Is it bad to run a 2 cycle motorized bike on ethanol E85

Z Man

New Member
Oct 10, 2018
10
0
1
24
I have a 66cc motorized bike with the high compression head cylinder it gets a compression PSI of a hundred sixty I run on ethanol the only way I can get the head to work it will not run on regular fuel with high compression head just wanted to know if it could damage the engine running it on ethanol instead of regular fuel and I would also like to know what the best bike frame style would be for a engine
 

crassius

Well-Known Member
Sep 30, 2012
4,032
156
63
USA
don't know for sure, but also don't know why it doesn't run on normal gas (GF's bike is at 165 and runs fine on 87 cheap gas)

back in the 70s, I had to start out with jets at 150% oversize to run methanol (and sometimes had to go larger)
 

Z Man

New Member
Oct 10, 2018
10
0
1
24
Thanks for the reply
I have the stock Jets that the engine would have straight out of the box. The only difference is I have that high compression head I don't know if that would make the difference.
I read somewhere that the compressibility of ethanol fuel is a lot greater than regular gas.
On nice cool days down here in Arkansas I can get the engine with a 32 tooth sprocket to go 40 mph but on hot sunny days it will only go 38 or 37 mph
 

crassius

Well-Known Member
Sep 30, 2012
4,032
156
63
USA
doesn't sound bad, but my curiosity would make me want to know why it can't run on same gas that every other one runs on
 

Z Man

New Member
Oct 10, 2018
10
0
1
24
I guess I'll just keep on running it as it is until something happens to it and then if if something does happen pretty soon and I'll report that ethanol is bad for two cycles
I did have it running on regular fuel when I had a speed carburetor with the proper jet in it from bbr but I kind of screwed up the carburetor a little bit and had to switch the stock one.
 
Last edited:

Z Man

New Member
Oct 10, 2018
10
0
1
24
I found out when I first got the high compression head that when I run ethanol in it, I could just switch the head out from the high compression head to the stock head without changing the Jet size and it would run perfectly fine for both.
The stock had has a compression PSI of 110 and the high compression head has a compression PSI of 160