clarkp Posted January 24, 2004 Author Report Share Posted January 24, 2004 Interesting Nigel - don't leave us hanging... how do we get in contact with John Lampkin? Does his business have a web site? I assume he / they are in the UK? More info please! Quote Link to comment Share on other sites More sharing options...
kinell Posted January 24, 2004 Report Share Posted January 24, 2004 I've seen a picture of it somewhere (motomerlin site maybe ??) I think the large nut on the bottom of the float bowl is replaced with a very deep hollow nut thingy. |---------------| bottom of float bowl |___| original nut |---------------| bottom of float bowl | | | | |___| deep hollow nut It doesn't look much but it must allow more fuel to be stored. Quote Link to comment Share on other sites More sharing options...
kinell Posted January 24, 2004 Report Share Posted January 24, 2004 (edited) Oops, my attempt at drawing didn't work Anyway, managed to find it on the BVM site Carb Float Bowl Mod. As used by Team GP Beta. To fit Beta Rev 3. Sustains constant supply of fuel to main jet. PRICE JUST Edited January 24, 2004 by kinell Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted January 24, 2004 Report Share Posted January 24, 2004 www.bvm-moto.co.uk Quote Link to comment Share on other sites More sharing options...
clarkp Posted January 26, 2004 Author Report Share Posted January 26, 2004 kinell, Dabster, and r2wtrials - thanks for the information - I have an email in to the Lampkins inquiring about getting that super-secret trick part for my machine - thanks again for the follow-up! Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted January 26, 2004 Report Share Posted January 26, 2004 So billy what do you say now? Quote Link to comment Share on other sites More sharing options...
superflytx270 Posted January 26, 2004 Report Share Posted January 26, 2004 I guess he must be at physics class brushing up on the laws of gravity and the like seeing as he hasnt responded to my drawings and theories Quote Link to comment Share on other sites More sharing options...
ronm Posted January 26, 2004 Report Share Posted January 26, 2004 Does anybody know if the float bowl extender pictured above includes an extension to lower the main jet into the the new little chamber, or does it work strictly by increasing the volume of the bowl? Quote Link to comment Share on other sites More sharing options...
billyt Posted January 26, 2004 Report Share Posted January 26, 2004 (edited) Now now superfly any more of your cheek and I will not provide you with any more physics leasons. The bowl extender......... This carb is about 30 years old now, do you really think that if this extendor was needed that Mikuni would not make one and offer it as an option? I have not seen the particular extendor mentioned, but I have seen others. BUT as Ron M was hopefully getting to if its lowers the main jet into the float bowl it increases the head pressure required to lift up the same amount of fuel from the bowl. Think of it as when you lower the jet towards the bottom of the float bowl the venturi has to lift the fuel higher with the same amount of vacuumm to get into the jet stream and in to the cylinder. This is not a good thing as it can cause all sorts of problems at higher RPM's. The tube now becomes (through the jet and then the extender) longer that the fuel has to travel up (fighting against gravity), you have increased its length but not the amount of vacuumm. If that were the case there could simply be a long tube attached to each jet with the jet at the bottom of the tube. If it mearly gives more fuel capacity in the bowl and the jet does not protude further into the float bowl any further it is redundant. The other problem because of the extended cap protuding down from the bowl it can hit/touch on the top of the crankcase when dropping off of larger obstacles or even during regular installation. Keep in mind that if it clears the the top of the cases by say 1/32 it can and will move down when the bikes if under stress such as a jump or travelling down the trail at a fair clip. The rubber boot on either side of the carb does flex somewhat. When the float bowl or the float bowl extender touches the top of the cases it causes foaming or excitation of the fuel not to mention what it does for your float level. The bike can run lean and then rich just because the bowl is sitting/touching on the cases and vibrating away. Look at the earlier Gas Gas bikes that had the float bowl ground away on one corner for this very reason of its carb touching the cases. I do not see this option for a Kehin or a Dellorto either. Sorry dont buy it.............. Not needed if the carb is set up correctly. Superfly. nice drawings and I think you really understand what I am saying. but the Beta's gas tank is not quite as simple as you drew. BillyT Edited January 27, 2004 by BillyT Quote Link to comment Share on other sites More sharing options...
hrc1 Posted January 27, 2004 Report Share Posted January 27, 2004 I fitted the float bowl extender to my last 2 betas. Can say there is no difference in before & after performance to me. I was told it was only required for truly advanced riders undertaking massive jap zaps & double steps. Some thing I rarely encounter. Had to try it though. I'm a mug for gizmos...........that's the trouble with trials, not enough gizmos. Quote Link to comment Share on other sites More sharing options...
ronm Posted January 27, 2004 Report Share Posted January 27, 2004 (edited) If we are going to use physics, we have to use it all the time. Lowering the main jet deeper into the bowl will not affect the pressure differential at the throat because it is the fuel level, not the jet position that determines this. My question had a different motivation. I set up my carb according to the float specs Billy posted (and we all greatly appreciate the advice). At the same time, I also made a couple of other changes (pilot and needle position). The bike runs cleaner now. How much was jetting changes and how much of the down hill improvement was float related, who knows. One thing is certain though, when you lay the bike down (as in fall down), it starves for fuel and cuts off quicker than my GasGas. This is not a good thing if you happen to be in a tricky spot and have to restart. I am wondering if the reduced fuel volume allows the main and pilot jets to suck air sooner. Perhaps extending the main into such a chamber could help keep it submerged. There is another fix for the fuel level problem besides setting the float level lower. I found it on the Davefin Beta website. He says that this mod is used by the Beta factory. It involves a little drilling and plugging of the carb body. Basically, the overflow hole from the float chamber is located forward of the center of the carb by about 16 mm or so. There is another vent hole location that is cast into the body about 10-12 mm rear of this hole. But, this hole location is not drilled. The modification mainly involves drilling this hole and plugging the other one. There are good pics and a good explanation of how to do it. I have not tried it myself, but it looks like the proper fix to me, and I might do it when I feel like taking the carb back off. The article is on the news page of the Davefin site. The url is Davefin_Beta. Just for additional info, I found some Mikuni info on the carb. They say that the maximum mounting angle for the carb is 20 degrees. I haven't checked it with a protractor, but it doesn't look like the Beta mounting is much steeper than that. Edited January 27, 2004 by RonM Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted January 27, 2004 Report Share Posted January 27, 2004 The rider concearned who told me about it is a good expert and said it works, so B*****kss to all this carb set up ballony billy what should he have done buy the gizmo as advised by john lampkin or listen to you? Quote Link to comment Share on other sites More sharing options...
charliechitlins Posted January 27, 2004 Report Share Posted January 27, 2004 With as much talk as there is on this BB about getting those things to run right, it seems like that mickey rooney carburetor should be tossed over the left shoulder (for good luck), and replaced with something that works from the get-go. Quote Link to comment Share on other sites More sharing options...
clarkp Posted January 27, 2004 Author Report Share Posted January 27, 2004 Charlie - its not so much an issue of it working... witness all the Beta machines in the US and the UK. A highly competitive machine regardless of whether it is in the hands of a novice (me) or a more advanced rider. This thread started with my post and I enjoy piddling around with my scooter during the week and have enjoyed the discussions this thread has generated. I would rather have a Mikuni carb than a DelOrto, Amal or the like due to the fact that you can get jets at just about any motorcycle shop; again to facilitate my mid-week piddling with the bike. I'll always enjoy just messing around with things that aren't broke - that STILL need fixing! So, don't kill the thread... go swing a leg over your Harley and leave us to rail at each other about physics and such - its just too much fun! Quote Link to comment Share on other sites More sharing options...
charliechitlins Posted January 27, 2004 Report Share Posted January 27, 2004 Clark, I completely understand what you're saying. I'm a chronic tinkerer, and there's little I like to do more than work on bikes and discuss the hypotheticals, realities and intricacies. I've also been a professional mechanic for many years, so I'm not just a computer rider, and it does seem to me that the Mikuni on the Beta is the only carburetor that almost requires its own forum on the board. Billy Traynor is clearly has an awesome understanding of these carbs and the physics involved in how they work, and it's great that so many of these bikes are running beautifully because of what he has accomplished. It just seems strange to me that a particular part of a particular motorcycle warrants such a disproportionate amount of discussion. In my limited experience, when I'm at a trial, if someone is nearby clearing out a rough-running bike before going into a section, it's generally a Beta. I also happen to be a huge fan of the Beta. It is a beautiful and excellent machine, and their only real flaw seems to be their occasional tendency to have picky carburetion; and the 3 '04's that I recently rode with ran/carbureted flawlessly, so maybe the problems have been sorted out. And I have to say that I'm not quite sure how to react to your suggestion to "swing a leg over [my] Harley" and back off. Why not my Indian or my Sherco? Sounds like a swipe. Good thing I've got Nomex undies! Quote Link to comment Share on other sites More sharing options...
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