mcman56 Posted July 1, 2011 Report Share Posted July 1, 2011 I have had a 08 rev 3 200 for a few months and it has run OK at sea level and 1200 feet. Last weekend I rode a trial at 5500 feet and the power felt "flat" or soft. So I tried very quickly opening the throttle and it would bog and then ping when the throttle was shut. Back to sea level, I have cleaned the carb twice, raised the needle two notches and still have the same result. I'm not that quick on the throttle so it may have always been that way. The plug looks slightly rich. My question is, what else could cause that symptom? It seems that stator issues would mimic rich. The idle is very strong so I would think that rules out crank seals. Could this just be a lean pilot jet? Adjusting the mixture screw has almost zero effect. Quote Link to comment Share on other sites More sharing options...
chewy Posted July 1, 2011 Report Share Posted July 1, 2011 Just to offer current experience for us; we are riding at 2.500 mtrs (7500 ft) ..no pinking, slight loss of power mostly at top end of revs..we are running pretty lean oil mix 1.5%)for maximum petrol/air mix.. have you changed your fuel supply?..clean filter etc. Quote Link to comment Share on other sites More sharing options...
copemech Posted July 2, 2011 Report Share Posted July 2, 2011 I have had a 08 rev 3 200 for a few months and it has run OK at sea level and 1200 feet. Last weekend I rode a trial at 5500 feet and the power felt "flat" or soft. So I tried very quickly opening the throttle and it would bog and then ping when the throttle was shut. Back to sea level, I have cleaned the carb twice, raised the needle two notches and still have the same result. I'm not that quick on the throttle so it may have always been that way. The plug looks slightly rich. My question is, what else could cause that symptom? It seems that stator issues would mimic rich. The idle is very strong so I would think that rules out crank seals. Could this just be a lean pilot jet? Adjusting the mixture screw has almost zero effect. Is this a Kiehin bike or Mikuni? Principals all the same, both symptome are consistant with a lean pilot circuit or blocked jet or passage.. Do you recall jet sizes? Quote Link to comment Share on other sites More sharing options...
mcman56 Posted July 2, 2011 Author Report Share Posted July 2, 2011 Is this a Kiehin bike or Mikuni? Principals all the same, both symptome are consistant with a lean pilot circuit or blocked jet or passage.. Do you recall jet sizes? This is a Mikuni, 27.5 and 145. What are the symptoms of a bad stator? On throttle is probably the same thing as high combustion pressure to fire a plug. Quote Link to comment Share on other sites More sharing options...
copemech Posted July 2, 2011 Report Share Posted July 2, 2011 This is a Mikuni, 27.5 and 145. What are the symptoms of a bad stator? On throttle is probably the same thing as high combustion pressure to fire a plug. Those jet sizes seem odd to me, too small and too large, but we will have to wait untill someone with more Beta/Mikuni experience chimes in. On the stators, well, for the most part, they quit running! Quote Link to comment Share on other sites More sharing options...
copemech Posted July 3, 2011 Report Share Posted July 3, 2011 Bump, where is Dan? Need US jetting for the Mikuni! Quote Link to comment Share on other sites More sharing options...
dan williams Posted July 3, 2011 Report Share Posted July 3, 2011 A stator usually runs crappy at the higher RPM then just dies. The 27.5 and 145 are normal around here (sea level) for a 250-270. Not sure if they are the same for a 200. Should be pretty close though going one size up on the pilot won't hurt. The fact that you have a 27.5 in there means somebody's already tuned it as the standard pilot is a 30. Since your mixture adjust screw has no effect I'd call blocked pilot as most likely. Watery or just plain lousy gas can mimic the effect of a blocked pilot. When you clean you have to really disassemble and go after the jets and body passages with compressed air. Make sure you assembled the needle correctly under the retaining plate. I've seen carbs with the splash shield under the main jet on upside down run weird too. Make sure your air boots and the clamps are sitting properly on the carb. It's easy to tighten them too much and have them slide off the carb throat. You've described where it runs screwy can you tell us if there is somewhere in the throttle range it runs good? Under load? Helps to debug which carb circuit may be at fault. Oh yeah make sure your choke is all the way off. I've seen bent ones stuck partially on. No wait one more thing is to make sure there isn't dirt in the intake holes for the pilot circuit in the intake bell. That can make it act funky too. Quote Link to comment Share on other sites More sharing options...
mcman56 Posted July 3, 2011 Author Report Share Posted July 3, 2011 The bike started easily and had a very strong healthy idle. It was maybe OK when slowly opening the throttle but with a quick twist would bog. A quick twist brought an increase in rpm followed by sort of shutting off until the throttle was returned. I cleaned the carb twice by disassembling, using carb cleaner and high pressure air. All passages that could be seen were open to the eye and flowed air. The first cleaning included an air box cleaning and a look down the intake at the reeds. The second cleaning included raising the needle two positions. Neither had an effect. So..I pulled the stator cover and flywheel. It was very dirty inside and had some corrosion. The dirt was stuck on like it was wet when it got dirty. The stator itself looked OK. I cleaned it up with a tooth brush, contact cleaner. and an air hose. Upon reassembly there was no spark. Checking continunity wire to wire and wire to ground, the only connection is 1 ohm between the yellow wire and ground. I guess I need a rewind. I do have a couple of questions. 1. The parts list shows no gasket for the stator cover. On other brands, I have always used silicone in addition to whatever gasket was there. What is recommended for Beta? (I am aware of the acetic acid given off by RTV and the possible ill effects on electronics but have never had an issue.) 2. The rotor says Slovenia. Who makes ignitions in Slovenia? Quote Link to comment Share on other sites More sharing options...
dan williams Posted July 3, 2011 Report Share Posted July 3, 2011 (edited) Hate to say it but this sounds like classic broken reed. If you slowly open the throttle does the RPM increase linearly? Duh, read the above post Dan you dumbass. Edited July 4, 2011 by Dan Williams Quote Link to comment Share on other sites More sharing options...
mcman56 Posted July 21, 2011 Author Report Share Posted July 21, 2011 Following advice on this site, I sent the stator off to West Country Windings. They confirmed it was dead and rewound for 93 pounds including shipping. It arrived back two weeks after I shipped it too them. This has cured the odd bog issue, at least in a backyard test. Quote Link to comment Share on other sites More sharing options...
dan williams Posted July 21, 2011 Report Share Posted July 21, 2011 Excellent. I'll file away this in the brain case for future reference. Thinking it through the bad stator may have been affecting your timing advance which would cause a delay in engine acceleration. Quote Link to comment Share on other sites More sharing options...
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