Scratched cylinder and piston?

Apr 3, 2019
3
0
1
30
Hi guys, i currently have a stock CDH motor, about 2 months old (I abuse the poor thing using it to deliver food with uber eats) I run about 60-80 km daily but after 1 rear mounting stud broke and began to vibrate a lot in the way home the motor never recovered it took a lot of time to get to 45 mph and only in declines or plane streets, After extracting the stud and replace it, it broke again stripping the threads from 1 of the rear motor mount holes.

I gave up on the motor and remove it from the bike but several days I opened the cylinder to review the status and found several scratchings on the intake side, also noticed that the piston is full of carbon including the bottom part and found some scratches on the piston itself and an area which is totally polished , like if the piston was hitting some part of the cylinder constantly.

Does it worth cleaning it and continue using it or I should purchase a new piston, rings and jug?

The carb is I think a stock speed carb (red cover) e clip on 2nd notch running 32:1
 

Attachments

Greg58

Well-Known Member
May 1, 2011
4,140
1,032
113
62
Newnan,Georgia U.S.A.
Its hard to tell how deep the scratches are, in the picture they don't look bad. The location at the bottom of the cylinder is probably the piston skirt rubbing, if the scratches do not go up to the area where the rings contact compression should be OK. What oil are you using? Looks like its not burning clean or you have the wrong sparkplug.
 

javy mcdees

Active Member
Jul 30, 2018
143
58
28
49
[/ATTACH]
20190429_194229.jpg
buy more pistons and jugs but meanwhile that one looks fine,
bike.jpg.jpg
normal wear, getter better carb maybe 2 cause they cheap and break easy. I have already stepped up to a larger carb than the one pictured the 19mm Dellorto carb upgrade was a good decision after about a week now of use.
 
Apr 3, 2019
3
0
1
30
Its hard to tell how deep the scratches are, in the picture they don't look bad. The location at the bottom of the cylinder is probably the piston skirt rubbing, if the scratches do not go up to the area where the rings contact compression should be OK. What oil are you using? Looks like its not burning clean or you have the wrong sparkplug.
Thanks for the answer, the piston skirt rubbing can be solved? or is a normal behavior on this engines?

I think the scratches does not go up to the compression area, and I can feel them with my fingernail

The last oil that I used was yamalube 2t and the sparkplug is the stock one.. I don't k ow the brand but I found a picture on Ebay.
20190503_222858.jpg
20190503_222347.jpg
 

Greg58

Well-Known Member
May 1, 2011
4,140
1,032
113
62
Newnan,Georgia U.S.A.
If it were mine I would use them, I would try to repair the rear stud and test it before spending money. If a stud breaks its sometime because its being pulled at an angle, make sure the rear mount sits flush to the frame and make height adjustments to the front mount.
 
  • Like
Reactions: javy mcdees