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xs650 > > Motorcycle Systems > > Engine > > Running on one cylinder only ...


Running on one cylinder only ...
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nobradovic
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Joined: Jun 25, 2008
Posts: 17
Location: Belgrade, Serbia, Europe

PostPosted: November 3, 2008, 10:43 am    Post subject: Running on one cylinder only ...

Hello everybody. Only few km (about 20 km) after rebuilding, my engine is running on one cylinder only (left one). I checked electrical systems, and everything is fine on both cyl. I have spark. When engine is cold, everything work perfect, but when she reach working temperature (few km), right cyl. fails. I didn't recheck valves. (just 20km), or retorque the head. I did whole top end rebuild, including valves. Boyer ignition, brand new. Dellorto PHF36 carbs, brand new. Can anybody help with sugestion, please ??? Maybe, left intake valve loose it's clearance, and there is no fuel, when its worm up.

XS 650 SF '79
in: 0.05 mm
ex:0.15 mm

Thanks in advace, dear friends.
Nicolas.
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Retiredgentleman
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Joined: Mar 03, 2007
Posts: 2258
Location: Calgary, Alberta 1978 XS650 SE

PostPosted: November 3, 2008, 1:34 pm    Post subject: Re: Running on one cylinder only ...

Check the simple things first. How do the spark plugs look..............is one wet? You could try putting in new plugs. Are you sure the petcock is delivering fuel to both carbs? I guess you have a new coil as well.............are the plug leads new or used?
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RI_rider
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Joined: Jun 25, 2006
Posts: 36
Location: narragansett, rhode island

PostPosted: November 3, 2008, 2:15 pm    Post subject: Re: Running on one cylinder only ...

I had that same problem a few months ago, but mine was the left that would shut off after it got warm. i bought a new spark plug, and it fixed it.
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Jake68
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Joined: Mar 23, 2007
Posts: 841

PostPosted: November 4, 2008, 12:20 am    Post subject: Re: Running on one cylinder only ...

Get the other one running and it will really haul ....

Sorry..I couldnt help that..

First off..swap the plugs over..does the broken cylinder change sides? If so..RI has got it nailed..

You said you used the boyer ignition, which if new and running their setup means that its not ignition. They have one effective coil which fires both..Check the leads first, then check the compression with compression test meter..do this when its warm and only running on one pot.

Hopefully compression is close between the two..

y Boyer will run on both or not run at all. The coil is a basically singular.
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nobradovic
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Joined: Jun 25, 2008
Posts: 17
Location: Belgrade, Serbia, Europe

PostPosted: November 4, 2008, 8:41 am    Post subject: Re: Running on one cylinder only ...

Thank You All !!! There are a lot of clever suggestions here. In a meanwhile i fixed the problem. I went to my garage last night, and after closer examination, I found that my brand new fuel filter is faulty, and there was just a few drops of gas coming from it. So, I have just removed it and put a new hose, without filter. And that was it. I thought that the symptoms was proportional to engine temperature, because, when I start the engine, she was working properly for a 5 minutes, until she has been used all gas from the carbs. When I left her for a few minutes (i was thinking that I wait for her to cool down), some fuel filled the carb, and then she have been working again for the next 5-10 minutes, depending of riding style.

any thanks to everyone, especially to Retiredgentleman, because he was the closest to the solution. ("Are you sure the petcock is delivering fuel to both carbs?") I was running Mikuni BS38 with fuel balance pipe before Dellorto, so it was enough that one petcock have been working properly to have some gas in both carbs. Now, there are two separate carbs, with separate fuel lines.

r. Retiredgentleman, I really admire Your help and competence on this forum, really !!! Thanks again to everyone, to your prompt answers.

PS. I will post the pictures of my bike soon. I really want to know your opinions.

Nicolas
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Retiredgentleman
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Joined: Mar 03, 2007
Posts: 2258
Location: Calgary, Alberta 1978 XS650 SE

PostPosted: November 4, 2008, 1:40 pm    Post subject: Re: Running on one cylinder only ...

Glad to help out nobradovic, get your bike all tuned up and post some pictures.
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