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I recently posted about my up coming chopper build and that I purchased an 07 865cc SM engine. I was going to put 10.5:1 Wiseco forged pistons in it at the stock bore. I couldn't find them on the web site so I called them and ,sadly, those have been discontinued. I was going to pop a set of those in while the engine was out on the ground and a set of 790 cams. I wanted to see what I could get out of that set up with the Amal carbs I have.

did you contact TPUSA? I thought they machined their own 865 cc high compression pistons

Haven't gotten that far yet just checked Wiseco since they were always the best in the past.

what about this?

http://www.wiseco.com/ProductDetail.aspx...&AppID=5024

That is a replacement piston for the 904.

This outfit carries them Ian: web page I can't imagine they would insist on you buying the kit, when all you want are pistons.

Thanks Ryk, I already knew about this kit. I haven't asked them about it yet but I agree, they will probably sell me pistons.I am hesitant about pistons that I do not know the manufacturer or the manufacturers history. I know Wiseco is a top quality forged piston.

Wiseco is quality, but if I recall, they are not the 10.5:1 compression ratio as claimed. More like the stock 9something:1

865 pistons were discontinued few years ago... I managed to get brand new set few years ago but what I read they are not what wiseco claimed at the time saying that checking compression on my two bikes reading was; america 904 wiseco both cylinders 150, bonnie with 865 wiseco so call hi comp pistons 165 170.....cheapest way to upgrade is to buy 865 cylinders and pistons from ebay and do what I call cheapo ghetto big bore (my bonnie has it plus better pistons I got but otherwise would get stock pistons) keeping 790 cams ...TP usa piston kit cost 994$ with cams did ask in the past about pistons only but they never been back to me, and you really need low milage 865 cylinders for that kit......from my expirience they 813 cams are not much better from 790 cams....they probably works better on higher reves

The engine I have has 8,000 miles on it, I figured that should be low enough miles to swap out pistons for higher compression pistons. I had planned to go with 790 cams as I don't think they can really be improved on much for street purposes.
When I spoke to Wiseco they told me they stopped making those pistons because there was almost no demand for them.

Ian I used the TPUSA HC pistons in my bike. I don't know that helps you much but if you wanted to get eyes on them there is a pic or two of them in my build thread.

Thanks but pictures don't help. Have to hold them and weigh and mic them.

I still have a triple beam you can borrow from the old days.

I still have mine too.

GRZGORZ THAT IS NOT THE WAY TO MEASURE PISTON COMPRESSION RATIO. YOU WERE ONLY MEASURING CYLINDER PRESSURE. THE CORRECT WAY IS:
COMPRESSION RATIO=(CYLINDER VOLUME + COMBUSTION CHAMBER VOLUME) / COMBUSTION CHAMBER VOLUME......FORGIVE ME. I'M NOT BEING A [Email]SMART@$$.[/Email] I JUST LIKE TO HELP PEOPLE UNDERSTAND HOW ENGINES WORK AND HOW TO DO THE MATH....IAN, YOU CAN ORDER A PAIR FROM JE OR MAHLE BY SENDING THEM THE BORE AND HEIGHT OF YOUR CYLINDER AND STROKE OF YOUR CRANKSHAFT WHICH IS WRITTEN IN THE SPEC SECTION OF YOUR TRIUMPH MANUAL

Are they making 1 off?