Help!! My bike won't stay on anymore

Bbish

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Sep 10, 2015
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Hi so I built a 2 stroke motorized bike and it's been sort of a pain so far but it was finally working good but then I took it out yesterday and I would get up to speed then drop the clutch and give it gas and it seemed like it started but really weak then when I give to more gas it comes to a stop, so I took apart my bike and replaced the bottom cyclinder gasket because I thought that was why it wasn't starting but I got the same problem. As soon as I try and start it it starts but there is like 0 power produced. Also if I try and pull in the clutch to let the motor idle it dies right away. I haven't messed with the carb at all after I got it to idle right when it ran so I have no idea what's going on. Also when the bike "started" yesterday it would rapidly slow the bike down then start sputtering. I don't know if this is important but when I took apart the motor yesterday the plug was black. I am on my 2nd tank running 16-1. Please help me I'm getting frustrated and don't know what to do. Thank you.
 


KCvale

In memory of KCvale 1959-2019
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...so I took apart my bike and replaced the bottom cyclinder gasket because I thought that was why it wasn't starting but I got the same problem.
As soon as I try and start it it starts but there is like 0 power produced...
Do you have a torque wrench and know how to use it?

I have seen people crack heads leading to the same symptoms you have, no compression, because they tried to Torque a Head by hand 'feel' and warped or cracked it.

I usually paint and twist the head 180 so the spark plug points forward on new 2-stroke 66cc engines anyway and have found torquing the nuts down 4 at a time in an X pattern 5# at a time to 20# for each to be the best.
 

crassius

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Jul 23, 2012
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why did you replace bottom gasket????

was new gasket exactly the same as the old one? some motors use different thicknesses of gasket at bottom to correct port timing or to keep piston from hitting head

did you check wiring? loose connection can go bad only after motor begins vibration (note that soldered connection at top of coil can start motor. but then fail)
 

Bbish

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Sep 10, 2015
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No I do not have a torque wrench but when I took the motor apart I did not notice any cracks or warping. I replaced the gasket with a higher quality one because the stock one was leaking even when the bolts where tight. They are the same thickness
 

Bbish

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Sep 10, 2015
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Just took my bike out and I tried to start it and it started but sounded weird and there was no power whatsoever. And still no idle . Also I just added new gas if that helps
 

FurryOnTheInside

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Sep 23, 2013
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I have not reached this stage in my build yet, but as I try to plan ahead I have read that..

The aluminium (stock) head gasket is only good once. It will not seal if you take it off and try to reuse it.

The copper gaskets that you can buy in packs of 20 can be reused if you have a torch to heat them up.

Teflon tape can be used in place of an actual gasket. This seems like the ideal material and is what I am planning to use. I think it's the same as P.T.F.E. tape.

Use the search (top right) to read all you can about Teflon tape.

Torque the head down correctly and keep the tape in your emergency tool bag.
 

Bbish

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Sep 10, 2015
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Do you think this is a blown head gasket ?When I replaced the bottom gasket the head gasket was like formed to the head
 

crassius

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if gaskets were leaking when nuts were tight on studs, then you don't have enough flat washers on the studs to keep acorn nut from sticking to top of stud - add washers or break the caps off the nuts
 

Bbish

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Sep 10, 2015
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I made sure they don't hit the top now because I screwed the thread rod more in to the bottom of the motor and it still won't start and stay on
 

Frankenstein

In memory of Frankenstein 1991 - 2018
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Jun 24, 2016
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I did notice that once an a while an over rich carb or a fuel with just really crappy oil or too much oil will coat the sparky plug over in soot or just layered in carbon, when this happens the power can drop dramatically especially as you try to hit higher rpms.

How did you figure you had a leaking base gasket, I mean of all the ones that go bad that is the one that's pretty low in the list. Personally I've not actually even had a base gasket leak even on a motor where I stacked it 3 high.

You even proved to yourself it's not the base gasket. If you can keep an idle or slightly more than idle running then take it outside and grab a can of brake clean or carb clean or even a propane torch set up and lightly spray joining points like the carb connection and other places like gasket areas. With a propane torch you can set it for a very very low adjustment (like it would be too hard to keep a stable flame) and bring the tip of the torch to the different areas where a leak might be.

Don't get crazy doesn't take much to catch the leak, most sprays will choke the motor when you hit the leak (if there is one) but some like starting fluid will make it race.

Propane is heavier than normal air if I remember correctly and many solvents in cleaners are as well, basically they float around in low spots and accumulate, and of course they can be set on fire in a big firey ball of death that you'll probably be involved in.

Make sure there is very proper ventilation like working outside where the bad stuff won't build up easily and set you on fire. Again, it shouldn't take much or long to hit all gaskets and determine if and where a leak is. If you can't find a solid on a leak, then move on to electrical.
 
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