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This is the carb on the new-to-me DRZ: I don't know much about these bikes but I'm guessing that's not stock, and that it's a Mikuni TM40-6 (which seems like a mod some people do on these bikes, the reasons for which I don't understand since I know next to nothing about carbs). It has started to leak fuel when I pull the choke out. What gives, and what should I do to fix it? Parts seem to be readily available at least so I guess that's good. I think the bike is running too rich as well, but again I know nothing about carbs. E: I know enough to tell that it obviously isn't sealing against the air filter box. That's not great. Invalido fucked around with this message at 12:02 on Apr 19, 2024 |
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Apr 19, 2024 09:02
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| # ? Apr 25, 2024 04:48 |
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That’s what’s known as a flat slide carb. The dirt-only DRZ E’s came with them (although I’m not sure if they came with THIS specific one). A flat slide is an upgrade in throttle responsiveness and adjustability (not necessarily raw gay horsepower) over the stock carb. So, this is something fitted by the PO Take a peek at the exploded view here: https://www.jetsrus.com/carburetor/carb_mikuni_TM36-TM40-HS40_pumper_carb_exploded_view_parts.html Gasket part #09 should fix your rear leak (E: you might not need this, it looks like your rear gasket and horn just has crud on it O-ring #81 is where I’d start with the choke leak Beve Stuscemi fucked around with this message at 12:53 on Apr 19, 2024 |
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Apr 19, 2024 12:41
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The choke leak fixed itself. To clarify, there was a stream of fuel pissing out of the little hose nipple at the bottom of the float bowl (visible directly below the left side of the plastic idle(?) thumb screw in the picture) when the choke was pulled out, but not otherwise. I rode it back to the garage for some wrenching and it no longer did this. Then I had to mess with the carb some and remove some stuff including the fuel tank for access so I could get at or at least see most of the intake boot or whatever you call it, got that sorted with a hose clamp and buttoned everything up again. Still no fuel pissing out. Hopefully this bike hasn't been breathing a bunch of dirt under PO because of this. I'm gonna call this good for now and ride the thing once the weather turns acceptable again. The heated grips don't work on it and there was snow in the air just now. I'm basing my assumption on this bike running rich on a sooty exhaust tip and all the decel popping it does, and the fact that it doesn't really need choke unless very cold. When garage temperature it starts fine with just a bit of throttle, then runs and idles fine right away with no choke. It doesn't smell like unburnt fuel or anything though. Maybe everything is fine. Bro has a friend who's ridden lots of dirt on all sorts of bikes (and also wants to buy the steering damper for his KTM "for riding in sand" ) so we'll let him ride the bike a bit and give his more informed opinion on how it runs. More generally I've been riding a bit on asphalt and it's obvious that this bike isn't built for it, especially not on its current knobby tires, I even had a little buyer's remorse at one point. On what little gravel I have found around the city so far it transforms into a super fun rear wheel spinning beast of a toy and I think I'll really enjoy this bike once I get it into its element for real. The throttle response is something else, not sure if it's this carb or carbs in general or just being a thumper but giving it a little brap and immediately having the rear wheel step out a little is just so much fun  I also did babby's first little wheelie this morning which was fun too.
Invalido fucked around with this message at 16:13 on Apr 19, 2024 |
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Apr 19, 2024 16:10
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I regret selling my DRZ
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Apr 19, 2024 17:53
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The pissing-fuel thing can often be traced back to a dirty air filter in my experience. Crud gets into the carb and the bowl just fills up without remorse
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Apr 19, 2024 18:12
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Not knowing carbs in general or this one in particular I'm just gonna wildly blame today's pissing on some type of crud fouling the float valve seating right and then getting dislodged or washed away. The fitting at the bottom that was pissing seems to indeed be the float bowl overflow, so I don't see what would cause too much fuel in the bowl other than the float either not floating when it should or its floating failing to prevent more fuel coming into the carb when the bowl was full. Why the choke should have anything to do with it is a mystery to me. To my knowledge a choke is something that restricts airflow, not making fuel flow out of the carb and onto the ground. The choke shaft thing clearly has o-rings in the parts diagram though so maybe there's some intricate fuckery going on here that's beyond my limited understanding. Since the carb wasn't actually sealing against the air filter since whenever and until this afternoon there's potential for all sorts of crud that could have gotten in that way (air filter looks okay by the way). The likeliest destination for such crud must be into the cylinder but it doesn't take much contamination to mess up a carb, at least I know that much. Also when I bought the bike it had brightly colored green/blue fuel in the tank with bits of some sinking jelly-like substance in it. Small bits of that might have made it past the screen google says should be at the petcock. Or something. At some point I'll take it apart and try to understand more and see if it looks OK or at the very least drop the bowl and have a peek, but not today. For all I know this thing could be packed full of dirt or really varnished or whatever. E: there's another possibility I guess. Mikuni says not to mount this carb at an angle of more than 15 degrees. Before I messed with the intake boot it was sitting in the bike kind of crooked. Maybe the parking spot I used at work and my forensic kickstand welding caused the bike to lean over just enough that it compounded with the mounting angle to the point where fuel went a-pissing. Only when the choke was pulled, because...  Double edit: Because I pushed the choke lever in hard enough to make the bike sit ever so slightly more upright off course! I'm feeling like Sherlock Holmes over here! You gotta admit it's a good story regardless of wether it's true or not. Invalido fucked around with this message at 19:25 on Apr 19, 2024 |
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Apr 19, 2024 19:10
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I put a flatside on the xr650r and it did Not Like being anything other than vertical, to the point of losing the top end quite significantly until I used a heat gun on the tank to make the carb fit just a bit better
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Apr 19, 2024 21:24
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Beve Stuscemi posted:That’s what’s known as a flat slide carb. The dirt-only DRZ E’s came with them (although I’m not sure if they came with THIS specific one). FCR39s were stock on the K/E bikes and are The Standard upgrade for all others. The TM40 is fine, a simpler flatslide than the FCR with less tuneability but it's generally a fine carb. I ran one on a dr650 that was punched out to 790. Finicky thing that it was.
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Apr 19, 2024 22:45
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When I had my DRZ it was much easier (and cheaper) to source a TM than an FCR in Sweden.
Nidhg00670000 fucked around with this message at 23:02 on Apr 19, 2024 |
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Apr 19, 2024 22:55
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| # ? Apr 25, 2024 04:48 |
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Mikuni SBN series is what I'm familiar with. Used over decades in personal watercraft. Only Kawasaki used Keihins. Maybe Polaris.
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Apr 19, 2024 23:03
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