First build on China

[66cc]

Hey GuysnGals

My first 26" std 21sp mountain bike conversion to 66cc china.
1st time start and ran like a dream!
Sounded nice pulled nicer.
So 4days in I lose my muffler cover/baffle? gets louder and faster so I take it on long trip ~20km...
it was broken in with 16:1 for four tank fulls and was now on a 20:1 with 91octane.

So on my journey Im at 75%-WOT for the duration...i come to a red light and pull in clutch and engine slows... and dies...
So after many tries still not starting...
time for research.... adjusting....research adjusting... still nothing...
checked fuel..okay
check air...okay
check spark...nothing..

so researched... and found out CDI/mag/spark plug could be the culprits..
replace china plug with NGKs
time for resistance check! CDI...no change :S
Mag check... 355OHMS :S WTH??
replaced CDI...still no spark..
replaced MAG... VOI -FINALLY- ****ING -LA

So that was my story

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.
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So Now some questions?
Why was I getting no reading from CDI and it was good?
and Why was a reading of 355 on MAG and still magneto is bad...

Would the long time at WOT have anything to do with it burning out??

and finally
My mufflers baffle/end cover fell off... reallly loud and a lot more powerfull...

and theres back fire.... oooooooh yeaaaa

it this bad for the engine at all? Okay to ride it like that?
Not down to spend anymore on a new muffler just yet....
ANY remedies?

Thanks a lot PPL ....and for the patience of reading my long asss story

 

[2door]

Yes you can do damage if you run without the baffle/end cap. 2 stroke engines need the back pressure created by the muffler or expansion chamber. Running without it can cause the engine to run lean and hot. The lean burn is why you feel a little more power but it won't last if you continue to ride it like that.

Not only can you damage the engine but you're not doing the hobby any favors either. You might like the sound but the folks around you won't be impressed. Muffle it with a new muffler or go for the expansion chamber.

Tom

 

[wheelbender6]

There are many posts where riders lost the muffler end cap and replaced it with the end of a beer can to restore that back pressure. A Harley sounds good with open straight pipes but two strokes don't.

 

[bigbutterbean]

Pshhhhh. I hate the way harleys sound with straight pipes. Ought to be a law against it. A 66 ht is nowhere near as loud as a harley, but still, not having enough back pressure will throw off your timing and the engine will not run correctly. Either get a new muffler or an expansion chamber. The expansion chamber will give you some performance increase, but there is some tuning involved. The shorter the had pipe, the higher thr rpm it will take to get on the pipe. So with a short header, it will only kick in around max rpm. With a longer header, it will kick in at lower rpm without affecting your top speed.

 

[porkchop]

66cc i just did the same first build...congrats to you...logged 50 miles on it today after getting back home letting it cool down i went around & checked everything to make sure its tightened down vibration on these little "bone shakers" is something else.maybe once a week check for loose bolts etc...my 2 cents worth on preventative maintenance

 

[66cc]

Thanks everyone for the feedback! I'm definitely going to look into the muffler ordeal.
Thanks porkchop! I learned about the tightening nuts and bolts the hard way-lost baffle-in any case I make it part of the routine to tighten down nuts and bolts.

Any of you guys look into lock tight for the screws/bolts?
What about weather proofing magneto cover?

One more question : What do I lube the clutch assembly and the engine drive sprocket with? there was grease on it from manf.? which grease!?

 

[bigbutterbean]

You can use just about any kind of grease on the gears. I have used both red grease and white hi-temp grease, but truth be told, they don't really need greased very often, if at all. ÷ probably grease mine 3 or 4 times a year. Don't put too much grease on the clutch side, or the gears will slip.