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^^^^^^^^^^^^^ MY FTP! |
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An interesting bike that I have barely used as I like to segment it’s use purely for green laning.. Where it belongs. It landed in my lap along with a second bike of the same model of ‘84 vintage. My brother had that one, and seeing as I paid the most I took the better one. This machine was not road legal when I received it and with inspection several things (albeit small) were required before it would pass an MOT. No headlight, speedometer cable, rear brake light, a horn. The 6 volt electrical system is somewhat of an annoyance. A single thing I must mention is that the front drum brake was quite rusty inside, and only using it would rub it off which added to some pretty poor brake performances until it was bedded in properly with some fresh steel. Seeing as this is a motorcycle that has recently come into my possession and even so rarely use there is little to mention regarding it. I have however replaced the piston and in doing so bored out the cylinder for a new oversized piston. |
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After the exhaust header bolts blew of and were obviously threaded in the past, I required to take the barrel off in order to give that to a friend to tap new threads and also to make some new bolts too, one side being 8mm for the new hole and the other 6mm. This allowed me not to require modifying the clamp. I came across this monstrosity of a piston. It had severe piston slap (which I did detect in previous running) but flanges of the piston are cracked and pretty close to flying off entirely. The recess at the top of the piston is caused by excessive lean running partly detonating the top of the piston, which means it would have run excessively hot and therefore be at least one major reason why the piston and rings are so very scored. This piston was a time bomb. |
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New piston installed and in the barrel. A new small end bearing was also purchased in this process of replacement. The barrel was obviously re-bored to accommodate the 1mm oversized piston. |
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These pictures were taken on one of my first proper rides after installing the new piston. This was a fun day but I have subsequently come across issues where the bike does not idle. It seems after a bump or drop the idle jet gets blocked and that requires to be sorted each time. This is very annoying! After these pictures were taken I headed to the Caerphilly mountain for some fun. On the way back down the A470 for home at about 50 mph the rear wheel skidded as the engine locked through seizure. I kept the bike up, and coasted to the hard shoulder. After letting the bike cool down and I was back at home the piston was not too much more damaged. A typical ‘square seizure’ caused by the piston expanding through heat faster than the barrel was apparent. I sanded down the burs and put it all back together again. It is quite possible that at that speed it was running lean due to some air box leaks that have now been closed. The bike (according to the spark plug condition) seemed to run fine otherwise between the idle to mid rpm range.
Regardless, after a few more outings on it the kick start broke. It spins on the shaft due to it being the incorrect (and obviously too large) kick start lever. I have to source another one as I can’t be bump starting it all the time, which although is no real issue on the road, it will be impossible to do this on a trail with slick mud. |
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