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New to me S40 ,need to solve rough running issue (Read 185 times)
antmanbee
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4 Moto Guzzis and an
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Re: New to me S40 ,need to solve rough running iss
Reply #15 - 07/01/17 at 11:31:30
 
I've rebuilt quite a few carbs but I don't recall one this dirty in the jets and float bowl.
The butterfly valve and bore and exterior look like new. What a contrast.
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antmanbee
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4 Moto Guzzis and an
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NE Florida
Re: New to me S40 ,need to solve rough running iss
Reply #16 - 07/01/17 at 16:28:47
 
Well I got fresh oil and filter (rotella), Raptor petcock and a cleaned carb.

It runs better but still not good. I rode it around the block ant it was hiccuping and backfiring quite a bit even all warmed up.

I have the airbox out, so no filter, just the rubber air intake attached to the carb. The jets are stock size I am sure. I removed the idle mixture plug and the screw was all the way in. I backed it out a few turns till the bike idled higher and that helped a lot. I will be putting a uni filter on the rubber air intake so the engine intake breathing will be apparently more open than stock. I have a hard time believing that the stock is so restrictive that it would run so poorly with it removed.

Tomorrow I will remove the carb again and shim the needle as prescribed
by many here and see what that does.
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justin_o_guy2
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Re: New to me S40 ,need to solve rough running iss
Reply #17 - 07/01/17 at 17:28:52
 
Removed the idle mixture plug and the screw was all the way in.

That's new.. don't remember seeing that ever..
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batman
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Re: New to me S40 ,need to solve rough running iss
Reply #18 - 07/01/17 at 22:28:02
 
Without a filter the bike runs really bad,it is jetted lean  from the factory and removing the filter makes it much worse.a cone filter won't be much better you'll have to rejet the carb .
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my old work mates called me MacGyver
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antmanbee
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4 Moto Guzzis and an
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Re: New to me S40 ,need to solve rough running iss
Reply #19 - 07/02/17 at 05:06:45
 
I ordered one of the UNI filters. I don't think it will be much different than running without a filter jeting wise.

I got this,
https://www.amazon.com/gp/product/B000WJGTDG/ref=od_aui_detailpages00?ie=UTF8...

I will get a short piece of 2" schedule 40 PVC to attach it to the stock rubber intake tube. When I use a pod filter I always use the stock intake tube if possible to smooth the airflow into the carb or throttle body. Similar to a velocity stack.
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UNI_UP4245.jpg
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antmanbee
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4 Moto Guzzis and an
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Re: New to me S40 ,need to solve rough running iss
Reply #20 - 07/02/17 at 13:01:55
 
Well I got it running better today.
Pulled the carb and took out the white spacer from the top of the needle and ground it down about half. Put it all back together and I could barely get it to run at all. Pulled the carb again and checked the float bowl and it was still clean, but I noticed when I blew it all out with air there was liquid that would keep coming from one of the brass floats near to where it was soldered onto the bracket.
So I cleaned, sanded, wire brushed the float where the leak was and tried to get all the gas out of it and then attempted to solder where it was leaking.
After soldering I dipped it in a bowl of water and saw no air bubbles, so maybe fixed, time will tell.
Adjusted the float level to just slightly over an inch and popped it all back together and onto the bike.
Checked the fuel/float level with a clear hose attached to the bottom of the bowl and unscrewed the drain screw. Fuel level looks like it is right at the gasket level. When I re-jet I will probably lower the fuel level a bit more.

So it runs decently now but not great, but I will hold off re-jetting till I get it registered and my filter comes in and maybe until I can find a harley muffler.

I got other stuff to do on it like replace the 12 year old tires that look great, no cracking or anything as the bike was stored inside.
It also has the infamous bit of seeping of oil on the left of the engine where the head joins the block. I will probably get the aluminum plug for the fix but I will see how bad it is first.
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ohiomoto
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Re: New to me S40 ,need to solve rough running iss
Reply #21 - 07/03/17 at 05:48:17
 
I would throw the aribox back on and get it running right before I'd start jetting with that UNI.  If it runs right with the stock airbox, then you know the carb is good.  This will keep you from chasing your tail with the UNI.
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