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Post by 90GTVert on Oct 16, 2015 8:31:04 GMT -5
I'm guessing you have compression since it's tough to move the kick starter and it's not cranking over fast with the e-start. By all means do a compression test if you can, but otherwise move on to looking for spark and fuel... www.49ccscoot.com/faq/wontstart.htmlAlso, if you have a battery maintainer or charger around you may want to keep it hooked up so you can retain some battery power while you're figuring this out.
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Post by Fox on Oct 16, 2015 8:45:40 GMT -5
I have to ask, is the kill switch on the handlebars set to run? Also, did you remember to hook up the main engine ground wire? (the big wire that runs from the frame to the engine) When you worked the kicker slowly with your hand it was fighting you pretty hard at certain points. That's the compression building up and releasing over and over just like it's supposed to do and from the looks of it it looks like you have plenty of compression so next, you have to check for spark as already stated. Remove the spark plug, put the plug into the plug wire and then hold it against the valve cover (ground) with one hand while you squeeze the front (RH) brake lever and push the start button with your other hand. If it has spark you will see it jump across the plug. If you don't see a spark, then there's your issue and we'll have to figure out why. You might wanna use a glove or a rag to hold the plug cause you could possibly get a jolt. The last thing to check would be a lack of fuel also stated. Reversed fuel/vac lines? Has the carb been sitting with fuel in it for a few weeks? Maybe it's gummed up?
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Post by astray on Oct 16, 2015 14:24:59 GMT -5
I'll check for spark one I get home from work, hopefully it's not a fuel problem as I'm not sure how I'd go about fixing that right now. If it's spark I have another ignition coil I can put in and the spark plug I can find at any auto parts store most likely. I'll update once I know, but I think spark is the most likely cause given it's the only parts that weren't changed it checked from the scooter's previous state.
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Post by astray on Oct 19, 2015 0:18:09 GMT -5
Alrighty, sorry it took me a bit but I've been catching up on some things this weekend and got around to the scooter only a bit ago. So I managed to get it to start and go for a little bit (I believe this was because the spark plug did not have a good connection to the ignition coil plug as taking out the spark plug and making sure it connector was in securely was all I changed it started up), but then it dies. At first it started off needing some throttle and then it would actually get up to speed a bit but would die in idle. Now it's able to idle for a bit before dying, though there was a point where I was able to get to idle for a good while (like 2-3 minutes). If I can get it to idle for a bit the moment I open up the throttle the damn thing dies right away where briefly before it would actually get the back tire moving a bit. Not entirely sure what's going on so I'll give you everything I've got evidence wise and see if you might have a better idea. Here's a picture of the spark plug: drive.google.com/file/d/1Be2e6cuF_j_TmRbCMY7YpB-goNlS4OZkhA/view?usp=sharingFrom what I've read the spark plug seems to be carbon fouled though I'm not entirely sure what this means or how to fix it. Also I need to know how to keep it from happening if I just replace the spark plug. Are there tests I can do for my ignition coil to make sure the plug burns hot enough so carbon deposits don't build up. Does the engine even get hot enough to burn off those deposits in the first place? What's a good operating temperature for a 72CC 139qmb? And two videos, one where it showed it was idling successfully and another where it dies shortly after starting to idle:
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Post by 90GTVert on Oct 19, 2015 9:10:26 GMT -5
If messing witht eh plug wire allowed it to start, the first thing I'd do is inspect the plug wire and cap and connections. Most will screw on, so you can make sure they're tight at least. If anything is suspicious there, replace it. A good NGK plug boot is roughly $5 and you can find stock replacement coils complete with the plug wire for $10-20 online. Checking spark when it will and won't start may tell you something.
My scooter runs pretty well and does what yours does in the 2nd video at times. I play with the throttle and start it and then rev it up if I need to for a sec when it's cold. Once it's warm it runs well. Since you've just installed a BBK and just got it running, I'm guessing you really haven't done much tuning. If you can get it to idle and warm up, try adjusting the idle mixture and speed screws once it's warm.
Essentially you've just idled at this point, so I wouldn't worry a lot about plug chops. With idle issues I pretty much only see if the plug is wet or dry. At least the last pic doesn't appear to be wet like it's fouled and won't start.
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Post by astray on Oct 19, 2015 10:28:40 GMT -5
If I'm able to get it to accelerate then it dies as it nears idle but I haven't been able to do that like I was initially. Even if I can get it to idle and warm up (which it doesn't want to do for long) once I give it gas the damn thing just dies regardless. It's really confusing.
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Post by Fox on Oct 19, 2015 13:44:26 GMT -5
Go to the tech section. Look at carburetor tech specifically idle mixture adjustment
If you idle mixture screw is capped off then look at thread called unsealing carbs wuth sealed mixture screws.
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Post by astray on Oct 19, 2015 18:11:19 GMT -5
So it was a fuel problem, something was up with my petcock. Replaced it with a manual one and it started working finally. However now we're into much worse problems as I was breaking in the engine following 90GT's steps for breaking in BBKs and while I was doing the full throttle part something went terribly wrong. The scooter started making an awful noise that sounded like it was coming from the CVT and just died on me. Now it won't even turn over at all. I think I left it in WOT too long before the wear in period was finished. I'm hoping it's just the belt going bad and getting stuck on the crank so it can't turn over. Otherwise it's something probably way worse I fear.
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Post by astray on Oct 19, 2015 21:57:06 GMT -5
It works! I hadn't torqued the variator enough and it came loose. Once I opened it up and torqued the nut back on it started running fine. It is running somewhat slowly though. I was expecting 50 mph easy with the new gears and increase in cylinder volume (only went from 44mm to 47mm though) but I'm only getting 40 or so tops (will have more information tomorrow with a GPS speedometer on my phone). I think I can attribute that to being running with both the carb and variator weights not being tuned yet. I ran the scooter around at variable RPM settings for 20 miles and then changed the oil. Here's the spark plug after opening it WOT for bit and then hitting the kill switch too: drive.google.com/file/d/1raPG5f6-ikiCq4FHS6pGp7mRBTsXTCRy4w/view?usp=sharingdrive.google.com/file/d/1AHu9_aErqK8y2E6rlBDxStbxRTfzV4CZmA/view?usp=sharingWhat are your thoughts, do I need to tune the carb or does the spark plug look okay (I can't see anything wrong with it)? And what's the best way to go about testing the rollers/sliders (which one is better btw)?
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Post by 90GTVert on Oct 20, 2015 5:21:20 GMT -5
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Post by astray on Oct 21, 2015 8:21:42 GMT -5
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Post by 90GTVert on Oct 21, 2015 8:36:42 GMT -5
The powerband is a range of RPM where the scooter is making the most power. It's the area between torque and horsepower peaks. So say for example that you make peak torque at 6500RPM and maximum horsepower at 8000RPM, then your powerband is about 6500-8000RPM. You will find the best performance if you can keep then engine within that RPM range as much as possible at WOT. The ideal RPM or powerband is a little different for every scooter. I get the best results out of my nearly stock 4T at 7800-8200RPM. If there were a known figure for every engine, we wouldn't need to bother with trial and error CVT tuning. We could all just set the CVT up to keep revs between ___RPM and ___RPM. Trial and error tuning and recording the results allows us to figure out where the best power is without prior knowledge.
You can make a new thread about the tuning or continue here. Your call.
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Post by strgazr27 on Oct 21, 2015 12:55:49 GMT -5
I have almost the exact same parts list you do except I'm running a 50mm piston and I DO. NOT have the 49/17 gearset. My scoot is tuned about as good as it can be. I'm running 8gr rollers in the same variator you are. Same clutch setup. I'm 160lbs and the best I have ever seen on a dead flat, just over 1/4 mile section of road is 43.2 at 7650 rpm on the Trail Tech. That was flat out, tucked with full face helmet and no mirrors lol. I don't think you'll see 50 unless you're running downhill, have a 15-20mph tailwind or you weight about 120lbs. A much more realistic figure is 40-45,
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Post by astray on Oct 21, 2015 13:14:12 GMT -5
The gear set is supposed to add a decent bit of speed on the top end, 5 to 10 mph.
The problem I'm having is that I'm going slower than when my scooter was using the stock parts (44mm bore)
+ carb with 88 jet + performance exhaust. I weigh 225 and was getting 45 on a flat and 40 average. Now I'm getting 33 to 35.
So I'm an idiot and my rear tire was still severely deflated, only 10 PSI. After putting air into it (40 PSI) I am finally getting speeds that were comparable to my original stock scooter with the performance exhaust and chinese keihin carb. I got up to 43 on a flat and it felt like it could've gone a bit higher (44-45) given a bit more time. However it still feels like the scooter just isn't quite in the RPM range it needs to be for everything to work together completely. I'm going to try putting the stock CDI and ignition coil back in and then do the timing advance mod 90GT did on his Tao Tao and see how that goes. Definitely not taking the stator off though, it seems like there's enough room to cut into it with the stator still attached. If that doesn't do anything it was recommended I open the exhaust valve a bit more to .005/.006 so more air can get out through the exhaust, what are your thoughts on this? Regardless I still need to do some tuning on the carb and variator on top of the other stuff I've mentioned above. And a question to 90GT, what exactly is the definition of peak torque and peak RPM so I know what to be looking for when I'm tuning the CVT?
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Post by strgazr27 on Oct 21, 2015 17:51:18 GMT -5
I understand 5-10 up top. If stock is 30-maybe 35 than modes with gears is going to be 40-45. Another thing to remember is those gears will require more torque to get that additional 5-10mph. The motor has to have enough torque in the right spot of the band to allow the gears to do their thing. Probably looking at at least 1/2 mile or more for the scoot to reach max speed with those gears and your body weight. Keep plugging at it, you may get there I'm Just not confident you see it consistently and reliably.
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