Honda XR650L Thumpster

Repurposed the stock tail light
 

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I cleaned the carb body by soaking it for about 18 hours in Pine-Sol. Got a rebuild kit to replace some key parts and gaskets. I have to say for the outside being so dirty the inside of the carb was really really clean.

I also did Dave's Carb mods that I read about over at Thumper Talk.

http://www.4strokes.com/tech/honda/xr650lcarbmods/

I shimmed the needle with a 0.02" washer, drilled out the slide holes to 5/32", went up to a 55 pilot and 158 main jet.

I took her for a ride and I'm getting a little bit of popping when i'm decelerating while in gear. Thinking about putting some of the supertrap discs back on that came with the bike when I bought it. Maybe too much back pressure for how free flowing everything is now?
 

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By not using the air box you have opened up the intake way to much which like sonic says leads to lean popping. Your getting to much air.
 
Scott84 said:
By not using the air box you have opened up the intake way to much which like sonic says leads to lean popping. Your getting to much air.

I did richen the jetting at the same time but maybe not far enough.

Started building my own muffler out of a exhaust tip for a car. I like the oval shape, it fits the width of the bike nicely. I have a perforated straight pipe that will be welded into the exhaust tip, then the surrounding space will be packed with fiberglass. As you can see I welded a restrictive washer on the end of the exhaust pipe to narrow the diameter at the last point. Worried that it was going to be too loud.
 

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Finished up the muffler and exhaust routing.

I have to say I'm surprised at how quiet it is...and how much less power it makes :-[

It sounds great but when I get into the higher rpm range it felt like the bike started to choke, almost like the feeling of hitting a rev limiter in a car, it kinda just lost power at the top end.

I'm really happy with the position and shape of the entire exhaust, I might cut this muffler open and remove the restrictive washer I welded to the end of the internal exhaust pipe, I think it's too small. Darn.
 

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Another option for XR650L is an aftermarket GB500 exhaust. Trimming is involved or else new exhaust studs since the XR studs are 3mm shorter than GB studs.
 

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Thanks guys. I think I might just build another one. I think I can do it better a second time and the car muffler tip was only $27. Small price to pay to get it right.
 
Any updates on this build? I too am building an XR600R/XR650L hybrid, and am keen to see where you take this project...
 
when you say you hit a rev limiter....at what RPM? These thumpers aren't good for much past 6500 rpm... On the KLR forum they say if you advance the exhaust cam 1 tooth you get about 10hp more usable power up until 6k where it just falls off. Not sure if it's doable on this but i'd look into it for sure (doesn't cost anything to do)
 
I think i found out what the stuttering came from at higher RPM's. I don't have a tach so I don't know exactly where I was at when it happened BUT I made the bonehead mistake of not setting my mixture screw after the carb rebuild...it was turned all the way in. I think I had set it two turns out when I re-installed, but I guess I forgot.

More pics coming soon, along with yet another exhaust configuration. 8)
 
As promised, yet another exhaust configuration. This is basically trying to copy a flowmaster baffle type muffler except this one is curved on the bottom and doubles as a mudguard. The curved design was particularly tricky when trying to fit the baffle pieces. Also, figuring out how to weld up and enclosed object was also a bit of fun. The flat top piece ended up going on last. A series of holes was drilled in the top matching the baffle pattern and tack weld were done through the holes.
 

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As you can see in the pic taken from the rear wheel, there was some heat distortion that seemed to twist the entire muffler. I think this can be torqued back straight once some mounts are in place. The chain is just there for support so I could take it for a ride and see how it performed. It works surprisingly well. A little on the loud side but still very street capable and seemed to deliver the same amount of power as when I had the supertrapp on there. Gonna clean up some welds, mount it up, and do some more road testing.

Definitely need to fab up some heat shields for the exhaust.
 

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