Modified 1000 pistons

[pizza for you]

Hi everyone. I was able to find a set of SP 1000 cylinders with lightened pistons from a local person. Told me the pistons were lightened to within 2 to 3 ounces of 850 T pistons. I thought about using them for my 850T Got them for $ 75.00. So I took a chance on them. I figured the cylinders were worth it. I was concerned about the strength of the pistons. I took them to a local performance machine shop to ask them what they thought about the amount of material removed from the underside of pistons. The person I talked to is very knowledgeable in many types of engines. He is a very good machinist and has many years of experience. Has built mainly Ford engines such as 427 soch and other engines for racing. He told me the pistons would be good to go. As I get ready to assemble the engine I'm still a little hesitant on using them. I wanted some more opinions on this. Here are some pictures of the underside of the pistons.

 

[Mc Tool]

Ooooooh , very dodgy I think you should send them to me ( with the cylinders ) and let me fit them to my bike and test them properly, for you , long term would be best

 

[pizza for you]

Ooooooh , very dodgy I think you should send them to me ( with the cylinders ) and let me fit them to my bike and test them properly, for you , long term would be best

Ooooooh , very dodgy I think you should send them to me ( with the cylinders ) and let me fit them to my bike and test them properly, for you , long term would be best

Yes maybe I'll send them to you ! Hate to see what the shipping would be. The previous owner had the cylinder spigots machined to fit the 850 engine he had.

 

[Mc Tool]

Ha ha yeah ,all jokes aside tho ,I think you got a bargin there , international freight prices are crazy .... I got a whole Yam RD400 engine from Canada for less than a rifle scope mount from Italy

 

[pizza for you]

The more I look at the old chrome cylinders I'm thinking of throwing them on with new rings on the pistons. The chrome is in excellent condition. No peeling, almost looks like new.

 

[john zibell]

The more I look at the old chrome cylinders I'm thinking of throwing them on with new rings on the pistons. The chrome is in excellent condition. No peeling, almost looks like new.

If they have been sitting, moisture has found it's way behind the chrome. When you run it, the moisture will expand causing the chrome to fail. Don't put them on. It is not "if" chrome lined cylinders will fail but "when".

 

[pizza for you]

If they have been sitting, moisture has found it's way behind the chrome. When you run it, the moisture will expand causing the chrome to fail. Don't put them on. It is not "if" chrome lined cylinders will fail but "when".

Yes they have been sitting on the shelf. I guess if I cant bring myself to use the modified pistons I might have to bite the bullet on a set of new 850 cylinder and pistons. If I can find a set of new 1000 cc pistons I would go that route. Just don't know of anyone who sells them. Find it hard to believe no one seems to offer oversize pistons for the iron lined cylinders.

 

[john zibell]

Any dealer can get you new 1000cc pistons. Just tell them the class (A, B, or C) of the cylinder. It should be stamped on the cylinder. Or measure the bores of the cylinders you want to use to get correctly sized pistons.

 

[abbienormal]

As for your modified pistons, many years ago I bored out a Honda CB650 from the stock 636 to 672 using Wiseco forged pistons. They were much heavier than the stock pistons so I took them to a local auto speed specialist who milled the underside just like yours plus removed some under the wrist pin area to get them down to the same weight. Like you I questioned the integrity of these in an engine that spun 10,500 rpm with a compression ratio in the range of 10.5:1 or higher (I forget). When I sold the bike many thousands of miles later all was still fine. I'd put those slugs in there is it was me.

 

[pizza for you]

Any dealer can get you new 1000cc pistons. Just tell them the class (A, B, or C) of the cylinder. It should be stamped on the cylinder. Or measure the bores of the cylinders you want to use to get correctly sized pistons.

Wow ! Thanks for the information. Thank you very much.

 

[Mc Tool]

http://www.mgcycle.com/index.php?main_page=product_info&cPath=68_129&products_id=2131

 

[pizza for you]

http://www.mgcycle.com/index.php?main_page=product_info&cPath=68_129&products_id=2131

I'm going to go with

As for your modified pistons, many years ago I bored out a Honda CB650 from the stock 636 to 672 using Wiseco forged pistons. They were much heavier than the stock pistons so I took them to a local auto speed specialist who milled the underside just like yours plus removed some under the wrist pin area to get them down to the same weight. Like you I questioned the integrity of these in an engine that spun 10,500 rpm with a compression ratio in the range of 10.5:1 or higher (I forget). When I sold the bike many thousands of miles later all was still fine. I'd put those slugs in there is it was me.

I'm going to go with the modified pistons. I'll take the crank, rods, and flywheel and get the whole lot rebalanced . Do I need to have the whole clutch assembly i.e. pressure plate or just the flywheel to be rebalanced. I'll still keep my fingers crossed.

 

[john zibell]

Balance the flywheel with the ring gear attached using all bolts. The SP flywheel is a bit heavy, if the machinist can lighten and balance, you will notice a big improvement in response. A few pounds means quite a bit in rotating mass reduction. Acceleration will become quite brisk, as will engine breaking.

 

[pizza for you]

Balance the flywheel with the ring gear attached using all bolts. The SP flywheel is a bit heavy, if the machinist can lighten and balance, you will notice a big improvement in response. A few pounds means quite a bit in rotating mass reduction. Acceleration will become quite brisk, as will engine breaking.

I will do. Thanks for all your help. Thanks to all who responded. Much appreciated !