Scooterotica

Views needed, my brand new top end (GT240) got me to the Euro in Adria and back with absolutely no bother but did feel a little down on power by the time I'd got back (2200 miles). Investigation revealed that the piston and bore are shagged It was being run open mouthed at 4% but I believe that is a tad excessive. When I stripped it there was a thick build up of carbon filling the depth of the squish band on one side of the piston and a corresponding build up on the piston crown. This carbon was as hard as fek and causing the piston to rock sideways. I can just get a 10mm feeler in from the bottom of the cylinder with the piston at TDC and the same with it part way down the bore. I put my cheap digital vernier on the barrel and get 70.04 at the top and 70.10 at the bottom. Piston measured 69.8 inline with the gudgeon pin, 69.78 just below the bottom ring and 69.8 at the very bottom. The ring gap is a snug 35 thou on one and a lot bigger on the other.

Subsequently found brown deposits in the banjo and a fine deposit of brownish silt in the carb bowl. Petcock out and the filter had a load of brown stuff clinging to it. Tank out and on the bench I can now see it is very rusty. My question is, would rust particles be abrasive enough to cause this level of accelerated wear?

Sorry to hear you've had trouble, Coaster.

I would think that any particles could contribute to wear, and I do worry about running open mouthed on my GT240 & may look at a filter at some point.

You can get oversizes to 72mm so it may not be a massive expense to get this fixed & your 240cc becomes 250cc.

What oil are you running? Do I remember reading on the 'other' site that your main jet was 120-something? If so, could a small jet contribute to the build up?

I have spoken to Rich about it via text message and he said a smaller main would have contributed to it seizing but I never said it had siezed It had no apparent sign of over heating at all. The main is a 130 but we were running at 2/3rd throttle of less for most of the trip and the blug was always a bit oily when checked so tbh I struggle to see that as a significant issue hence my thoughts about the tank.
I was slow to consider the tank until it struck me whilst out on a long ride the other week that I'd had trouble with my TS1 engine a year earlier which had failed due to a leaking cylinder head but also had a badly worn piston. That had been in my other scooter but I'd borrowed the tank out of it as the GT has the carb on the same side and I needed the cut out.
I've searched the internet but not found a technical opinion on the effect of rust. I will be going down the caustic soda followed by drain cleaner (Hydrochloric acid) followed by POR 15 tank sealer

Be careful what you use in the trank , these have had good press and i know a few people who have used their products and services

http://www.tankcareproducts.co.uk/

If you get a POR15 kit from Frost's you get all you need to do the job. I have done several tanks including two of mine and I have no trouble since.

Tractorman wrote: ↑Wed Sep 06, 2017 8:47 am If you get a POR15 kit from Frost's you get all you need to do the job. I have done several tanks including two of mine and I have no trouble since.

I bought the kit from Mike Phoenix and think it's just the sealer, I was going to visit B&Q for caustic and drain cleaner acid.....just wondering how I will be received if arriving on a scooter and asking for a bottle of acid in East London Probably end up being nicked

Agree with tractorman, I've used the por range from frosts. Think it was prep and ready I used prior to sealing. I Tape a couple of small strong magnets on bend of fuel pipe as well just incase any rusty bits escape and they stick to were magnet is. Belt and braces

chippy wrote: ↑Wed Sep 06, 2017 3:26 pm Agree with tractorman, I've used the por range from frosts. Think it was prep and ready I used prior to sealing. I Tape a couple of small strong magnets on bend of fuel pipe as well just incase any rusty bits escape and they stick to were magnet is. Belt and braces

Good tip, like the sound of that although just wondering how magnetic is rust

I saw the idea on one of the forums, thought that's a good idea but I suppose in theory nothing of any great size should get through petrol tap filter. I had bike at rayspeed for a problem and they said they found debris in carb and I had sealed tank but I was running without a filter so not sure we're it came from

Another idea was just to put the magnets on bottom of tank and seeing they are so powerful they would draw anything metallic to them so it wouldn't go into fuel line. Idea's in action