Franken engine

Malanca

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12:28 PM
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Jul 2, 2010
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34
kinda like Frankenstein haha.
so back in march or april my needle bearing inside the piston collapsed into its self and broke apart inside the engine...it resulted in horrible damage to the piston housing and pretty much the engine seized up. so that engine is sitting on the side lines and being used as a salvage engine.

I bought a bottom half of an engine off of a site and a buddy of mine gave me a top half of a spare engine he had lying around. so i put the 2 together. everything fit in perfectly
my main question is i wanted to test it to see if it would actually work...i tried checking for a spark by walking with the bike but the back tire just freezes up// what would cause this?
also i dont know if its relevant but i did adjust the clutch plate. i did notice my clutch handle is a tad bit harder to work. maybe too tight?

i'm a paranoid person so...
my worry is are these 2 parts not compatible??
or since theres no gas or oil maybe it needs it in order to move the piston? any help or advice would be greatly appreciated.
 
umm, you need some weight on the rear tire to turn it, even with the spark plug removed. the best way to do it is to get the rear wheel up off the ground and turn it by hand. squirt some 2 stroke oil down into the cylinder to help lubricate the rings. When you assembled it did you assemble it dry or did you lube up everything?
as long as the piston and rings fit into the cylinder and are not bound up it might be ok.
the other thing to watch out for is piston to head clearance. If the cylinder you used is shorter than the cylinder that came off of the engine, the pistoon could be going up too high and hitting the head.

if the clutch handle is too tight or too hard to pull you may have it adjusted too much. you want to have some free play in the clutch cable and the clutch handle should be pretty easy to pull in.
 
THANKS!..i kinda forgot to mention my chain from the engine isnt actually all that tight still needs a bit of tension so thats something i'll add.

when i inserted everything it was dry. i'm hoping that isnt going to delay me or set me back. it went in smoothly the O rings weren't any trouble i aligned them with that little mark.

the whole clearance thing..i havent checked and it didnt even occur to me so i'll be sure to check that as well.

with adjusting the clutch...thats done with the cable on the clutch arm? right now i have alot of excess wire on the arm...maybe giving some back?

thanks motorpsycho
 
you can either adjust the clutch by the cable and arm, or by adjusting the flower nut on the clutch itself.
the easiest way is by the cable, but sometimes it won't give you enough and you can really fine tune the clutch adjustment with the flower nut.
It's all trial and error.
 
Thanks/ i've done adjusting thru the flower bolt but i wasnt sure if that was the right thing to do or if it would damage the pads or plate in the long run/ i'm going to attempt all that was listed.
 
My piston was all the way up when i took off the head pretty much touching the headcase. i have one of those slant spark pugs.. it slid all the way down smoothly.
 
the past few days i've been doing a little here and there..
bottom line is got the bike running for a block but it was only going at 5mph or around there it was pretty slow. (I HAVE NO IDEA WHY ANY INPUT ON THIS?)
few times before that it would stutter a bit like it would wanna turn on but after a few seconds it would just die out.

the whole cylinder to piston size wasn't cooperating because i forgot to put on those metal gaskets right before the head. so i added 2 extra homemade ones and thats when it started to run for the distance of the block like i mentioned earlier..

after that it just died out slowly and it wouldnt turn on anymore after that.
an uncle of mine told me its most likely the timing.
I have checked for spark (got a small orange one) the bottom half is a brand new engine so i doubt its the magneto or the CDI since its emitting spark.

any input / suggestions / ideas how to get my bike back and running.

i will post pics later on. my bike is a little modified with a strange new expansion chamber (i havent been able to test it out yet! :/ )
and i got a seat post that leans pretty low ;)
 
Engine

Hey Malanca, Red here again.
First, Only ONE head gasket goes on between the cylinder and the head. Two could make THAT your weak connection. MOST, (not ALL,) chinese engines have pretty close to the same spec's so you should have the clearance you need for the piston. Check it by pulling the plug and turning the engine over SLOWLY. If it turns easily then the only difference after that will be the spark plug clearance. Put in the plug and turn it over ONCE, SLOWLY, as gentle as possible. If it stops, DON'T force it. Check the plug to see if the electrode is bent. If it is you just might have the wrong size cylinder. I doubt you will have this problem, BUT, like I said, don't force anything. It sounds to me like you lost compression due to a blown head gasket. as it got worse you lost power and got slower and slower as the gasket blew out more and more. If your bike is a little loud you might not have heard the TISH-TISH-TISH sound of a blown head gasket.
Timing is factory set and it's almost impossible to mess it up. Everything concerning the timing is "keyed" to fit and to go together one way only. I'm sure your uncle is a real good guy and a great 4-stroke mechanic. But it's likely not the timing.
Try a NEW head gasket or if you have some copper cote(spelling?) that will also help seal the head gasket. Make sure the head itself is flat. You can check it by getting some emory cloth and a small sheet of glass. Run the head's sealing surface gently on the cloth while laying flat on the glass. You'll be able to see if the surface is flat just by looking to see if the emory cloth "missed" any part of the surface. If it did, Keeping it as flat as possible, Keep going untill it all looks the same. Some guys tell me they do this anyway just to mill the head for higher compression. I don't bother with things like that normally. IF IT WORKS, DON'T FIX IT!!!
If none of this helps, get back here and we'll all do our best to get you on the road again.
Thanks,
Big Red.
 
Engine

THANKS!..i kinda forgot to mention my chain from the engine isnt actually all that tight still needs a bit of tension so thats something i'll add.

when i inserted everything it was dry. i'm hoping that isnt going to delay me or set me back. it went in smoothly the O rings weren't any trouble i aligned them with that little mark.

the whole clearance thing..i havent checked and it didnt even occur to me so i'll be sure to check that as well.

with adjusting the clutch...thats done with the cable on the clutch arm? right now i have alot of excess wire on the arm...maybe giving some back?

thanks motorpsycho

By "O rings" I think you mean the piston rings. And yeah, if you take it slow they slip in pretty easily. Motorpsycho is right, You NEVER want to run anything dry. a little light oil down the plug hole will do the trick.
If your chain is loose it could be binding in the engine case. A loose chain will bunch up inside the drive gear case and things will come to a stop in a big hurry. A friend of mine put a hole in his case this way. So keep that chain adjusted properly.
I also want to ad that if you were running with more than one head gasket, then you are in reality giving it more cylinder space and that in turn will give you LESS compression when the piston is at T.D.C. (top dead center). So like I said, Only one head gasket.
Thanks,
Big Red.
 
Last edited:
Thanks a lot Big Red once again!

i wont be near my bike till the end of the week. but i am going to take all your advice and try to work it all into my mess. i'll have an update by friday or so to see how everything works out.

I added the extra head gaskets because i was paranoid thinking that the piston was actually hitting the plug. when i had 4 it ran at the low speed. when there was 3, it didnt want to start up. maybe it was gas too because i put a little bit in i'm also going to try to put in a good amount..since it was a brand new engine and never had gas in it.

thanks!:bowdown:
 
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