Motorcycles, Snowmobiles, Go-Carts, ATV's and Golf Carts - 85 Virago xv1000

Ok I just bought this bike a few months ago, and when I ride it, it backfires sometimes. A friend of mine that dabbles with motorcycles told me it was not due to the carb but due to the after market pipes put on by previous owner. He said that I will always have that problem as long as I have those pipes on and should put on the orginial pipes. Well I priced them and they are expensive. Now before I go out and buy them I would like a second opnion. I think its the carb that needs to be adjusted. What do you all think?

Most likely it's a carb adjustment. I bet it only backfires when you let off the throttle? That is a lean condition on the pilot circuit. A bigger pilot jet or an adjustment to the carb's fuel screws would help. Most manufactures have "tamper proof" plugs made of brass over the fuel screws to prevent someone messing around with the emissions of the bike. These need to be removed to adjust the screws. (someone may have already removed them when they installed the pipes you have) Usually you can adjust the screws without removing the carbs, look for a small hole with a brass flat head screw in it towards the lower front or underneith the carbs. One for each carb. Turning the screw clockwise will lean out the pilot and counterclockwise will richen the pilot circuit. You want to richen it

This is very common for the Viragos. (even with stock pipes) When does it backfire? Just cruising? On acceleration? On deceleration?
What year is it?

its a 1985 xv1000 it back fires when I am changing gears so I guess when I let go of gas

I may be off base here, but if my memory serves me right, it seems the Virago uses an air induction system. What this does, is feeds fresh air to the exhaust at or near the cylinder head (where the pipe connects) In theory, this fresh air is to dilute any unburned gas going out the exhaust to reduce the emissions. The air is controlled by a set of reed valves to open and close with each "puff" of exhaust. It seems they are also "piped" into the intake so on hard deceleration the reeds remain closed. It was such a fine tuned system that any variances, such as age or modifying any part of fuel/exhaust system would interfere with the operation of these reeds. Going back to the stock exhaust would help the "poping" but because of the nature of the system probably won't fix it completely. The only true fix would be to go back to the stock exhaust and replace the reed values which could get costly as you saw with the price of the exhaust. But without testing the system my advice would only be an educated guess.

So what's going on with this and the aftermarket exhaust? There is a certain amount of back pressure in the exhaust and when an aftermarket pipe is installed, this back pressure will more then likely change or be reduced affecting the opening and closing of these reeds, thus feeding more fresh air to the exhaust gas then should be... result, a lean condition, noted more on deceleration (when you want this fresh air to be shut off). One thing we used to do (even though not exactly legal because of emissions) is the 2 heavy rubber hose (usually inside a coil); we would block these lines by stuffing a large tight fitting ball bearing into the hoses. This would eliminate the induction system all together. Although it would fix the lean pop it would introduce a rich back fire which was usually not as bad as the lean back fire. So this was not a proper fix, but one that sometimes worked better with aftermarket pipes installed. For a quick test, you can locate these 2 hoses and just clamp them off with a couple small pairs of vise grips or hose clamps. Then take it for a drive to see if the condition improves any.

I make no claims to your fixing the problem and any advice you try, it is at your own risk. (I just need to say this because this is not supported by Yamaha)

could be time to have the valves adjusted??

the aftermarket pipes on your bike may have been installed without a re-jet performed on the carbs. many times a re-jet is necessary to keep the proper fuel/air mix and if not done can cause backfire and other symptoms. i'm still learning myself so i could be way off...