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Post by brob305 on Jan 10, 2018 14:40:46 GMT -5
I’ve had my 50mm bbk for almost 2 years and 3000 miles. Stock head, a9 cam, 8 gram rollers, Kevlar belt , and 24mm carb with 106 jet. Oh and performance muffler.
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Post by dexameth on Feb 18, 2018 17:39:41 GMT -5
I’ve had my 50mm bbk for almost 2 years and 3000 miles. Stock head, a9 cam, 8 gram rollers, Kevlar belt , and 24mm carb with 106 jet. Oh and performance muffler. Stock head with 50mm kit and 24mm carb... Have you done a compression test? Just curious, sounds like it rips if you are rocking 8g rollers. |
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Post by 3strokeengine on Mar 18, 2018 16:16:38 GMT -5
I have a 52mm bbk (88cc) 139qmb with 2900 miles and still going
*24mm gy6 150cc carb and intake with 107 main jet
*9 gram dr pulley sliders
*a9 camshaft
*MRP exhaust and header pipe
*Big valve and ported head
*2 headgaskets installed to lower compression
*Stock crank and flywheel and transmisson parts
With me tucked down WOT on flatground it does 55mph pretty reliably and cruises at 45-50mph for extended periods.
This same top end was in a 93cc stroker motor running E85 and the crank bearing failed on both stroker cranks around 1000 miles, so the top end really has around 4900 miles on it.
Pics comming soon
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Post by Happypancake! on Mar 19, 2018 4:57:23 GMT -5
58cc Honda GET w/ no issues. Air box is deleted with small crankcase vents. Link below.
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Post by dexameth on Mar 19, 2018 14:10:04 GMT -5
I have a 52mm bbk (88cc) 139qmb with 2900 miles and still going *24mm gy6 150cc carb and intake with 107 main jet *9 gram dr pulley sliders *a9 camshaft *MRP exhaust and header pipe *Big valve and ported head *2 headgaskets installed to lower compression *Stock crank and flywheel and transmisson parts With me tucked down WOT on flatground it does 55mph pretty reliably and cruises at 45-50mph for extended periods. This same top end was in a 93cc stroker motor running E85 and the crank bearing failed on both stroker cranks around 1000 miles, so the top end really has around 4900 miles on it. Pics comming soon Why lower the compression? haha and I gotta ask what stroker crank were you using? |
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Post by 3strokeengine on Mar 19, 2018 20:29:57 GMT -5
I have a 52mm bbk (88cc) 139qmb with 2900 miles and still going *24mm gy6 150cc carb and intake with 107 main jet *9 gram dr pulley sliders *a9 camshaft *MRP exhaust and header pipe *Big valve and ported head *2 headgaskets installed to lower compression *Stock crank and flywheel and transmisson parts With me tucked down WOT on flatground it does 55mph pretty reliably and cruises at 45-50mph for extended periods. This same top end was in a 93cc stroker motor running E85 and the crank bearing failed on both stroker cranks around 1000 miles, so the top end really has around 4900 miles on it. Pics comming soon Why lower the compression? haha and I gotta ask what stroker crank were you using? You know its been about 3 years since i had the stroker in it and I really cant remember the brand name, i bought it through a local scooter shop I used to work at. As for lowering the compression I figured that what was killing my connecting rod bearings so i added the extra gasket to be on the safe side. Mind you, this is a 47mm head on a 52mm cylinder so compression was already high. |
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Post by scootnewb on May 17, 2018 20:51:15 GMT -5
I recently installed a 50mm BBK with the stock head. It ran fine for the past couple of days but started cutting out when accelerating. Like it would blip as if there was no fuel. I'm going to re-do all the fuel lines etc etc but wondering if this is a warning sign that something is failing on the bottom end.
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Post by dexameth on May 18, 2018 6:15:56 GMT -5
My 52mm BBK finally died after 13,000+ miles. But--- it was MY fault, and not wear and tear (to my belief). The failure came from me not checking ring gap, the top one expanded after a long day of WOT riding and blew the land on the piston, and gouged the cylinder. Rebuilt with stroker crank and other tidbits a couple weeks ago.    |
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Post by fugaziiv on May 18, 2018 8:22:03 GMT -5
I recently installed a 50mm BBK with the stock head. It ran fine for the past couple of days but started cutting out when accelerating. Like it would blip as if there was no fuel. I'm going to re-do all the fuel lines etc etc but wondering if this is a warning sign that something is failing on the bottom end. We've seen a lot of piston failure in 50mm kits with stock heads, and not the bottom end. That's why we never recommend that combo. Matt |
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Post by scooterted on May 18, 2018 8:38:44 GMT -5
I recently installed a 50mm BBK with the stock head. It ran fine for the past couple of days but started cutting out when accelerating. Like it would blip as if there was no fuel. I'm going to re-do all the fuel lines etc etc but wondering if this is a warning sign that something is failing on the bottom end. I wish i knew you had the stock head. Otherwise i would have told you that you have too much compression and are probably detonating when under load. I couldnt hear it in your videos because at idle and rev youre not under load. :/ |
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Post by scootnewb on May 18, 2018 9:41:14 GMT -5
Dang, the places I've read and others I've spoken to recommended the stock head to get more compression. Except for this thread. Can you recommend a good head for 69mm valves. Oddly enough, I added some seafoam to the gas tank and put on a different air filter... On the way back from getting things I needed to drain the gas tank, run new fuel lines, and some beer, it did not 'blip'. So IDK what is going on. Anyone live North of Boston and want to install a stroker crank, 52mm, and BVH so I can be done with this.  I am sorta serious though. I would like to beef up the bottom end properly but my limited skill set and lack of decent tools, it would either take a year or I would jank it up. |
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Post by humanshield on May 18, 2018 10:12:29 GMT -5
I recently installed a 50mm BBK with the stock head. It ran fine for the past couple of days but started cutting out when accelerating. Like it would blip as if there was no fuel. I'm going to re-do all the fuel lines etc etc but wondering if this is a warning sign that something is failing on the bottom end. Running a 50mm BBK with the stock head is the first mistake. Too much compression. Too much heat. IMO, break in procedure on these small engines is more critical than on larger motors. They just don't have much room for error such as overheating. If you didn't break it in properly, early failure is likely. Good luck. |
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Post by humanshield on May 18, 2018 10:14:36 GMT -5
Dexameth, You can't really "complain" about getting 13,000 miles out of it  |
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Post by humanshield on May 18, 2018 10:15:51 GMT -5
Dang, the places I've read and others I've spoken to recommended the stock head to get more compression. Except for this thread. Can you recommend a good head for 69mm valves. Oddly enough, I added some seafoam to the gas tank and put on a different air filter... On the way back from getting things I needed to drain the gas tank, run new fuel lines, and some beer, it did not 'blip'. So IDK what is going on. Anyone live North of Boston and want to install a stroker crank, 52mm, and BVH so I can be done with this. I am sorta serious though. I would like to beef up the bottom end properly but my limited skill set and lack of decent tools, it would either take a year or I would jank it up. Sorry you got that bad advice. The compression with that BBK and a stock head is over 200psi. Sometimes way over. If you try to kick start it and it feels like there a solid rock in there....it's probably too much compression. Sometimes the electric starter can;t even crank it over. |
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Post by scootnewb on May 18, 2018 10:31:53 GMT -5
My kick start mechanism was broken before I installed the bbk, but it starts right up with the electric start. I have the replacement kick start parts. It is on the to-do list.
For the break in, I have been babying it and going for short ride and letting it cool. I changed the oil before the BBK install. Drove it 10 miles (in 1 to 2 mile runs), then changed the oil again.
But yes, I think some luck may be needed. I did gap the rings though. I was trying to do everything 'by the book'.
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I am sorta serious though. I would like to beef up the bottom end properly but my limited skill set and lack of decent tools, it would either take a year or I would jank it up. 
