Front cylinder backfire

SOURCE: virago cyl flooding xv700 1984

let me tell you how i check to see if the float and needle valve is working properley in a carb. take the carb off git a hand pump off a out board motor. hose and all take the ends off put the suction end in a can of gas and the outlit end to the gas inlit on the carb. squeez liteley on the bulb that should let you no if the carb is leaking some ware. if not then you no for sure that the problem is some were else.goodluck davidbaxley.

SOURCE: 2007 650 yamaha vstar popping through the rear cylinder exhaust

First off did you buy it new? Second has it gone through its break in tune up yet?Did you do the re jeting? My guess is it was re jeted wrong & neeeds to be re jeted again or could also need more air(upgraded air kit) or a tfi or power comand fuel mod.My bike also poped untill I did the air & fuel upgrades & them upgrades will also give you a much needed house power needed for this rig.


Bring it to a shop & have it looked at.......


Good luck

SOURCE: backfiring through the carb

Yes, the boots may well be the problem. The cracks can let raw air into the intake which leans the air/fuel mix. This makes the engine run hotter. Carbon build up on the head and pistons can get red hot and on the cylinder(s) involved, can ignite the incoming fuel shortly after the intake valve opens. To lessen the problem, replace the boots, burn only premium gas w/o ethanol, and install a set of spark plugs that are one heat range colder than the stock plugs.
A “very helpful” rating for this answer? Thanks!

SOURCE: motorcycle "back-fires" and often runs on one cylinder

Does the bike backfire only when the throttle is being closed? The carbs have a idle enrichment circuit. If the idle enrichment diaphragms are stuck in the closed position, the bike will backfire when the throttle is shut down. You can't remove these parts for cleaning without seperating the two carb bodies (and then needing to synchronize the carbs after reassembly). A trick that worked for me...fresh fuel, and some fuel system cleaner in the tank...ride the bike at highway speeds for 20 -30 minutes...repetedly rev the engine to a high RPM then shut the throttle closed. The repeted application of high engine vaccum to the enrichment diaphragms freed the stuck diaphragms and the fresh fuel cleaned any gum and varnish that caused the trouble. I've put 20,000 miles on it since then with no backfiring.

SOURCE: My FZR600 won't start. No mods, all stock. I got

it is possible that th eplugs might be fouled but it seems unlikely after only two weeks running-my fzr would foul plugs but it usually takes months not weeks-also the engine would start but run on2 or 3 cyls. I found using one heat range hotter than standard plugs helped,esp. around town you seem to have been fairly methodical on your troubleshooting-if you have fuel and spark the next thing to check is comp. -if the plugs are wet it is likely fuel not oil-when I first bought mine it had sat over winter and would not start -it turned out that the valve clearances had closed up enough that it was low on comp. when ridden frequently it was ok but as soon as the oil had drained off the cyl walls it would not start-squirting oil in the cyls. would get it started but I pulled the cams and set valves to solve problem-starts ok now but I don't use the choke-you could lift the cover and check your valve clearances -it would be a good idea on a bike that you just bought-don't give up -be methodical and check one thing at a time-when you get it going it will be worht it