with the Supertrapp, unless they took off the end cap and the discs, you can remove discs until the sound is reasonable for you. It may still prove to be less restrictive than the OEM muffler. Just get a new joint gasket to seal it up.

I wouldn't get too worried about the fan since the KLX650C dual sport came with one, but oddly enough the KLX650R off roader didn't. There was no issue with overheating. My 650 only comes on briefly when stuck for a bit on a trail and more continuous when stuck in traffic on a hot day. I don't remember the 250 having its fan run yet, but I don't have a lot of time on it in instances where it might. Another thought - no two stroke off roaders had fans either.

 

That's because when they are running they are normally being ridden and air is flowing. Dualsports/street bikes that are water-cooled have fans due to long traffic light stops on hot pavement.

 

Obviously you've never been on a bike totally covered with mud and stuck in a mud hole trying to get the bike out - longer than most traffic lights. Bottlenecks like that happen in harescrambles and cross country races rather frequently. Fact is I've had the fins packed with mud on my two stroke air cooled bikes in those circumstances too.

Like I said, they don't have fans on two strokes so I wouldn't worry too much.

In all my time on the dual sport KLX650C the only time the fan would come on was when in extremely slow (post races) traffic for more than five minutes at less than 5 mph. Every bit as often it would come on when trail riding when I got stuck and was turning around on a trail, yet the off road KLX650R that is expected to do that does NOT have a fan. So I'm thinking as long as the OP wasn't in some parade they're good to go.

 

Honestly, the Supertrapp has packaging tape on connecting end and I bet it never fit the bike right in the first place.

The PO said he never used it because it didn't seem to do anything other than make bike louder, and I can't find any reports/impressions of using a Supertrapp on this bike.

At any rate, I ride on dirt trails right in or near neighborhood so I'd prefer to be quieter at this point in time regardless I'd prefer to spend money on 351 kit in the future rather than equivalent money on new muffler.

The bolts I got from Ace Hardware didn't work too well on the radiator fan, so I ordered the actual OEM bolts and will bolt it on tonight. I just wish there was an easy way for me to test the temp sensor and fan!

 

All you need to do is disconnect the harness from the fan switch located in the rad below the fan motor and use a suitable jumper wire to connect the two wires. The fan should operate when the ignition is on. If it doesn't then check for 12v on the harness and also verify that the ground wire for the fan is good.

The other switch in the LH rad should be for the warning light in the instrument panel and if you disconnect the lead and ground that wire the warning light should operate when the key is on.

 

My fan on comes on a lot, depends on how many mud holes and rock gardens you get stuck in. If she blows then, you may be in trouble.
If you only ride on the street, probably don't need a fan.

 

I have a Pro Circuit slip on reverse cone megaphone with the Supertrapp on it, but have yet to install it. I have a full BajaDesigns exhaust system with the Supertrapp on it, works great. The whole idea of the Supertrapp was adjustability in sound and restriction. My 650 uses 12 discs, I'm thinking my 250 would do fine with half that. My 650 is loud, but "**** the neighbors off" loud. I know... I asked them.

Realize too, that the Supertrapp portion itself is mainly the muffler. If it is the reverse cone megaphone set up it should help performance once jetted properly. If it is a can (pipe to a glass packed muffler) with the Supertrapp disc end on it, it likely won't do any more for the bike than any other can. The reverse cone megaphone is the trick - that is seldom done anymore on singles because they aren't cheap. You will notice the MotoGP bikes use one on each pipe (4 into 4). Flat trackers frequently do the same (2 into 2). a large number of the dirt trackers use the Supertrapp ends on the megaphones.

Hope that makes some sense.

As for the packing tape, if the pipe was made for the bike it would slip on over the thick gasket that is used with the stock pipe. Mine is made that way. The OEM gasket was stuck inside the flaired end on mine when I got it.


You could pull the sensor out of the bike, connect an Ohm meter to it, then put it in a pan of oil with a candy thermometer in it. Heat the oil up until the sensor trips, it will be infinite resistance until it connects then it will be 0 (zero) resistance.

I honestly have no idea if mine works, never got it to the point where the fan comes on. Maybe I should check sometime. But knowing how often my 650 trips and how long it runs, I'm not too worried about it.

 

If you must stay stock exhaust quiet, the 351 is the way to go. According to Bill Blues' dyno chart, the 351 on a 100% stock bike still makes a little more power than a uncorked, MCM'd, stage 2 (loud) KLX.

But we get pretty close - at this point - and I hope to find another couple of HP with a few new ideas some of us are working on.

 

Based on my experience with the big bores there is the other advantage of the big bore - it adds power through the entire range. Most hop ups will add mainly in the upper range, although I think the MCM cam timing adds over the range too.

If I could do one performance modification on an engine regardless of cost and effort, it would be bigger bore. Adding power without adding weight is always good. The one time when I wouldn't say if you want faster buy bigger. Adding a shade more power without hurting rideability is always a nice thing. I have both the 250 and the 650. I can tell you on the road bigger is good, but off road lighter is better.

 

Captain Obvious would say the 351BB is very expensive when you add in the cost of the DJ jet kit and the clutch upgrade springs. And it requires an extensive tear down of an engine.

My bike doesn't need a tear down and I can make pretty close to 351bb-on-stock-bike power for about 1/3 the money ( Using the DG-R + DJ + MCM = $215 )

I hope to close that power gap soon with a airbox insert and proper jetting/AFR for the uncorked, stage 2, MCM bikes near sea level.