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Running on one cylinder


Spike101uk
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Hi guys,

 

My 125 Virago is going to garage for service tomorrow but would like some advice so I have a rough idea what to expect, basically

The front cylinder runs fine but rear one doesn't at all, so I swapped the leads round and now neither starts, anyone know what would be the problem, it's been Sat around for 4 months

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Just go to a mechanic, it's either a compression problem, spark, or fuel. A mechanic will be able to tell you which one of those it is in just a few minuets, then you can go about fixing it in whatever way you want. The chances are this is an easy fix, it usually is. 

Like Blackhat said, it's more than likely old fuel blocking jets and stopping the rear cylinder from getting fuel. You need to rebuild both carbs, clean them out with a solvent and reassemble as the owners manual dictates. Machines do not like to sit, engines. cars, bikes, even lawn mowers don't survive well if you let them rot, an engine lasts best when run reguarly, otherwise fuel goes bad, seals dry out, ect ect. 

 

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Been to mechanic and he said due to a great big hole in filter box of exhaust it's affecting the back pressure and that's why it's only running one cylinder, however, when I was checking the leads before it went in, I swapped the leads over and nothing started , does that mean there is the problem with the rear cylinder ht lead and or whatever that connects to. He didn't check that he said he changed plugs and fuel and drained carbs.

When I say I swapped leads I mean the lead going to the cylinder that started I put on one that didn't and vice versa

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That engine will run without an exhaust, not efficiently and loud but running all the same, yet another mechanic talking bollocks.

Have you swapped the plugs across the cyl. The rear cyl gets pretty warm and that can shorten the life of the plug, cap and lead. 

Have you checked the cap has a good connection. Or take the plug cap off and just offer the end of the lead to the tip of the good cyl (reccomend gloves and insulated pliers as it can give you a good zaping,your talking 50000v). Should get a nice blue spark.

 

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You went to a mechanic with a bike that didn't start and he didn't check for spark? You're going to a shit mechanic. Like Cynic said you don't need the "correct back pressure" to run the engine. My utterly fucked YBR ran with no muffler or cat for longer than I like to admit, and didn't skip a beat for the entire time. 

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Started at higher revs, still sounds like a poor spark to me. May not be but start easy and checking the spark is engine diagnosis 101.

Basic steps, go to a halfrauds and buy a Haynes manual. Not sarcasm, nor taking the piss, its the first thing I do with every vehicle I have and it will save whatever it costs plus interest the very first time you work on the bike. Even if it just lets you know where the odd bolt is that you would not find and cause you to break stuff. Yes there are better manuals than Haynes but it is millions of percent better than nowt and the more comprehensive workshop manuals like the one for my TDR assume workshop knowledge which I'm assuming you don't have.

It will also give part specs for your oil, plugs etc, and quantities and some even give fixes for common problems on a long running mark.

Short quick checks, the plug caps swapping the leads across cylinders may or may not work, depends if your bike uses 1 or 2 coils. Don't know personally. 

You need to check for a spark on the rear cyl, easily done by putting the plug (use the one from the cyl not a substitute and DONT clean it either just as it comes) against the engine firmly on an unlaquerd part of the bike. Again be carefull, and crank the engine. All the better if it starts and see what spark you get.

All you need to do that is a plug spanner and a rag, the spanner will be in the bike tools if your bike has some.

 

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Words of wisdom above, the manual will save you time money and frustration. We all need to start somewhere, might be an idea to say where you are in the world you never know some kind soul might live nearby and be willing to help out for a cup of tea and a biscuit.

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The basics spike,  if you have a spark,[ on both ,]  fire some propellant  in the back of carb [ that's not running] if it runs , then its a fuel problem ,

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23 hours ago, Spike101uk said:

Also is the 250 virago featured in the Haynes Manuel, as ain't they the same bike as the 125 with regards to everything but cc size 

Nope, the Haynes doesnt include the xv250 eaither

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