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tbounds02
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VBMWMO #8592
Joined: 07/30/2013
Posts: 118

My right cylinder keeps backfiring on deceleration not bad but enough I have gone thru carbs ,tightened intakes no air leaks I can find ,adjusted valves . Bike runs great just annoying backfire only right cylinder can timing be cause ? Only one side plugs appear to be running rich on both sides I haven't ridden much since purchase been sorting out . Ridden less than100 miles ,does anyone have a website on how to check timing ,I know bike has a points backing plate that enables use of gm points supposedly easier to adjust
Thanks for your help
Tony

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6898
Best to check timing with an

Best to check timing with an inductive timing light. You'll need to use another vehcile's 12v battery to power the light since the bike is 6v. Look for timing marks at idle and especially at full advance. You may see a split image in the window, indicating differential timing. That could be why the problem is on one side only. Typically if the difference is less than say 6-7mm, you can adjust the timing to split the difference. More than that, you'll have to look into making modifications to the cam shaft tip (should be done by an expert) or maybe your advance unit is worn out.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Vin
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Dayton, Ohio
Joined: 08/30/2012
Posts: 264
You should check your timing.

You should check your timing. It is possible that is the source of your issues. Check the Ben h Mark Works website. I believe Vech has a tech article there on magneto and points timing. I I believe his article tells you how to do it with an ohm or multi meter. That is how you will need to do it when you are setting the timing. Then you can verify with a strobe timing ligh. But for a quick che k right now that will not involve taking anything apart you can use the strobe light . That will tell you qucklyicif you have an issue. I bought a relatively cheap strobe inductive timing light from Sears. It does run fine off the /2 6 volt system but it will drain the battery so a charging will be needed afterwards. Or as Kurt suggests pull up next to a lawnmower or something with a 12 volt and hook your black and red lines up to that battery. Then hang the inductor line on one of your spark plug wires and remove the rubber timing hole cover on the bike and shine the light at the hole. At idle the line above the S should be at the case mark and you should only see one S or perhaps the S will look like it is bouncing a little. That iz good timing at idle. Now roll the throttle on and the F mark should roll up into the hole and as you rev it the line above the F should come to rest at the case mark. That means timing at speed is proper. Again you want to see one F mark or see the F only slightly bouncing around. If you have two images your differential timing may be excessive probably due to a worn advance unit. Vechs article explains this too. My bike has a little differential timing so my right plug is darker than my left plug. To compensate I set my left side a little with a little advanced timing and my right side is then only slightly retarded and that clears up the darker plug on the right. ThT is what split the difference means. Without doing that my left side would be timed exactly causing my right side to be too retarded with a dark plug. So I just advance the left a little to bring the right side timing closer to perfect but still slightly retarded. If you find an issue with your timing by using a light you will need to dig in with a multi meter. It is not hard but I find it very time consuming. Others may be a lot faster. The quickest I have ever set my tkming was 2 hours. But the first time it took me a lot of tinkering and figuring. If you have to go that route and Re not sure what to do come back and ask.

Vin

tbounds02
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VBMWMO #8592
Joined: 07/30/2013
Posts: 118
backfiring

You all were exactly correct timing was retarded on both sides bad , Vech didn't know how it even started. That new tool he has is so neat for setting timing makes it simple for a dummy like me.

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