upper cylinder rebuild

agrogod · Post by **agrogod** » Sat Apr 13, 2013 10:34 pm

Well I finally got a good weekend here in PA with no rain and above 40 temps. so I was finally able to do my rebuild. Got all the parts together and started my tear down, it went better than expected with no real problems.

Last year had noticed at the end of 2012 the power was dropping off at various times during riding. Having worked for a landscaping company at one time, and dealing with 2 stroke equipment, when the power dropped off with the equipment we would re-ring the misbehaving offenders and all would be well with the world. So I felt the culprit to my power issue was probably in the cylinder. I purchased the Prima kit because I wanted to go with the cast iron cylinder and it had everything that I was looking for, including an affordable price. Here are some pics of the rebuild.

agrogod · Post by **agrogod** » Sat Apr 13, 2013 10:38 pm

Lotrat · Post by **Lotrat** » Mon Apr 15, 2013 3:56 pm

How many miles did you get before the rebuild? Have you started it up yet? Make sure you break it in to seat the rings properly. No synthetic oil during break in.

agrogod · Post by **agrogod** » Tue Apr 16, 2013 10:12 am

I had 1600 miles on it, and as stated it was giving not so great performance. After I got the old piston out and took a good look at it found that it had warped (pics will be coming).
Also was disappointed with the old cylinder and piston overall, they felt thin and flimsy compared to the replacement. And just to clarify, the replacement was not a high compression cylinder.

And yes it has been started and ridden, nice smooth sound like when it was new, with good acceleration. Only thing left to do is the rollers, just had enough rolling around on the concrete for 1 day. I'm still feeling it as I type this out, makes me wish I was a younger man.

Lotrat · Post by **Lotrat** » Tue Apr 16, 2013 3:13 pm

1,600? That doesn't seem right.

VinylDoctor · Post by **VinylDoctor** » Tue Apr 16, 2013 3:25 pm

yeah something is wrong with 1600 miles.
thats what you would expect from a cheap no name chinese scooter.

agrogod · Post by **agrogod** » Wed Apr 17, 2013 2:15 am

Here's the pics to prove it. You can see the carbon scoring down the sides where gasses were getting past the rings. And the definite warping around the top of the piston. No worries though. As I explained to my work friends, a $124 fix for the scoot as compared to $2000 for their car/truck for the same type of repair. Even if I had to replace the whole engine it would still have been relatively inexpensive. And now more knowledge and a repair with satisfactory results makes it a job well done.

B02S4 · Post by **B02S4** » Fri Apr 19, 2013 2:58 am

This isn't a BBK?

agrogod · Post by **agrogod** » Fri Apr 19, 2013 9:07 am

Ooops. Meant to say that it wasn't a high compression cylinder. Thanks B02S4 for pointing that out. Edited post.

agrogod · Post by **agrogod** » Fri Apr 19, 2013 9:54 am

One other thing that still bothers me about the rebuild. When I removed the old cylinder I was fully expecting to have to scrape off old gaskets or sealing material. There was absolutely none to be found. And there was leaking around where the cylinder mated up with the engine. Seems to me somebody was asleep on the job when they were supposed to be assembling.

Lotrat · Post by **Lotrat** » Fri Apr 19, 2013 2:21 pm

It's not out of the ordinary. Tight tolerances and properly torqued head bolts will eliminate the need for gaskets and sealants. High temps will cook most sealants anyway. Home mechanics love RTV, but it's not needed everywhere. I'm more impressed that nothing was used at the factory.

rentonhighlander · Post by **rentonhighlander** » Fri Apr 19, 2013 10:25 pm

Something is not right. These bikes are designed to run much longer then 1600 between rebuilds. It's not like these are racing engines. My buddy (same engine) has over 3300 miles and that is not unique. There are people in the general forum who have well over 10k without any rebuilds.

SuperCyclone.81 · Post by **SuperCyclone.81** » Wed Apr 24, 2013 2:03 am

^ Agreed. My top end and crank were replaced at 7,500 and I've got a good 4-5k on this set up and still running strong... I guess your rig wasn't under warranty anymore?