My engine has lost some power

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A

aa_ron

New Member
May 17, 2013
8
0
0
Idaho
Hi everybody my name is Aaron, and I am new to this forum.

My problem I'm currently having is with my 48cc mega motors engine I bought from bikeberry. I built this bike about a year ago and have put 1500++ miles on it and it has ran great the whole time, but as of recently i have lost some power mostly in the top end. It just does not rev as high. I am thinking maybe it could use a set of piston rings. Any thoughts?

Thank you all in advance for any advise you may have.

drn2
 
CTripps

CTripps

Active Member
Aug 22, 2011
1,310
1
38
Vancouver, B.C.
Have you checked your head gasket for leaks? If you're losing compression you'll lose power but a blown head gasket won't always kill the motor. (My cruiser blew the front and back of the head gasket out one day and still pulled me home, just couldn't climb the last hill.) If you can't tell by looking, roll up a piece of paper towel and slide it between the top of the jug and the head, and check it for gunk. Repeat for each side. If there's a lot of gunk, I wipe everything off and start the motor for a couple of minutes and repeat the above check to see where there's fresh gunk.
 
Nashville Kat

Nashville Kat

Well-Known Member
Apr 20, 2009
1,501
55
48
Jacksonville, Florida
Could be an air leak?

Rebuilding is a little tricky until you get to know the ropes-

but parts are relatively cheap- so yes, maybe a new set of rings- even a new piston?
needle bearing,
and a head gasket- intake and exhaust gaskets you'll probably need if you take those things off
The risk is that you don't get it seated right and it catches a ring and tears up the jug-
so try not to do that

I must have twice that on my 50, but I screwed up a jug and the top end has been replaced- but I can't believe how it's been running on and on and on

Once you've done it, it's pretty easy

the speedo is on the 66 build- mistake I guess- the miles are oin the 50 build
 
A

aa_ron

New Member
May 17, 2013
8
0
0
Idaho
Ok I will check the head gasket and go from there. I've rebuilt a few v8s so I figure if it comes down to it I could probably do this little guy but would rather not.

Ill check it out and let you guys know what I find. Thank you
 
Nashville Kat

Nashville Kat

Well-Known Member
Apr 20, 2009
1,501
55
48
Jacksonville, Florida
When I said "air leak" I was talking carb intake- that happens a lot-
get an "O" ring gasket from Sick Bikes

Yeah- the head gasket is only four little nuts-
you could also lightly file the head to make sure it's even
the stock gaskets are crap if you look at them- they could cover at least twice the area around the cylinder with a bit more material- but they don't
designed to fail eventually, and make you buy more stuff later I think
 
A

aa_ron

New Member
May 17, 2013
8
0
0
Idaho
So I checked my head gasket and it does appear to have a leak. I assume when I change the head gasket I should check the head for flatness, but if its not flat can I get it flat enough with a file or is there some other method I should try? And I will check the carb and intake as well I'm sure it could use an o ring cause it has that junk stock intake and no gasket or anything where the carb mounts to it.
 
Desert Rat

Desert Rat

New Member
Jul 30, 2012
565
9
0
Apache Junctoin Az
BigBlue said:
230 grit or finer(higher grit grade) Sandpaper and a flat piece of glass.

Good Luck,

Chris
AKA: BigBlue
Click to expand...
I agree, I also take a sharpy and mark the whole surface black (before sanding) so that you may see any non flat areas, and I switched to coupling nuts.
makes a big difference see my post and pic here
http://motorbicycling.com/showthread.php?t=46808
torqued them with T wrench twice and never again:)
P.S. make sure where your piston is at TDC before sanding to much
luckily mine is about a 1/16 of an inch below top of jug
 
Last edited:
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
when needed I always work with the barrel so as not to remove much from the cinching ring of the head (seen some almost flat that would never again bite into the gasket enough to seal)
 
Desert Rat

Desert Rat

New Member
Jul 30, 2012
565
9
0
Apache Junctoin Az
crassius said:
when needed I always work with the barrel so as not to remove much from the cinching ring of the head (seen some almost flat that would never again bite into the gasket enough to seal)
Click to expand...
I removed the ring (almost) to get it flat I was left with it flat at four screw points half the ring on 2 sides gone the other half sticking up about .0004
put paper thin layer of copper high heat permatex on head side, none on base
and replaced alum. gasket worked out great, really increased compression only problem now is dialing in the
carb, on the needle c clip slot 2 down to rich top groove to lean, time to rejet,
thankfully I have an extra one.
Always make sure you change one thing at a time, test it then move on!
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
old school way is to paint gasket with either copper or aluminum METAL BASED paint - if it is metal based, it will still transfer heat nicely out of the head to the fins on the barrel
 
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