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Post by sai on Jul 15, 2014 21:38:33 GMT -5
Okay... this is the 2nd time in 2 seasons that I had my Malossi 70cc cylinder seized on me. I was going downhill at 50mph and it just turned the engine off...
I had to flood the engine and cycle it to cool the engine down and had a car jump start the battery while I keep the throttle open and do the electric start...
It finally started and I was able to get home, but I lost so much power, take off power and speed.
Does this mean I have to buy a new malossi cylinder and piston again? -_-
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Post by moofus02 on Jul 16, 2014 3:28:50 GMT -5
Sounds like it has a lean spot in the tune. A part throttle lean spot is what kills coming down a hill. A soft seize sucks but it's not the end of the World. If that kit is a cast iron Cylinder you are probably ok. If you are way down on power pull the top end and have a look. Probably have a ring stuck in the ring landof the piston from the seize. Probably get away with a hone of the Cylinder and a new piston and rings.
Sent from my SPH-L720 using proboards
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Post by sai on Jul 16, 2014 9:33:23 GMT -5
I'm going to try to ride it again right now.
WHat are the chances that it'll soft seize again even if I were careful with my throttle?
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Post by moofus02 on Jul 16, 2014 10:18:56 GMT -5
If it is lean somewhere it's possible. I like to jet a little rich everywhere for safety but especially part throttle
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Post by sai on Jul 16, 2014 10:26:33 GMT -5
well, it started fine as usual and take off is great, but then 1 second later I lost quite some power at 1/2 - 3/4 throttle...
Haven't opened the engine yet, since I still need to do errands for the next 2 days and it's been raining non stop here -_-
Does this mean the BBK is pretty much done or...?
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Post by 2TDave on Jul 16, 2014 10:54:52 GMT -5
As said before if it's iron you can get a piston, rings and hone the cylinder. You'll need to fix the lean issue.
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Post by 90GTVert on Jul 16, 2014 11:31:13 GMT -5
I'd expect it to happen again unless you richen up the part throttle mixture and/or avoid low throttle at high speeds. You're going to need to do a compression test if possible and/or have a look to see how the cylinder and rings are doing.
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Post by sai on Jul 16, 2014 12:56:23 GMT -5
So I took the bike down to the shop. Going 3/4 throttle at 20mph. The mechanic did a compression test and results is 125lbs!!
I put the spark plug back in and he rode it down the block and it topped out at 50mph full throttle. We didn't do anything to it!! Aside from spark plug off to do compression test then plug back in.
(I haven't even taken the bbk off to look at the piston nor cylinder walls)
What's going on here?
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Post by bclivewire on Jul 16, 2014 13:52:36 GMT -5
well im going say the one thing you dot want to hear
even though there is many guys on this forum saying you can run a 70cc scooter that hard
you are proving to your self that you need something more
ether more cc,s like a bigger scooter .... or ... more modds on this scooter ... or ... booth
I took time to read your old threads about you scooter and what your asking out of this scooter
my $0.02 is you need water cooling !
wither you get water cooling in a bigger scooter or this 70cc scooter it is up you
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Post by 90GTVert on Jul 16, 2014 13:54:34 GMT -5
You'll need to look over the cylinder, pistons, and rings and check the ring end gaps.
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Post by moofus02 on Jul 16, 2014 14:28:21 GMT -5
If the bike is in tune and you don't over Rev it you can run these real hard. I ride my 50cc piped Zuma wfo for 25 miles at a shot without issue but I'm on the rich side of the tune. If you need to run real fast all the time a bigger scooter has advantages but air or liquid cooled doesn't matter if you are lean. I holed the center piston on a gt750 2t triple when I ran out of gas and it leaned out under power. Brent is right you should inspect the top end. Sounds like the main might be close but you might be lean on the needle
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Post by sai on Jul 16, 2014 14:57:49 GMT -5
Yea, I was going down hill and it was peaking at 50mph which I know I should have slowed down a little.
I will takt the BBK apart when it stops raining and post a photo. It's running normal right now....
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Post by sai on Jul 17, 2014 19:04:20 GMT -5
I'm trying to upload the photos but it says forum exceeded attachment limits.
Anyways, I opened the bbk and there's a slight scoring on the piston and cylinder wall at:
1 o'clock 5 o'clock 7 o'clock.
The bike is running at 95% and the compression is at 125lbs
Mi was told that this is a heat issue and not jetting issue? do I need to buy a new bbk?
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Post by 2TDave on Jul 17, 2014 19:12:12 GMT -5
A heat issue on an air cooled two stroke is a jetting issue. Compression is a bit low but doable.
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Post by moofus02 on Jul 17, 2014 21:03:17 GMT -5
Being leanbe it mid range or wide open will make heat and expand the piston faster than the Cylinder causing a soft seize on a cast iron kit. On a aluminum kit the piston and cylinder expand the same but the heat will melt a hole in the piston. Being on the rich side on the main with a rich sputter on the needle is a safe Street set up.
Sent from my SPH-L720 using proboards
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