TL125S

[Johnny4428]

Makes me sweat the thought of all that things to sort Dave. Says a lot about previous owner/s that clutch bolts!😳

[Bryanj]

I think i have a spare cb550 liner knocking about if you think it may fit mate

[taysidedragon]

Some of these old engines have really been abused by incompetent idiots. It's amazing that they keep running at all.

[Laverda Dave]

Some more progress to report over the past few days.

Thanks to Bryan, Rozabikes Tim and Ash for all the very helpful advice over the past few weeks with leads etc.

I have located a s/h barrel on the still standard but rusty bore to replace the existing barrel that had been taken out to 150cc and that I found was marked and scored (photos). I don’t know if the engine had suffered a partial seizure at some point but there was only ½ litre of very thick grey oil in the sump. There are certainly some strange marks on the liner and vertical scoring. On Tim’s advice I’m going to take the bore out to 138cc using a CB550+1mm oversize piston as 150cc will leave very little liner left. I will locate a 550 genuine Honda piston and rings if I can before sending to Bryan.

Next up was removing the cam chain sprocket on the crankshaft that was so badly worn I am surprised the chain didn’t jump off  . I had to modify my 100mm three legged puller with a big file to fit behind the sprocket and applied heat, nothing, it wouldn’t move. I didn’t want to apply too much heat as I was concerned about potentially damaging any heat treatment applied to the crank at manufacture. I then tried a split bearing puller without any success and the lip was too thick to go under the sprocket. The dremmel then made an appearance and I very, very carefully cut a slot in the sprocket and after a while I heard a pleasing snap when the sprocket let go and I was able to pull it off with the three legged puller. No damage at all was done to the crankshaft, not a mark on it

Now, I assume I am going to need to put the crank in the freezer and the new sprocket in the over at 200c when it comes to fitting the new one and tap it home with a suitable drift. Has anyone done this before?

Off to Kempton Park tomorrow for a rummage.

[Laverda Dave]

I forgot to add the photos of the old 150cc barrel!

[Johnny4428]

You would have thought the puller would have taken that Dave, quite a big boss on that sprocket giving it a big area to grip I guess. Nice work getting that off.

[Laverda Dave]

The engine is now fully stripped, cleaned and measured with more horrors being revealed. A shim was missing on the mainshaft and this appears to have allowed the shaft to drift leaving marks on the crankcase. A washer had been placed behind the countershaft shim pushing the shaft to the right. I don’t know if the above are connected but the teeth on the idle starter gear are completly chewed up.

Moving to the oil pump and something big has passed through the rotors leaving these and the main body casting mangled (technical term) as well. I am surprised there was any oil pressure at all in the engine considering the state of the pump. Surprisingly though the main bearings are fine as are the rest of the gears, these engines were built to be abused! Upon taking the alternator cover off I notice a small 'dink' in the case. When I removed the coils the dink turned out to be a crack. considering this is oil filled I will have to get it welded.

So far the engine parts needed are, new piston and rings (CB550+1mm to give 138cc), new barrel (I managed to get one of these on eBay) cam chain, crankshaft end sprocket, Kickstart idler gear, shims, three ball bearing races, complete oil pump.

I’m back on to making more of the missing brackets today and hopefully I’ll be taking the frame off to be alignment checked in the next week or two.

[Skoti]

Aye Dave,

I seem to remember the early TL125's having problems with broken kick start gears.
Which meant splitting the crankcases to repair them.

But yours appears to be the later engine with the detachable cam cover on the head, which allegedly had the kick start problem solved.

Maybe some others can remember doing this work as well back then?



Anyhow we sold many of those bikes to local farmers before the quad days.

Great wee machines, good luck with the resto.

Skoti

[Oddjob]

This any use to you Dave, seems cheap enough.

https://www.ebay.co.uk/p/1215949232?iid=134482012557&fitmentTarget=Make%3AHonda%7CModel%3ATL

[Laverda Dave]

Thanks for the heads up Ken.
I'm not sure if that set would suit the 'S' model with what is called the split head. I'm also looking at going out to 138cc (hence the 550+1mm piston. I'm still investigating what head gasket I need to use with the 138cc as a 150 will likely be to big and the 125 probably to small although I understand the 550 piston is flat topped (you probably know better than I do as you build 550 engines in your sleep!).
It's a shame though with that set being a genuine Honda set.

[Oddjob]

Yeah, looks to be different.

I've found 3x1.00mm over 550 pistons today Dave, they are not genuine by the look of them. Plus all of them have scoring marks down the side of the piston top down to the top ring groove, like something went down there at some point. Some are worse than others, they are flat topped BTW, same as the 500. What size would a standard 550 piston come out at?

[McCabe-Thiele (Ted)]

I've just read this whole thread again Dave, I salute your persistence in getting this far.

I would certainly have trouble sleeping at night trying to work out how to get past the obstacles you have encountered so far, only one word fits, respect Dave.👍👍👍

[Bryanj]

Without being silly i think your best bet is to make sure you can get all the bits for the bottom end BEFORE worrying about piston and bore 0.5 mm o/s 550 is 3mm o/s for 500

[Laverda Dave]

Thanks for the advice all.
I think I'm going to go with a standard 125cc especially considering this isn't my bike but a mates and he wants me to fit all the road kit (indicators etc) and as he's the same age as me (63) it's doubtful if he's going to go off roading. I've also discovered the big bore kits are marked as NOT suitable for road use, they are intended for trials riding where short bursts of high revs can be tolerated.
I'm playing safe with this one!
I would also think (hope) it will be a lot easier to get a genuine Honda oversized piston and rings for a standard 125.

[Bryanj]

Dont buy a 0.25 till the bore has been done as i am finding a lot of 500/550 need to go to 0.5 as the liners have "barrelled" enough to not clean at 0.25.
You can have it done to a bit undersize then honed to fit piston