Ok guys I want to take my kawi 650 from Indiana 800ft above sea level to the rockies 11000ft above see level. I really dont want to do any thing major for 3 weeks riding will a k&n filter do the job?

 

Well, I was riding at 8000~11000 ft and my top speed was down to something like 40~45 max on a flat ground with stock jet settings. Not only the low top speed, but engine was like puffing and coughing and obnoxiously cutting off rhythemically at WOT. Then next day, I chaged the main jets from original 138(Front)/142(Rear) to 130/132 (as recommended on service manual on page 2-2) and it was day and night difference. The top speed impoved to about 50-55 mph and there was no more obnoxious cutting out. The jets were only $7.08/ea. from a Kawi dealer. I am not sure how much K&N filter will make the fuel/air mixture leaner at where you will be riding, so I am not sure how well 130/132 will work in your case. But it was way too rich with stock air box/filter and stock main jets at that high altitude in my case.

By the way, be careful not to strip the screw heads on the carb fuel bowl covers. Those screws are damn tight and damn soft! You'd better use a good quality Phillips #2 bit. I ended up damaging 2 out of 8 screws!

 

WHY ARE THE JETS NOT THE SAME SIZE FOR EACH CYLINIDER? ALSO 138-142 SEEMS SMALL TO ME MY OLD AC 454 HAD A 152.5 MAIN FROM THE FACTORY.I LIVE AT ABOUT 1200-1500 ABOVE SEA LEVEL WITH STOCK EVERYTHING, GOT 63 MPH ON IT THE OTHER DAY, IF I JETTED DOWN ONE SIZE, DO YOU THINK IT WOULD RUN BETTER OR WORSE?

 

Basically two reasons:

1). Since it's V-Twin engine, the head pipe length is different between front and rear cylinder (obviously!) and requires different tuning (fuel/air mixture) for smoother runnability.

2). Also, the rear cylinder tends to run hotter than the front (because it's V-Twin), using richer mixture in the rear cylinder will bring down the flame temperature during the combustion process. Excessively hot cylinder will backfire in the exhaust pipe, especially when you shut off the engine.

The main jet sizes, 138/142, are normal for TWIN cyinder 650 cc engine. Like Prairie 300cc (single) uses size 140, and 400cc (single)uses size 150. So, TWIN 650cc (or 325 cc each) using 138/142 makes a sense. Just don't compare to large cc SINGLE jug engine.

The 650 service manual states that stock main jets are good from sea level to 1600ft. Also, since it's getting cooler (meaning more densed air) nowdays, I wouldn't change to smaller jets.

 

I know most people have to rejet after putting on a k&n filter. I just thought it might be good enough for 2 to 3 week in the mountains this spring. Did not want to rejet for that short of time. Think it will work?

 

I'd rejet rather than risk a bad experience. You should probably lean out the idle mixture screw too or you may have a problem starting the machine at altitude. And expect to lose about 100 rpm of idle speed at altitude, maybe more. I bring a tach with me and adjust the machine at the altitude I'll be riding at. It'll idle faster down low, but be right on up at high altitude. You can tolerate that for a few weeks.

If you don't want to rejet beforehand, bring the smaller jets with you and if you're having problems, you can rejet back in camp or at the hotel.

Where do you plan on riding that high?

Mark

 

I guess I wont be quit that high. I was looking ant the map and where we are going only one pass is even close (around 9k). My dad is 68 years old and were goning to colorado next spring to ride on some of the 4x4 trails he's always wanted to go on. We went on a few when I was younger on dirt bike. I just did not want to rejet but remember how bad our dirt bike did when we got up that high. I told him I would rent him a quad when we got there. What he dosent know is if I like my kawi650 I buying one for the wife and taking it. He and I are realy looking foward to it and I just want every thing to be great.

 

Rowdy,
That's a great thing you're doing for your Dad. If you get two 650's, he'll love it even more. If you rent one for him, it will probably already jetted for altitude. Hope you have a great time.

Mark

 

Ok guys I was talking to a guy who lives in Arizona and he said he takes his polaris from 0ft to 6000ft just by putting in a k&n filter and adjusting his SuperTrapp. Does this sound right?

 

Sounds possible. Everything he is doing is making the engine breath easier, therefore the intake stroke sucks in more air and the engine can run leaner. The SuperTrapp is adjustable by adding discs in the muffler. It can take up to 12 discs. The more discs, the less back pressure, the leaner the engine runs.

It'll cost your at least $170 for a SuperTrapp, and about $40 for a K&N filter. Just rejet. [img]i/expressions/face-icon-small-smile.gif[/img]

Mark