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Discussion Starter #1 (Edited)
I have been having issues with my '04 Vstar650 classic for some time. Backfire on deceleration, smoke from rear cylinder exhaust, poor acceleration- and on my first over 100 Mile ride, I found out the reserve tank fuel wasn't flowing (as I ran out of gas at 102 miles and switched to reserve) and i was getting horrible gas mileage. Thank goodness my son was home to bring me gas.
So I went back to the drawing board. Pulled the carbs, checked everything again. Found the sleeve around the jet needle (on rear carb) is held in place by a small pin and mine was not set correctly allowing the sleeve to move. Fixed. Set the Float level. This took about 3-4 hours. But now i have them both in spec (7.5 to 8.5 mm on tubing) front was good, rear one was too rich.
Never have been able to get airbox to stay down tight against carbs (wants to slip up and away) so I Zip Tied them down before screwing clamps down.
Set PMS Screws back to 2.5. Synchronized Carbs. Changed oil and filter again, even though oil was only about 3 months and 500 miles old. It looked grayish and milky? and was above the sight (slightly overfill). I've been having oily residue from rear cylinder exhaust. Took my time and got it right.
Took petcock off and cleaned the filters on the two stalks. The reserve one was gunky. Flushed out tank with gas, didn't see a lot of stuff come out, but there was a little debris.
Went out and got 89 fuel instead of the 92 I had been using (don't know why-but I read it likes 89 better somewhere) measured the correct amount of seafoam instead of guessing.
Took the bike out for a ride... and Wow! I have power, and no smoke no backfire. Not sure what fixed it, but it is running better than anytime since I have owned it. Feels like a completely different bike. Like I added 50 more Horsepower or something. I can go up hills without having to gear down, It actually yanked me back in the seat when i accelerated. I'm stoked right now.
 

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Super Moderator "Loose Nut"
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That's great you got it running good. Sounds like you covered most items. Some more to maybe check is the fuel filter and air filter if you haven't already, those can and will effect engine running to it's potential.
 

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Not sure what fixed it, ...Feels like ... I added 50 more Horsepower or something.
Its all all of the above, and you did a lot of other good things before, while trying to debug the problem, which helped more once you got the fuel/air mixture right.

Had to laugh about adding 50HP, its a 40HP engine so that is about right, before it was sucking all the energy out of you

now its giving it back

I use to fly R/C gas airplanes. The engine had a screw main jet that you cranked out half a turn to get it rich to start, then with the prop spinning (engine loaded) you slowly turned that screw in, and when you hit the correct fuel/air ratio that little 1/4 HP engine wound up like a giant angry bee.

An engine will start and run with the fuel/air mixture way off... barely... but when you get it right then you got some power.

Dont know if I mentioned before, the peak HP curve on a 650 maxes at 55 in 4th gear, and 75 in 5th gear. Most people think these engines should sound like a HD, and tend to shift too soon. Try it on your next ride on the open road - WFO at 55mph in 4th gear the air intake box growls with glee, then again at 75 mph in 5th. The engine has a rev limiter, so as long as you dont down shift too soon and let the clutch out you will not red line the bike.

Those hose clamps in the air box to the top of the carbs are a PITA. Spent half an hour on mine once getting it to stay seated, almost like the top of the carbs are tapered, and when you tighten the clamp its like squeezing a bar of soap. Maybe wiping the top of the carbs, and the inside lip of the air box with 90% Isopropal alcohol might clean all the oil off so they will get a good grip on each other.
 

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Discussion Starter #4
I have a two lane Highway I ride close by. There is a bit of a hill that I usually have to downshift to 3rd to get up it. I stayed in 4th today and it felt good. I'm thinking this bike is OK. And no backfire. Responds to throttle much, much better.
It was too cold to ride very long (39-40 degrees) but next warm day I get, I'm going to try another 100+ mile trip and see how the mileage is. I will stop and check it at about 75 miles to see how much fuel I'm using. I don't want to run out again. lol
 

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tbzg, next time someone has similar issues make sure and post how you fixed yours. Sometimes it's not a single thing that fixes it but a combination of things.
 

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Discussion Starter #6
Not sure exactly which thing I did corrected it, but I'll sure tell anyone what all I did. I've never been the smartest guy in the room, but I am doggedly persistent. It has served me well. Just keep after it.
 

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my 2005 is completely stock. Commuting at 45mph I get about 58mpg. On country roads running 55 to 60 I get about 60mpg.

It has a 4.2 gallon tank, so I should be able to get 250 miles before it runs dry. I stopped for gas once and PUT 4.2 gallons in it, so the only gas left when I pulled in was the 2 tablespoons in the float bowls.

I usually filp to reserve between 190 and 200 miles on the trip odo. For a while I waited till it started to stumble to get an idea how much was left, but I realized that could lead to a bad situation, pulling out into traffic or in a good curve you dont want your engine to stumble at a bad time.

From your first post I think my Royal Star might have some gunk on the main petcock filter. It starts to stumble around 170miles, it should be good almost to 190 (it gets 45mpg, but has a bigger tank). Something I will have to look into this summer.
 
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