Can you take piston cylinder off without messing with cam timing?

[DualSport]

I got parts from RPS to repair my dinged up piston and messed up valves and head, and am wondering if I can pull the piston cylinder without having to reset the cam etc..

I tried searching here and google for it being documented for either the Hawk or original CG 125 and came up with nothing.. I don't want to offset the cam, crank, and magneto and see that the cam adjuster is on the piston-head, but it looks like it's just in the cavity under the push-rod holes.

Thanks

[ben2go]

No. It usually turns just a bit while feeding the chain around the sprockets.

[JerryHawk250]

The CG250 is a push ROD engine so yes you can remove the cylinder without messing up the timing. No timing chain on the CG250.

[NzBrakelathes]

CG yeah cause cam inside bottom cases
Maybe add in roller rockers while you are there
Messing with cam timing can’t be an issue cause such a simple motor n line up the dots I assume

[ben2go]

The CG250 is a push ROD engine so yes you can remove the cylinder without messing up the timing. No timing chain on the CG250.
:tup:




:doh: Forgot that that engine is a pushy rod type.

[JerryHawk250]

Perfect opportunity to throw in some roller rockers. :tup:https://www.aliexpress.com/item/Brand-Quality-Motorcycle-Universal-Arm-Shaft-O-Ring-Valve-Rocker-Arm-for-CG125-CG150-CG175-CG200/32822679247.html?spm=2114.10010108.1000014.1.48b57 1874hkGo3&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.13338.112281.000000000000000&scm_id=1007.13338.112281.000000000000000&scm-url=1007.13338.112281.000000000000000&pvid=91d073f5-03e7-4392-b7b9-7f354bbbe4f6
https://ae01.alicdn.com/kf/HTB1oXIaSXXXXXclXFXXq6xXFXXXN.jpg?size=73349&height=570&width=808&hash=2a6dc817842e17d90d95eedddf01bb16

[Red Hawk]

WOW I am seriously tempted to try those !
It's snowing here now :tdown: so im running out of dust to knock off the Hawk.

[JerryHawk250]

WOW I am seriously tempted to try those !
It's snowing here now :tdown: so im running out of dust to knock off the Hawk. Even though any performance gain will be very small if any at all. Less friction does equal more power. It's one of the mods that I would do only if I was already pulling the cylinder off. I wouldn't pull the cylinder just to install them.

[Sochin]

Porting the head is simply a must if you're already in there, smooth out and open the intake/exhaust will give you tremendous performance for the money. And port the stock exhaust header to match the opening, as it has a big arse weld inside, forming a doughnut restricting flow..........unless you have an aftermarket exhaust?

[Megadan]

I would be more interested in those rockers if they offered an increased ratio. For the dollar I think that would be the best "bang for the buck" if it could be done.

[pete]

if the cam lobe ramp angle is not steep enough to
require the use of a roller to climb it..
there is NO gain from a roller..

( if the cam lobe angle is steep enough it will try and
push a lifter side ways... then you need a roller)

but they are cheap..So why not put them in ..
i would just for the hell of it and because I can...

.

[Weldangrind]

I'm shy about using rollers, because the needle rollers are another point of failure. I've seen roller rockers grenade inside V8 engines, and those needles go places you don't want them. As Dan says, I'd be more interested in a different ratio.

[DualSport]

Can someone tell me why my rockers wouldn't be moving? Got the piston and new head installed(great compression etc...), and rotated engine with pushrods set in the rocker joints and they don't move.. Exhaust is really high up and intake really low, and cam is moving etc..

I have the rocker pin set with the bolt tightened I'm hoping I can fix this there instead of pulling up the piston sleeve. Even though doing work on the piston sleeve is surprisingly fast and requires no special tools.

[pete]

are the push rods the same length ?


..

[DualSport]

rods were same length they worked after I pushed harder on the exhaust rocker. I'll upload pics tomorrow of everything.

[JerryHawk250]

Are the followers ( lower rockers) moving freely? Push rods seated in the followers?

[DualSport]

Yeah I got them working. The exhaust rocker just needed pushed down on the cam lobe.

Tomorrow I'm going to use a cheap 40w oil to flush the old oil and burn out condensation from it sitting in rain and cold(covered). It's got strong compression with the original cylinder so all should be good.

I prefer hydraulic lifters and roller rockers in car engines, but the way these engines are I'm going to wait for someone else to try them out over time..
'

[Ariel Red Hunter]

I got parts from RPS to repair my dinged up piston and messed up valves and head, and am wondering if I can pull the piston cylinder without having to reset the cam etc..

I tried searching here and google for it being documented for either the Hawk or original CG 125 and came up with nothing.. I don't want to offset the cam, crank, and magneto and see that the cam adjuster is on the piston-head, but it looks like it's just in the cavity under the push-rod holes.

ThanksOn the Hawk (and other non balancer shaft or non overhead cam) engines, the cam is in the crank case, and because it is a four stroke, the cam is geared to run half as fast as the crankshaft. In the lower part of the barrel/cylinder is a pin that the rockers (cam followers) pivot on. The push rods fit into little cups on the cam followers. Oil this area well, but not more than an ounce, total. Then add the pushrods, put on the head, add the overhead valve gear. I used to use my sister's clarinet cork grease on the upper end of the push rods, just a little bit, to make sure they weren't dry on start-up. Next comes valve adjustment. If you use the T method, don't get excited about problems, because you are only going to be right 1/2 of the time. Not to worry, because it only matters once every two revolutions if the valves check out to be .003 inch on the intake, and .004 on the exhaust at the T position....ARH

[NzBrakelathes]

Perfect opportunity to throw in some roller rockers. :tup:https://www.aliexpress.com/item/Brand-Quality-Motorcycle-Universal-Arm-Shaft-O-Ring-Valve-Rocker-Arm-for-CG125-CG150-CG175-CG200/32822679247.html?spm=2114.10010108.1000014.1.48b57 1874hkGo3&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.13338.112281.000000000000000&scm_id=1007.13338.112281.000000000000000&scm-url=1007.13338.112281.000000000000000&pvid=91d073f5-03e7-4392-b7b9-7f354bbbe4f6
https://ae01.alicdn.com/kf/HTB1oXIaSXXXXXclXFXXq6xXFXXXN.jpg?size=73349&height=570&width=808&hash=2a6dc817842e17d90d95eedddf01bb16

Did you notice it listed them for 200cc or below only? not a 250.
Is there a difference? careful with Chinese details huh - around half the time I get stuff they are wrong and I am left fixing the issue.

[ben2go]

Did you notice it listed them for 200cc or below only? not a 250.
Is there a difference? careful with Chinese details huh - around half the time I get stuff they are wrong and I am left fixing the issue.
Most of these bikes aren't 250cc. They are between 200 and 230cc depending on engine model. Cam profile and max RPMs are the contributing factors to roller rockers having problems.

[DualSport]

UPDATE: I got everything together, and after some fresh oil and starter fluid it ran fine, BUT it billows smoke out the header connection and there is what looks like gas darkened by exhaust or oil coming out there and the clamp further back. I checked the two fasteners and they are fine.. Seems like something is off; it runs though..

No regional motorcycle or scooter repair shop will touch it for some reason, so I basically have to work on it on my off time which is very little..

I kind of suspect something with rockers and/or the rocker pin, but I could be wrong.. I still don't know what that external rocker pin does, but it seems to effect timing somehow.. I put a #110 jet from the motocheez amazon link on the PZ30 but it does it in pilot and choke too so I kind of suspect something in the block.. Valves are both 0.00285

[Sochin]

There is an o-ring supposed to go on one of the cylinder bolts before you get the head on? Did you get that in before you torqued it down? It has to do with the oil flowback to the engine I recall?

[DualSport]

There is an o-ring supposed to go on one of the cylinder bolts before you get the head on? Did you get that in before you torqued it down? It has to do with the oil flowback to the engine I recall?

That's probably it cause all fasteners are properly torqued, gaskets are good, valves are working, ignition is good, and compression is like new. I know I didn't put it in too so I'm confident. I'll do it tomorrow.

[JerryHawk250]

I noticed that you have the piston in backwards. The "IN" on top the piston should face the intake. Glad to see you're taking this on and working on it. It will be a good learning experience. You'll know that engine inside and out before you know it. :tup:
Here's a link to a manual that will help you out on the engine.
https://josemaco.files.wordpress.com/2013/03/storm-english-62ktjam5.pdf

[DualSport]

I noticed that you have the piston in backwards. The "IN" on top the piston should face the intake. Glad to see you're taking this on and working on it. It will be a good learning experience. You'll know that engine inside and out before you know it. :tup:
Here's a link to a manual that will help you out on the engine.
https://josemaco.files.wordpress.com/2013/03/storm-english-62ktjam5.pdf

I didn't think it mattered it looks symmetrical.

Mine didn't come with a exhaust header gasket. I need to find a generic one I guess..

The seal fixed the oil issue, but the plug still gets wet and the engine dies after twenty seconds of running.. It won't even fire with a dry plug, starter fluid, and in any of the upper two choke states.. It was 40F today so I was trying cold starts with no throttle or starter fluid.

My compression is great but it dies after twenty seconds of running and I need to get the header gasket. Is this do to the backwards piston, or is it a carb issue? It's the stock PZ30 with a 110 main and the mix screw 1.5 turns out.. Valves were set to 0.00285 with both valves out/loose piston-up and on T|.

[JerryHawk250]

Here's a link to the header gasket. https://www.amazon.com/dp/B01MZDNDMH/?coliid=I3F4ZRWQBILDYP&colid=2TIDKN14UQSQ&psc=0&ref_=lv_ov_lig_dp_it
110 jet should be fine. I would try another plug just in case there is a crack in the insulator causing a week spark. I would pull the piston and rotate it to the correct position. Also ring gaps should be staggered at 120 degree intervals.

[DualSport]

Here's a link to the header gasket. https://www.amazon.com/dp/B01MZDNDMH/?coliid=I3F4ZRWQBILDYP&colid=2TIDKN14UQSQ&psc=0&ref_=lv_ov_lig_dp_it
110 jet should be fine. I would try another plug just in case there is a crack in the insulator causing a week spark. I would pull the piston and rotate it to the correct position. Also ring gaps should be staggered at 120 degree intervals.

I'll do all of that. This time I'm taking the engine off, fighting the head beneath the top mount brackets is what makes it takes hours to do stuff..

[JerryHawk250]

I'll do all of that. This time I'm taking the engine off, fighting the head beneath the top mount brackets is what makes it takes hours to do stuff..

If you lived close by I would be more than happy to give a hand. By the time your done you'll be an expert on taking it down and putting it back together.

[DualSport]

If you lived close by I would be more than happy to give a hand. By the time your done you'll be an expert on taking it down and putting it back together.

I'm all the way in Charlotte, NC. I'd have it done tomorrow morning if I didn't have to go to work. I'll either do it throughout the week or do it in a day next weekend.

I'm going to put a new iridium plug in(like the NGK already in it), flip the piston, and put the header gasket in. Probably do a base gasket too("FN200-010014-0000" at RPS) cause it looked like it was cheap paper and dissolving.. It looks like another thing only TX is selling

[DualSport]

Summary

Brand new header gasket from amazon link in this thread(fits perfectly)
Brand new NGK iridium plug around 0.7mm gap(my carcraft gauges only have 0.628 and 0.8 and it's in between; it's the factory gap of the plug)
Brand new piston and rings; ring openings rotated 180 degrees of last ring opening and "IN" carb-side and rings are in the order of the stock piston
Brand new head with factory rubber back-flow seal placed on stud with metal spacer where there is a drain cut in the nut-seat as was from factory. Head gasket has no marks or cracks
Valves both 0.00285 on the compression stroke where plug hole pushes+both valves have slack+On T| line
Carb mix screw 1.5 turns out, #110 needle jet and factory PZ30 pilot. Always ran with choke fully open and idle screw just a little out to get to idle on engine sticker when warm
Factory battery properly leveled and float charged with 1.5A smart charger. It's been out in the cold and abused a little but the bike runs when kickstarted with it.. I use starter fluid so it's one-kick starts when cold and it cranks without once warm on one-kick


I've got this bike running and idling smoothly, but it still billows smoke. I let it idle a while with just the header on seeing if it was pooled oil in exhaust, but it never stopped smoking once exhaust was hot a while, and plug had some oil on it after but didn't foul. It ran find till I turned it off once warmed up with a couple of starts with starter fluid.

From what I see oil can only come from piston rings, head gasket or backflow seal, and valve seals. Rings and valve seals are new with rings "staggered", head gasket has no cracks or marks and is on correct, backflow seal is on with no stretching or cracks..

[Ariel Red Hunter]

Summary

Brand new header gasket from amazon link in this thread(fits perfectly)
Brand new NGK iridium plug around 0.7mm gap(my carcraft gauges only have 0.628 and 0.8 and it's in between; it's the factory gap of the plug)
Brand new piston and rings; ring openings rotated 180 degrees of last ring opening and "IN" carb-side and rings are in the order of the stock piston
Brand new head with factory rubber back-flow seal placed on stud with metal spacer where there is a drain cut in the nut-seat as was from factory. Head gasket has no marks or cracks
Valves both 0.00285 on the compression stroke where plug hole pushes+both valves have slack+On T| line
Carb mix screw 1.5 turns out, #110 needle jet and factory PZ30 pilot. Always ran with choke fully open and idle screw just a little out to get to idle on engine sticker when warm
Factory battery properly leveled and float charged with 1.5A smart charger. It's been out in the cold and abused a little but the bike runs when kickstarted with it.. I use starter fluid so it's one-kick starts when cold and it cranks without once warm on one-kick


I've got this bike running and idling smoothly, but it still billows smoke. I let it idle a while with just the header on seeing if it was pooled oil in exhaust, but it never stopped smoking once exhaust was hot a while, and plug had some oil on it after but didn't foul. It ran find till I turned it off once warmed up with a couple of starts with starter fluid.

From what I see oil can only come from piston rings, head gasket or backflow seal, and valve seals. Rings and valve seals are new with rings "staggered", head gasket has no cracks or marks and is on correct, backflow seal is on with no stretching or cracks..My question would be 'did you hone the cylinder before assembly?'. You can also take the rocker cover off and run the engine to make sure the oil is draining ok. I'd elevate the front of the bike to get the engine level first, though...ARH

[DualSport]

My question would be 'did you hone the cylinder before assembly?'. You can also take the rocker cover off and run the engine to make sure the oil is draining ok. I'd elevate the front of the bike to get the engine level first, though...ARH

I just had the valve cover off and no pooling oil. I checked torque on all the stud bolts too..

I didn't hone the cylinder it still had the factory honing and was without pitting or scratches from old piston, and the bike had no run time since it came dead..

It's looking like just giving TXPowersports $500.00 for a engine is the only solution since I don't have the home time a lot of people do and need to get this done and no shop will touch it.. I don't know of any test to find what is leaking oil into the chamber besides a leak-down test and that doesn't tell whether it's valve seals, rings, backflow, or head gasket just that there is a leak which I already know..

Would putting oil in cylinder help tell if it's rings or cylinder, or something else like Marvel Mystery Oil or something?

[Weldangrind]

Before tearing into it again, I'd perform a couple of tests. See if you can borrow a compression tester from a local auto parts place and get a sense of what the compression is with the throttle wide open.
Also, see if you can borrow a leakdown tester. The simplest way is to use a hose that has the appropriate plug thread on one end and a compressor quick connect on the other. Thread it into the head, hook it up to a compressor and give it 100 pounds or so (with the engine at TDC, as if you were going to set the valves). Where do you hear air escaping? If it is out the crank vent, the ring seal is bad. If it is coming from the rocker area, either the valve guides or seals are bad (or both). If you don't hear any air coming out of the muffler or carb, your valves are sealing as they should.
Were the rings pre-installed on the piston, or did you install them?

[DualSport]

Before tearing into it again, I'd perform a couple of tests. See if you can borrow a compression tester from a local auto parts place and get a sense of what the compression is with the throttle wide open.
Also, see if you can borrow a leakdown tester. The simplest way is to use a hose that has the appropriate plug thread on one end and a compressor quick connect on the other. Thread it into the head, hook it up to a compressor and give it 100 pounds or so (with the engine at TDC, as if you were going to set the valves). Where do you hear air escaping? If it is out the crank vent, the ring seal is bad. If it is coming from the rocker area, either the valve guides or seals are bad (or both). If you don't hear any air coming out of the muffler or carb, your valves are sealing as they should.
Were the rings pre-installed on the piston, or did you install them?

I installed them. I "staggered" each 180 degrees of the last ring's opening even on the two around the oil control ring. I have the two thin with the oil control ring, and then a thick compression ring on each of the other two upper slots. Rings and piston were brand new I didn't reuse old rings. The head preloaded with valves came with the new rings and piston in the mail.

Leak test sounds promising but I have to source a compressor that can handle it.. I didn't know you could actually trace the problem by sound of air flow..

[ben2go]

It would be a bad leak if you can hear it. Keeping an eye on the pressure over time will be the thing to look for. Of course, no engine holds compression. It will leak down. If it leaks down in a few minutes, there's a problem. If it leaks down over hours and the compression is good, there are likely no problems.


Smoking after starting an engine that's been apart is common. You've been handling the parts with oily hands I bet. That oil could be in the pores of the castings and it's burning off. If it's exhaust smoke, it could be from the earlier problems. There may be oil coating the inside of the header and muffler.

[Weldangrind]

Also ring gaps should be staggered at 120 degree intervals.

I'm not suggesting that you should pull it apart again, but if you do, 120 degree intervals is preferred over 180 degrees, as Jerry indicated.
X2 on everything Ben just said.

[Ariel Red Hunter]

I just had the valve cover off and no pooling oil. I checked torque on all the stud bolts too..

I didn't hone the cylinder it still had the factory honing and was without pitting or scratches from old piston, and the bike had no run time since it came dead..

It's looking like just giving TXPowersports $500.00 for a engine is the only solution since I don't have the home time a lot of people do and need to get this done and no shop will touch it.. I don't know of any test to find what is leaking oil into the chamber besides a leak-down test and that doesn't tell whether it's valve seals, rings, backflow, or head gasket just that there is a leak which I already know..

Would putting oil in cylinder help tell if it's rings or cylinder, or something else like Marvel Mystery Oil or something?I'M almost afraid to bring up the method used in down state Illinois to solve this very problem on Farmall 966 and 1066 tractors. A wee bit of Bon-Ami introduced through the intake of a running and preferably loaded engine to break the glaze on the cylinder walls. Then change the oil after 15 minutes of running. I'm not recommending this, and neither did Mother Harvester. But sometimes desperate men do desperate deeds...

[DualSport]

I will take it out on a back-road and try and smoke it out my next free day. My compressor has too small a tank and doesn't have the standard coupler the kits all use.

I've seen thicker oil and additives used to fix or detect bad rings and main bearings too. People use diesel oil to flip cars with bad engines..

[NzBrakelathes]

Hi
Why not buy a cylinder with piston set etc?
I would rush out n buy another cheap brand engine
If an engine is needed you got more choices if you extend the budget
Other thing did you replace the O ring on the head bolts between the cylinder?
I wonder if you didn’t break an oil ring?
I think there are many more options or possibilities rather then rushing out to buy a cheap made non Zongshen engine

[DualSport]

Hi
Why not buy a cylinder with piston set etc?
I would rush out n buy another cheap brand engine
If an engine is needed you got more choices if you extend the budget
Other thing did you replace the O ring on the head bolts between the cylinder?
I wonder if you didn’t break an oil ring?
I think there are many more options or possibilities rather then rushing out to buy a cheap made non Zongshen engine


If you're referring to the rubber ring on the block-stud back-right it's securely seated and not cracked or fatigued. The head and valves and piston and rings are new so I'm thinking of a new cylinder too. The one on it had no pits or scratches but I've pretty much eliminated valve seals, back-flow ring, and head gasket by taking it apart again and triple checking everything that can let oil in to the chamber with visual analysis.

The base gasket and anything below cylinder section of head can't cause this so it's a very small area for the problem to exist.. It's basically down to cylinder, ring rotation(rings new at 180 degree rotated based on openings), head gasket(no visible defects orange seal not cracked), back-flow seal(like new+seated), and valve seals(new)..

By the way I've had the engine apart a few times and never looked how that head backflow actually flows just that there is that seal and a slot under the stud-bolt&washer under the valve cover.. I didn't see and place for it to flow down the bolt on the bottom of the head though so I assume there is a channel inside the head going over to the pushrod part or it flows through the stud-sleeve..

[DualSport]

Just wanted to close this thread out. The new rings RPS sent me through Q9 were too small.. I compared them to the old and used the old after realizing it and now no smoke.. I'm not sure what those rings go to but it's not a Hawk or Magician....

A few notes:

The engine is heavier than you think. I'm a 6,3 250lb guy who drives trucks and does labor and I had to grip it good and keep my back straight and still felt pressure on my legs.. I did everything without a shop though you can dolly it around if you have a concrete surface..
Drop the subframe to do any head work or to remove the engine. It'll catch on the back when trying to remove the engine if not and there isn't enough space to get it free out the sides. Head work is very time consuming if you don't drop subframe and you'll scratch some stuff.. Do back engine mounts before bolting the front of the subframe.
Unplug red starter wire, plug wire, green ground, detach shifter, remove chain with master link, and unplug shift and stator harnesses and you're ready to pull the engine. It's all modular(except ground and starter which are screwed on) so just unplug
If you really "wrench" on a RPS bike a lot be prepared to redo the threads on the under-tank engine mounts, or be smarter than the engineers and just put grade 8 fasters through the stripped holes and never worry again..
RPS ring compression and scraper markings are "DN" and "D" unlike any CG 250 or CG 250 clone manual. The stagger of the three oil rings doesn't matter but the others are 120 degrees and never pin-side
The RPS head and base gasket are garbage.. Supplement them with red or "ultra copper" permatex..
Grade 8 fasteners with lock washers should be put everywhere, and red locktite on sprocket bolts, shifter retainer bolt, and handle bar hex bolts.. What is on there is crazy brittle and it looks like they painted them to hide it..
I used dollar store SN wet clutch 10-40 to flush oil and do run tests and went to Rotella T4 for final.
Avoid buying anything from a RPS dealer or RPS directly. The markup compared to alibaba and alixpress is insane.. $40.00 for a head gasket compared to $10.00 for a complete rebuild gasket kit kind of insane.. Also fake holiday sales where they literally don't change a single price on the whole site.. Also fraudulent warranties by most dealers and a chance of getting used or broken stuff..
I use kerosene and Liquid Wrench chain lube/protect just like a lot of jap dealership shops for the chain. Also the stock chain isn't "sealed" no matter what dealer sites and forums say... There are no rubber rings anywhere on this chain..
Don't use ANY torque values listed in tech manuals like the Honda CGR125-5 manual linked in this thread. They are all CG clone engines but the actual torque values wildly vary you'll likely do something like snap a cylinder bolt.I recommend tightening with a standard length ratchet till it feel pretty tight and then measuring and noting with a calibrated torque bar..

[NzBrakelathes]

Agreed that often basic parts are way over priced in the USA but they wanna make a quick buck!

I’m thinking of getting this bike as a tester but we will see
Have a good New Years lad :)

[Weldangrind]

Glad to hear it's not smoking anymore, DS. I hope you enjoy your new bike.