to "catch". Couldn't find an electrical problem so I rebuilt the carb. No change. Then the second time around I found that the vent hole in the side of the float bowl had been almost toally plugged with some white cruddy gas residue.

Cleaned it out with solvent and a torch tip cleaner and now she runs like a house on fire! Just in time for spring riding too.

Good luck,
George
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Re: virago only fires on one cylinder

dive4bugz
I have the same problem with an '89 xv1100. The bike starts up and idles on the rear cyl only. When I crack the throttle up to 1500-2000 rpm, the front cyl starts to kick in. Both carbs have been gone through, replaced the CDI box and the coil. No better, and I'm tired of spending $ on unnecessary parts. I am going to check the breather tubes and such ASAP... any other suggestions will be greatly appreciated... thanx...
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Re: virago only fires on one cylinder

bill.stigall
In reply to this post by trxstunter
This is a typical symptom of TCI failure. Due to the heating and cooling and vibration, the components tend to deteriate over time causing intermittent problems. There is a guy in San Mateo, CA that rebuilds them. Go to www.viragotech.com and search for TCI rebuild and you should find his contact information. There are two types of TCI's used on early Viragos, one is the Metal case type which has long pig tails, which you probably have; and the other is a plastic case type that has plugins on the unit and no pig tails. There is a guy in Illinois who rebuilds the latter unit. Both charge around $100 bucks which includes shipping.
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Re: virago only fires on one cylinder

trikesg
In reply to this post by trxstunter
Hi

I have recently got a xv750 (13 years old) and on occasions it does as you have described fires only on the one cylinder and then when the revs are cranked up it seems to fire up and go fine, i have replaced coils and all wiring has been checked over and all connections replaced. pick up coil tested and all fine, ignition box checked all fine, it was suggested to me that it could be a problem with the fuel as it only seems to be doing it when the fuel gets low in the tank, have run system cleaner through and checked injectors and all clean. Fuel is getting to the cylinder so only thing i can think would be carb or breather pipes. but only intermitant fault will sometimes do it and other times not. any other suggestions, and hope details have helped others
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Re: virago only fires on one cylinder

bill.stigall
Try adjusting your idle mixture screws (pilot screws), to where you get the best idle, then sync the carbs. It's also possible that you have some junk in the fuel bowl. Try draining it into and clear bottle to see if there is any sediment. If so, you will need to remove the carbs and clean them. Then clean your fuel tank and add an inline fuel filter if it doesn't have one.
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Re: virago only fires on one cylinder

trikesg
In reply to this post by trxstunter
Thank you for the advice will give it a go today, will any standard carb cleaner do the job or is there something more specific to use?
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Re: virago only fires on one cylinder

bill.stigall
Carb cleaner should work, but don't get it on the rubber or neopreme parts as it will eat them up. Use pressurized air to blow out the passages if you have to tear the carbs down.
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Re: virago only fires on one cylinder

trikesg
In reply to this post by trxstunter
I have a bit more of a serious problem than i thought, few puffs of black smoke from the exhaust and a little more white smoke than norm, upon removing the air filter found oily deposits in the tubes and inside where it goes down into the carbs in the frame. when i consulted the haines manual it suggested a carb overhaul for the choke, poor acceleration and carbon build up, then a possible overhaul on cylinders as piston rings might need doing, any ideas on a rough sort of cost for the work to be carried out?
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Re: virago only fires on one cylinder

bill.stigall
A compression check will tell if there is problems with the rings or valves. Black smoke is too much fuel. White smoke can be moisture, oil or a combination of the two. Oil smoke is usually blue. How many miles on the bike?
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Re: virago only fires on one cylinder

trikesg
In reply to this post by trxstunter
there is just over 12000 on the clock, although the bike was stood for 10 months or so not being used, i think a good clean on the fuel system is in need as there is some deposits in the bottom of the tank, so maybe it has been pulled through, have taken the previous advice and brought an inline filter for the tank and it is having a carb refresh early next week, also ran some fuel cleaner through, how much would i be looking for a decent compression tester? and how easy is it to complete.
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