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99-02 SV650 tech Info, advice or questions specific to the 99-02 model SV650.

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Old 04-08-2008, 03:19 PM   #1
allawd
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Carb rebuild advice

I am looking for some help from some more mechanically minded people.

I have a 2001 SV with ~8,000 miles that I bought last year. The bike sat quite a bit before I got it. I initially had a shop go over it and give it the ok, but I don't trust they did a good job.

The bike stumbles at idle and backfires about 3 seconds after I kill the engine. My gas mileage is bad (~32mpg) but it is in bad traffic (avg 40 min for 10 miles). I feel like it is down on power. I've never ridden another SV this so I don't know what is normal.

I'm going to have the carbs cleaned, but I would like some advice. What should I do while the carbs are off? new jets? new o-rings? shims?

I'm throwing out what I saw from searching, but I don't know much about carbs.
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Old 04-08-2008, 03:26 PM   #2
allawd
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Re: Carb rebuild advice

Previously, I have:
replaced the air filter
techron concentrate in the gas tank
seafoam, poured through the throttle body
water misted into the throttle body (to clean combustion chamber)
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Old 04-08-2008, 03:41 PM   #3
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Re: Carb rebuild advice

I had a set of carbs that sat for 2 years with gas in them. I had almost identical idle problems. If you want to do a rebuild, I would get new jets and all new gaskets. Also, get a huge can of chem dip and leave the carbs in there all stripped down for a day or two. That will clear out most of the junk.

I never got the original carbs working right. I ended up paying 50$ and got a known good set off ebay.
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Old 04-08-2008, 08:12 PM   #4
andyauger
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Re: Carb rebuild advice

Check the plugs as well. If the bike's been idle for a long you should pretty much check and clean everything. Don't forget the brake fluid.
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Old 04-09-2008, 01:24 PM   #5
allawd
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Re: Carb rebuild advice

Quote:
Originally Posted by andyauger View Post
Check the plugs as well. If the bike's been idle for a long you should pretty much check and clean everything. Don't forget the brake fluid.
I did clean and check gaps on the plugs not long ago.

Changed brake fluid a couple weeks ago. It was nasty...200% improvement in brake feel after new fluid.

UPDATE: Based on dantheman's input, I'm buying used working carbs. It's <$100 for a used set or $350 for a shop to clean the old ones. Then I'll take the old ones apart and see if I can fix it...at worst case it will make a great coffee table piece!
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Old 04-09-2008, 04:13 PM   #6
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Re: Carb rebuild advice

Quote:
Originally Posted by allawd View Post
UPDATE: Based on dantheman's input, I'm buying used working carbs. It's <$100 for a used set or $350 for a shop to clean the old ones. Then I'll take the old ones apart and see if I can fix it...at worst case it will make a great coffee table piece!
Excellent choice sir. I have rebuilt a ton of carbs in the past, but it was because cheep rebuild kits were out there. There isn't such a thing out yet as the bikes are still "new" enough not to need them I believe. I am cleaning up my old carbs to use as a paperweight on my desk at work. Going to seperate them so I will have 2.
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Old 04-09-2008, 11:00 PM   #7
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Re: Carb rebuild advice

Good advice from Andy about the plugs.

But I strongly disagree with Dan. The only jets I've ever had to replace are those with the screw-slot mangled by previous owners. Jets do not wear out and they're made of brass so they don't rust. If you don't mangle them, they will work long after all of us are dead.

On older CV carbs (from the 70's) the rubber diaphragm around the slide/piston would eventually dry out and crack, but I've never seen it on a bike that was less than twenty years old. Same for the rubber float bowl gasket. You might eventually have to replace it a decade from now, but unless you cut it it the one you have now will be fine.

The worst part of any carb overhaul is getting them off the bike. If you're going to buy a used set and swap them out yourself, you can do the overhaul, too.

Get the carbs off the bike and remove the float bowls and top covers. It will feel like the screws were set with Loctite and you'll probably strip the heads off of every other screw. A needle-nose Vice Grip is great for breaking frozen screws loose.

I use this as an opportunity to replace all of these screws with stainless allen-head cap screws. You can get them through Ace Hardware under ten bucks for a bike with two carbs like the SV. It will make any future carb work much easier. On a straight overhaul these screws are the only parts I replace.

Clean the float bowl with a rag and carburetor cleaner. Wear chemical resistant gloves and do this in an open area away from any flames - carb cleaner is nasty stuff. The level of tarnish here is a good indicator of how dirty the jets will be.

Remove the slide from the top of the carb and set the carb upside down on a clean rag. You'll see the three jets between the floats. There's a pin on the bottom right that attaches the floats to the carb body. The pin should slide out easily if you push it with a ball point pen. Lift the floats out and set them aside.

You'll notice there is a small, pencil tipped brass plunger sitting between the mounting points for the floats. This is the float valve. It's not screwed in, you should be able to pluck it out with your fingers. Set it aside.

Now you can remove the three jets you see in the bottom of the carburetor, but you don't need to if you're just cleaning it. All of the work in the carburetor is done through these jets. If you clean these three jets, you've overhauled the carburetor.

I disagree with Dan again about dipping. That is handy on automotive carburetors because they typically have more complex route for the fuel to take between the float bowls and the venturi, but as you can see on a bike - its a straight shot.

I simply attach the spray tip to the can of carb cleaner, hold it firmly against the bottom of the jet, and blast away. For a severe case I keep some guitar strings in my tool box to push out junk, but its rarely necessary. I've only seen a couple of cases where the jets were clogged shut with varnish and those were bikes that flooded the float bowls and sat for over a year.

After you flush these three you're ready to put everything back together. You've just overhauled your carburetor. While you have everything apart you can change the jets to get a little more power. Jets from your dealer will cost another ten bucks, plus fifty cents or so for the shims for your main jet needle. Check out the sticky for the recommended jet sizes and on how to adjust the idle mixture screw.

A couple of reassembly tips: Put the slides and floatbowl gaskets in the freezer before reassembling the carb. The rubber expands quickly in heat and its much easier to get it into the grooves if you use some cold to shrink it a bit.

Be patient reinstalling the carbs and setting your cables. While you're here you might as well sync the carbs if you can borrow access to a set of vacuum gages or Carb Stix.

That's it. Once I get the carbs off the bike it takes me less time to do all of this than it did for me to write it. It will be almost as easy for you.
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Old 04-21-2008, 08:36 AM   #8
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Re: Carb rebuild advice

Thanks for this write up baldheadeddork!

Quote:
Originally Posted by baldheadeddork View Post
A couple of reassembly tips: Put the slides and floatbowl gaskets in the freezer before reassembling the carb. The rubber expands quickly in heat and its much easier to get it into the grooves if you use some cold to shrink it a bit.
Great tip!
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Old 04-25-2008, 04:22 PM   #9
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Re: Carb rebuild advice

+1 to Baldy's advice.

If you can take a carb off, you can EASILY take it apart and clean it.

Take it apart, take lots of pics of it while doing it, and dump all the parts into a bucket of carb cleaner. Hit everything with your ex's old toothbrush. Put every thing back together.

Easy as pie.
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Old 04-25-2008, 04:30 PM   #10
allawd
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Re: Carb rebuild advice

You know what's easier? Not being dumb newb. I had a vacuum leak because I didn't secure the airbox to the carbs right. Then I installed a tach and found out I was idling at nearly 3000rpm. I didn't know what an SV was suppossed to sound like...

So now I've got extra carbs and ket kit in a box. The bike runs great, 45mpg compared to 32mpg previously.
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