"CG125" Clone

[JerryHawk250]

I'm pretty sure that is an OHC engine. I see it has a cam chain tensioner. Lifan made something similar.

[franque]

It's definitely ohc, just not Honda based. I forgot to mention, even if it was, unless something has recently changed, they changed the stud spacing when they went over 200ccs, so even if it was Honda CB/CG based, you'd still be limited to under 200ccs unless you made a custom stroker crank.

[jamrock876]

Originally Posted by franque

It's definitely ohc, just not Honda based. I forgot to mention, even if it was, unless something has recently changed, they changed the stud spacing when they went over 200ccs, so even if it was Honda CB/CG based, you'd still be limited to under 200ccs unless you made a custom stroker crank.

I still have a lot to learn about these engines it seems. Was of the opinion that the bolt patterns were relatively standard with only the crank and cylinder/bore changing between the different cc ratings.

Seems on this engine I might be limited to just the porting, cam and an offeset flywheel key. The additional displacement from a bigger bore would have been nice but I also like the revvy nature of a 150 so not all is lost.

[franque]

Where did you find a cam for it? I didn't think there was much available for it.

Honda changed the bore spacing when the CRF230 came out, because otherwise they were running into the cylinder studs and oil supply (technically at least the second or third revision of these crankcases that date back to the SL/CB100 of the early 70s).

[jamrock876]

I have not received the cam as yet and so cannot say for certain that it will actually work. I went with the crf150 cam as it looked visually similar to mine. I will be testing that once it gets in, possibly before pulling the head off completely as I am unable to locate a head gasket locally.

[franque]

Yeah, I would be inclined to think that it won't work unfortunately, though I'm excited to see what you come up with!

If your cylinder head is the same as what I posted in the other thread (trying to figure out what the engine was), it appears to have three plain bearings for the cam to run on, as opposed to two roller bearings on the 03-06 CRF150F/CRF230 cams; that was the major update to that engine family, besides the increased stroke on the 230, which reminds me, apparently the stud spacing wasn't changed for the 230, just an increase in stroke.

I think for the 'clone' engines, they did increase the stud spacing, but I would have to double check.

You'll probably have to cut the bearing off of the sprocket side of the cam to make it work, and press off the bearing on the non-drive side, but even then there is the distinct probability of different measurements for the length of the cam, the diameter of the plain bearings, etc.

I would invest in a pair of calipers to double check everything, and plan on making friends with a welder/machinist if you really want to make the cam fit/work.

Another option, if you want to keep the engine, is possibly have a cam reprofiled by somebody like Webcams. I'd get a spare cam and send that to them, because if any aftermarket cams are available, they will be coming out of the UK.

I think your best bet is to get a CB or CG style engine and hot rod one of them, this way you can find parts without having to make your own (or get them custom made).

I'm along for the ride, in any case!

[jamrock876]

Originally Posted by franque

Yeah, I would be inclined to think that it won't work unfortunately, though I'm excited to see what you come up with!

If your cylinder head is the same as what I posted in the other thread (trying to figure out what the engine was), it appears to have three plain bearings for the cam to run on, as opposed to two roller bearings on the 03-06 CRF150F/CRF230 cams; that was the major update to that engine family, besides the increased stroke on the 230, which reminds me, apparently the stud spacing wasn't changed for the 230, just an increase in stroke.

I think for the 'clone' engines, they did increase the stud spacing, but I would have to double check.

You'll probably have to cut the bearing off of the sprocket side of the cam to make it work, and press off the bearing on the non-drive side, but even then there is the distinct probability of different measurements for the length of the cam, the diameter of the plain bearings, etc.

The cam uses two roller bearings and has a removable cam gear if I remember correctly. I had removed the cam cover to do a quick visual check before ordering. For some reason trying to remember now I cannot say if I actually verified that the gear was removable.

I was unable to check the actual spacings of the bearings and lobes as I am still waiting on my calipers to get in. Got the alert yesterday that they were delivered to my freight forwarder in Miami.

Originally Posted by franque

I would invest in a pair of calipers to double check everything, and plan on making friends with a welder/machinist if you really want to make the cam fit/work.

Another option, if you want to keep the engine, is possibly have a cam reprofiled by somebody like Webcams. I'd get a spare cam and send that to them, because if any aftermarket cams are available, they will be coming out of the UK.

I think your best bet is to get a CB or CG style engine and hot rod one of them, this way you can find parts without having to make your own (or get them custom made).

I'm along for the ride, in any case!

I intend to get the engine apart and actually take some proper measurements once the remainder of my tools get in. My biggest issue currently is that I am unable to source a head-gasket from the dealer and without that, I am a bit hesitant to pull the engine apart. I might get lucky and have it be MLS so I can re-use it with a slight coating of copper spray but I would have to take it apart to be sure.

My thought process currently in getting parts are that if they work for this engine great, if not I am likely to grab an engine from a crf230 clone. I think they go by the "Monster" / "Hi Rev" brand locally.

These are the only pictures I can find online which show the possible donor engine/bike.

[jamrock876]

The previous message by @franque had me concerned as I really could not remember if the cam gear was removable.

Curiosity got the better of me and I ended up taking the valve cover off this morning to be sure. While there I decided to snap some pics and pay more attention to details.



As can be seen above the cam gear is actually removable , however, the third lobe that I had originally ignored is now a concern. The lobe seems to have some function in the oiling system, as it has a corresponding spring-loaded pin in the cover that lines up with the oil passages. This can be seen just above the rockers in the following image.



Any guesses as to what this might be? My first thought was a pressure relief or some sort of splash oiling or the cam rollers. The scoring in the cam journals above is hopefully not anything I need to worry about, it doesn't catch my nails and should only really need to hold the outer race for the cam bearings. I checked the bearings to be sure and they still spin freely. One other interesting fact I found was that this engine uses head bolts instead of the seemingly more popular head studs and nuts combo.

The following are two random snaps I took of the cam, one showing the bearing size and the other showing some form of identifying mark. The TY139 designation produces results of the same - or similar - cam on aliexpress but not much else.

Edit: After more digging, it would seem the engine is a TYAN TY150 or a variant thereof. They come with a 49.5mm stroke, 62mm bore and are loosely based on the CB150. Sadly all indicators point to it having a 13mm wrist pin so there are no bigger cylinders that would readily fit. I will confirm all this when I have it apart in a few weeks however at present it seems I would be better served to purchase the 250/230 engine from the bike shown in the post above.

I was also able to tell that the undriven side bearing is a 6203Z.

[jamrock876]

Originally Posted by JerryHawk250

I'm pretty sure that is an OHC engine. I see it has a cam chain tensioner. Lifan made something similar.

I know it has been some time since you did your x22r but by any chance do you remember the size bearings that were on the cam? I am still in the information discovery stage and trying to gather as much information and parts for when I tear this engine apart next month.

[jamrock876]

As the date draws closer, I am starting to get cold feet on attempting to port the head. Not sure I should make my first attempt at a P&P on a head I cannot seem to find a replacement for. I have been searching aliexpress, alibaba and ebay for a potential replacement head - just in case - but have so far only been able to find cylinders.

I think I might try to get by with changing out to a cheapo pwk28 (not Nibbi sadly, I try to keep my purchases under 50USD for customs), and cam for the time being. Wondering what that would be like with the mods I have done so far.

[jamrock876]

I guess there isn't much interest in these styles of bikes .

Nevertheless, the mods must go on. One problem that has plagued me since owning the bike was its poor headlight. The stock headlight was unfocused and seemed to bother oncoming vehicles on low and high beams while not producing much usable light. I first tried changing out the bulb for a generic H4 LED, however, that seemed to have only made the problem worst.

The solution to that problem for me was a cheap 7" LED headlight from ebay. While it was a really tight fit getting the replacement into the stock housing the results are a night/day difference.

Installed:


Results:

I decided to turn lemons into lemonade and went with the amber lights for my drl. Had really thought the version I purchased came with the integrated turn signals.


Low Beam - I am really loving the defined cutoff.


High Beam



Also installed a phone holder, I travel approximately 80km daily, which really helps with music on the road.

[JerryHawk250]

Wow! those lights are bright!

[jamrock876]

Had to cancel my vacation due to teammates getting sick so decided to start playing with mods I had lined up for the "rebuild". My first attempt was the PWK28 carb, sadly the intake I purchased was incorrect so I had to improvise.

I started by cutting the flange off a stock intake and attached the carb to that using a bit of rubber hose. I then used the intake boot from a pz30 carb heated and stretched it to the 50mm required for the PWK.

Completed install:


Sadly while the bike started and idled immediately and had good low-end torque with the new carb, it was running way too rich. I also think my makeshift intake manifold was causing issues as the fuel would puddle inside the intake making the bike unpredictable and impossible to tune.

I have since reverted these mods and ordered what I think to be the correct intake, an inexpensive kit of jets, and a short (approximately 40mm) velocity stack. I am hoping that with these I can finally get this bike to run well with the carb.

[jamrock876]

Since my last post, I have since taken things back a bit.

I eventually got the PWK carb to a point where I was comfortable running a 35 pilot with 3 turns out on the air screw, HHJ needle on the second clip from the top, and a 120 main jet. Shortly thereafter my cousin's bike started having issues, had a dropped exhaust valve which took out the piston. This caused me to reconsider constantly messing with my primary mode of transportation, especially asking this much from a little 150.

I have since removed the PWK and purchased another bike for approx USD500 that has some variant of the "RE250" CB250 clone. While the body wasn't in good condition I was able to get parts relatively cheaply and have since gotten it to a point where it is okay, just need to get the engine dialed now. After which I can continue the pursuit of power. I will post pics once I get into the teardown (hopefully today).

[jamrock876]

A question though, I have been battling an odd issue with my cousin's CG-based engine. The valves, primarily exhaust, repeatedly "get tight" or drop entirely shortly after being properly adjusted. I have checked the pushrods are straight, checked that the timing is correct and the camshaft is within spec.

This all started after the rebuild from the first dropped valve, my working theory is that it is running lean and overheating which leads to the valve stretching and or the seat receding, is this a possibility

I am aiming to have both bikes -CB250 "Hi rev" and my cousin's CG150 "zhujiang"- down today for maintenance and service and would appreciate any input provided.