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Post by sickopsycho on Jul 27, 2013 20:03:51 GMT -5
I just installed a bbk (72cc) and love it. I am a trained automotive mechanic and was METICULOUS with my install. I pulled the engine, cleaned and degreased it, replaced cylinder and piston using assembly lube in a CLEAN work area and torqued everything down to spec. There were no instructions regarding the piston rings so I went with the old reliable (one compression had a silver edge, it went on top- all ring gaps were 180 degrees from each other). I even removed carbon from my head/valves before reinstall. I broke it in per retailers instructions which were simply vary the throttle for the first 50 miles and no extended WOT. I actually ran 100 miles or so under these conditions. Anyway it has quite a bit more pulling power now but I don't seem to be able to hit top speed anymore (since the bbk install). I get right up to to the edge of my speedo but even going downhill it wont seem to peg the needle. Before the bbk install the needle would (eventually) peg when going downhill. Now it will get up there and get there quick- even hold pretty much 40mph uphill but won't seem to go any faster. I'm pretty sure I'm not hitting the rev limiter- I'm just not sure whats up. I have a hot coil and wire plus an iridium plug, I have a brand new name brand Keihn or something carb with a  # main jet installed with a short ram performance air filter. My exhaust is stock. I also purchased a 1500rpm set of clutch springs and and 1500rpm torque spring along with a set of 5gram slider rollers that I havent installed yet. I think the rollers I have in there now are 5 gram and I don't think I'll get any more speed out of the springs (clutch or torque). Any advice? Funny side note- my carb... I went to tune the air/fuel mixture and it's acting funny. It ran well at the factory setting but I thought maybe a little rich. I let the bike warm up completely and adjusted the idle to just before the clutch started to engage. I turned the mixture adjust all the way clockwise (to lean it out) and this would normally cause the bike to cut off. Instead, as I turned it right, the idle continued to increase until the screw was bottomed out. The way I'm used to tuning this carb you turn the screw all the way right until the engine almost dies and then *slowly* back it back to the left (to richen the mixture) and listen to the idle. It will increase to a point then pretty much stop before it begins to decrease again. The point at which the idle is the fastest is pretty much stoich (the proper setting). I can't seem to tune it since the best setting seems to be lower than it can go. Would this be because of the bigger main jet I installed? If so is there a way to tune this carb? I also noticed that with the mixture adjust almost all the way closed (turned to the right) the idle is the fastest there but when I come off of WOT I get more backfires as if it's even richer? ? I'm totally confused. Any help would be greatly appreciated.  |
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Post by scoots on Jul 27, 2013 20:25:31 GMT -5
solve ur problem buy a performance exaust
or chop ur pipe...it is flow think more in but still backed up with exit for flow
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Post by sickopsycho on Jul 27, 2013 20:31:45 GMT -5
Yeah I was just looking into that- what's up with chopping the pipe? I read about people drilling them, what would I need to do? Where do I drill out? I don't really have another $100+ to dump into a performance exhaust right now...
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Post by scoots on Jul 27, 2013 20:36:56 GMT -5
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Post by tvnacman on Jul 27, 2013 20:38:13 GMT -5
you have the tork change the tranny gears . BBK's give you more tork not rpm's .
see if the oring is damaged on the a/f adjusting screw tip .
John
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Post by sickopsycho on Jul 27, 2013 20:44:41 GMT -5
[replyingto=scoots]scoots[/replyingto]Thats what I was wondering- but how do I take the baffle out? It seems to be inside the muffler and the whole thing is welded shut. Do I have to cut it and weld it back or what? I can take the muffler off no problem but after I took off all of the silly looking chrome stuff it's all welds from there... where is this baffle if not physically inside the muffler?
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Post by sickopsycho on Jul 27, 2013 20:47:21 GMT -5
[replyingto=tvnacman]tvnacman[/replyingto]Thanks for the tip, John. I'll check the o-ring but it's a brand new carb. I'm wondering if it's not due to the # jet I installed? maybe it's too big? The carb came with an  # jet which might have actually been more appropriate because I think the stock 49cc jet is smaller than that if I'm correct? It is still running rich because I get backfires after WOT like I said and if I snap the throttle it bogs down before settling at idle. A lean condition should run higher rpms before settling after a snapping the throttle... What do you think about the jet size? |
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Post by tvnacman on Jul 27, 2013 21:01:37 GMT -5
check your vacuume . carbs are not my bag I just get by with them I will leave that to a select few . If the carb is new it should be ok then right ? wrong check it with your own eyes . #1 rule of trouble shooting never take anything for granted . Some pod filters flow too much air so it could still be lean how does the plug look ?
You could offset your gearing with a larger diameter variator .
John
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Post by sickopsycho on Jul 27, 2013 21:06:46 GMT -5
[replyingto=tvnacman]tvnacman[/replyingto]I'll give it another good once over tomorrow. I'm pretty sure vacuum is good as I replaced all lines due to rot and secured with quality hose clamps. As a side note- for whatever reason my kick start never worked before the bbk install. It would turn the engine over fine but I could kick it all day and it would never crank- even with starter fluid. Compression was fine in my old cylinder so idk what that was about- but now it will kick right up the first time it hits the compression stroke. I actually was turning the engine over with the kick start right after i put it back together (to test for interference or anything wrong with reassembly) and was ever so gently turning it over when, by mistake, i started the motor. I was holding the brake and didnt realize the key was on (even though the battery was disconnected). LOL- it startled me because I never got it to work before but imagine my delight when my hard work sprang to life before I even expected it to! =)
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Post by tvnacman on Jul 27, 2013 21:14:45 GMT -5
unplug your enrichener see if it runs better all around . if so you need to upjet .
John
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Post by scoots on Jul 27, 2013 21:17:23 GMT -5
baffle u gotta cut ur way in the metal not the chrome BS
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Post by brandjur on Jul 27, 2013 23:14:29 GMT -5
You might need to upjet to #  or #92. First move the needle lower (clip higher) on the carb. See if that has any effect on your backfire. Also, what does the plug look like? As far as top speed, since you have the torque springs, you might need heavier sliders to reach higher speeds. I would recommend getting 6g sliders and trying those. If the 6g are a tad too heavy, you could mix the 6g/5g for an effective 5.5g sliders. With the idle, did you see what size pilot jet the new carb came with? If it is larger than your old carb, you could always switch. |
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Post by sickopsycho on Jul 27, 2013 23:45:31 GMT -5
[replyingto=brandjur]brandjur[/replyingto]Thanks for the tips. I'll try adjusting the needle but I dont think I need a bigger main jet, as i said im rich not lean. This carb came with an # jet but i installed an # and thats the one im running and running rich with now. My old carb is an epa carb and i cannot get the bottom off to check/change the jet without cutting it open... even though i guess i dont need it so i suppose i could cut it. Think I'll try the # jet first. As far as the drivetrain- I havent yet installed the torque spring... what exactly does it do? It puts pressure on the variator to keep it from spreading (speeding up) right? How does this affect performance? My sliders havent been installed yet either- but I didnt know you could mix and match them but now that you mention it makes sense. Thanks for the tip! |
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Post by brandjur on Jul 28, 2013 12:40:43 GMT -5
Did the plug read rich?
Since you are a trained automotive mechanic like me, I will try to explain the concept of the torque springs vs variator weights.
The torque springs are installed on the clutch side. It's kind of like putting an automatic car in sport mode. It will have a higher rev point before switching gears, but you know how transmissions can vary gears based on load. The torque springs will try to keep it in lower gears so when you approach a hill or are, cruising-let go of throttle-on throttle again, it is ready in a lower gear for the load.
The variator weights are more rpm dependent on the upshift of gears. However, since increase torque springs want to keep gears lower, you may need heavier weights to counter that force for the appropriate upshift.
The two are not mutually exclusive...which is like driving a car. It is the balance of rpm speed and load when choosing the correct gear for a given vehicle speed. So, yes, if you increase the torque spring, then you may need to increase the variator weights to find your balance. There is no magic formula, but to try a combination and adjust from there for your specific needs and rider weight.
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Post by sickopsycho on Jul 28, 2013 19:50:58 GMT -5
[replyingto=brandjur]brandjur[/replyingto]Thanks for the cvt explanation. There are very few cars that use a similar setup (the Honda CRV uses a cvt- not sure of any others). I actually had a grasp of the way it works before when I worked at a scooter shop but it's been a few years and without seeing it it was baffling to me. It's a simple setup, when you think about it, but hey... anyway today when I installed the contra spring and the clutch springs- along with 5g slider rollers- i started the bike without the tranny cover on it and "ran it through the gears" and it all came back to me. Still having the air/fuel mixture issue but man does it run up at ~40mph in a hurry now! When I give it WOT from a stop the rpms run right up to the limiter and hold while the bike jumps right up to about 40. I got up to 42 going down a hill but thats cheating. Think I'm gonna try the 6g sliders now that I've got the power... I installed my old # main jet and didn't get much of a difference- still getting some popping when I come off WOFT from high speed. When I snap the throttle it will bog down a little then rev- when the rpms come back down it runs a little slow then settles at the proper idle speed. Thanks for all the input guys, I REALLY appreciate it! |
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# main jet installed with a short ram performance air filter. My exhaust is stock. I also purchased a 1500rpm set of clutch springs and and 1500rpm torque spring along with a set of 5gram slider rollers that I havent installed yet. I think the rollers I have in there now are 5 gram and I don't think I'll get any more speed out of the springs (clutch or torque). Any advice? Funny side note- my carb... I went to tune the air/fuel mixture and it's acting funny. It ran well at the factory setting but I thought maybe a little rich. I let the bike warm up completely and adjusted the idle to just before the clutch started to engage. I turned the mixture adjust all the way clockwise (to lean it out) and this would normally cause the bike to cut off. Instead, as I turned it right, the idle continued to increase until the screw was bottomed out. The way I'm used to tuning this carb you turn the screw all the way right until the engine almost dies and then *slowly* back it back to the left (to richen the mixture) and listen to the idle. It will increase to a point then pretty much stop before it begins to decrease again. The point at which the idle is the fastest is pretty much stoich (the proper setting). I can't seem to tune it since the best setting seems to be lower than it can go. Would this be because of the bigger main jet I installed? If so is there a way to tune this carb? I also noticed that with the mixture adjust almost all the way closed (turned to the right) the idle is the fastest there but when I come off of WOT I get more backfires as if it's even richer? ? I'm totally confused. Any help would be greatly appreciated. 
# jet which might have actually been more appropriate because I think the stock 49cc jet is smaller than that if I'm correct? It is still running rich because I get backfires after WOT like I said and if I snap the throttle it bogs down before settling at idle. A lean condition should run higher rpms before settling after a snapping the throttle... What do you think about the jet size?
or #92. First move the needle lower (clip higher) on the carb. See if that has any effect on your backfire. Also, what does the plug look like?