250cc OHC Air Cooled rebuild Issues!

[JohnWayne007]

Hey hows it going. well to start it off, i have a 166fmm zongshen 250cc OHC Air Cooled engine im working on, it ran alright before winter but just before i noticed it started smoking a bit. so i decided to replace a bunch of things...

- 65.5mm Honda xr200 Piston with Rings
- Honda xr200 Head & Base Gaskets
-Valves & Springs
-Muffler Gasket
- Carburetor Rebuild Kit

everything went perfectly fine up until after the rebuild. now this is where it gets interesting, i can get the bike started BUT it will only let me kick it maybe twice and on the 3rd or 4th kick it stops dead in its tracks like theres compression buildup, so i have to wait a minute or two and try again (never happend before rebuild) . now problem 2, when i do eventually get the bike running, it Idles really high, like half throttle reving. if i turn the idle screw it turns down but almost falls out before it actually makes a difference. if anyone can give me some insight on this i would be VERY greatful! you guys rock

[Bruce's]

Have you checked to see if the carb slide is in correctly ?

[JohnWayne007]

Originally Posted by Bruce's

Have you checked to see if the carb slide is in correctly ?

Carb slide is seated correctly, that was the first thing i checked, throttle cable is working smoothly i had even installed a friends brand new makuni carb with the stock jetting to see if it was just mine and his did the same thing. Im stumped im thinking a possible vacuum leak?

[Weldangrind]

It certainly could be a vacuum leak.

I'm stuck on how you got XR stuff to fit. I have a CB250, and the frame of architecture is larger in almost every way. That said, I'm working with a 69mm bore, so the mouth in the bottom end is larger, and will not accept an XR200 base gasket. I'm intrigued that you got a Honda 65.5 piston to fit; that's good news for another build I'm considering.

Is it a genuine Honda piston, or a Wiseco? Perhaps the compression is too much for a stock China setup that does not have a compression release (like the XR does).

[JohnWayne007]

Originally Posted by Weldangrind

It certainly could be a vacuum leak.

I'm stuck on how you got XR stuff to fit. I have a CB250, and the frame of architecture is larger in almost every way. That said, I'm working with a 69mm bore, so the mouth in the bottom end is larger, and will not accept an XR200 base gasket. I'm intrigued that you got a Honda 65.5 piston to fit; that's good news for another build I'm considering.

Is it a genuine Honda piston, or a Wiseco? Perhaps the compression is too much for a stock China setup that does not have a compression release (like the XR does).

Well the piston & rings kit is Stock OEM honda 65.5mm with the same specs as my original piston, i had searched everywhere for a piston kit and gasket kit for my bike and came up with nothing so i emailed around and contacted a manufacturer in China and he had told me that the 166fmm engines Normally take a 65.5mm piston with a 15mm wrist pin, so it took alot of research and sure enough the piston and rings ect. matched to the T. now not everything from an xr200 will fit, but as far as i have been told the piston and head gaskets are the same. i compared my piston and rings to the new ones, and also the gasket kit i had ordered was a Cometic Honda XR200 2002 gasket kit, i think only 93-02 parts work with the 166fmm engine. You also may be right about the compression being to much, but i did a test and i put my old piston back in with the new rings and same thing happens. i can get the bike to run and actually pretty decent other than a really high idle and my kick start has become very hard, you have to start it in 1 to 3 kicks and on the 3 or 4th your lucky if it doesnt stop before you can kick it down. its kind of odd because this never happend before the rebuild

[Weldangrind]

That's all really good information; I hadn't considered the '93-'02 XR200, since all of my junk is older.

Is it possible that the cam chain is off by one tooth? If the ignition was advanced, I could see starting difficulties.

[Weldangrind]

It just occurred to me that the stud spacing on the CB200 I'm working with is wider than an XR200, but again, that's due to the 69mm piston. It's good to know that newer XR200 stuff fits the 65.5mm bore size.

I've also considered putting an XR200 transmission into a CB motor to get six gears.

[Weldangrind]

Originally Posted by JohnWayne007

Carb slide is seated correctly, that was the first thing i checked, throttle cable is working smoothly i had even installed a friends brand new makuni carb with the stock jetting to see if it was just mine and his did the same thing. Im stumped im thinking a possible vacuum leak?

I'm struggling to understand how the idle could be that high with the slider all the way down. Even with a bad vacuum leak, the idle would most likely settle eventually.

No disrespect intended when I ask, are you certain that the slider is in the right way? You seem to be very experienced, but it is an easy mistake to make. The slider has a small ramp at the bottom that lines up with the idle screw, and I suspect it's above the screw or 180 degrees out.

[JohnWayne007]

Originally Posted by Weldangrind

I'm struggling to understand how the idle could be that high with the slider all the way down. Even with a bad vacuum leak, the idle would most likely settle eventually.

No disrespect intended when I ask, are you certain that the slider is in the right way? You seem to be very experienced, but it is an easy mistake to make. The slider has a small ramp at the bottom that lines up with the idle screw, and I suspect it's above the screw or 180 degrees out.

I wasn't too sure at first so what i did was removed the carb so i could get to it easier, i installed the slider correctly and looked through the intake to make sure it was sitting all the way down, this was my first thought aswell. as for the timing it may be possible that it is off by a tooth, at first i had no clue about timing and all that i mostly work on CG engines so the whole cam/timing thing was a little new to me. after searching and searching i found the timing marks on both the cam chain sprocket at the top, and the one on bottom. i lined everything up accordingly but i do think that the first time i did this i installed the cam with the lobes in the upward position while timing it at TDC

[JohnWayne007]

i also never thought of switching the transmission to an xr200. thats actually a good idea, i may have to look further into that. might just be my next project

[humanbeing]

Originally Posted by Weldangrind

... stud spacing on the CB200 I'm working with is wider than an XR200, but again, that's due to the 69mm piston...

Zongshen CB200? 17mm wrist pin
Rings spec: http://www.dongya.cn/prodlist.asp?page=8&tp=4
http://item.taobao.com/item.htm?id=36744024764 | http://item.taobao.com/item.htm?id=41515872521

[humanbeing]

To whom needs OHC 223 parts ,the alternative (ie. needs agent)
As stock
http://item.taobao.com/item.htm?id=35517374143
Higher grade:
http://item.taobao.com/item.htm?id=17587251271

[JohnWayne007]

Originally Posted by humanbeing

To whom needs OHC 223 parts ,the alternative (ie. needs agent)
As stock
http://item.taobao.com/item.htm?id=35517374143
Higher grade:
http://item.taobao.com/item.htm?id=17587251271

Thanks for the links ill have to check those out next time i need parts! very Helpful.

Update* I got my bike running good today, cleaned the carb and blew through all the passages with a air compressor, still idles a little high but way better none the less. now one last problem, my bike while running sounds like its making pop corn out of the exhaust, not loud, but loud enough to notice is. now is this normal? i wouldn't call it "back firing" because it happens almost the whole time the bike is idling even while riding it, i have my fuel screw set to 1-1/8 turns out and my throttle needle on the 4th clip with great throttle response and doesn't bog out. Starts first kick almost every time accept for when its cold. What do you guys think could be causing this weird "popping" noise? i took a video of it running but you cant really hear it

[Weldangrind]

Maybe it needs a fatter slow jet. Have you tried crutching it by backing off the pilot mixture screw a little more?

When you say the clip is in the fourth groove, is that from the top or bottom?

[Weldangrind]

Originally Posted by JohnWayne007

...at first i had no clue about timing and all that i mostly work on CG engines so the whole cam/timing thing was a little new to me.

So glad to hear that! I love CG engines, and very few around here share my disorder.