First post. 1981 XS650. The bike has a long history of sitting for long periods of time. I got it running 15 years ago after sitting for 10. Then, due to a family feud too long to describe, the bike sat again for until two years ago. Changed the oil, rebuilt and cleaned the carb and some new plugs and the bike fired up. It runs ok. Backfires some. I also notice that the exhaust report is louder from the muffler on the left side. I'm looking for some advice on where to start. Is it a muffler issue? An exhaust valve remaining open too long? Maybe a carb adjustment? Any suggestions would be appreciated.
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angus67
Welder's penetrate deeper!!
If you suspect the valves are staying open too long, adjust them, but not befor checking the cam chain. You might have a exhaust leak on the loud side
Are you sure it's not running on one cylinder and occasionally firing on the other cylinder?
So check the cam chain for ? Wear?Loose? Thanks
So one cylinder is getting more or less fuel and that cylinder is adding more power to the cycle???
Thanks
angus67
Welder's penetrate deeper!!
what is meant by this? if you don't know if you are running a cam chain or not, ....get a manual and read it.
You can check the temp of the header pipe and exiting exhaust to get an idea of the cylinder firing or occasional firing. A compression test could rule out many things.Scott
Welcome aboard! Post some pics of that bike when you can.
Two carbs, two cylinders and dual exhaust. Which side is acting up?
Two carbs, two cylinders and dual exhaust. Which side is acting up?
Left Side
As I said earlier, check your carb sync. Your carbs are bolted together as a "bank". The shafts that hold the butterfly plates also mate together. You have one throttle cable connected to the left carb. It opens both butterfly plates together because of the way they're linked. This insures both begin opening at the same time. But, they must also be open the same amount to begin with or one cylinder will be running faster or slower than the other. That will continue throughout the lift range. There is an adjustment screw on the shaft linkage between the carbs. This allows you to adjust the position of the right carb's butterfly plate and match it to the opening of the left one.
Idle speed is adjusted and/or controlled on these carbs by opening the throttle plates a very small amount, just a hair really. Adjusting the idle speed screw on the left carb opens or closes the left carb's plate, and the right carb's plate at the same time because they're linked. But, to get the same running speed on each cylinder, the two plate openings must be matched or "synced".
Idle speed is adjusted and/or controlled on these carbs by opening the throttle plates a very small amount, just a hair really. Adjusting the idle speed screw on the left carb opens or closes the left carb's plate, and the right carb's plate at the same time because they're linked. But, to get the same running speed on each cylinder, the two plate openings must be matched or "synced".
I'll add here on bench synching.
Any new to me carbs get bench synched to get the throttle plates as close together in their gap opening as possible. I borrow a couple of straight pins from the wife's sewing box and use them as a gauge. Place a pin under each plate and compare the drag or grip, you might say. I'll adjust that right carb to match the left carb if there's any difference between the two and only adjust the right carb.....only the right carb.....only the right carb...lol . Easy peasy.
Any new to me carbs get bench synched to get the throttle plates as close together in their gap opening as possible. I borrow a couple of straight pins from the wife's sewing box and use them as a gauge. Place a pin under each plate and compare the drag or grip, you might say. I'll adjust that right carb to match the left carb if there's any difference between the two and only adjust the right carb.....only the right carb.....only the right carb...lol . Easy peasy.
