Jetting???????????

[SOLDIER]

Hopeing spme wone can help. I known this BF 750 has issues. Ive got this thing running pretty good finally. Im thinking I have some sort of jetting issue. Ok guess ill go straight to it. Load test. flat sarface high range 2x4. hold front brakes light them up. with me so far. she will spin them pretty easy but there is an isuue any throttle above 1/4 the RPMs just do not build. full throttle/ 3/4 throttle/ 1/2 throttle there is just no building rpms. Sorry this is the only way to exsplain. May be its just me but she should just continue building RPMS under load. I exspct some weakness but not this much. I hate thes fuc-in CV carbs Any suggestions on what in the hell is up with the jetting. She will set and idle grate, hit the throttle she will rev up pretty good there is a some lag tword the top end full throttle. kinda like it waiting on more fuel I guess. Hell just dont konw she should pull from idle to full throttle but shes acting like shes pulling idle to maybe 1/2 throttle even with it wide open. Im not getting back fire. its just weak. if you take the air cleaner off to watch the slides if you can pull through the back fire with the air cleaner off the slides only rise about aquarter of the way up at 3/4 throttle.
This thing starts awsome. barely need much choke. So i am figureing shes alittle rich on the Pilots .Oh just to awnser any MOD questions. this is a stock. the only thing done to it is the damb engine break is removed. other than that it is completly stock.
Can any on think of something to check or change. Im really getting fed up doolin with this thing. Im just using her to plow with now. But think my 300 honda would just out push this thing.

[kevinryan7]

When was the last time you tore the carb apart, did a very thorough cleaning and reset the mixture screw to the stock setting? Before I had any mods done to mine it seemed like I had to do that every now and then. These carbs don't like any kind of deposits in them. Mine would start fine, idle fine and take a little throttle.....then when I gave it a good punch it would try and cut out. I'd tear it apart, clean it and reset the mixture screw to the factory setting which I believe is 2 1/4 times out (don't quote me on that, check for your manual to be sure) I'd give that a shot and see how it works. If all that is done and it still isn't working then we can go from there. You could also try shimming the needles with a .004 washer if you feel like you're not getting enough fuel. These things come running a little lean from the factory anyway......I did that to mine as well.

[cdcbarr]

I may be reading it wrong, but if your at a dead stop and pin it. How does it perform (nevermind what its doing during a burnout, that could be a traction thing depending on tires)

[dman66]

soldier,you posted about this a while back - still having issues? What type of jets are in there,and what size jets? Snorkles or just factory air box. Is air box lid sealed good.Are the rubber carb and intake boots good.Are the carb slide diaphrams sealed on the caps properly and is the brass orfice installed on each diaphram.Did you shimm needles.Stock fuel pump or changed to a Mr. Gasket 42s.What do the spk plugs look like - I can keep going.Sorry,but these are the questions that need to be looked at.Yes,it's a pain to jet.

[SOLDIER]

Sorry I work alot and am only on here a little bit of the evenings. Sorry didnt give any specifics. Ive been fool with this thing for a while trying to get it right. There Ive tore into these carbs like 5 time now cleaned as everytime. It is very close to being right. there are no mods its stock. Big issue I found cleaned it up alot. that darn rear bus connector was burnt. fixing that cleared it out a lot.
I have completly checked each diafram they look good. and made sure they were seated correctly when putting back together. I honestly cant rember what size the jets were when I had it apart. funny thing there is i was going to write it down but forgot to.
As far as the tire issushe. yeah there pretty much bold. she will act like this bottem end like just crawling around slow shes ok if you pen the throttle she goes but has this wierd mid range thing. I dont really want to say its a bog. its more of a flat spot. once it gets past that it will start pulling then flat again. I dont know if I need to check fuel pump isses or wht. Let me put it this way there is no way any one could pull the fronts up on this girl with out a jack.

[dman66]

Hate to say it ,but you should know or should go back into the carbs and see what pilot jets,main jets,and needles are in there.Then we can help better. I found when I got my bike,I tried the Keihin main jets of #152 front,and 158 rear didn't work for me.A 152 front/155 rear main jet may work better - some say the same size jets work better.If your bike idles good,flattens out mid range,and regains full power to WOT,You may need to shimm each needle with one or two #4 washers - also is your A/F screws turned out to 2 1/2 turns out each carb - also make sure your slide needles are NFKK front/NFKL rear or both NFKL needles.

[NovaKaw650]

Quote: Originally Posted by SOLDIER

As far as the tire issushe. yeah there pretty much bold. she will act like this bottem end like just crawling around slow shes ok if you pen the throttle she goes but has this wierd mid range thing.

Are you saying you're basing it's performance and your troubleshooting on how well it brake burns (spins it's tires)?? Please say it ain't so.

[SOLDIER]

Thanks thanks for the info. think I just vent on here more than any think. Ill try the carb shimes again. I may spray the boots with some carb cleaner make sure shes not sucking air. I know this old girl has more in her just got to lossin her up a bit more.

[SOLDIER]

Well if this doesnt say much. try this my 300 four trax will Eat this brute up. speed pulling climbing what ever. the hondas a straight horse compared to this brute. the brute just has no pick up. and its piss me off. this thing ought to run circles around that old ass honda. Dont get me wrong here the brute ist that bad and is coming along the motor sounds pretty good. but its just lacking. I changed out the belt thinking maybe it was worn with only a fine gain. hell my honda will light up all 4 26's and there new. and its stock short the lift kit. I shouldnt need to even hold the front breaks to get the brute to light them up.maybe im just to use to having having gears. but I swear that old 250 polarish I had pulled harded than this thing to and it was CV//// 2 stroke but never the less I know you alls brutes for the most parts are not dogs like this one. I am not sure on this but I just dont think the motor is spinning up enought> recon all I can do is just keep pluging away. trying to figure this thing out.

[NovaKaw650]

Quote: Originally Posted by NovaKaw650

Quote: Originally Posted by SOLDIER

As far as the tire issushe. yeah there pretty much bold. she will act like this bottem end like just crawling around slow shes ok if you pen the throttle she goes but has this wierd mid range thing.

Are you saying you're basing it's performance and your troubleshooting on how well it brake burns (spins it's tires)?? Please say it ain't so.

Quote: Originally Posted by SOLDIER

Well if this doesnt say much. try this my 300 four trax will Eat this brute up. speed pulling climbing what ever. the hondas a straight horse compared to this brute. the brute just has no pick up. and its piss me off. this thing ought to run circles around that old ass honda. Dont get me wrong here the brute ist that bad and is coming along the motor sounds pretty good. but its just lacking. I changed out the belt thinking maybe it was worn with only a fine gain. hell my honda will light up all 4 26's and there new. and its stock short the lift kit. I shouldnt need to even hold the front breaks to get the brute to light them up.maybe im just to use to having having gears. but I swear that old 250 polarish I had pulled harded than this thing to and it was CV//// 2 stroke but never the less I know you alls brutes for the most parts are not dogs like this one. I am not sure on this but I just dont think the motor is spinning up enought> recon all I can do is just keep pluging away. trying to figure this thing out.

Again..... have you actually driven it at speed to see how it works, or are still basing preformance on how well it spins? If you are basing it on the ability to spin, then please find yourself a good tuning shop to do the work for you rather than torturing that poor BF.
A normally running stock BF750 will outrun a TRX300 with one spark plug removed.