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88 Yamaha Virago750: backfiring during idle; uphill ride has no 'guts'. new plugs, carbs & fuel lines clean, air filter ok. what should I look for next?

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Sink the care well help alot

Posted on Jun 07, 2017

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Hi, Bedofroses49 and the usual suspects are:
1. Severely discharged or a damaged battery should have 12.5 volts or more and be able to pass a proper "LOAD" test if necessary, you may have a preliminary reading of 12.5 volts or more but little or zero amperage the battery is faulty and must be replaced, AGM batteries fail in this scenario more so than lead acid batteries.
2. Check battery terminals for damage or corrosion, check the battery cables at "BOTH" ends for loose, corroded, or broken connectors, "INSIDE" and outside the cable harness, perform connector wiggle test and check cables with an ohmmeter if necessary.
3. Faulty main circuit breaker and or connections.
4. Faulty ignition coil and or connections.
5. Faulty spark plug, oil or gas fouled, wrong heat range or service type, wrong gap, loose in the cylinder head, broken electrode or insulator.
6. Faulty spark plug cables, leaking or broken, internal damage check for spark leakage in the dark.
7. Faulty ignition module, switch, CKP, MAP, CMP, sensor and or any connector in the ignition circuit could have corroded, loose, or broken pins/sockets
8. Burnt exhaust valve or air leak in the exhaust system.
For more information about your issue and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have a wonderful day.
ViragoTechForum com
Got Backfiring Tech Tips Inside Cobra Cobra USA
Yamaha XV535 Owners Workshop Manual
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YAMAHA XV535 Owner Manual

Posted on Jun 07, 2017

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6 Suggested Answers

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Posted on Jan 02, 2017

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SOURCE: 1983 FLHS starts and idles fine,pops and backfires when riding

In 1983 the carb used on this model was a kehin. They can be made to work well, with a couple of tweaks. First, on the top about midway, you will see a boss sticking straight up. Unless it has already been done, use a jabsaw and cut the top 1/8 inch off the top. Using a tiny improvised screwdriver, back out the idle adjustment screw which is down inside about a half a turn. Then remove the float bowl. You will see 2 tubes hanging down. Remove the rubber plug from the larger one and remove the low speed jet. The jet and the mixture screw are soft brass, so make sure you don't shred them. The jet has a number stamped on the end. Go to a knowlegble shop and get the next size up. For example if you have a 52 and they say the next size is a 54, that's what you want. Take the old jet with you and compair the size of the air holes along the side. They should be the same size. If not, they are selling you a jet for a cv carb and that will not work. (common mistake) Don't forget to shove that rubber plug back when you reassemble it. If I have your problem pegged correctly, the bike will be less cold blooded and the driveability will be much better.

Posted on Jan 06, 2009

  • 9 Answers

SOURCE: 2005 yamaha yzf 250-unstable idle

I had the same problem, Turns out that my shims were finished, replace the chims and check clearences.

Posted on Mar 12, 2009

  • 2 Answers

SOURCE: vstar 650 loosing power and missing during acceleration

check your coils and wires to them had same proplem and found 1 of the grey wires to the coil was disconnected

Posted on May 18, 2009

  • 9 Answers

SOURCE: won't idle steadily

Check the rubber boot that joins the carby to the engine to often have seen the hose clamps over tightened therefore creating a split in the rubber letting to much air in giving the rough idle eventually you wont be able to start it at all (have a good thorough look inside an outside of boot doesnt take much)

Posted on May 22, 2009

  • 4 Answers

SOURCE: backfire during shifting between gears

could be few probs, carbon build up on piston crown try a good cleaner fuel additive, your exaust is leaking or blowing allowing air to be sucked back in on revdown as well as you could have a inlet fault overfueling leaving to much unburnt fuel to enter your exaust, might be simple fix by just replacing the air filter and checking for burn marks around the air intake.

Posted on Jul 10, 2009

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Hi, Anonymous and the usual suspects are:
1. Fuel cap or fuel tank is not venting properly.
2. Fuel filter clogged.
3. Fuel line pinched or kinked.
4. Float needle and seat sticking.
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1986 yamaha royale venture...XVZ13DSC running a little rough when idle. Runs fine after up to speed... Backfires on delceleration sometimes... replaced spark plugs, all looked good with consistant tan...


The first thing that I would check is the choke. Is it sticking?? the backfire on decel indicates that it is getting to much fuel.
A new fuel filter is a very good idea but I would look at the old one and see if it is contaminated.
My concern is the fuel tank. If the carbs were done properly they should be fine. If there is a problem it could be rust in the fuel tank that is still polluting the carbs. I have had many bikes that age that require the fuel tank to be removed, cleaned and possibly coated inside.

I would also drain all of the carbs. Each float bowl has a drain screw and can be loosened up slightly to remove the fuel in the carb. Make sure to take a close look at the fuel that comes out to check for water or contamination.

I hope that this helps,
Steve

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