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by: rcq92130 - Jul 29, 2014 23:10:25 GMT -5
Post by rcq92130 on Jul 29, 2014 23:10:25 GMT -5
Have a 150cc BMS Heritage and looking for more POW! Doing the slider thing; have a better exhaust & intake, was about to rejet the teensy little 25cm carb.
Then I thought: these carbs are not very expensive --- maybe it would be better to just get a 30cm carb.
Good idea or crappy idea???
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by: rockynv - Jul 29, 2014 23:52:58 GMT -5
Post by rockynv on Jul 29, 2014 23:52:58 GMT -5
How much more are you looking for? If you need interstate speeds then you really need a 250.
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by: rcq92130 - Jul 30, 2014 0:05:00 GMT -5
Post by rcq92130 on Jul 30, 2014 0:05:00 GMT -5
Not that much - still just using it as a fun (non-freeway) commuter. But wondering if a larger carb would make a significant difference.
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by: alleyoop - Jul 30, 2014 0:10:51 GMT -5
Post by alleyoop on Jul 30, 2014 0:10:51 GMT -5
Have a 150cc BMS Heritage and looking for more POW! Doing the slider thing; have a better exhaust & intake, was about to rejet the teensy little 25cm carb. Then I thought: these carbs are not very expensive --- maybe it would be better to just get a 30cm carb. Good idea or crappy idea??? Bad Idea, a 30mm is to big of a carb for a 150cc motor. Just to give you an example My 157QMJ motor 149.6 is bored out and with a stroker crank is now 182cc's and I have a 24mm carb jetted, Main 122.5 and a 125 main to much fuel also Pilot 38 and 40 was to much fuel. In addition what you are contemplating putting in will not do much for any "POW" factor. Alleyoop |
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by: rcq92130 - Jul 30, 2014 0:16:40 GMT -5
Post by rcq92130 on Jul 30, 2014 0:16:40 GMT -5
I have the same engine. I see there are some big bore kits - some to 180 w/o milling the crankcase. Did that increase in size give a big boost for yours?
If NOT increasing the bore, what main jet would be good (and when you said "pilot" is that the idle jet?)
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by: alleyoop - Jul 30, 2014 0:29:53 GMT -5
Post by alleyoop on Jul 30, 2014 0:29:53 GMT -5
Pretty hard to get 180cc without boring the case, whoever is selling that kit I would like to see the kit and tell you if its true or not.
Main jet for a stock motor no performance exhaust or free flow filter I would try a #110 main jet but also have a the next one smaller just in case it is to much. Remember all motors are different all depends on their compression. Rule of thumb is add a free flow go up 2 on the main jet if you add a free flow muffler go up 2 more. The Pilot no bigger than a #35.
Alleyoop
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by: alleyoop - Jul 30, 2014 0:39:10 GMT -5
Post by alleyoop on Jul 30, 2014 0:39:10 GMT -5
Also remember just because you have more power does not mean it will get more top end speed. What you just built is a motor with more power so to get to speed you will get there much faster. But now that you have more power you can put in taller tranny gears for more top end speed and you will have the power to pull them. Also putting in a Stroker Crank the Stroker crank will cause of some loss of RPMS.
Alleyoop
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by: alleyoop - Jul 30, 2014 0:45:11 GMT -5
Post by alleyoop on Jul 30, 2014 0:45:11 GMT -5
Working and tuning your CVT you can possibly get up to 5 more mph on your top end. That would include a 115mm Variaator and 11-12 gram weights. In addition if you scoot does not have a tach I would suggest you get one they are not expensive but are critical to tuning your carb, motor and cvt.
Alleyoop
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by: rcq92130 - Jul 30, 2014 9:22:07 GMT -5
Post by rcq92130 on Jul 30, 2014 9:22:07 GMT -5
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by: millsc - Jul 30, 2014 11:16:17 GMT -5
via mobile
Post by millsc on Jul 30, 2014 11:16:17 GMT -5
Go with a taida 61mm kit fits no boring I matched it with a 3mm stroker big gain.
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by: rcq92130 - Jul 30, 2014 21:28:06 GMT -5
Post by rcq92130 on Jul 30, 2014 21:28:06 GMT -5
Millsc - what engine did you put this on?
Read up on what Taida offers .... assuming you didn't get the full shebang with modified crankcases, etc but only a big bore kit of cylinder, head, etc .... I couldn't figure out what to get. Some kits said, Milling definitely required", others said, "Milling might be required .... but will be on all Chinese-made engines". Mine IS a Chinese-made engine (BN157QMJ).
Would like to big bore it, but no so much as to completely strip the engine and get it bored.
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by: pmatulew - Jul 31, 2014 11:43:27 GMT -5
Post by pmatulew on Jul 31, 2014 11:43:27 GMT -5
Milling for oversize: The cylinder sleeve needs to be able to fit down inside the engine block.  You would need to ream out the opening in the top of the block. No practical way to contain the mess without stripping it down. +1 on getting a tach. Hard to judge by ear what's going on. +1 on a free flow exhaust Carbs are a fiddly business. More is not necessarily better. Too much available throughput and you lose intake velocity and vacuum. Consequently less fuel draw from the jets. Also intake stack length can have a big effect on how the motor behaves. Get it right and the resonant frequencies help give it some intake boost. Aside from bore and stroke changes, most of your benefit is going to come from tuning the CVT properties. |
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by: rcq92130 - Jul 31, 2014 13:59:39 GMT -5
Post by rcq92130 on Jul 31, 2014 13:59:39 GMT -5
Damn those Chinese! Why on earth would they not make the opening sized properly  ? Took my Goldwing engine down a few years ago and that kind of cured me of wanting to strip down another cycle engine. Too bad - would have enjoyed running this thing up to 170 or 180 cc. Just for yuks - whats the max sleeve size on a Chinese BN157QMJ? |
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by: rcq92130 - Jul 31, 2014 14:01:21 GMT -5
Post by rcq92130 on Jul 31, 2014 14:01:21 GMT -5
Oh - and also about the variator.
Some guy told me there is little gain putting in a larger variator unless I increase the displacement of the engine. Is that correct, or should I also get a larger diameter variator (have 11 g sliders on the way already).
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by: alleyoop - Jul 31, 2014 14:54:09 GMT -5
Post by alleyoop on Jul 31, 2014 14:54:09 GMT -5
Whoever that guy was that told you about little gain putting in a larger variator unless you increase the displacement tell him this and you can tell him I said it.
"THOSE WHO DO NOT KNOW, DO NOT KNOW THAT THEY DO NOT KNOW"
The thing a larger diameter variator will give you is more top end due to being able to get the belt to climb higher in the variator face thereby creating a bigger wheel. Remember a bigger wheel will turn a smaller wheel more times per revolution, same applies to the tranny gears.
Just ask yourself, What Turns the Clutch Pulley which in Turn Turns your Wheel..ANSWER..The Front Driven Pulley(Variator) which is turned by the crank. So the faster the crank turns the faster it turns the rear pulley that turns your wheel. Now how can one get the Rear Pulley to turn more times.. 1 way is to bump up the RPMS turning the crank faster, 2 get a bigger diameter Variator, 3 put in taller tranny gears.
More displacement gives the motor more power BUT if nothing else is changed it will not give you more top end. What it will do is get your scoot up to speed faster being able to pull the weight with the extra power.
Alleyoop
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..BAD TO THE BONE..
