overbore in order - Which pistons?

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Shadow24v

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Over in my repair/restore thread (HERE) I was able to take the jugs and new used pistons to the machine shop yesterday.

Bad news, both bores had out of spec taper and were also out of round. The used pistons were also worn to where the piston to bore clearance was beyond service limits. Since at this point, a re-bore is needed, I am searching for pistons to put into the motor. I am also on a bit of a budget, so the $700 for a 750cc kit from Mikesxs is out. I emailed a bunch of the piston companies (JE, CP, Wiseco, BTC, Arias, Venolia and I think one other) to see about 1st over pistons as Yamaha OEM ones are hard to come by.

I did see that Hoos has the 700cc pistons which can be accommodated for in the stock sleeves and are only about $365 with rings. Depending on what the other companies come back with, hopefully something will come within the budget. I do have a few other Q's for those that have used non-OEM pistons...



1) Do we know who makes the 1st over pistons at Mikesxs?

2) Has anyone used pistons by any of the aftermarket piston companies in a near stock application? (I saw the picture Hugh posted of the JE 700 & 750 and Mikes 750 pistons, and the JE's look really nice.)

3) What are the Pros or cons to running aftermarket vs. Mikesxs pistons?
 
Gotta be cheaper to go OEM than any of those other companies. I see a few on ebay, should be more around at other shops.
 
OEM seems to be running $80-$100 per piston for 1st over.

There's also the catch of "you get what you pay for". Mainly, are the other piston companies products of higher quality than Mikesxs / OEM pistons to warrant the extra cost?
 
Jay760, Thanks for the link, but I was looking to keep machine shop costs down to a basic re-bore on the stock sleeves. The kit you linked, plus shipping and Hoos sleeves would run about $470, not counting the bore, hone and sleeve installation costs.
 
Shadow24v said:
OEM seems to be running $80-$100 per piston for 1st over.

There's also the catch of "you get what you pay for". Mainly, are the other piston companies products of higher quality than Mikesxs / OEM pistons to warrant the extra cost?
Click to expand...


These are OEM, $75 per piston. No way you're going to find fancy weisco or JE for less, but if you're looking for more cc you have to shell out for the aftermarket ones.
 
Hotdog, nice find on the 2nd over set, but they don't ship to the USA. Also mimic your concern on their quality.

I'm hoping one of the piston companies comes in at a good price point compared to OEM cast pistons. Materials etc. have improved a lot since the 70's.
 
Precisely, and since I have the motor apart due to a failed piston already, I'm considering aftermarket newer material pistons than NOS cast aluminum that have been sitting for 40+ years. Hopefully the price point is decent enough on someone's pistons that it makes better sense than NOS pistons.
 
I ran the MikesXS pistons without incident, and then built a 2nd motor with the 750cc kit they sell.

I'm rebuilding another engine and have picked up a set of pistons and rings from XSCycle Performance. They have coatings on them and a different oil ring than you typically find. The engine is getting a ported head also by XS Cycle and an XS1 cam mated to the 36t sprocket degreed for a thinner copper gasket, again, also source from XS Cycle. They're nearby me in Toronto and Andy is a good guy to work with.

http://www.ebay.com/itm/Two-Yamaha-...Parts_Accessories&hash=item4d0871c9ba&vxp=mtr

They look for all the world identical to the MikesXS units - likely from the same source.

Least expensive I've found is these, shipping out of Japan. $100 shipped for two pistons and rings etc. A solid $50+ less than MikesXS and again, likely same or better quality.

http://www.ebay.com/itm/74-76-YAMAH...Parts_Accessories&hash=item1e7411a9c9&vxp=mtr
 
The coating on the skirts is a waste of money and time as there are no benefits as the dry film is completely worn off the skirts within a few engine cycles and this applies to MikesXS pistons also, as I've seen their pistons from tear downs.I've experimented with Tech Line,K-kote,etc products in the past with negative results and it's not recommended you coat the piston lands nor the inner surfaces of the ring lands for obvious reasons:doh: . My plans are to have Swain coat my KZ pistons. My advise is to contact Swain for proper coating needs.
 
The area around the rings is not coated. Just the skirts and the dome.

So, you're saying all coatings are a waste of time and money, but you're having yours coated by Swain, is that it?

Swain looks like the real deal, no question, and $40 per piston for their recommended skirt and top coatings seems reasonable. Just want to clarify your assertion that coatings is a waste, except for Swain.
 
Another thought is that if I have pistons made, is it worth bumping the compression ratio? If I remember correctly the 700cc kit is a 9.5 CR, and the JE 750cc pistons are 10.5 CR. I wonder if a 1st over with 9.5 or 10:1 CR would give any noticeable gains from the stock 8.4 CR.

Regarding coatings though, I seem to usually hear the extremes. Either people call them snake oil or that they had great results. If the cost is marginal enough, it may not hurt to try though. I don't see how it could cause any real harm in the end.
 
Having pistons made is not as easy/cheap as you think, you'll have to spec up your requirments also.
However, I am having some custom made at the moment & they cost about the same as the je pistons from hoos racing.
 

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