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Sputtering at 5000 RPM
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Dallas
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Joined: Apr 22, 2009
Posts: 34

PostPosted: May 2, 2009, 8:07 pm    Post subject: Sputtering at 5000 RPM

Got a question for all of you. Just got a 79 650 with an 81 engine in it. Once it revs up to about 5000 RPM it begins to sputter pretty bad. Any ideas on where I should start?

Also, second question, I just saw a oil puddle on my left engine cover, cant seem to find exactly where it is leaking but it seems to be from the front middle of the engine, is there a known issue there ?

Thanks for helping the new guy.

Dallas
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yamaman
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Joined: Jan 04, 2007
Posts: 1638
Location: Perth Western Australia

PostPosted: May 3, 2009, 7:33 am    Post subject: Re: Sputtering at 5000 RPM

G'day & welcome to the board Dallas. Well you say it's a '81 motor, that engine should have the TCI, not points, but as it's a bitsa, we wont know till you tell us!

A first guess at that problem would be either float level or flow from tank to carb, it could be running out of fuel perhaps?
2nd guess could be to small a main jet, though we need more bike history again! The '81 standard had BS 34 carbs & the '79 had BS 38's. Check mikesXS site, they have a good carb checker to id the different carbs these came with!

Oil leak - behind the rotor? That could be crank seal!
Behind countershaft sprocket? could be the seal there, just tighten the sprocket nut, can stop it.
The other one is the clutch pushrod seal?

Once you've done your homework let us know whats going on, cheers.

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Dallas
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Joined: Apr 22, 2009
Posts: 34

PostPosted: May 3, 2009, 8:52 pm    Post subject: Re: Sputtering at 5000 RPM

So I took a look, I have the BS34 CV Carbs.

Dallas
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Jake68
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Joined: Mar 23, 2007
Posts: 841

PostPosted: May 4, 2009, 3:45 pm    Post subject: Re: Sputtering at 5000 RPM

Do you have POD Filters on your carbs? If so try it very briefly without them..So POD filters are incompatible with some XS Carbs because of an inner lip.

The crank seal isn't that much of a problem as the seal designed to replace and sold by Mikes XS has been re-specified without the locating lip, so its possible to replace this seal without tearing down the whole engine.

These old bikes all run better with high quality fuel filters. I'd take this opportunity to fit some. Briggs and Stratton are very good filters for this, I use 30 Micron.
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Dallas
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Joined: Apr 22, 2009
Posts: 34

PostPosted: May 4, 2009, 3:58 pm    Post subject: Re: Sputtering at 5000 RPM

Yeah, it has PODS. I do have inline filters also. I ran some seafoam and the issue seems to be a bit better, I finally have everything back together so I will be able to take it out today and check it out.

Thanks
Dallas
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xsleo
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Joined: Oct 28, 2007
Posts: 1528
Location: Earlville NY

PostPosted: May 6, 2009, 2:58 am    Post subject: Re: Sputtering at 5000 RPM

If you have an oil leak on the front and center of the engine, it could be the oil feed pipe to the head or the two bolts behind the pipe. snug the bolts down a little, on the pipe snug up the fittings.
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Jake68
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Joined: Mar 23, 2007
Posts: 841

PostPosted: May 6, 2009, 7:29 am    Post subject: Re: Sputtering at 5000 RPM

Dallas the problem you describe seems very similar to one that I had.

If your POD filters are of a certain type, they have an inner lip or step? perhaps that interupts air flow to parts of the carb needed for a CV to work properly. (Sorry I cant remember the exact details here) ..

Its also possible they are oiley or wet?
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Dallas
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Joined: Apr 22, 2009
Posts: 34

PostPosted: May 11, 2009, 12:37 pm    Post subject: Re: Sputtering at 5000 RPM

So just an update on the sputtering problem. I ran some sea foam through the engine to see if that helped. It didnt. I had a leaking left side petcock that was starting to leak really bad. I found that if I ran it in the reserve setting that it didnt leak. Once I switched that the sputtering began to go away. Im not sure if it was the petcock or some junk that got cleaned out by the seafoam (or a combo of both). But the engine is running very good now.

Thanks for all the help!

Dallas
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