noise in motor

[chevyman]

I have a 83 920 and at an idle it sounds great.but if i rev it up it sounds like a tapping noise or rattle but not sure if it sounds like a rattle just because of the rpms or not.But it rides great but noise at crusing speed no strain on motor and if i twist the throttle back it gets worst but it i let off of it it stops.Does anyone have any ideas it would be great.Im at a lost with this thing. Thanks Buddy

[bstig60]

The 920 is not a quiet engine. If its a tapping sound it could be the valve adjustment. The other thing could be detonation or Pinging. Try putting some premium fuel in it and see if the problem persists. What weight oil are you using?

[chevyman]

Im using mobil 1 oil 20w 50 v twin oil. Thanks alot some people i talk to said it sounds like a rispin noise but that would be odd because it only has 11000 miles on it wouldnt think that. well thanks again Buddy

[bstig60]

With the bike warm and idling, crack the oil line nuts for the cam shafts ione at a time and make sure they are getting oil. You should see oil seeping out right away. If so, then that eliminates cam problems. Unless it gets worse, I wouldn't worry about it. You might try going to www.viragotechforum.com and post the question and see if anyone has had something similar. There are several thousand Virago owners there from around the world.

Bill

[chevyman]

Well I did check and see if any oil is get to the cams and yes they are.Thanks for everything I will go to that web site and see what i find thanks buddy

[chevyman]

I started my bike and at a idle it sounds great. but when i rev it up to about 2500 to 3000 rpms on and off real quick you can hear the noise. and going down the road at about 3000 rpms or higher it does it but not all the time but most of the time,does that make since.I puilled the plugs and the back one was a tanisk color and the front one was white and i check the front one for spark and it is getting a deep blue spark but didnt check the back one.Im waiting for a responce from that web site so i can post looked through it but nothing.The noise sounds like it is coming from the back jug or left side somewhere not sure really.Any help? Thanks Buddy

[bstig60]

Both plugs should be tan in color. If the front one is white, increase the pilot screw adjustment by half a turn counter clockwise and see if the color changes. White on a plug is a sign of overheating. Like I said with the noise, its really hard to try and diagnose it without hearing it. Since the XV engines are noisy by nature, unless you are overheating, not getting oil to the cams  and are running the proper heat range of plugs, I would not worry about it. If it concerns you, I would suggest taking it to a local shop (not a dealer), and have someone listen to it that works on vintage bikes. Where are you located?

Bill

[chevyman]

Where is the pi;ot screw at im pretty lost on that stuff. I call auto parts store and cross ref. the plugs and they are the same heat as the book calls for.I located in fleming county kentucky. Buddy

[bstig60]

It is located on the bottom of the carb toward the end of the carb farthest away from its cylinder. This is the low speed adjustment mixture screw. The high speed mixture is adjusted by adjusting the floatlevel.. The link has pictures. a href="http://viragotechforum.com/phpBB/viewtopic.php?t=2126">http://viragotechforum.com/phpBB/viewtopic.php?t=2126

Bill

[pofarm]

I just bought an 83 920 that has what sounds like the same noise, only it is coming from the front cylinder. It's so bad that you can hear it at idle and gets really loud at higher RPMs.
My 82 750 is starting to do it on the front cylinder, too. It doesn't happen all the time on it, though, and I can't hear it at idle. It only sometimes makes noise when it is under load and 3500 RPMs or higher.
My 750 is real easy to start without the choke and runs out real well. I haven't has the 920 out to see what it does from a cold start.  

[bstig60]

As previously mentioned, it could be detonation caused by overheating. Check the plug color after you run it a few miles. The color should be tan or darker. If it is white, then you will want to richen your mixture. Fuel mixture is used the assist in cooling these engines, particularly on the rear cylinder as it has a restricted air flow.
Make sure you are using the proper range of plugs as well. Personally, I use Autolite AP63 Platinum plugs gapped at .028 thousands. I find they have better performance, are more resistant to fowling and last longer than the stock NGK plugs.

[chevyman]

So from the pics I guess these adj.are inside the carb right?
     Buddy

[chevyman]

Well I went to web site about carbs and I took a black vacum hose and cut it and hook to bottom of carb like it said and i open the drain screw and held the open end to at the crack where the bowl meets the carb and nothing on either one but when i lower the tube to where gas comes out it is only about 1/4 way up on the bowls is that right.Im i doing this right or not? Thanks Buddy

[chevyman]

Im using the same plug auto lite 63 also but mine is in the front cylinderthat the plug is white.

[bstig60]

I guess a black hose would work if you used it that way, but you should use a clear hose so you can see the fuel level. The fuel level should be 1-2mm below the gasket line on the bowl. If fuel is coming out 1/4 way up the side of the bowl from the bottom, you are running way too lean. The adjustment requires taking the bowl off and bending the tab on the float.