mcman56 Posted June 3, 2015 Report Share Posted June 3, 2015 I have an 08 Beta Rev3 250 with poor throttle response. (much much softer than a well worn GG200) I have tried all sorts of things and someone on here suggested that there could be an issue with the ignition advance curve. I ran a timing light and got 15 degress BTDC at idle and reved up got 20 degrees. This seems like too much advance at idle and I believe 5 degrees of additional advance is a byproduct of the circuit and not a planned advance curve. For comparison, I once did this on a 97 techno and got 6 degrees at idle, 20 at mid range and 25 to 30 at full scream. I can't find a specification for this anywhere. Does anyone know what it should be? I'm wondering if the CDI is bad and stuck at semi full advance. I hate to buy a new one and find out that they are that way by design. Quote Link to comment Share on other sites More sharing options...
2stroke4stroke Posted June 3, 2015 Report Share Posted June 3, 2015 You'll be lucky. Nobody connected with Beta seems to be able to provide any information about timing in terms of mm BTDC or degrees of advance to enable checking. The best I could get from the importer's workshop some years ago was that having the screw head near the centre of the slot in the backplate "seemed to be about right". Which of course does not provide any sort of info that you need. Quote Link to comment Share on other sites More sharing options...
dadof2 Posted June 3, 2015 Report Share Posted June 3, 2015 I think the 07 125 was the last Beta with fixed timing so your 08 250 should have a timing curve of some sort, certainly not the lack of variation you have. Trials bikes timing curves are a bit strange in that the timing is not set to give peak power or best economy, they are set to give a certain torque curve and softish controllable power. Can you post a photo of your stator? Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 3, 2015 Report Share Posted June 3, 2015 The best I could get from the importer's workshop some years ago was that having the screw head near the centre of the slot in the backplate "seemed to be about right".Ok this made me laugh. Reminds me of the guy looking at a Triumph in a dealership and asking where it will leak the most oil and being told, "Wherever you park it the longest." 2 Quote Link to comment Share on other sites More sharing options...
mcman56 Posted June 4, 2015 Author Report Share Posted June 4, 2015 (edited) Here is the stator. There seems to be more than one brand of ignition on Betas. I believe this one was made in Slovenia. It has been rewound since the picture. I have heard that all lignitions with triggering coils have an advance curve . This is a 2008 200 with a 250 top end installed. Edited June 4, 2015 by mcman56 Quote Link to comment Share on other sites More sharing options...
copemech Posted June 4, 2015 Report Share Posted June 4, 2015 I cannot tell you just how this stuff works together, bit logic seems to dictate that the CDI would be the controller of advance as the trigger unit(s) are fixed. I think a bad trigger unit could cause this as well though, as things get erratic. I do not recall a lot of timing swing ability with the single pickups, though. Normal timing would be around 2.5mm BTDC, just like points. Not sure just how that relates to degrees on that, but close. Excess initial setting would cause kickback on starting and easy stalling I would think. Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 4, 2015 Report Share Posted June 4, 2015 Have to do a little research on this. The fact that it is a hybrid 200 bottom with a 250 cylinder may be significant. Quote Link to comment Share on other sites More sharing options...
mcman56 Posted June 4, 2015 Author Report Share Posted June 4, 2015 Looking at the parts list, all ignition, intake and exhaust components are the same for the 200 and 250. I bought the 250 top end on ebay so am not sure of the year. There is one thing I have never been able to figure out. Beta used to sell 270 kits for the 250 Rev3s but there were several different versions depending on the model year. Externally, all of the Rev3 top ends I have seen look the same reguardless of year so I don't know why there were different kits. Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 4, 2015 Report Share Posted June 4, 2015 I was thinking the crank volume might be different. The 200 originally started out as a bolt on for the 125 but they may all be using the same bottom end now. Quote Link to comment Share on other sites More sharing options...
mcman56 Posted June 4, 2015 Author Report Share Posted June 4, 2015 The Beta 200 is a sleeved down 250 not a big bore 125. At one point I actually split the cases to see if there were any stuffers in the crank but there are none. As far as I can tell, the only difference in the crank assembly is that the 200 assembly has a bronze bushing in the small end of the rod to size it down for the smaller gudgeon pin of the 200. The Gas Gas 200 (175) is a big bore 125. I believe Sherco is/ was the same. Quote Link to comment Share on other sites More sharing options...
dadof2 Posted June 4, 2015 Report Share Posted June 4, 2015 Stator photo shows a trigger device. Should have an advance curve similar to your Techno. The advance takes place electronically takes place in the CDI unit. Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 5, 2015 Report Share Posted June 5, 2015 The CDI has a uController in it. Basically a one chip computer. The advance is programmed into it. There are programming terminals once you remove the goop covering the CDI but you'd have to reverse engineer the software to change it. My guess is you're probably barking up the wrong tree with ignition and should look at your jetting. You might also want to see if you have the white throttle tube (fast). Also Keihin carbs are notorious for water affecting the pilot circuit and require a disassembly and blow out with compressed air. I usually have to do this twice a year when my bike starts acting sluggish off the bottom. Quote Link to comment Share on other sites More sharing options...
mcman56 Posted June 6, 2015 Author Report Share Posted June 6, 2015 The problem is that I have already barked up every tree I can find. It has the fast throttle. Carb cleaning, carb jetting rich to lean, OEM and Boysen Reeds, Keihin 28 and OKO 26, pack muffler, inspect head pipe, alter static timing at stator and probably a number of things I can not remember at the moment. Some of these had an effect but still did not change the basic flavor. The advance curve thing is one thing I had not considered. Maybe I'll try a CDI from a bike breaker. Actually, it is a very sweet bike, perfect for a rider that takes points in turns due less that perfect throttle control. (starts easy, etc.) I'm just at point where I could use better response. Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 6, 2015 Report Share Posted June 6, 2015 (edited) The 200s I've ridden have all been very sweet mellow bikes so you may be right. Then again as Ron Commo always told my friends and I, "You don't need anything bigger than a 200." He always said this as we were picking up our 280s, 270s, or 300s" But hey, we're idiots! Edited June 6, 2015 by dan williams Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 6, 2015 Report Share Posted June 6, 2015 The Beta 200 is a sleeved down 250 not a big bore 125. At one point I actually split the cases to see if there were any stuffers in the crank but there are none. As far as I can tell, the only difference in the crank assembly is that the 200 assembly has a bronze bushing in the small end of the rod to size it down for the smaller gudgeon pin of the 200. The Gas Gas 200 (175) is a big bore 125. I believe Sherco is/ was the same. Looking at the parts manuals on the Beta site I think you're wrong. The 250 and 270 have one number for the crank and the 125 and 200 have another number. All have the same base gasket so a 250 cylinder will fit on a 125 case but the stroke is wrong. This also means the ignition timing and port timing is wrong. You might want to stick a dowel down the spark hole and measure the stroke yourself. Quote Link to comment Share on other sites More sharing options...
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