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Post by strgazr27 on Oct 21, 2015 18:18:10 GMT -5
More likely sitting at the bottom of the crankcase. If it wasn't sitting on the head than it probably fell down the timing chain slot. The trough in the bottom of the case is probably holding it from moving anywhere. If it were my scoot I wouldn't ride it till I found it but I'm a little more a*** about things like that.
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Post by katastroff on Oct 21, 2015 18:27:31 GMT -5
I did run that same BBK from the same seller. I had 150 PSI with an open air filter, a free flow exhaust i had a 90 main jet and was running a bit rich. But that was mid summer with hot temperatures.
I'd give the cylinder a good hand honing and new ring, if it dont brink the compression back up, get a new kit, they aint that expensive.
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Post by Silar on Oct 26, 2015 5:18:09 GMT -5
I know you probably have other things wrong since it was ran hot but figured I'd give my 2 cents based on what I've experienced.
I am currently running that same kit with a POD style filter, but with the big valve head also and of course a few other mods. One thing I found out that shocked me a bit was that a #90 main jet was perfect. Anything more and my scooter was bogging. Anything less and it was running a bit lean. That kit comes with a #90. I figured I would need at least a #95 with the BBK and a POD filter. If it's dying when trying to give it throttle, then check your needle position. Also make sure you have the float set right. It's pretty easy to bend the tangs on the float accidentally when putting a main jet in..
I have to mention this also... If you still have the vacuum petcock, check it or even just go ahead and replace it with a manual petcock and cap the intake vacuum port. I couldn't even get my scooter to go over 10mph because the vacuum petcock had failed and gas was going from it directly into the intake manifold through the vacuum line.
Always check the simple things first.
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Post by humanshield on Oct 26, 2015 16:02:54 GMT -5
These 100cc big bore kits don't usually come with Big Valve Heads. Totally different. With the 64mm valve head that came with that kit, 120psi is very low.
If installed correctly, compression should be 170 or better right out of the box. And that is without oiling the cylinder. Over 200 is not uncommon.
When you ran it hot (being that everything was new, I suspect you may have damaged the rings. It's normal btw for a motor to run hot after installing a BBK. It takes about 200 - 300 miles for it to wear in and settle down. What I do is ride a new BBK very carefully and not to hard for the first 50 - 100 miles. I try to put at least 50 on them before handing the scoot back to the customer.
My advice would be to pull the cylinder back off and inspect the rings and the cylinder bore if the compression doesn't come back up through valve adjustment. 120 will run, but it will be sluggish.
Also, timing could be off. Check it again.
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chemi
Scoot Member
Posts: 34
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Post by chemi on Nov 7, 2015 3:10:45 GMT -5
We honed the cylinder and were waiting for the rings
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chemi
Scoot Member
Posts: 34
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Post by chemi on Jul 4, 2017 1:42:37 GMT -5
i figured out the engine ran too lean and overheated im gonna rebuild again
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Post by humanshield on Jul 4, 2017 11:23:49 GMT -5
i figured out the engine ran too lean and overheated im gonna rebuild again Not sure how you figured it out but is good to find a cause. Just be aware that if you had very high compression on a new top end, excess heat can disguise itself as running lean and will result in a similar outcome. Depends on how the motor was run initially at break in. You can totally seize (and ruin) a brand new motor due to excess heat during break in. It happens all the time. Combine a bit lean with that heat and BOOM! You don't want to make the same mistake JIC you figured wrong this time ya know? On the bright side...the more times you go through this....the better you'll get at it
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chemi
Scoot Member
Posts: 34
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Post by chemi on Jul 4, 2017 15:13:59 GMT -5
i figured out the engine ran too lean and overheated im gonna rebuild again Not sure how you figured it out but is good to find a cause. Just be aware that if you had very high compression on a new top end, excess heat can disguise itself as running lean and will result in a similar outcome. Depends on how the motor was run initially at break in. You can totally seize (and ruin) a brand new motor due to excess heat during break in. It happens all the time. Combine a bit lean with that heat and BOOM! You don't want to make the same mistake JIC you figured wrong this time ya know? On the bright side...the more times you go through this....the better you'll get at it yeah actually i'm gonna rebuild this motor i dropped it already and got a new one that im gonna use in a project build 49ccscoot.proboards.com/thread/19323/2013-dank-tao-buildsince you're very knowledgeable maybe you give some advice on this
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Post by greggkinney on Jul 6, 2017 0:20:28 GMT -5
wait!!!! lol ...you mean the nuts still in the case??!! i just had this happen a couple weeks ago myself. kinda figured the same thing myself about the nut being stuck to the magnetic plug ir in the screen. no such luck. i took the plug out ofthe side ofthe motor and used a telescopic magnet and found it. i tried using it down in the cam chain slot first tomake sure wasnt going to find its way in between the crank and chain or oil pump. if you cant find it like that then you could try lifting the cylinder some and check better. there a few different places for that thing to cause catastrophe. you'd think it would lay in bottom if the case but at 9-10,000 rpm id imagine things get to moving down there. anyway, hope you guys get er going. ive read some of johns work before his seems smart and im yall have it kickn butt soon
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Post by greggkinney on Jul 6, 2017 0:26:55 GMT -5
sorry for some reason there wasnt a 2nd page of responses showing untill after i submitted my post. didnt know you are now rebuilding. good luck with the new build...and find that nut lol
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chemi
Scoot Member
Posts: 34
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Post by chemi on Jul 6, 2017 4:30:08 GMT -5
sorry for some reason there wasnt a 2nd page of responses showing untill after i submitted my post. didnt know you are now rebuilding. good luck with the new build...and find that nut lol lmao yeah i found it. it was the nut for the valves so im gonna rebuild im well in my way researching seeing what i can do
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Post by greggkinney on Jul 6, 2017 18:19:36 GMT -5
good luck and enjoy! im fixing to year into a 52mm bbk ijust built with like 25 miles on it. leta frienf ride it and it wouldnt crank at the store and it sounds like it has very little compression
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chemi
Scoot Member
Posts: 34
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Post by chemi on Jul 6, 2017 22:49:04 GMT -5
good luck and enjoy! im fixing to year into a 52mm bbk ijust built with like 25 miles on it. leta frienf ride it and it wouldnt crank at the store and it sounds like it has very little compression if you wanna see the build log i created a thread and as i'm doing my research ill update if have questions about or even ideas or guides post here 49ccscoot.proboards.com/thread/19323/2013-dank-tao-build
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Post by mpdano on Jul 15, 2017 8:08:33 GMT -5
Previous owner on my BMS Tuscan 50 installed the same kit, but put the piston in backwards and bent the valve. I bought the large valve cylinder head that also has the functioning egr port. Finally totally finished yesterday. That included repainting all the trim, new headlight bulb, spark plug, cdi and battery. FYI, stock carb jets and it runs perfect.
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