Motorcycle will not turn over, Advice?

Question

82 Yamaha Virago 750. Two nights ago, after making some repairs, it fired up beautifully (though it was idling at 3000 RPM for some reason). I shut it off and left it for the night. Next night, I fired it up, it idled at 1000 (normal) then when I hit the throttle it climbed to 4000 then sputtered and died. Now wont start.

Battery fully charged. Recently dismantled and cleaned the carbs. Spark plugs arc when tested. Clean fuel flows from tank to petcocks, and from petcocks to float bowls. When I try to turn it over the starter motor revs and revs, I can hear the engine cranking, but the bike will not fire up. Occasionally it catches once and fires one piston.

I am fairly certain that the fuel is getting into the combustion chamber, as there is an occasional small backfire out the tailpipes, but I could be wrong.

Other things I have checked - the throttle cable and choke cables are limited correctly. The choke is open, kill switch to ON position, petcocks set to PR (prime). Advice?

I dropped the bike two weeks ago. It worked fine for a week, then quit. That's when the trouble began. I removed, dismantled, and cleaned the carbs by soaking the parts for an hour in brand new carburator cleaner. I checked all openings, gaskets, and hoses for signs of wear, damage, or obstruction - it was all clean as a whistle. During a spark test I noticed air was jetting out of the side cover when the engine turned over. Inspection revealed a broken part on top of the clutch cover (not a crucial part, thank god!) The part was a threaded cap with a gasket which retains compression in the engine, but allows access to remove the clutch. I replaced this part two nights ago, and the engine fired right up. Now, nothing.

in response to dogebetto - When I try to fire the engine up, it sounds like the starter is spinning and cranking the engine (ie, moving the pistons, etc), but occasionally, it will sound like the motor is just spinning really fast and gnashing teeth. Could that be a symptom of the problem you described?

Answer 1

Sounds a little like an air leak. Check the manifold (the rubber bit between the airbox and carb) for any cracks or leaks. A little bit of air coming in will make it very difficult for your motor to keep running. If it does run, it may vary wildly in rpm, and show signs of running lean. If it was running, or if you can get it running, set it to idle, then spray WD40 all around the rubber part of the manifold. If the rpm rises on its own with the WD40, you've confirmed and located your air leak.

Good luck!

Answer 2

The early Viragos were infamous for starter problems. When you say the starter revs do you mean it spins? Typical of the Viragos was the starter would spin but the gears inside the starter would spin and not turn the crankshaft. Inside the end cap of the starter is an orbit gear that is pressed into the cap. This gear would spin with the starting gear instead of providing the required resistance for those gears to mesh with to turn the crank. A cheap, but temporary, fix was to shim inside to apply pressure to the orbiting gear. The best fix was to tack weld the gear to the end cap. If your bike does not have this problem you can bet the house that it once did.

Answer 3

--After cleaning the carbs, can you say "positively" that the pilot jets are clean?
If you don't know what the pilot jet is, that may be your problem.
Look inside the fuel tank with a flashlight.
Any rust or junk floating around could re-clog the carbs.
--When you re-installed the carbs, the manifolds might not be sealed properly to the engine.
--The vacuum tube on the manifold could be leaking.
--The hose may not be on the tube or is leaking (remove it from the bike and check it).
--Change the spark plugs.
Semi fouled plugs will spark when testing, but the spark will blow out under compression.
--Check the valve adjustment - tight or leaking valves can produce erratic RPM changes and backfiring.

Answer 4

I'd like to know what you were repairing when this happened, and why you needed to make the initial repair. It sounds like a carburetor issue, did you use all new gaskets when you cleaned the carbs last? What did you use to clean the carbs? How were the air cut off valves and accelerator pumps?

Answer 5

Your greatest situation feels like inexperience. The extra you journey, the extra gentle and able you would be. somebody pronounced a motorbike driving course, it incredibly is an suggestions-blowing thought. you additionally can prepare in an unused parking zone (department shops, church homes in the course of the week, faculties on weekends). i'm an previous fart, (sixty 3) yet I remember my first motorbike became a 500cc Honda. i began out out doing only what you defined. It wasn't till I have been given some suggestion from a pal who were driving all his existence, and time interior the saddle, that i began out to enhance right into a miles better rider. you are going to be able to desire to remember, you're element of the gadget. Your physique place alongside with the mechanics and geometry of the motorbike will be sure the way you negotiate those turns. the subsequent time you're driving in the present day down the line, attempt changing lanes and pay interest to precisely what occurs. you're stepping into the present day. you opt for to alter lanes. you're interior the miraculous lane. You push slightly on the LEFT cope with bar. Lean slightly to the left. as a results of fact the guidance geometry takes over, your motorbike starts off to head to the left. on the suitable time you push slightly on the miraculous cope with bar and lean slightly to the miraculous. on the suitable time you development your physique to the upright place and steer in the present day forward. you only replaced lanes. yet think of concerning the way you began the maneuver. Pushing on the left cope with bar ought to make you change suggestions-blowing. yet once you furthermore mght lean to the left, your motorbike is now driving on the left fringe of the front tire. it incredibly is the way you initiate the turn. Your physique is an quintessential element of the geometry of the motorbike's guidance. only save driving and training. you will get the carry close of it. Be risk-free and continuously placed on a helmet.

Answer 6

1985 Virago 700 ratbike here.
Check the oil level in the engine. If there's too much, let some out. My motorcycle won't hit on the rear cylinder if there's too much oil.

Answer 7

carb needs work