1st build in the mail!!

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Dnoces

Dnoces

New Member
Sep 8, 2011
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United States
hello! im totaly new to gas engines on bikes. ive really enjoyed reading through these forums as a guest for the last couple of days and figured i could use a few like minded freinds that know what they are talking about!
ive tinkered with electric motors intended for go-carts and put them on a minibike frame for some 20mph fun in the past but ive stricken up a passion for long distance cross country riding and a motor assist sounds like a great evolution for my hobby, so i cant wait to get my new motor. i ordered a motovelo engine kit ( only one shipping to california that would talk to me ) and plan to put it on my kona shred dirt jumping bike. big thick frame and heavy suspension sound right to me!! ;P
 
Dnoces

Dnoces

New Member
Sep 8, 2011
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United States
please forgive my ignorace, but ive had very little experience with 2 cycle engines apart from a husky chainsaw. tbh i dont really have any idea what the oil is doing in the mixture, let alone the significance of changing the mixture after the break in period. which leads me to another gap in experience.... while i have had experience on trials motercyces, the newest one i ever rode was a 2004 sherco, far after the break in period, so i dont really know what id be looking for or how id know when im broken in and how to determin how much oil i should then put into the mixture. sofar ive just found alot of opinions and guess work, but id like to know the real science to the oil in 2 cycle and breaking in an engine. *deep breath*
 
GearNut

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
Nice looking bike you have there.
It looks like the engine will be a real tight fit inside the frame if you can even get it to fit.

One has to mix 2-stroke oil with the gas to provide lubricant to all the internal engine parts.
Without it the engine lifespan can be measured in minutes instead of miles.

They do not have an oil sump like a 4 stroke engine has. There is no drain plug or dip stick either.
A 2 stroke engine needs extra lubrication during the break in period to allow the parts to wear into each other properly. 24:1 is a good ratio to use with most pre-mix oils.
After break in is completed (about 2 to 3 gallons of fuel, 200 to 300 miles) there is no longer a need for the extra oil. The engine will run better and have less internal carbon buildup with a higher ratio. 32:1 is a good ratio to use with the aforementioned oil.

If you choose to use a higher ratio oil such as Amsoil Sabre, Opti2, ect. use the oil manufacturers recommendation for the ratio.
Note: Opti2 mixes at 100:1. Some folks are uncomfortable with this and have good results running as low as 70:1.
Other folks have broken in brand new engines with Opti2 at 100:1 and are more than delighted with the results.

It's your choice as to which type of pre-mix to use, but never ever ever never never mix traditional 32:1 pre-mix oils at such high ratios.

The oil debate is as old as the invention of oil. I do not want to debate it with anyone, just share what I know on the subject.
 
Dnoces

Dnoces

New Member
Sep 8, 2011
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United States
thats great advice thanks alot! ive been doing alot reading today and i think im going to get a higher gear ratio, the hills bother me alot more than speed. i also need to learn alot more about exhast systems and expansion chambers. i understand the fundementals,like that along with exhast being expelled by the explosion, there are powerful soundwaves that reverberate and pull the extra spent feul out of the chamber, resulting in the efficiency i would assume. but in terms of acual hp increase i would have no idea. these also make them mch louder im told, which ma not be a good thing for me XD

what do you guys think of engine modification? is it worth the effort? does the life span/efficiancy suffer?

thank you so much for your patience with a new builder.
 
Dnoces

Dnoces

New Member
Sep 8, 2011
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United States
im not so confident it will fit now, lol. i may have to start work on a back up plan.does this engine have strict seating arrangements? by that i mean could i feasibly rotate the engine roughly 90 degrees counter clockwise to make it fit? my old chainsaw never seemed to mind
which way was up.
 
Dnoces

Dnoces

New Member
Sep 8, 2011
14
0
0
United States

this is the only other frame i have right now.... and that just wouldnt look right to me but it may end up living there who knows.
 
GearNut

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
So long as the carburetor is reasonably level and the chain can still get to the rear wheel you can mount a 2-stroke engine in any position you please. There is no up or down on them. They don't care. They will happily run upside down if you want them to. As far as proper sprocket rotation out of the transmission, there is a left and right side. You cannot mount the engine backwards and expect the bicycle to go forwards.
You may have to fabricate an intake manifold if you get really creative with the mounting angle though.
 
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