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Discussion Starter #1
My SV 650 (1999) was running a bit rich so I decided to lower the float bowl height slightly.

I then put in new plugs and road 25 miles, with about the last mile in the 7500 rpm range often.

Here is a link to pics of the front plug. If you have experience reading plugs I would appreciate your feedback.

google photos album link here:

Thanks in advance for your time.
 

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They look fine to me, but honestly, I don't think any small adjustment is going to show up, and even if it were to, it probably would take way more than 25 miles of riding to do so.
 

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Why not just change the jetting?

If the carb is clean and assembled correctly it would be odd that the mixture across the entire RPM range and throttle openings would be rich.

I was told by a Mikuni Tech not to adjust mixture by changing float height.

Determining mixture by reading plugs is difficult to do. You are seeing an overall average of the mixture, but different fuel will produce different colors and you need to be able to look down into the plug to see the color at the base of the insulator. Not really a good indicator.
 

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From my carb experience (which was quite a bit back in my Honda days) there are two settings for float levels: factory setting and wrong. Obviously rules are made to be broken, if you're racing or highly modd-ing your bike that's different but most of us are just looking to get things working they way they were meant to. I really tend to shy away from "tuning" a carb by float level adjustments. Jets are a good route, some people shim the needles too. Some of us just clean everything, replace what's worn and put it back the way Suzuki made it ;)
 

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Best to set float height/fuel level by measuring. (IDK what the spec is.)
The plugs look to be OK, but on the ragged edge of being lean. If you live at a higher altitude it may develop a lean miss if and when you ride to a lower altitude.
 

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How do you know the bike is running rich?

As mentioned, set the float level to spec. Adjust the mixture with the jets/needle/air-screw only, that is what they are for.
 

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I recently did a full fuel system service on my 99 CV carby. One of the float heights was off-spec but as soon as I put the new Float Needle Valve and it's associated seat/filter from the Service kit the float came back to spec and the other carb was spot on again after the new bit of service kit. I have never adjusted or wanted to adjust the fuel ratio on CV carbs using,"float Heights" as it's not their function. They are there to meter the fuel flow.

Also when servicing CV carbs I always check and clean the ACV system(Air-Cut-Off) on the sides of the carbs. They might be called something else on the SV650s in the manual which I forget ATM.Any fault in these and you may know by popping and backfires on deceleration. They introduce extra fuel into the Carb system when the Throttle is rapidly closed to compensate for the,"Lean" mixture that happens when fast throttle shut-down.
 

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i have popping on decell i thought it might be a airleak. this morning i ordered #4 of the exhaust system , its a gaskit.thanks for the heads up.
 

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It can be exhaust leaks or Air-intake leaks that cause deceleration popping as well but the ACVs are the lesser known cause. It's a common fault with Harleys that use CV carbs if the owners don't know about the ACVs.

Parts 34 to 37 on here,


If the diaphragm is in good condition and not perforated I treat with a smear of AFC50 and make sure the Spring is not corroded. When I clean my carbs I blast them good with my Compressor/compressed air and then loads of Carb brake cleaner through all the jets and Venturi and rinse and repeat. I wish I had a Sonic cleaner but I cannot warrant the cost as I use fuel cleaners in my fuel so rarely have to do my carbs

After any Carb work I re-balance using my Carbtune2 Balancer as per,

 

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You must elaborate on running "rich". At what throttle opening? To tune jets, needles and slides you must know the theory. A brief tutorial to make my point: the first setting is always the main jet. At wide open throttle does it run better when you back off the throttle slightly? That would reduce airflow and make it richer indicating a too lean main. If you your mainjet is too large / rich. The mainjet circuit overlaps somewhat with the needle setting but not at all with the pilot jet. In general the needle setting is for midrange. Lowering the needle blocks fuel and makes it leaner. Pilot jet is for idle. Lowering the fuel level will make it run leaner but that is not the right way to go and is actually much more difficult than learning the circuits and either dropping the needle (leaner) or changing the main. Here's a decent theory article:

Carburetor Jet Tuning Effectiveness Guide
 

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Discussion Starter #11
everyone:

Following the drewski's and TeeRiver comment about "spec" being correct and everything else wrong, I used the service manual to set the float height. Interestingly, the Suzuki service manual has an "easy" method of setting float height where one measures the height of the float, at a given angle relative to the upper part of the carb. Neither were exactly spec but they are now.

I am sorting how it is running now, but, the seat of the pants feeling is good.

Thanks to everyone for the detailed information. I decided to not look at the plugs. I looked at hundreds on line and the broad range of acceptability means it really is not all that useful for me.
 
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