Well following on my previous post.. I decided to take the cylinder off to check what I had to work with.. ie if the piston and cylinder can be re-used or do I need to replace stuff. Knowing the size of the current piston would help sourcing a replacement. If it was standard I could go to the next bigger size etc. It's pretty easy on this bike to remove the cylinder as you only need to undo the exhaust collar followed by the spark plug lead and the 4 bolts holding the head on.

Well its not good news.. the cylinder and piston are pretty worn with deepish scratches down the side of the cylinder and piston...ouch!

What is worse.. the piston is marked 1.25. This is the size relative to the original bore in mm. The 1st oversize is usually 0.25 followed by 0.50 for 2nd oversize. I would imagine that this is the max as the spigot of the cylinder is already razor thin.. see the area circled in yellow below!

Size marked on the piston.

I'll probably clean it up and re-install the bits while I hunt up for a replacement cylinder or barrel.

Watch this space!

Overhaul time?

I rode the YG1 a fair bit over the last weekend (long weekend because of the Chinese New Year). I've had the bike around 2 months now and finally decided that the engine rumble is not something that I can live with and is probably causing more wear every time I run it. So it looks like an overhaul is in order.

Below is a list of stuff I'll probably need.

1. Con-rod kit (*)
2. Bearings. Anyone have the numbers for the crankshaft and gearbox bearings?
3. Oil-seals (ditto as per bearings) Managed to source some seals suitable for the crank, They are ok in ID and OD but thickness is one mm short. I may make a shim to take the slack. Your thoughts on this?
4. Gasket-set (**)
5. Piston + rings. WIll neet to get the head off to check what size is in the bike... they seem to be common enough on ebay in standard, 1st o/s and 2nd o/s.
6. Oil-pump seals (*).. I have a lead on a new pump but its made in Taiwan.. anyone have experience with Taiwan made oil-pumps?
7. Disc valve (**)
8. Disc valve cover (**).
9. Clutch plats (**).
10. Clutch springs.. I see 'bay springs which are listed for YB100 as well as the YG1 so I can probably source them locally.

Not related to the engine overhaul but required.
11. Rubber from crankcase to airfilter (**).
12. Air-filter (*)
13. Rubber from air-filter housing to frame (*).
14. Ignition coil (current wire is cracked in several places.
15. Clutch cable. The one on the bike is a generic cable with a screwed end (like on vespas).

(*) In hand
(**) On the way to me.


Can anyone think of anything else I will need? There are a lot of gearshift stuff on the 'bay but the bike shifts clean and theres not much free play in the shifting so I don't think I'll need to replace anything.

I have been buying bits as they come up and it has reached the stage where I and reasonably confident that there are no show stoppers unless theres some major damage to the internal components!

Wish me luck!

Oil sight glass replacement.

Two stroke bikes require the addition of oil to the petrol to lubricate the working bits. In theory the oil is atomised with the fuel and in the compression stage the oil is squeezed out and lubricates the piston/bearings before the spark ignites the whole lot. In the old days the usual way the oil is introduced into the engine was by mixing it in the fuel tank (hence the term pre-mix). This required some mental gymnastics to ensure the correct ration of oil to fuel. Older bikes use something like 20:1, something like the YG would probably require 50:1.. eg 50ml fuel and 1ml oil. So for a litre of fuel you would require 20ml of 2-stroke oil.  I remember the BSA Bantam had a measure built into the cap.. for every gallon you would fill the cap with 2-stroke oil twice. A bit tedious and some of the 2-stroke oil usually found its way onto the tank, gloves etc.

This was very messy and not very accurate. Most of the riders were of the school of thought which went "..if a little bit is good, more must be better!.. " Unfortunately this is not true. A carburetor will only draw a fixed volume of fuel/oil thru the jet. If there is more oil, it is at the cost of lesser fuel.. resulting in a weak mixture. A weak mixture runs hotter and defeats the benefits of the increase oil. Another problem was the inconvenience of carrying a bottle of 2-stroke oil around.

The Yamaha YG1 was one of the early bikes to have an automatic lubrication in that the 2-stroke oil was metered out by a separate pump. A separate tank held the oil and this was connected to a pump which fed into the crankcase (other types of 2-stroke oiling deliver oil to the carb). This was an excellent move in the right direction and all you had to do was ensure that the 2-stroke oil tank was kept filled. Yamaha figured a normal owner wouldn't want to peer down the fill-hole of the tank and conveniently built-in a window in the side so you could just bend over and check that the level was still ok.

50 years on and the sight window on my bike has seen better days. It is distorted and looks like someone has used some glue on it to seal it up.

The sight window is secured by a slotted ring. This usually requires a peg spanner to remove. My other hobby is watch-repair and I had this tool handy. Its usually use to remove watch backs and I thought I'd try it.

Unfortunately this did not work so I had to resort to the tried and true method of using a screw-driver and hammer.

This is the old sight-window.

Looks like there was some heat damage to the plastic..or maybe it cracked and the dark discoloration was caused by reaction to the stuff used to seal it.

I've been hunting for a replacement and found this advertised on ebay (seller oldpartsshop)

I took a gamble and found that while the diameter of the sigh-window was the same, the height was too low.

I did a dry fit and below you can see how much lower the sight-glass now sits.

But I have a cunning solution..

I did mention my other hobby was repairing watches right? Here I have a replacement plastic lens (called a crystal in horology) for a watch. I measured the opening in the fixing ring and it was 28mm wide. I dug out a 282 size crystal which is 28.2mm. The additional 0.2mm will make it a friction fit. Since it is not supported on the inside a hard knock will push it deeper. If it becomes a problem I'll make a spacer up but for the moment its good.

And with the side-cover over the oil-tank.

One problem was the seal for the sight glass was too hard and leaked. Since I didn't have a spare I made one by cutting a piece of high grade rubber (inner-tube) to shape. Rubber-tube may not last but it'll do. If it leaks I use something else.

I also spotted this filter sock on the inside to keep bigger bits out .

The outlet unscrews with the filter mesh attached.  This was rinsed in petrol.

I also rinsed the oil tank with petrol as there was some sludgy material on the bottom.

Reinstalled everything and put some 2-stroke oil in the tank. Its been 2 days and so far no leak!

Anil

Buying the YG1.. and bringing it home.

Hi Guys...

I've been keeping an eye out for a cheap Yamaha 2-stroke for a cheap runabout and I found out about this bike in Alor Setar which is around 300kms (@190miles) north of Kuala Lumpur where I work and live.

I requested the owner to send me a video .. well all that proved was that it started.



I did some investigating and found that it was a Yamaha YG1.. Not much info on the web..so I made a trip to Alor Setar.

Well I saw the bike in the flesh .. started it up and it was running for a while. I then shut it down to check the numbers (even though the seller had sent me close-ups of the engine and chassis number together with the registration card). When I tried to start it up it wouldn't start! Took about 20kicks before it started up! Probably flooded the carb.. once it started I took it for a ride .. felt a bit funny as my current ride is a 750 Kawasaki!

Plus points

• Owner claims clean title.
• Engine and chassis numbers match the registration card.
• Pretty much all there.
• It seems to be an older restoration. 
• No visible rust and the paint is in OK condition. 
• It starts.....after a few kicks.

 Negatives

•  Most of the alloy on the bike is pretty dulled and furred up (Nothing some elbow grease and metal polish can't solve!).
• The seat is obviously not original.
• Most of the chrome is pitted.
• While the paint is still ok.. the color really doesn't suit the bike.
• Even though the engine starts.. its pretty rough with a deep rumble from within the crankcase, this is usually a sign of bad bearings.. oh well.
• Throttle has a lot of play... almost half a turn before it revs the engine.
• Kicking the bike into life revealed a slipping clutch. Could be worn clutch plates.. or maybe the previous owner ran car oil ... this will cause motorcycle clutches to slip. Proper bike oils have additives to enable it to run with wet clutches. Car clutches live outside and don't get oiled unless the seals leaks. Look for MA on the oil container.. if you see it then its good for bikes.

I knocked the price down a bit and shook hands.. we then made a trip to the local JPJ (local vehicle agency) office to transfer the title. Took two hours.... that's about normal here in Malaysia.

Well now the bike was  officially mine, albeit 300kms from me. I had to head home so I left the bike in my friends place. He would sort out the insurance and road-tax (annual fee) which came to around RM156 (Less than USD40).

I first thought that I would get it shipped by train.. that's how we usually moved bikes before, but my friend suggested a bus. Did they even have space for a bike?

This is the bus... It started out as a double decker thing but they found passengers didn't like sitting on the lower lever. So they ripped out the seats and made the lower-deck a cargo space!

So the bus was duly loaded and my friend gave me the ETA of the bus in Kuala Lumpur. One bonus point was that the bus station was nearer to my house than the train-station. Furthermore, the train-station was in the middle of the city.. the bus-station was in the outskirts.. I didn't fancy riding an unfamiliar, underpowered bike thru the city centre! Well the bus was delayed about an hour and a half...Bus-drivers today have hand-phones and regularly update the office! Total cost for the bus-ride? RM150 (less than USD40).

First stop even before I got the bike home was the bike shop... the tyres were hard as a rock and probably the tubes were shot as well. On removing the front wheel we found the brake linings had come detached from the brake-shoes! That could have jammed and sent me head over heels! Really dodged a bullet there! Cost for two-tyres, two inner-tubes and a set of front brake shoes? (less than USD30). That's inclusive of labor folks.