dan williams Posted August 27, 2014 Report Share Posted August 27, 2014 OK I'll admit I'm out of my depth on this. A buddy of mine has an '08 Rev4 factory bike. Supposedly only one of 15 built that year and one of only two in the US. it's never run quite right so it has sat for a few years with the intention of getting it back to proper ridability. I've offered to help cleanup the carb. To a dyed in the wool two stroke guy this carb is a little disturbing but this is how I learn so... Any recommendations where I can find manuals, exploded diagrams and such for this carb. I've been to the usual Beta sites and have the Beta manuals but there are some rather large gaps in the information. I was also wondering if anybody has drilled out the pilot screw plug to open up that avenue of tuning? It's interesting to see the concessions on this bike done for emissions such as venting the crankcase through the airbox and plugging the pilot mixture screw. Also any recommended dealers for parts would be welcome as I'm fairly sure to break something in my poking and prodding. Quote Link to comment Share on other sites More sharing options...
zerorev3rev4 Posted August 27, 2014 Report Share Posted August 27, 2014 there should be a mixture screw on the front of carb underneath engine side , i think i got an adjuster screw by jitsei to enable it to be adjusted by hand , i would go up on the main jet as they seem lean from factory Quote Link to comment Share on other sites More sharing options...
dan williams Posted August 28, 2014 Author Report Share Posted August 28, 2014 Heh heh The original problem the carb had that allowed me to talk my buddy into letting me work on the bike was it was peeing fuel. I just looked at the carb and noticed it's missing two float bowl screws. That was easy. Quote Link to comment Share on other sites More sharing options...
reggie Posted August 28, 2014 Report Share Posted August 28, 2014 the carb needle has a delrin spacer under the needle clip, if this spacer is on the other side of the clip it will be very lean.It would probably run good just off of idle then really stumble and if you did manage to hang on long enough it would come on very strong.Good luck. Quote Link to comment Share on other sites More sharing options...
dan williams Posted August 29, 2014 Author Report Share Posted August 29, 2014 Thanks Reggie. I saw on a scooter site that some shave that spacer down. What about that 90 degree 10mm wide nipple that comes out the side pointing up. Does that connect to anything or is it just a rain catcher? Quote Link to comment Share on other sites More sharing options...
reggie Posted August 29, 2014 Report Share Posted August 29, 2014 Dan I believe that the nipple that you are talking about is the port that the carb uses for sensing the atmospheric pressure.The cap that comes stock on the carb is not 100% sealed, if you want to change this put on a length of hose with a filter on the end of it.There are websites with a lot of info on tuning the cv carb, maybe you can check them out. Quote Link to comment Share on other sites More sharing options...
dan williams Posted August 31, 2014 Author Report Share Posted August 31, 2014 Put it back together today. Bike starts cold with choke and seems to run proper. Attempt to restart and it backfires and refuses to catch. Time to go deeper. Quote Link to comment Share on other sites More sharing options...
dan williams Posted September 1, 2014 Author Report Share Posted September 1, 2014 Reading manuals and trying to come to terms with the complexity of the BSR33-79 I have to believe that much of the complexity is due to this being a last generation streetbike carb that has lots of baggage attached for emissions reduction. I think the same is true for the electrically controlled fuel tap. I know my wife's TTR125 carb is a lot simpler than this beastie. Is there a significant advantage to a CV carb over a variable venturi for a four stroke other than preventing a transient too rich mixture from messing up emissions? Quote Link to comment Share on other sites More sharing options...
slicktop Posted September 1, 2014 Report Share Posted September 1, 2014 Forgive me if this seems left field Dan, but if the bike is a keeper then I would just buy a new Lectron metering carb. I haven't had an issue yet with my Kehein, mainly because of the fuel quality that I use, but one day I'll have a 26-28mm Lectron on the Beta. Its as good as injection as far as response and its a set and forget on the jetting and self compensates for altitude. I haven't checked price on the 28 but my 36 was only 300 bucks. There is another company that makes a smart carb, but I think Lectron is the best. Motion Pro cables are a nice touch too. Just throwing it out there as a good fix for any two stroke carb issue. Quote Link to comment Share on other sites More sharing options...
dan williams Posted September 2, 2014 Author Report Share Posted September 2, 2014 Thanks slick but this is a four stroke and hence my confusion in tuning. I think this carb has more parts than my car. Quote Link to comment Share on other sites More sharing options...
copemech Posted September 2, 2014 Report Share Posted September 2, 2014 Dan, I feel your pain, them THANGS are weird at best and I have had mixed luck with them in the past. If this thing was an early or pre- production card, who knows if it was ever right? I am sure you may figure it out eventually, BUT! A new carb from Beta might be on the list of things to do if you know what I mean. Seems they work well, just realize that when you open the throttle, you are really NOT! Balance of pressures does that for you balanced against a spring. Yes there are jets , screws and passages, if you figure them all out let me know! Quote Link to comment Share on other sites More sharing options...
neil king Posted September 10, 2014 Report Share Posted September 10, 2014 Dan, any luck? I've worked on these carbs a little. It's the same As on the new 4t. The first thing I do to on the new ones is to install a Jitsie remote fuel screw. I had an '08 4t but did not have to pull the carb or change anything. There is very limited info out there on this carb. I found out a little about them from a 4 wheeler forum as the Yamaha Warrior used the BSR before it went fi. Quote Link to comment Share on other sites More sharing options...
dan williams Posted September 11, 2014 Author Report Share Posted September 11, 2014 Not as yet. Not really convinced it's carb but it was the easiest place to look first. Going to check compression and try to test ignition. Quote Link to comment Share on other sites More sharing options...
dan williams Posted September 11, 2014 Author Report Share Posted September 11, 2014 Oh yeah, what I thought might be part of pilot circuit I finally sussed was just cover for TPS location. I never said I was smart. Only non-standard jet was a 100 air jet instead of stock 60. Quote Link to comment Share on other sites More sharing options...
nzralphy Posted September 19, 2014 Report Share Posted September 19, 2014 There is nothing wrong with this type of carb! Do Not change it as it is very good at metering fuel for the difficult 4T engine. Seriously. Even the factory kitted 300cc bikes used this carb. The bikes ship with a very lean mud range to pass emissions. So you need to raise the needle - lower the clip to either the bottom or second bottom groove. Note that there is a plastic spacer either over or under the needle for a half groove adjustment. The main and idle jet is the correct size from the factory. The carb has a VERY thin air balance bellows and it can get a crease way too easy. Check it out. Fit a Jitse air screw to help tune the mixture to about 2.5-3 turns out The carb air ways are very small so take your time and inspect it with a torch Set the spark plug gap slightly large. Bin the original Beta kill button. Check the kill button earth and attach it really well to the frame. Quote Link to comment Share on other sites More sharing options...
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