50cc Chinese engines By triplej56 (Read 2,685 times)

[triplej56]

ok let me clarify the cam will NOT seat in the cradle due to the chain being too tight Before the nuts are put on the top of the bracket there is a 1/4 inch gap between the bearing on the cam opposite of away from the cam gear and the cradle where it is supposed to sit.the chain becomes super tight if you force the cam into place and put the top bracket with the valve rockers on .if you install the engine and attempt to run it the chain breaks within 5 minutes of engine running.<<<this is from my mechanic as of today please let me know if there is a cam with a smaller gear or if someone carries a longer chain so we can install the tensioner again

[sprocket]

Chains come in different lengths, need to know what is the link count...

Photos would help

[justbuggin]

make sure the chain glides are in their proper place and did you retract the tensioner

[triplej56]

Chain guides in place,as far as the tensioner,forget it.That chain is so tight you my as well throw the tensioner away.Sorry guys,but we did repairs for 6 years with no problems.We close 1 year and back in business now and all of a sudden the dam Chinese are doing all there bull to get me out the business.Sorry but we just do not know what exactly is going on.We got a feeling we need 1 or maybe 2 more links in the cam chain.My could be measurements is telling me 2.Again guys sorrry,but in the past we replaced many engines,etc.You name it we most likely did it.Back to where I started,we just never run into this.Maybe the Chinese sent us a oddball engine.Would sure not put it past them(lLOL)

[rob63]

Jul 14, 2012 12:55:06 GMT -6 triplej56 said:

New engine we put in had a good crank so we put it in with a new cyclinder(piston and rings),new cyclinder head(all from Parts for scooters).

It certainly is baffling.
Just pondering on the engine you`re fitting, was it a previously used engine, and did it have a barrel and head on it before you replaced with new parts ? Or did it come minus the barrel and head ?

[triplej56]

we do not know exactly what had happened to this different(old engine) we put in.It had no cycliner and head,but the crank seemed ok and cam chain seemed fine.We just put the new cyclinder and head on which measured the same as the old engine we were replacing with the bad crank.On the old engine we were not to happy with the scaring of the old cyclinder and valves,that is why we put new ones in.Both engines again read 139QMB.I will say again guys this sure is one dam confusing issue!

[rob63]

This is just a possibility, but maybe someone has tinkered with the engine before you got hold of it. Maybe they`ve put in the wrong crank or cam chain, realised their mistake when they went to rebuild the top end and just chucked it to one side ?
At this stage I`d be tempted to find another engine and worry about this one when you`ve got more time....or count the links on the chain and compare with the link count on a normal 139qmb chain

[justbuggin]

i have to go with what rob63 is saying could have def. cam sproket on the crank or the wrong chain in it

[triplej56]

I am starting to think it would be best to find another engine block.When we take this engine out I will see how many links are in the chain and compare it to one we are putting in,that is not going to have a problem.Will keep you guys informed as to what is going on.

[rob63]

Cheers buddy, I`ll be very interested to see what the problem turns out to be. If it`s of any use I recall that if you count the outside link plates on a standard 139qmb cam chain there is 41.

[royldoc]

If all the above fails you can always use a chain stretcher.

Roy

[triplej56]

hey Roy trying to find a chain stretcher with no luck(LOL).

[dagger75]

This site has 3 different size timing chains...maybe will help ya www.mbe-motorsports.com/catalog/product_info.php/cPath/16/products_id/301

Good Luck,
Gary

[triplej56]

we kind of think that we are getting to the bottom of our problem.our cam chain does measure 41 links.what i am going to do,is get a new 70cc kit,that comes with a cam(our old 80cc kits did not come with a cam).We will find out what is going on with a little bit of measuring.If we are ok with our new kits I will let u all know.Do not want anyone to run into the problem we are experiencing