genejohnson wrote on 03/01/10 at 18:46:54: I think some of the reason is because a large carb has to be used with the large (650cc single cyl ) displacement engine. At lower RPMs a lean condition occurs because of lower vacuum. Lancer hit on it slightly when he was recommending carb sizes to use on the engine. I think someone should design a splayed intake and install two smaller carbs that will provide a lot of vacuum at lower RPMs but still big enough to give it the collective volume it needs at higher RPMs. Whatcha think Lancer?? Gene
A Single carb of the correct size and jetted/tuned properly will work great on a big single like the LS650. I have been playing with assorted carbs and exhausts for quite a few years now, and this engine will run great, sound great, and not backfire when the carb is setup correctly.
For the stock carb on a stock engine with another muffler of you choice, you rejet & tune as needed for low-mid-high throttle ranges, using the pilot system, the needle and n/jet and main jet to make the adjustments.
Backfiring is not a normal engine function. Wth a well tuned carb/exhaust setup on an engine there can be popping/crackling on decel...
this sound is music to my ears. When you hear that sound you know that the engine is feeling great; like when you have been exercising for several months and are back in shape and feeling strong and energetic ...YOU JUST FEEL GOOD ! Same with the engine.
If you want or need a different carb; a performance carburetor; then the best bang for the buck is a Mikuni VM roundslide. It is inexpensive, parts a available and are cheap in comparison to many of the newer style flatslide carbs. This is why I use this carburetor in the Performance Carburetor Kits I created. The cost of the entire kit is $400, while many of the newer carbs cost that much just for the carb, then you still need all the other parts to make it functional.
For a roundslide carb on the LS650 engine, use a 36mm or 38mm model. The 36 mm is just fine for a stock engine with a Dyna muffler for ex. My Performance Carburetor Kits currently have the 38mm and that is modified for better performance and responsiveness. I made the change from the 36mm I used previously because most of the carb kits ordered were being used on engines with different air filters, high flow mufflers or complete aftermarket header/muffler system, Performance Camshaft install and some with ported heads. With this range of modifications on the engine the carburetor needs are better met with a modified 38mm model.
With changes of this magnitude, the LS650 is transformed into a
Savage Beast. It is quick, fast for its catagory and gearing limitatiions, and will flat eat up mountain roads or other curvey's. HD's are left way behind and you can run with sport bikes on the curves.
The torque increse is phenominal; there is usable power from idle to redline. It is freaking fun to ride...
talk about having a crazy grin plastered on your face...oh yea !With the light weight of this bike and its quick and easy handling, it is a pure joy to carve up almost any road you choose to ride.
With stock gearing it will top out at about 100; swap in a chain/sprocket setup and you can gear for arm stretching acceleratiion and top at 90 or gear for lower rpm at cruising speeds and gain some top end to boot. You could get up to 110 with the right gearing I expect. ..especially if you have the Stage 2 Performance Camshaft.
THIS IS A GREAT BIKE AND IT HAS A LOT OF POTENTIAL ... USE IT AND SEE HOW MUCH FUN YOU WILL HAVE