BBK fallacy?

[vvtr]

Dec 25, 2011 20:28:22 GMT -5 jmkjr72 said:

but in reality with a cvt set up it should be built to ride at wot or the very top of the power band all the time

with mine i find myself wot on major roads then backing off to cruise speeds of 45- 50+
if you take off the side cover with the motor running (on the stand) and actually watch how the cvt works, theres no need to be wot all the time on the road...
i found by backing off it still maintained a constant speed, then when i came to an incline, i still have throttle...

i was also a bit alarmed when i first heard the stories about bearing failure with the bbk.. as i have the 83 (sold as 100cc!) on my qt9 - as its in bits atm with a dead stator i decided to rebuild my spare motor (which has an oil leak behind the genny) with decent quality nsk c3 bearings & fit the larger oil pump i have.

i'll probably keep hold of the 4t for a while seeing as it still does 80mpg - not bad for a ped that tops out over 60!!
i do recommend the gear up kits on the 4t with bbk though... take advantage of the extra torque and keep the rpm down... maybe it will live a bit longer!

[vvtr]

Dec 27, 2011 6:08:16 GMT -5 usmcdoc said:

Sure I know a guy that ruined an engine with a 100cc BBK......cause after running it out of oil in the stock 50cc configuration with 4,200 miles on it....the top end seized..so he replaced it with a BBK which only gave him about 300 miles before the engine was junk.... But hell....when you run a stock engine dry of oil till it locks up....you can rest assured the piston and rings were not the only engine component that was compromised and prematurely worn.

a very valid point - engines do run better with oil in them!!!

on a recent endurance run with 3 of the peds running 139qmb motors, 2 with 70cc bbk & mine with the 83, we were all having to check & top up the oil at every fuel stop.
when you consider the small amount of lube in these motors, it's easy to see how people kill them so quick.
i think they fit the bbk then think cos its 'a new engine' they dont need to do anything to it, when in reality it'll probably burn more oil with the new kit, at least until it's bedded in nice.

also on mine, i noticed that after just 2-300 miles it was smoking quite a bit, so i stripped it at the roadside to find both rings stuck solid in their grooves.
this also happened to one of the 70 kits.
it's easy to fix with a bit of patience, but this coud be another factor in premature failure... the fact that these kits are made so cheap there is obviousy a compromise in quality...
just something you may need to check after a brief run-in
and also the valve stem seals.... the new ones i got in my kit were poor quality and were contributing to high oil consumption - i ended up fitting gen honda spacy seals instead.

there is a temptation to think, hey, this thing is well faster than it used to be, so they screw the nackers off them everywhere... run it dry in the process then moan when they fail lol.
so imo its not the bbk that fails, its the lack of basic maintenance after fitting the kit that lets so many down.
also bear in mind a lot of the people killing their peds are young kids with not a lot of experience in the workings of a motor!

[usmcdoc]

Jan 1, 2012 7:34:49 GMT -5 vvtr said:

Dec 27, 2011 6:08:16 GMT -5 usmcdoc said:

Sure I know a guy that ruined an engine with a 100cc BBK......cause after running it out of oil in the stock 50cc configuration with 4,200 miles on it....the top end seized..so he replaced it with a BBK which only gave him about 300 miles before the engine was junk.... But hell....when you run a stock engine dry of oil till it locks up....you can rest assured the piston and rings were not the only engine component that was compromised and prematurely worn.

a very valid point - engines do run better with oil in them!!!

on a recent endurance run with 3 of the peds running 139qmb motors, 2 with 70cc bbk & mine with the 83, we were all having to check & top up the oil at every fuel stop.
when you consider the small amount of lube in these motors, it's easy to see how people kill them so quick.
i think they fit the bbk then think cos its 'a new engine' they dont need to do anything to it, when in reality it'll probably burn more oil with the new kit, at least until it's bedded in nice.

also on mine, i noticed that after just 2-300 miles it was smoking quite a bit, so i stripped it at the roadside to find both rings stuck solid in their grooves.
this also happened to one of the 70 kits.
it's easy to fix with a bit of patience, but this coud be another factor in premature failure... the fact that these kits are made so cheap there is obviousy a compromise in quality...
just something you may need to check after a brief run-in
and also the valve stem seals.... the new ones i got in my kit were poor quality and were contributing to high oil consumption - i ended up fitting gen honda spacy seals instead.

there is a temptation to think, hey, this thing is well faster than it used to be, so they screw the nackers off them everywhere... run it dry in the process then moan when they fail lol.
so imo its not the bbk that fails, its the lack of basic maintenance after fitting the kit that lets so many down.
also bear in mind a lot of the people killing their peds are young kids with not a lot of experience in the workings of a motor!

Bingo! I see that often when I install a BBK for folks.Tell them to keep a watch on the oil level...as it will use more until the rings seat in....and you only have a quart to start with! Then they run it WOT from day one....and think that like their car....oil changes should be done every 3,000 miles. Hell I have rebuilt many nearly stock 50cc scoots for peeps due to an empty oil sump. Their reply was...It only has 2,000 miles on it and they did not even know how or where to check the oil....and ran it with the factory filled shipping oil... :stumped:

[vvtr]

i think a lot of these problems are also caused by poor pdi on these scoots.

partly this is because virtually anyone can now be a distributor of these things, with no experience in maintenance + also a lot of them (here anyway) are delivered still crated up and it's down to the owner to pdi them.
as a lot of them are inexperienced with bikes & spanners in general this is a recipe for disaster, with badly routed cables, poorly torqued fasteners, wrong oil levels, un-bled oil pumps etc.
over on the chinese scoot forum, one of the guys posted up a pdi checklist which imo should come with the ped.
very usefull, but its a shame people only find it when they go looking online for help when their engine has blown lol!

not that this has anything to do with fitting bbk's lol, just saying that in general people think all you have to do with these scoots is put petrol in & they'll run forever, when sadly they dont!
the bonus for us is there is an endless supply of cosmetically good used peds with engines in need of usually no more than a top end rebuild!