Author Topic: tapered wrist pins (Read 16963 times)

bwaller · « **on:** October 22, 2009, 05:26:13 AM »

Hi guys,

I would like only four 15x50mm tapered pins. The straight wall pins that came with my pistons are 0.100" thick and weigh 44g, short of trying to taper these I'm running out of options, does anyone have a source?

Also, Wiseco offer this size for 2-stroke application only?? They are not hard chrome so I suppose it is a question of a steel pin in an unbushed steel rod small-end and a galling issue, I'm unsure. One of their reps says don't use them, another says the're polished so I'm good to go.

Any expert comment?

HondaMan · « **Reply #1 on:** October 22, 2009, 06:37:14 AM »

Why tapered pins? The stock ones are straight.

bwaller · « **Reply #2 on:** October 22, 2009, 06:52:11 AM »

Inside the pin the width of the rod, that center section is straight wall, then tapers outward toward the outside edge of the pin. The pins I have weigh 44.5g, tapered ones may be up to 10 grams less.

I understand Yoshimura offered some 15x50 tapered pins for 810/812 pistons that were very light and strong thirty some years ago, surely some-one does today.

voxonda · « **Reply #3 on:** October 22, 2009, 06:58:23 AM »

Am certainly no expert, but have grinded a set of pins tapered on the inside, some years ago. But cannot recall if the weight advance was that big.
It certainly can be done.

Rob

bwaller · « **Reply #4 on:** October 22, 2009, 07:40:42 AM »

Thanks Rob,

I'm leaving this as a last option and will try to wittle a little out of them, but for the small price of new pins I thought I could save my time for other jobs!

bryanj · « **Reply #5 on:** October 22, 2009, 08:37:22 AM »

I have seen both sorts supplied under the same part number in honda bags, so they dont seem to think it matters

turboguzzi · « **Reply #6 on:** October 22, 2009, 09:26:33 AM »

guys, tapered pins mean less weight, ten grams is quite a lot less reciprocating mass @ 12,000 and well worth the effort. If you can find them like that, that is....

Brent,

first option might be to look into the better big bore kits for CRF's etc.

then waht about big jay @ APE? Honda man?

last, if you decide to DIY, I'd try to find a die maker who can do it with an electro erosion machine, much less stressful,

754 · « **Reply #7 on:** October 22, 2009, 09:29:11 AM »

pretty sure APEc an get them for you..

bwaller · « **Reply #8 on:** October 22, 2009, 09:48:13 AM »

I received back an e-mail from APE saying their 15mm pins are not tapered. I have not yet heard back from JE Pistons yet.

Anyone have any thoughts on the unchromed pins I mentioned from Wiseco?

Interesting bit of info TG, I'll investigate.

MRieck · « **Reply #9 on:** October 22, 2009, 12:35:58 PM »

Quote from: bwaller on October 22, 2009, 09:48:13 AM

I received back an e-mail from APE saying their 15mm pins are not tapered. I have not yet heard back from JE Pistons yet.

Anyone have any thoughts on the unchromed pins I mentioned from Wiseco?

Interesting bit of info TG, I'll investigate.

You can have them coated with DLC or similiar coating. Much harder than chrome Brent

bwaller · « **Reply #10 on:** October 22, 2009, 12:46:37 PM »

Where can I get that done Mike?

I don't think I should risk running steel on steel, what do you think?

turboguzzi · « **Reply #11 on:** October 22, 2009, 01:00:12 PM »

brent, I did see galling happening with a lower quality steel pin..... it didnt spoil the small end just because of the high quality of the honda rod. I was lucky.

I ended up shortening stock honda pins for my new set of pistons,

with electro erossion, the die maker simply makes a tapered male electrode and "eats" away material. it takes time but cant think how you could properly machine high quality steel pins after they went through heat treatment. maybe with very expensive cutting bits and plenty of patience.

I run currently non taper pins but it would be nice to find a set.

TG

Sam Green Racing · « **Reply #12 on:** October 22, 2009, 01:45:53 PM »

Stop faffing about and get the job done right

Titanium Wristpins

A standard or chrome-moly wristpin usually weighs up to 1/2 of what its’ corresponding forged aluminum piston weighs. By changing to titanium pins and using the "1/4th the weight and same strength" approach, the total reciprocating weight can be reduced drastically, resulting in big HP gains. As an example, a piston may weigh 400 grams and the pin 200 grams. By reducing the weight of the pin to 50 grams, we save 150 grams per rod/piston assembly, or 900 grams for a 6-cyl engine (approx. 2 pounds). At 6000 RPM, this would provide a gain of about 10 horsepower. At higher RPM, the gain would be even more. Wristpins are made to order. We must know both the diameter and length of the pin you need. The price is $150.00 per pin.

Sam.

736cc · « **Reply #13 on:** October 22, 2009, 01:53:39 PM »

recently sold these i found at an old-school bike shop, not much info available and they're gone anyway.
actually weighed more when i compared to a stock set, and ends were tapered inside.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220478566030&ssPageName=STRK:MESOX:IT

voxonda · « **Reply #14 on:** October 22, 2009, 02:10:06 PM »

Quote from: turboguzzi on October 22, 2009, 01:00:12 PM

brent, I did see galling happening with a lower quality steel pin..... it didnt spoil the small end just because of the high quality of the honda rod. I was lucky.

I ended up shortening stock honda pins for my new set of pistons,

with electro erossion, the die maker simply makes a tapered male electrode and "eats" away material. it takes time but cant think how you could properly machine high quality steel pins after they went through heat treatment. maybe with very expensive cutting bits and plenty of patience.

I run currently non taper pins but it would be nice to find a set.

TG

I grinded the pins on a lathe, with a lot of patience that I normally d onot have.

Rob

bwaller · « **Reply #15 on:** October 22, 2009, 02:46:54 PM »

The unchromed Wiseco tapered pins are cheap so I like the coating idea. I have this new set as well so can talk to a tool & die company or can attempt grinding them myself. I have options.

On the other hand Sam I'm one step ahead of you. I contacted a company about Ti pins, but now that I know what the price is I'll leave those for you.

Sam Green Racing · « **Reply #16 on:** October 22, 2009, 02:50:09 PM »

They might be cheaper than that Brent, those prices are for big car pins, might be a lot less for small bike ones.

Sam.

Bill/BentON Racing · « **Reply #17 on:** October 22, 2009, 04:51:33 PM »

TG,you right on the money,well worth it if you can find them,my Yosh 812 pistons,3 weigh 171.7 grams,1 weighs 172.2,Wiseco 836cc weighs 177.7,Venolia/RC 192.2(forged?),pins Yosh 31.2,57mm long,Wiseco 41.8 (Honda pins can't read the #),56mm long,Venolia/RC 39.7,53mm long.The Yosh pins on the 590 if I remember right were 10 grams less than stock,I think I'm going to use Yosh kit while I build 1000cc engine.Over 65 grams less reciprocating weight than Wiseco,115.5 on the Venolia/RC's.Anybody run either of the Mega cycle cams 65 or 75,or RC315 (still my favorite) with the 812 kit? Thanks,Bill

Jerry Rxman Griffin aka MuthaF'er · « **Reply #18 on:** October 22, 2009, 05:32:29 PM »

Bill,

Running the Yoshi Daytona cam in my 812. Probably not the best midrange but helluva top end. I'm thinking about getting a 125-75 and a 315 for the 900. I have Gordon's frame kit so all I'll need is a dyno. Why do you like the 315?

Interesting topic. Less weight only makes sense. Now that Big Jay has gotten fired up again maybe he needs to top it off with pins. I'm sure he'll be here shortly.

Bill/BentON Racing · « **Reply #19 on:** October 22, 2009, 06:43:10 PM »

Jerry, I guess I liked it cause it was NOTICEABLE,fair idle,made lots of usable power(we were drag racing then)they were streetable and fun,intake specs were close to my Yosh TT cam in 590cc bike,if I had been road racing then would have tried Yosh's cam,but never got to.Do you have specs for TT cam for 750? Looked up the specs on 65 and 75 Mega cycle,the 75 and the 315 would be interesting comparison,let us know.Are 315's still available?If my memory is correct,the 75 has the same intake #'s as the TT cam for 500/550's,26/53,MR,if you do group buy on 75's from Mega,count me in.Bill

bwaller · « **Reply #20 on:** October 24, 2009, 11:29:47 AM »

JE e-mailed back saying they could get those 15x50mm tapered pins on a special order for $10.10 each.... short money.

Not light weight like the old Yosh pins from the day, but still 9 grams less than the straight wall I have.

The pistons I had made have a huge pin boss so I know I can take a few g's off those as well. If it doesn't make a huge difference, at least I'll feel better.

754 · « **Reply #21 on:** October 24, 2009, 12:21:37 PM »

Wow that is reasonable..

A boat builder here has a buddy with a 44 ft cigarette boat, it now has 150 hrs on it, so needs to be freshened up! He said the wristpins are 77.00 EACH... worst part is it has 2 motors, so 16 needed!..

hope that makes someone feel better..

Bill/BentON Racing · « **Reply #22 on:** October 24, 2009, 06:57:54 PM »

Way reasonable,I'll take a set or two.Bill

voxonda · « **Reply #23 on:** October 25, 2009, 01:42:33 AM »

I would like a set or two also.

Regards, Rob

bwaller · « **Reply #24 on:** October 25, 2009, 06:35:52 AM »

I only ordered one set to be sure these are as advertised! I'll let you know.

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Author Topic: tapered wrist pins (Read 16963 times)