YX150 engine

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bse150cc

bse150cc

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Joined
Jul 30, 2009
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Canada, Ontario
So i have a BSE 150

The bike is good and i have fun on it, but my buddy has a Konker 125cc and if we race down the road he keeps up to me like nothing... his motor is completly stock

Mine is ported and polished high comp piston, 30mm makuni carb, jetted, uni filter, FMF factory 4.1 full exhasut system, Rev box, NGK plug, preium fuel....
Front sprocket 14 tooth (have a 15 tooth but it doesnt have enough bottom end then)
Rear sprocket 41 tooth

his bike has a 15 41 combo...

Are there anything else i can do easily to get more power out of this thing?? i think it should go faster for what it is.. other then a big bore kit for it or something like that.. i can lift the front tire up in 3rd gear leanign over the bars but it just drops off in the top end like i hit the rev limiter... so im not sure if thats normal or not.

Thanks guys
 
get a 16 front and 37 rear sprocket should make a huge difference
 
do you mean your mate with the 125 keeps up with you in regards to top speed, or acceleration?
15/41 sounds a little short... i'd go 16/37 like DVDrip said, or even 17/37.
I run 17/37 on my 140, and top speed is over 100kph..
but if it's acceleration that your mate is keeping up with, either he has a freak thursday motor, or yours is a friday motor... :p
 
no mine has WAY more balls then his does, i can just flick the throttle in 1st 2nd adn 3rd and lift the front end up like nothing.. he cant even get his up inless he pops the clutch.. kinda sad.. but down the pavement he can keep up just fine when were cruising he and he can slowly pull away at wide open throttle...

I put on a 15/41 to try and i couldnt get the front tire up in 3rd anymore only 2nd and didnt notice a whole lot more top speed just a loss of bottom end, so would going to a 16/37 make that even worse?? would getting more head work help at all?
 
yeah a 16/37 gearing set would decrease your rate of acceleration, and as you said, make it harder to lift the front tyre.. but top speed would be greatly increased...
I'm starting to think there may be an issue with your motor, as my 140 runs tall gearing as stated a couple of posts back, but has enough grunt to lift the front tyre in all four gears... and the fact you have already done a few mods to it, thus increasing power POTENTIAL, makes me think it might need a bit of a tune... Getting rid of the "30mm" Mikuni would be a good start.. i'm not a fan of them, but to each their own..
Going from 14 to 15 teeth on the front sprocket, is effectivel the same as taking 3-4 teeth off the rear sprocket... so you will notice a small decrease in acceleration and a small increase in top speed, which you have mentioned... small changes in gearing are like small changes to suspension... not overly noticeable... if you were to go from a 14 to a 17 tooth front, you would notice a bigger change in both acceleration and top speed...
I still reckon you have something wrong somewhere, cause with the work you have done, for a 150 motor it sounds a little down on outright power...
as far as getting that power back, may i suggest a more performance orientated carby eg OKO flatslide or Molkt? 26mm in diameter is more than enough in either carby. :)
 
oh will the power bug bite someone else :p

Get a real carby, tune it properly and gear it to suit your riding :)
 
the carb is tuned properlly... starts first kick always, and plug is a nice tan brown colour...

has a 25 pilot jet, 115 main jet, fuel screw 1.25 turns out... its hard as hell to kick over so i think its in healthy shape.. and it sucks because no one around here knows anything about these things!!
 
IM kinda starting to think it has something to do with the rev limiter... my buddy when hes at half or 3/4 throttle my bike is bouncing and off the rev limiter it seems.. just doesnt pull anymore...

but saying you 140 will pull the front tire up in all 4 gears with high gearing thats just crazy... i raced a 140 yesterday at a local track he couldnt get the front wheel up with out seat bouncing it in second gear.. maybe im just asking for power i cant have with getting a big bike who knows really i think i might try going down to a 110 main jet, and up to a 30 pilot jet see what happends
 
i tell you what the power bug keeps pn biting me i get more power that excites moe for some time then i get bored and keep upgrading....

my dream pitty engine would have to be a 155z crate motor with a 184cc big bore kit and a DOHC 4 valve head assy wether these fit the 155 i dunno but i wanna know how much balls that engine would have :D:D:D:D
 
to me your problem soudns like it the timing is outta whack by a little bit and your piston is just slightly touching the valves??? maybe bent valve??? but do your valve clearances
 
hahaha yeah, i dont care abou thaving that much power!! i just find it hard to get over a lot of the jumps on the long straights that are bigger at the track where as my buddies little 125 can clear them, but in the conrers i pull out os fasthe doesnt know what hit him... so i want to keep the grunt the 150 produces but get some more top end out of the damn thing basically

and if i find it to slack in the bottom end with 15/41 then 16/37 would make it take for ever to take off haha be sooo slow
 
valve clearances are at .004 i check the rebularily, the timing is all the way retarded, its the only way it prodices any power... called the dealer asked them what it should be at they looked at a few engine in the shop from other BSE bikes, and all of them the timing is all the way retarded... so thats where it should be i guess??
 
oh do you meant valve timing?? well at TDC the YX stamped on the cam sprocket lines up with the > perfectly and i did stick a screw driver in the spark plug whole to make sure its truely at TDC
 
bse150cc said:
IM kinda starting to think it has something to do with the rev limiter... my buddy when hes at half or 3/4 throttle my bike is bouncing and off the rev limiter it seems.. just doesnt pull anymore...

but saying you 140 will pull the front tire up in all 4 gears with high gearing thats just crazy... i raced a 140 yesterday at a local track he couldnt get the front wheel up with out seat bouncing it in second gear.. maybe im just asking for power i cant have with getting a big bike who knows really i think i might try going down to a 110 main jet, and up to a 30 pilot jet see what happends
Click to expand...

hmm... think that just answered the question... you arent running out of revs or power, your running out of gearing... whilst gearing your bike up may take away some of the ability to pop wheelies in third, it will allow you to smoke your 125-piloting mate in a top speed roll on...
And yeah, the 140 will pop top in all four gears... never said it didnt require a clutch pop and a wee seat bounce, but it will still hold it.... mind you, it's a long way from standard as well... am hanging to get some of this monster on you tube, but cant for the life of me figure out how to get digital video tape, (old cam-corder, before flash drives and HD camcorders were invented.. my bad, i'm old.. ha ha) onto computer digital, and then get it small enough to post...
But yeah, you will never get big bike power out of what is essentially a motor with the technology of a boat anchor, or massey ferguson tractor...
ps: you're jetting sounds pretty right, and the plug is tan.... sounds pretty close to me..
 
hmm alright, well ya i could seat bounce and pop the clutch to get it up in any gear also.. but with the 14/41 sprockets i can just give her a lil snap of the throttle even in third and shell flip hahah

Ill order up a 16 tooth front and try 16/41 see how i like that i find when i put the 15 on i can actually use first gear haha with the 14 front first gear is like crawling speed so slow yet so snappy!!
 
Alright so after some research and talking to my buddy at a performance shop, i think what i need to do to make me happy is

Buy a big bore kit like a 180cc
buy a cam for it that gives more bottom end torque
than go buy a 16 or 17/37 combo

you think that will make it rip shit??
 
also do any of you happen to have a service manual for this engine??

And do these things help with power deliver at all i read a bunch of threads with people doing this mod??

sgr-usa.com

thanks
 
Last edited:
Alright, well after 4 hours of research i think i got it figured out as to what i need to do for a good engine!!!

YX150cc

60mm Akunar high comp piston
TB V2 race head with de-comp cam shaft installed

i think that will give me the drunt i want to run a taller gear selection, i was gonna just throw in a high compresion piston but i read up that you can easily crack your case starting it then?? weird... so i will need a cam also then mine as well do a new head with the cam to get the most out of it!
 
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