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

[Ariel Red Hunter]

Originally Posted by 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..

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]

Originally Posted by Ariel Red Hunter

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]

Originally Posted by 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?

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]

Originally Posted by JerryHawk250

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]

Originally Posted by DualSport

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]

Originally Posted by 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

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.