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Discussion Starter #1
I finally talked myself into installing the 70mm piston on my parts bike. I am not sure I did the right thing as it was a very sweet running machine but it is done now so no need to dwell on it.

I was going to post pictures of the change but reality is that it is no more than a base gasket change and there are already plenty of pictures of that. So instead I thought I would concentrate on the cylinder itself and different stages along the way.

I spent $13.50 on the cylinder and honestly, I think I overpaid. I sprayed degreaser on it before I took the picture. My mistake. Not a true "before picture".
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Cylinder cleaned up and rust hand sanded from inside cylinder. The cylinder is mounted to a board and ready for the hone. One can see this has been sitting around a while and is badly pitted.
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The pitting cleaned up very early in the honing and I think a 67.5mm piston would have worked. It seems most pitting just isn't that bad.
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Final hone. Tried for the cross hatching -- could have been better but it will work OK.
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I lapped the gasket surface to make it flat and clean. I placed a stock sized piston in the bore to show how much bigger the new bore is. I don't have any pictures of the outside of the cylinder but trust me, it is every bit as clean as what you see here.
Std piston 70mm bore (2).JPG

So that is it. So far I have 8 miles on it and my concern for the thin walls seems unfounded. I am doing a "hard break in" which is WOT followed by a shut throttle followed by WOT again followed by a shut throttle and repeat , repeat, repeat for 25 miles while using dino oil. Change the oil at the 25 mile mark and continue using dino oil for the next 1000 miles and you are done and can change to synthetic if you desire. I will most likely stop break in around 15 miles but will stay with the dino for at least 1000 miles. (Is 25 miles necessary? I bet 4 or 5 miles is plenty.)

As for increase in performance -- reports to follow. It seems peppier but it is hard to tell if that is placebo or real. I have to go for a ride in the hills to truly evaluate it and that will come after the first oil change. Tony
 

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The first few miles will make or break the ring seating. I think you did it right.
You may want to take a compression test reading, then take one at 1,000 and then the next couple oil changes to see if it continues to seal, or you got it done with the break-in.
 

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I'm always interested in watching yours and TW-Brian's engine rebuild threads. I may actually learn something, though I don't always know it at the time.

Last night I removed the remains of the dead Mayflower engine from the frame. When removing it I was surprised, some oil poured out onto the floor when I tipped it. The surprising part is I thought all the oil had been spewed out of the bleed screw area. So far the only real damage is the piston and cylinder. I looked real hard at the connecting rod wrist pin and it looks fine from my untrained eye.

I now have to buy a honer (I can say that right?) and the measuring devices. Pretty sure my carpenters ruler isn't set up for the tolerances I need to be measuring! Doing this is above the hammer technology I possess! I'm not 100% sure the head didn't receive any damage, but by-gosh I can't see any. And I used a flashlight and everything!

I don't think I'd take apart a good running stock engine just for the piston upgrade, but you guys keep pumping out these wiseco pistons got me thinking to fix my damaged cylinder and make it into a wiseco beast!

Thanks for posting this stuff. It really helps and motivates!
 

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Discussion Starter #4
So far the only real damage is the piston and cylinder. I looked real hard at the connecting rod wrist pin and it looks fine from my untrained eye.
You jog my memory: Around 1985 I bought an essentially new 1957 Johnson 7.5 hp outboard motor a guy had lent to his brother who thought mixing oil with gasoline was foolish lubricating overkill. Long story very short the piston over heated and transferred aluminum to the cylinder wall which made it look terrible. After a little honing with a flex hone the soft aluminum was gone and the cylinder -- to my surprise and relief -- look great! A new piston and set of rings along with getting a hole welded shut and the little motor was back in business.

So see if the walls are truly damaged. Maybe it just needs cleaning and a new piston and rings.
 

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Hey Admiral, this is the new "wife's bike". Didn't you recently post that she rode your TW and liked it????? Just sayin'.
 

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Hey Admiral, this is the new "wife's bike". Didn't you recently post that she rode your TW and liked it????? Just sayin'.
He he! I get to keep the new TW. She just discovered she likes riding. The Mayflower was always going to be rebuilt, if anything as a spare for Moab. We know some people need a spare (me, Fred :D). When I get done fixing the old TW, it will mainly be a spare for me as Mrs. Admiral wouldn't be comfortable riding in our normal habitat (to rough).

Of course my plans for a spare TW may be a little "less manly"! Mrs. Admiral is already talking about which parts she wants painted pink!
 

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Hahahahaha... You must be very comfortable with your manly man-ness to paint your parts pink. lol
 

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Kris, have you considered going with a pink urban cammo motif? Stylish yet not excessively feminine.. images-3.jpeg images-2.jpeg images.jpeg
 

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I ran my '95 TW out of oil at one point and was worried about the lower end and connecting rods. My Honda dealer friend said, "don't worry, those TW are real strong in the bottom end". Next size piston and over bore to match and much joy was realized.

BTW. I used the "ride it like you stole it" break-in method also. Changed oil at 25 miles and 100 miles. Plan to change again at 1000. She runs fine.
 

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I ran my '95 TW out of oil at one point and was worried about the lower end and connecting rods. My Honda dealer friend said, "don't worry, those TW are real strong in the bottom end". Next size piston and over bore to match and much joy was realized.

BTW. I used the "ride it like you stole it" break-in method also. Changed oil at 25 miles and 100 miles. Plan to change again at 1000. She runs fine.
Tomorrow I'm hoping to start it up! Nobody will have to worry about me babying a TW. I pretend it has 160 horse power and I hang on. Then Georgie runs up beside me and ruins it! Back to 16 hp! or 13 or 15, what ever it is!
 

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Admiral,good luck with the test firing. I miss your old color scheme of the Mayflower. I know you have 3,000+ miles on the new TW but I still envision you and Georgie astride a Sand Hollow tinted machine. Stock seems so tame for what you, Lori, and Georgie usually ackomplish.
 

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Discussion Starter #15
I rode The Parts Bike with the 70mm piston 40 miles yesterday. It might be me with an over active imagination but I swear it has a new vibration in the higher RPM range.

So, should I have weighed the original piston and then made the new Wiseco weigh the same amount? I am thinking maybe the new piston is to heavy.............

Again, maybe it is me with unreasonable expectations, but I was hoping for a bigger increase in performance. It seems my other TW with the 68mm piston (and the 14/55 sprockets) had a greater improvement in performance.

All this concern maybe premature, and maybe it just isn't broken in enough yet -- it still has less than 75 miles vs. the 68mm TW has 330 miles.
 

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I'll be watching to see how this turns out. I need to get a measuring too (inside caliper) or something so I can make the measurements when I hone/bore the damage 93 cylinder I going to work on. I can't believe how well the cylinder looks compared to the piston which came out of it. Piston and deep grooves where the cylinders are barely noticeable to sight and feel.

If your 68mm feels better than the 70mm, I guess I should try to hone/bore as little as I can. I have to find your tolerance specs between what to hone/bore for the size piston being used.

Thanks for this info on the 70mm testing.
 

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Discussion Starter #17
The Parts Bike has a high speed miss -- over 8400 rpms -- I ultrasoniced the carb. and it runs better but the miss is still there. Closed the gap on the plug slightly and it didn't make a difference. I swapped CDI with my other bike and the miss stayed the same so either it is not the CDI or I have two bad ones.

I ordered a new #114 jet -- three times in the past this has solved a high speed miss, twice for me and once for Big D, but since the jet in there now is fairly new I didn't consider it. However, Big D suggested I replace it just to make sure and I await the delivery of the new one. I also ordered a #110 -- I wanted a #112 but they are now obsolete -- if the #114 is to large I will slightly enlarge the #110. If this doesn't work then it is on to the electronic stuff -- coils and pickups and the like.

Other than the miss the more I ride the bike the better it seems to get. Not an earth shaking amount of additional power but a noticeable amount more. The clutch which was marginally OK is now marginally not OK and I have to shim the springs to stop the slippage -- in 5fth gear if I hit the gas hard sometimes the clutch loses it grip.
 

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It's always something!

I noticed my TW getting more "power" as the new rings broke-in. It was obviously very tight at first.
 

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The Parts Bike has a high speed miss -- over 8400 rpms -- I ultrasoniced the carb. and it runs better but the miss is still there. Closed the gap on the plug slightly and it didn't make a difference. I swapped CDI with my other bike and the miss stayed the same so either it is not the CDI or I have two bad ones.

I ordered a new #114 jet -- three times in the past this has solved a high speed miss, twice for me and once for Big D, but since the jet in there now is fairly new I didn't consider it. However, Big D suggested I replace it just to make sure and I await the delivery of the new one. I also ordered a #110 -- I wanted a #112 but they are now obsolete -- if the #114 is to large I will slightly enlarge the #110. If this doesn't work then it is on to the electronic stuff -- coils and pickups and the like.

Other than the miss the more I ride the bike the better it seems to get. Not an earth shaking amount of additional power but a noticeable amount more. The clutch which was marginally OK is now marginally not OK and I have to shim the springs to stop the slippage -- in 5fth gear if I hit the gas hard sometimes the clutch loses it grip.
Sounds like you need to internally adjust that clutch so the mark lines up again too.
 
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