Motorcycle Safety & Driveability: Carborator cleaning/rebuild, yamaha virago xv 535, virago xv 535

Question
Hello.  I am a new motorcycle rider and new to motorcycle repairs.  I just got my first bike in july, took a motorcycle class and got my license.  I bought a used motorcycle and suspected that it needed a carburetor rebuild and cleaning.  I contemplated doing it myself, but opted to have a repair shop do it, given that although I am familiar with car repairs it is my first bike and don't know what to expect.  (just to let you know the bike would stall when the choke was turned off until the bike warmed up and it did not seem to have as much power as I thought it should).  The bike is a 1993 Yamaha virago XV 535 with 10k miles on it.  After the repair the bike had much more power and given what the mechanic said, relay need a cleaning and such.  He said one of the floats was such, one of the jets (I think, i could have been just an air or fuel line in the carb) was clog to the point that he needed drill bit to clean it, and the carbs were far from being synchronized (dual carbs).  Although, immediately after the repair the bike seemed fine, the performance started slipping again.  It would state with the choke off until warm and I felt small hesitation and coughing at low throttle.  I took it back and was told to put premium gas in for now and to drive it for 500 miles or so until things stabiles and he would readjust things then.  After a period of time things did get much better and have stabilized.  It still has a couple of issues although.  The main one is there is still small hesitation/coughing at low throttle and large hesitation/coughing until the bike warms up (which is the season we are in takes a little bit).  I took the bike back, but made the mistake of telling him that the bike was back firing (which I consider to be the same issue as back firing, but other may consider to be completely different)  and he made some minor adjustment, I think.  He told me that the bike was not backfiring (which I had taken, at the time, to mean after his adjustments).  Anyways, I took the bike home and still found the small hesitations and low throttle and large ones until the bikes warms up.  I have also discovered that the throttle adjustment is all the way out (meaning if I wanted to slow the idle down a little I would not be able to).  That in it self to me sounds like things are still not adjusted correctly or there is some clean in the carb that needs to be done.  Additionally the acceleration sounds funny (almost a gurgling) under harder accelerations.  It sounds good at lower accelerations.  Finally the bike does not go faster then 75MPh.  Not that I drive that fast, but I have done it to test the bike out.  

Ok now the questions.  Does this sound like the carbs need a relearning or could it be something else (I have not tried changing the spark plugs, air/fuel filters, yet)?  Should the bike cough or hesitate like I have described at low idle or when still warming up, even colder temperatures (temps between 45F-60F)? The hesitations/coughs are very light at the low idles. The fact that the idle is max out is suspicious.  And finally what about the acceleration and max speed for this bike (I am 175lbs.)?  Should I take the bike back?  What should I tell him?  Each time I have picked the bike up he has said the bike is running great.  (This repair shop has been recommended by a couple of people, so I don't think that he is intentionally playing with me)

thanks for your help. Let me know if I can clearify anything.

keith


Answer
Keith,

Thanks for the question.

It is not unusual for a bike to have a bit of a cough and hesitation while it is warming up. In fact, this is very common for V-twin engines. I have a 920 Virago that is in perfect tune and it does the same thing. So here's a new term for you: "cold blooded".

When someone says their bike is cold blooded, that basically means it runs poorly when the engine is cold. Once it's warmed up all the way, all is good. Basically, you have a cold-blooded bike. 535's are known for that, so don't worry about it.

As for the constant trips to your mechanic, I think you could solve this in a few steps. Not really cheap steps, but it can be fixed.

First off, the idle being set so high is not good. Basically it sounds like your mechanic has worked around the steps below by just jacking up the idle. It's not good for your engine, and wastes gas. The bike should have a good, slow, lumpy idle that you can almost count the pulses. If it sounds like a sewing machine at idle (running fast), that's not right.

Since your bike sat for so long before you got it, the carbs really got blocked up. Since your mechanic had to drill them out, that's not a good sign. Also, drilling out a carb can alter the way it works, usually for the worst. It can be done "right" but what you really need to do is have the carbs rebuilt.

That means new jets, new gaskets, new fuel lines, and a solid cleaning, sometimes called a "dip" since the carb bodies are dipped in a rather caustic liquid that removes all the old fuel buildup but is also tough on plastic and rubber parts.

At the same time, you need to just clean-slate the bike with a new air filter, new oil, new spark plugs, new oil filter and a new fuel filter. If the bike has not had a valve adjustment while you've owned it, it's probably due for one. At the same time, the timing needs to be checked and adjusted to spec.

Basically, you need a complete tune-up and a carburetor rebuild. I think if you get those two things done, the bike will run as designed, and should get up close to 90mph for a top speed. A 500+cc bike should easily top 75mph. After all, that's the speed limit on Nevada highways (and other states) and my old Honda 250 could go that fast with a bit to spare, so your bigger Virago should do that easily. Since it can't, something is not right.

I'm not trying to say your mechanic is trying to cheat or decieve you. But after so many trips, the bike is not running right to be sure. You need another opinion. Take the bike to a Yamaha dealer and tell them what you told me, and look into the cost of a complete tune and carb rebuild from a Yamaha-certified mechanic at the dealership. It might not be cheap, but if you get it done and then take care of your bike, it should be good to go for another 10,000 miles (except oil changes) before another tune-up is needed.

As for being cold blooded, it probably always will be, but a complete tune-up will help that as well.

Good luck,

Bill Roberson