sammyd173 Posted December 24, 2015 Report Share Posted December 24, 2015 Please do post back on here when you get to your carb and see where that one hose goes! For me, choke is one click out for cold starting. The engine fires in three kicks and revs immediately climb higher than I am comfortable with so I put the choke all the way in right away. With stock, leaner jetting perhaps you would pull it out two clicks? Regardless the choke will always be all the way in once the bike is warm. That spacer is a mystery. It won't raise the needle if you remove it, unlike the clip. If anything it will lessen the tension on the little spring and that's it. I'm sure it does richen the mixture some way, I just don't see how. Quote Link to comment Share on other sites More sharing options...
timp Posted December 24, 2015 Report Share Posted December 24, 2015 Please do post back on here when you get to your carb and see where that one hose goes! For me, choke is one click out for cold starting. The engine fires in three kicks and revs immediately climb higher than I am comfortable with so I put the choke all the way in right away. With stock, leaner jetting perhaps you would pull it out two clicks? Regardless the choke will always be all the way in once the bike is warm. That spacer is a mystery. It won't raise the needle if you remove it, unlike the clip. If anything it will lessen the tension on the little spring and that's it. I'm sure it does richen the mixture some way, I just don't see how. Is there more than one position for the choke to be on? Can't say I have noticed any extra positions. Quote Link to comment Share on other sites More sharing options...
undertheoaks3 Posted February 7, 2016 Report Share Posted February 7, 2016 I have the 2015 300 4T, all stock jetting, runs perfect and will start on first kick and idles perfect you also do notice the difference in the idle when you switch from wet to dry mapping. My question is about the compression popping or backfiring that only happens when off the throttle and going down a hill or sudden compression braking...normal or ? Quote Link to comment Share on other sites More sharing options...
sammyd173 Posted February 8, 2016 Report Share Posted February 8, 2016 It's normal for these bikes but it's not correct. Popping is due to lean jetting. Try the jetting recommendations on the sheet at the start of this thread - Beta themselves are telling you what the correct jetting should be. I finally figured out where my issues were coming from. The jubilee clips are very hard to get to on the boot that goes between the air box and the carb. When sliding everything back together it's tempting to cinch up the one on the left to the air box because it's easier to get to. Don't! You have to make sure the boot is 100% flat and aligned with the carb. Do that one and then do the one on the air box, which has a lot more room for alignment. If you do the air box side first then it's a stretch to get the other side on the carb, which leads to a poor seal and rough idle, especially after you hop the back end around which shakes things looser. Quote Link to comment Share on other sites More sharing options...
sammyd173 Posted June 7, 2016 Report Share Posted June 7, 2016 Update: swapped slow jet from 22.5 to recommended 27.5 and the bike rips off the bottom. Very significant difference, especially when snapping open the throttle in a section and the bike responding much faster. On a side note, I tried my bike with an arrow exhaust and it's a remarkable boost in power. I didn't notice too much more noise but I bought this bike specifically for its quietness so I'm not sure if I want to take the plunge. Quote Link to comment Share on other sites More sharing options...
trapezeartist Posted September 6, 2017 Report Share Posted September 6, 2017 I'm finding this thread very useful. I just bought a 2012 300 4T. At the moment I have no idea what is inside the carb, except the dealer I bought it from said they changed the needle height and the idle in the workshop before delivery. My first task is to get the carb off . So far I've successfully removed the airbox and the CDI unit, and loosened the jubilee clip holding the carb to the manifold. Next it looks like I'll have to remove the rear shock to allow the carb to come out backwards. What a pain! First I'm waiting on delivery of a stand so I can take the weight off the rear wheel. Given my raw novice status and the punchy performance of the engine, my main aim will be to try to get the engine to be a little more gentle and progressive at the bottom end. Any thoughts? I'd also like to get rid of all the popping on the overrun, which this thread seems to suggest is due to a lean slow jet and/or lean setting on the needle. Quote Link to comment Share on other sites More sharing options...
lineaway Posted September 6, 2017 Report Share Posted September 6, 2017 Remove the exhaust, much easier. Quote Link to comment Share on other sites More sharing options...
trapezeartist Posted September 6, 2017 Report Share Posted September 6, 2017 5 hours ago, lineaway said: Remove the exhaust, much easier. Yes, that's off as well. 1 Quote Link to comment Share on other sites More sharing options...
markbxr400 Posted October 10, 2017 Report Share Posted October 10, 2017 Just bought a used 16 EVO 300 4T up in Colorado (first trials bike for me). Rode it while up there (5-6,000 feet elevation). Starts easy, however, it had a lot of decel pop, and flamed out a large number of times. I assume it's running very lean. I actually live at sea level in Alabama. Just got home yesterday to a hurricane, so haven't ridden it here yet. Assume it's going be even leaner down here. Also, the PO said he put the blue spring in, and he provided me with the stiffer spring. Q: Where can I find jets for this carb, and does anyone have any info on what jets are recommended for different altitudes? Also, any instructions on how to replace the spring and the jets? Many thanks, Mark Quote Link to comment Share on other sites More sharing options...
trapezeartist Posted October 10, 2017 Report Share Posted October 10, 2017 This is the table I found somewhere with the recommended settings: I followed the 300 competition settings and got a lot of popping in the exhaust. I've now wound the idle mixture out from 2 to 2.5 turns (it's actually a "fuel screw", not an "air screw") and that stopped it. The engine is obviously a lot happier as the idle speed went way up, and had to be adjusted down with the normal idle adjustment screw. As you can see there is no allowance for altitude. I would guess that these would work up to 1000m. Above that, you're on your own. Taking the carb off is a pig of a job, but once it's out the rest is easy. Remove the plastic top cover (2 screws) to get to the spring and diaphragm. Remove four screws on the bottom to drop off the float chamber and get access to the jets. 1 Quote Link to comment Share on other sites More sharing options...
markbxr400 Posted October 11, 2017 Report Share Posted October 11, 2017 5 hours ago, trapezeartist said: This is the table I found somewhere with the recommended settings: I followed the 300 competition settings and got a lot of popping in the exhaust. I've now wound the idle mixture out from 2 to 2.5 turns (it's actually a "fuel screw", not an "air screw") and that stopped it. The engine is obviously a lot happier as the idle speed went way up, and had to be adjusted down with the normal idle adjustment screw. As you can see there is no allowance for altitude. I would guess that these would work up to 1000m. Above that, you're on your own. Taking the carb off is a pig of a job, but once it's out the rest is easy. Remove the plastic top cover (2 screws) to get to the spring and diaphragm. Remove four screws on the bottom to drop off the float chamber and get access to the jets. Thanks for the help. I am assuming mine has the stock competition jets in it (a reply from Mike Cozza at Beta USA indicated it should have 127.5 main and 27.5 pilot). I think I'll order a few jets larger for the main before I pull the carb, so that hopefully I only have to go through the process at one time. Any trick to replacing the spring once the top is off? Thanks again. Mark Quote Link to comment Share on other sites More sharing options...
trapezeartist Posted October 11, 2017 Report Share Posted October 11, 2017 Some people have suggested to me that I should use 127.5 main jet but 120 seems to be working fine for me. There's nothing tricky about the spring. The difficult bit is removing and refitting the carb on the engine. I wouldn't suggest this is definitive, but it goes something like this: Remove rear mudguard. Remove airbox (The jubilee clip may be difficult to access and there are two hidden rubber pipes under the main part.) Disconnect the top of the rear shock and lean it back. Remove CDI unit on right hand side. Remove the finned aluminium ignition box that lies on top of the gearbox. Remove the rubber connector to the carb. (Another tricky jubilee clip). Disconnect the fuel pipe and throttle cable. Undo the jubilee clip fixing the carb to the engine stub (this one may be easier). Twist, fiddle, wiggle and turn the carb until it comes out, probably on the left side. When you come to refit the carb, take care to make sure none of the breather pipes are going to touch the exhaust and try to point the jubilee clips in the direction that is easiest for access. I found it was easiest to leave all the jubilee clips loose until everything was together, then tighten them all. It helps with the alignment. 1 Quote Link to comment Share on other sites More sharing options...
klonheadd Posted October 11, 2017 Report Share Posted October 11, 2017 (edited) I have managed to pull my carb out after removing just mudguard, silencer and then airbox on my evo 4t '12. I didn't need to undo the shock, cdi or regulator - but it's tricky. A lot of observation and some turning/wigling and it will come out. Edited October 11, 2017 by klonheadd 1 Quote Link to comment Share on other sites More sharing options...
lineaway Posted October 11, 2017 Report Share Posted October 11, 2017 (edited) You will have to move the shock to get it in. Edited October 11, 2017 by lineaway 1 Quote Link to comment Share on other sites More sharing options...
klonheadd Posted October 11, 2017 Report Share Posted October 11, 2017 (edited) 6 minutes ago, lineaway said: You will have to move the shock to get it in. After you remove airbox theres enough room to operate. Didn't need to touch shock. It worked for me. Edited October 11, 2017 by klonheadd 1 Quote Link to comment Share on other sites More sharing options...
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