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Wiseco Piston problem

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plasticadam:
I'm having to re-bore the FT and just want to retain standard compression on a single size overbore. Got a NOS Wiseco piston (correct part number) off Fleabay which I took to the engineer doing the machining and he said that it was hi comp and not worth using unless I wanted to stress the starter and do a load of other mods to make it run right. I didn't and returned it to the seller who has refunded (but not the $50 carriage or $30 import duty I had to pay in the UK).
Decided to cut my losses and pay for the full price piston from the UK importers. It was sent direct to the engineer to save time. I get a phone call from him to say its the same as the other one >:(. I've looked at and its got a way higher crown with big valve cut outs compared to the flat topped Honda original. It is stamped with the correct part number as well. I am utterly confused. Still waiting after a week for some comment from the manufacturer (via the importer).
Question - this piston has been offered for years for FT/XL engines - has this question not been asked before? Has anyone got any experience of this and can you advise?
The only other piston I've seen available is manufactured by an Australian company called Forseti - does anyone know of them? They are loads cheaper than Wiseco and look much more like the standard piston, but I don't know what reputation they may have.

J6G1Z:
I'm not familiar with the FT piston & the replacements available. Most folks want to raise the compression when they replace a piston. From what I hear, that is the main performance modification that FT's respond to the best, aside from a performance camshaft.

Do these replacement pistons have enough material in the top of the piston to machine the dome down or off completely?

As long as your starter has been maintaned regularly, you have a strong battery & you remember to prime the engine well prior to starting, you shouldn't experience much problem. I believe that the main trick to extending starter life on the FT, is having a good tune on the engine so it starts promptly. Prior to starting, I always rotate my throttle 4-5 times to operate the accelerator pump in the carb. This shoots a squirt of raw fuel into the intake tract with each twist of the throttle, providing a nice rich starting mixture & the bike fires right up without excessive cranking of the starter. Avoid the over cranking & your starter will last.

Good luck & please let us know what you find out.
J.

PS. You will gain some compression from the over bore even if you use a flat top piston. Embrace it, compression is not the enemy, poor fuel quality is.

Slyphon:
Can you provide a link to the Wiseco Piston you ordered?

I don't know compression / pistons, but from what I've read the 10:5:1 are the standard compression and 12:5:1 are high compression. So for my standard bore (89mm) and standard compression, this is the wiseco piston I would order: http://www.ebay.com/itm/HONDA-FT500-FT-500-WISECO-PISTON-KIT-89MM-10-5-1-1982-1984-/140959104771

plasticadam:
Hi guys, thanks for your suggestions and ideas.

J, I know what you are saying about the potential improvement to performance with a hi comp piston, but additional strain on the starter aside, I think it could bring in other issues such as increased vibration possibly, and the need to set up other areas of the bike (valves/carb) to match up. Fuel quality is not a problem , but this bike is going to be my wife's commuter/occasional tourer so I want to maintain most of it as low stress as possible for reliability

Slyphon, you are 100% correct and this is the piston I ordered (twice!). The part number was even stamped on it. If it looked like the one pictured that wouldn't be a problem, but I think that is a standard Wiseco illustration - both items I received had much higher crowns - hence the raised compression

Still waiting for the importers/manufacturers to get back to me - after 10 days that's a pretty slack service I think. If that was my only form of transport I'd be jumping up and down a bit.

Will update on progress!

J6G1Z:
I understand now. I just built a bike for my girlfriend. I plan to leave that engine bone stock as long as she is riding it.

I think I would still measure the thickness of that piston dome to determine if it can be machined flat.

Good luck
J.

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