copemech Posted March 31, 2012 Report Share Posted March 31, 2012 I seen on a new Evo where they are runnine one verticle tube and one horizontal. The one goes up and the other goes down. The carb itself has been modded. Quote Link to comment Share on other sites More sharing options...
nicos Posted March 31, 2012 Author Report Share Posted March 31, 2012 moded? is there any way we can find out what mod they did? thanks! Quote Link to comment Share on other sites More sharing options...
overdale Posted March 31, 2012 Report Share Posted March 31, 2012 Hi Nicos, Just make a small cut like a V in the pipe where I indicated on the picture and that allows breathing but breaks any siphoning effect. The left hand pipe on the bottom of the float bowl is purely the overflow. Hope that this solves the problem! Quote Link to comment Share on other sites More sharing options...
nicos Posted March 31, 2012 Author Report Share Posted March 31, 2012 i did the mod today,didnt cut a V instead i fitted T fittings to both vent tubes and ran another vent. dont know if this was the fix or the drilled drain bolt but after 4hrs on the bike today it ran perfect! thanks for the info guys! Quote Link to comment Share on other sites More sharing options...
copemech Posted April 2, 2012 Report Share Posted April 2, 2012 (edited) This is what I was referring to. It is a factory job. Presume by Kiehin! Not being a betafhile, I have no idea exactly when this was implemented. Edited April 2, 2012 by copemech Quote Link to comment Share on other sites More sharing options...
nicos Posted April 2, 2012 Author Report Share Posted April 2, 2012 I see,so a built in T, thanks for sharing this info! i would have been going round in circles with jetting changes still if it werent for you! thanks again! Quote Link to comment Share on other sites More sharing options...
baldilocks Posted April 7, 2012 Report Share Posted April 7, 2012 hi copey keihin make a carb with those vents for the mx boys. bought one used off an rm85 a while ago. going to make the v cut in the keihin breather on my sherco and see if it works the same. Quote Link to comment Share on other sites More sharing options...
nicos Posted April 7, 2012 Author Report Share Posted April 7, 2012 if the carb you baught has the extra vertical vent fitting built in,then you dont need to cut a V in the tube. Quote Link to comment Share on other sites More sharing options...
baldilocks Posted April 7, 2012 Report Share Posted April 7, 2012 sold that carb a couple of years ago unfortunately. keihin on my new sherco doesnt have this feature. ta anyway Quote Link to comment Share on other sites More sharing options...
jse Posted April 7, 2012 Report Share Posted April 7, 2012 hi copey keihin make a carb with those vents for the mx boys. bought one used off an rm85 a while ago. going to make the v cut in the keihin breather on my sherco and see if it works the same. Baldilocks, Some background on the T-vents and to explain Copey's observation: We used to have some serious issues with the MX/Supercross bikes bogging on the first ramp on the steep double/triple jumps and traced it down to accumulated fuel in the long vent lines being sucked down/out the tube when the bike hit the steep uphill for the jumps. This would cause a quick drop in atmospheric pressure in the float bowl and temporarily cut off fuel to the engine at the worst possible time. The sudden loss of power would cause the rider to short jump and miss the last landing ramp, often "casing" the bike, or landing directly on the skid plate, which does not allow the suspension to absorb the shock. This is like dropping several stories and landing directly on the ground and resulted is a lot of shattered bones and careers ended. We started adding a "T" at the vent outlet and running extra lines up to avoid this and Keihin later added this feature as standard to the carb body. That extra vertical T vent outlet is probably not as necessary for Trials use, but is standard on most carbs now. Jon Quote Link to comment Share on other sites More sharing options...
baldilocks Posted April 7, 2012 Report Share Posted April 7, 2012 did some investigating today and started by cutting a v shape out of the pipe in the prescribed place as my new sherco had ran lean on a couple of steeper sections last week . I thought given the pilot jet is in front of the main jet that perhaps float hieght was wrong but the cut in the pipe was easy to try first. I did the cut then put the bike on the rear wheel with the front up against a wall and after 15 seconds or so bike started to run lean. So stripped carb and checked float per Beta guidance in the Beta forum, my floats were parralel when the carb was upside down rather than at 45 degrees so adjusted carb and bike seems ok but will know better tomorrow. Quote Link to comment Share on other sites More sharing options...
copemech Posted April 8, 2012 Report Share Posted April 8, 2012 Couple things to note here, I ran into a bowl vent problem early on when installing a Kiehin on my '07 Sherco due to the proximity to the exhaust, the hose pinched off. As the basic carb body casting has a provision on the opposite side not used, it is easy enough to drill out that port ti use dual vent tubes ala dellorto. Yet I still run short tubes to prevent trapped fuel in them. The issue is the same on the OKO carb I am currently running, yet it has no provision on the left side for a second vent, However the basic carb casting on the right is like the K carb, so I drilled out the upper part and installed a verticle tube like on the Beta pic, blocking the horizontal one that gets jammed unless one removes the hose. just ran it up then down and kept it short trimmed to bottom of bowl so no fuel accumulation in it, this mod seemed to work fine for me. In a situ with more room to play, the carb could easily be modded to use the "T" on the one side like the one pictured, yet I would still prefer to loose the long drain hose as that is the culprit to begin with. I do not mind a bit of spatter directly on the motor. Quote Link to comment Share on other sites More sharing options...
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