Cosmic-WizardStandard MemberPosts: 23
Joined: Feb 2014
Joined: Feb 2014
While putting pics up of my ST70 I thought I'd show you my Chaly.
I'm no stranger to small bikes, my first being a Yamaha SA50 Passola which I bought when I was 17 (1996). I still have the Passola and have had various scoots over the years, but when I saw the Chaly back in 2010, I had to have it. A friend at the time had bought it to go in his VW camper, but the bike was slightly too long and he really wanted a Z50, so he said he was thinking of selling. I said I'd buy it and the deal was done a fortnight later
Here's the Chaly when I first saw him at a classic car show in Essex:
This pic was taken a couple of days before a little freshen-up:
The bike itself was very sound and had had a lovely paint job done some time in the past. He's been painted in Ford Electric Orange
I bought a new barrel, piston and rings, plus a gasket set, some 3 inch wide alloy wheel rims and a pair of Bridgestone tyres. Everything on the engine was held together with gasket sealer and the head had a sheared exhaust stud. I carried on and rebuilt the engine, but would have to come back to the missing stud as someone had tried to drill it out and made a right mess of it.
Sometime later I bought a head on eBay and fitted it, but he needed a new fuel tap so he was never run.
Now fast forward a year or so and I decide I want to MoT him. I should mention at this point that he was kept at my mates house and the plan was to MoT him on the way back to mine, so making the MoT was quite important.
After spending a morning dragging him out, fitting a new fuel tap, some new 'Honda' stickers and giving him a nice clean and polish, the time then came to start him up. I kicked him over and I could feel a knocking and realised something wasn't right. I checked the cam timing but that was okay; It had to be the head I fitted. At the time, I didn't know there were two types of piston & head and what I'd actually done was fit a 12v head over a 6v piston. The knocking was the piston hitting the edges of the combustion chamber. With less than an hour before the MoT and dripping with sweat, I decided to carefully file the edges of the chamber, put it back together and hope that it gets to the MoT station.
I managed to make the MoT on time but the engine had seriously over heated and top speed was down to 15mph. After he cooled down a bit, he was tested and he passed
Cooling down while waiting for his MoT:
I got him home and did some research. I kept an eye out for a decent second-hand 6v head, but the ones I saw didn't look too clever and they were selling for around the £50 mark. I decided to buy a new head from OORacing, but when that turned up, it was the same as the one I had fitted (12v). I then ordered a 12v piston and took the engine apart.
Upon refitting I noticed what I thought would be a problem - the piston didn't come all the way to the top of the bore on TDC. This means the compression ratio will be badly affected and the engine may not run right, if at all. Anyway, I put it all back together and kicked it over. He fired up and seemed to run quite happily once I'd altered the carburettor settings, however, when I got him on the road it became apparent that my suspicions were confirmed. He was very sluggish and wouldn't go up hills
Test ride after fitting 12v piston. 30mph was just about achievable but he wouldn't climb hills.
Back to the drawing board then lol.
After speaking to Adrian at OORacing, he confirmed that all barrels are the same height but 12v pistons are shorter in height than 6v ones. To make up for the difference in height, 12v con-rods are longer than 6v ones, but he couldn't remember the exact measurement.
I had to decide whether to buy a 12v con rod, strip the complete engine down and then get someone to fit it, or think of another way round the problem. I measured the pistons from the top of the gudgeon pin to the shoulder of the crown and also to the top of the top ring. I ended up with a measurement of 2.5mm. A couple of days later I dropped the barrel off at Dartford Rebore for them to work their magic. They decided it was better machining the bottom of the barrel than the top and a week or so later I popped down there on my ST70 to pick it up.
Mmm, shiny
Here is a pic of the piston and barrel fitted:
I could've gone an extra couple of thou, but I suspect it's shifted down a bit more after torquing the head down on top. If I have to, I can take that little bit off the top of the barrel at a later date.
On rebuilding, I came across another problem which was the timing chain. Decking the barrel 2.5mm has in effect made the timing chain too long. Okay, no problem I thought, I'll adjust the tensioner. That turned out to be yet another problem, but fortunately it was easily sorted. All I had to do was cut and file a piece out from the end of the tensioner arm which allowed it to have a few extra mm of travel
Before:
After:
All back together:
And that's where we are at the moment. He runs well now, gets up hill but still could do with a 'bit more'. I confess that I forgot to check the timing and after the difference that made on "The Beast" (my ST70), I'm hoping it's a bit retarded. I plan to get out in the shed this weekend and check, but I'm recovering from a hip replacement so progress has been slow.
Hope you've enjoyed reading.
Cheers
Jim
I'm no stranger to small bikes, my first being a Yamaha SA50 Passola which I bought when I was 17 (1996). I still have the Passola and have had various scoots over the years, but when I saw the Chaly back in 2010, I had to have it. A friend at the time had bought it to go in his VW camper, but the bike was slightly too long and he really wanted a Z50, so he said he was thinking of selling. I said I'd buy it and the deal was done a fortnight later
Here's the Chaly when I first saw him at a classic car show in Essex:
This pic was taken a couple of days before a little freshen-up:
The bike itself was very sound and had had a lovely paint job done some time in the past. He's been painted in Ford Electric Orange
I bought a new barrel, piston and rings, plus a gasket set, some 3 inch wide alloy wheel rims and a pair of Bridgestone tyres. Everything on the engine was held together with gasket sealer and the head had a sheared exhaust stud. I carried on and rebuilt the engine, but would have to come back to the missing stud as someone had tried to drill it out and made a right mess of it.Sometime later I bought a head on eBay and fitted it, but he needed a new fuel tap so he was never run.
Now fast forward a year or so and I decide I want to MoT him. I should mention at this point that he was kept at my mates house and the plan was to MoT him on the way back to mine, so making the MoT was quite important.
After spending a morning dragging him out, fitting a new fuel tap, some new 'Honda' stickers and giving him a nice clean and polish, the time then came to start him up. I kicked him over and I could feel a knocking and realised something wasn't right. I checked the cam timing but that was okay; It had to be the head I fitted. At the time, I didn't know there were two types of piston & head and what I'd actually done was fit a 12v head over a 6v piston. The knocking was the piston hitting the edges of the combustion chamber. With less than an hour before the MoT and dripping with sweat, I decided to carefully file the edges of the chamber, put it back together and hope that it gets to the MoT station.
I managed to make the MoT on time but the engine had seriously over heated and top speed was down to 15mph. After he cooled down a bit, he was tested and he passed
Cooling down while waiting for his MoT:
I got him home and did some research. I kept an eye out for a decent second-hand 6v head, but the ones I saw didn't look too clever and they were selling for around the £50 mark. I decided to buy a new head from OORacing, but when that turned up, it was the same as the one I had fitted (12v). I then ordered a 12v piston and took the engine apart.
Upon refitting I noticed what I thought would be a problem - the piston didn't come all the way to the top of the bore on TDC. This means the compression ratio will be badly affected and the engine may not run right, if at all. Anyway, I put it all back together and kicked it over. He fired up and seemed to run quite happily once I'd altered the carburettor settings, however, when I got him on the road it became apparent that my suspicions were confirmed. He was very sluggish and wouldn't go up hills
Test ride after fitting 12v piston. 30mph was just about achievable but he wouldn't climb hills.
Back to the drawing board then lol.
After speaking to Adrian at OORacing, he confirmed that all barrels are the same height but 12v pistons are shorter in height than 6v ones. To make up for the difference in height, 12v con-rods are longer than 6v ones, but he couldn't remember the exact measurement.
I had to decide whether to buy a 12v con rod, strip the complete engine down and then get someone to fit it, or think of another way round the problem. I measured the pistons from the top of the gudgeon pin to the shoulder of the crown and also to the top of the top ring. I ended up with a measurement of 2.5mm. A couple of days later I dropped the barrel off at Dartford Rebore for them to work their magic. They decided it was better machining the bottom of the barrel than the top and a week or so later I popped down there on my ST70 to pick it up.
Mmm, shiny
Here is a pic of the piston and barrel fitted:
I could've gone an extra couple of thou, but I suspect it's shifted down a bit more after torquing the head down on top. If I have to, I can take that little bit off the top of the barrel at a later date.
On rebuilding, I came across another problem which was the timing chain. Decking the barrel 2.5mm has in effect made the timing chain too long. Okay, no problem I thought, I'll adjust the tensioner. That turned out to be yet another problem, but fortunately it was easily sorted. All I had to do was cut and file a piece out from the end of the tensioner arm which allowed it to have a few extra mm of travel
Before:
After:
All back together:
And that's where we are at the moment. He runs well now, gets up hill but still could do with a 'bit more'. I confess that I forgot to check the timing and after the difference that made on "The Beast" (my ST70), I'm hoping it's a bit retarded. I plan to get out in the shed this weekend and check, but I'm recovering from a hip replacement so progress has been slow.
Hope you've enjoyed reading.
Cheers
Jim
Good luck, I'll be keeping an eye on your progress.