CG-125 ES4 - Engine

[G0FHM]

Hi Guys,

It would appear that our resident teenager has run his CG dry, and heat seized it.

It's now free, but the engine bearings are slapping like a good un (I suspect big end).

What I need to know is, if anybody has any info on the bearing numbers for the big end and mains (ie the standard 4 digit number such as 6203 or 6309 you would find on a SKF or NSK bearing).

I'd rather put decent bearings in it than generic, probably Chinese made ones (I know of SKF bearings that regularly carry out 16 million rotations and still survive), plus i'll bet I can get them cheaper than say from DSS, from the local specialist bearing factor.

Also, anyone have a compression figure? It's breathing a bit on the heavy side too, but it does have 18k on the clock and gets thrashed daily by an 18 stone teenager!

More work I could do without....

Thanks,

J

[hmmmnz]

easiest way to find bearings is go on https://www.bike-parts-honda.com/moto-honda-identification-CG125ES4-3570.html

and find the bearing number
91001-KGA-901 and
91001-KGA-902

which also tells you its a 28X72X18 bearing

now all you have to do is search through bearing sites for one that matches,
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[Ariel Badger]

If the bearings have gone the crank will have gone as well (along with cams and just about everything else), regardless of the milage the motor is stuffed beyond economic repair and will need replacing.
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Bikers make great organ donors, get 115 on your licence today.

[G0FHM]

Well, I've just given it a litre of oil, and it appears to have shut it up.

The loud metallic clacking has disappeared. There is a bit of tappet tick, but hopefully they can be adjusted. Compression is at the lower end of within the limits.

He may have dodged a bullet.

If the engine is indeed already shafted, then it will have to stay as it is until it blows up. Then he'll have to ring his father and explain why it has blown up, and can he please have another engine?.

Having had a look at the Haynes manual and seen what's involved, then I'm not touching it! I've got my hands full with restoring the Katana - that's taking all the shed time up at the moment, as I've been told it has to be ready by xmas morning (don't ask).

Thanks for the advice!

J
____________________
1996 Triumph Sprint 900, 1981 GS-650 Katana, 2008 Sukida SK-125 Pharoah.
Twitter @triplemeister

[G0FHM]

Well the rain has held off long enough for me to road test it.....

The (what I thought) was tappet noise is a bit strange.

Cruise along at a steady speed, it's very quiet. Open the throttle a bit and it get's louder.

To me, that would point to big end as the bearing is under increased load with the throttle open.

Would I be right?

J
____________________
1996 Triumph Sprint 900, 1981 GS-650 Katana, 2008 Sukida SK-125 Pharoah.
Twitter @triplemeister

[G0FHM]

Incidentally @hmmmnz

The bearing you referred to in your post is actually a main... Mains are not a problem, I can get them easily enough!

I suspect the big end bearing is listed as number 15 (Needle - 28x36x15.8) but is not shown on the diagram.

Can anyone confirm this?

J
____________________
1996 Triumph Sprint 900, 1981 GS-650 Katana, 2008 Sukida SK-125 Pharoah.
Twitter @triplemeister

[Ariel Badger]

Last time I threw a big end it made my fingers sting it vibrated the bike so much.
____________________
Bikers make great organ donors, get 115 on your licence today.

[G0FHM]

Had a chance to strip it down and have a look at it since my last post.

Somewhat near to a miracle, but the bearings have come out of it relatively unscathed.

The real damage has been to the piston. I'd say he seized it due to lack of oil splash up the bore - The piston skirt has all kinds of marks on it. Saw a similar thing with my mates '51 AJS 350 Jampot during the heatwave.

Looks like we can get away with a new piston. I've had the bore checked by the local bike mechanic, and the measurement is within tolerance and there is no scoring or other rough spots, so we can get away with a hone. He measured the piston too, and said it's quite badly worn, and all in all we can away with a standard.

Piston is on it's way from Wemoto (and no, it is not Chinese made, I made the point of asking!).

Here is a picture of said piston:

https://t.co/V2Eu7FDdmW

While I am on the subject, has anyone any info on the torque settings for the head bolts?

Cheers,

J
____________________
1996 Triumph Sprint 900, 1981 GS-650 Katana, 2008 Sukida SK-125 Pharoah.
Twitter @triplemeister

[Ariel Badger]

You were lucky it has roller rather than shell big ends, Shells will take a crank out in moments with no oil.
____________________
Bikers make great organ donors, get 115 on your licence today.

[Walloper]

[G0FHM]

Hi Walloper,

Managed to get away with busting the glaze with some 220 wet n dry - got a second opinion on the bore, and there was no scoring, and the measurement was still within standard tolerance. My honing tool was too big, so I used the Haynes method of slotting the end of an old screwdriver shaft, sticking the paper in the end, and the other end in the drill. Crude, but effective.

I'm aware that piston seizure is heat related - but it beats me how he managed to do it, as when it happened it was a full on rainstorm in progress, which what with the rain falling and the spray etc, should have been a bit kinder to the engine! I can only put it down to lack of oil splash up the bore.

Bought a TKRJ Piston kit (Japanese made) from wemoto.com for £38 including postage.

Anyway, it's all done now! Compression checks out at 140psi cold and 145psi warm, so more than happy. It's a little tight when warm, but he has been read the riot act regarding running it in. It's a pity that model CG has no rev counter - else my instructions would be easier. Don't take it over 3k RPM!

And the best bit? Junior had a cheque come for £50 a few weeks back, which he had to pay into his mum's bank account as he hasn't got one. Guess who has paid for his own piston??

J
____________________
1996 Triumph Sprint 900, 1981 GS-650 Katana, 2008 Sukida SK-125 Pharoah.
Twitter @triplemeister

[G0FHM]

Incidentally, while the compression tester was out, I warmed up the Chinese "Taliban Taxi" and thought I'd have a giggle.

It's basically a CG-125 copy, with 11k miles on the clock.

145psi warm!

I was expecting about 85psi.

Best £100 I've ever spent, that little pile of crap!

J
____________________
1996 Triumph Sprint 900, 1981 GS-650 Katana, 2008 Sukida SK-125 Pharoah.
Twitter @triplemeister

[Walloper]

[G0FHM]

Yep, the oil pump works.....

I found that out turning it over on the button when setting the valve clearances!

Really, the bike is not suitable for an 18 stone 17 year old - but with the new laws that were introduced back in January of this year, he is stuck on it for at least another 14 months until he hits 19, and can go onto something a bit bigger.

His father bought him a restricted ZZR600 this time last year, unaware of the imminent law change. Bearing in mind his birthday is 20th December and the rule changes came about on the 8th January (I think). Speaking to our friendly local bike instructor, he could see no way that he would be able to get him through Mod 1 & Mod 2 in such a short space of time, even if the test availability worked out in his favour. So the ZZR went, and the CG was delivered.

So far, he's put nearly 7000 miles on the CG since February - I ride my Trumph nearly every day, and I struggle to hit 3000 in a year!

Looking at getting an 80's CB400 or similar if we can, as a rebuild project, ready for when he hits 19. A mate is getting his lad one of the new Enfield caff racers, but we aren't that rich!

Really, I think it's done well to go as long as it has without something breaking!

J
____________________
1996 Triumph Sprint 900, 1981 GS-650 Katana, 2008 Sukida SK-125 Pharoah.
Twitter @triplemeister

[Mark65]

Really, the bike is not suitable for an 18 stone 17 year old

Im 16.5 stone and have no problems riding my cg125 at all daily, I do 155 miles a week on it and it now has 14699 miles on it, starts first time.


Really, I think it's done well to go as long as it has without something breaking!

If he cant look after a CG how is he going to go on with a bigger more expensive machine. Maybe teach him to check things over a few times a week.
____________________
07 Yamaha YBR125, 07 Honda CG125 , 15 CBR300R (Chocolate Crank, Deaded), 16 CB500FA, 19 Honda Forza 300, 70 Suzuki SV650

[gavcarter]

Haynes need to do the "still have acne" version of their workshop manuals just for teenagers - " ya piston is like ya bellend in ya best m8s missus innit. Keep it nice n wet so it slides wif-out burnin' and if it doesn touch the sides summits wrong innit"

This would probably appear after the first 400 pages of " this is a spanner, your ( dad / stepdad / next door neighbour / postie )has told you on numerous occasions how to use one. But they know noffin' blood so here we go!

Step 1 ..."

[Walloper]