Identify these Yoshimura pistons "POPY" PIX ADDED

irishwill wrote:

hope you enjoy it

very and i mean VERY cool old school stuff....thanks for sharing

irishwill wrote:

they are pops yosh pistons from when they were building kaw superbikes....they had several "kits" available....
stage 1 to 4
i have a buch of literature here somewhere....they are probably 1015 slipper pistons....

ill try and post some info tomorrow

BTW....I have a complete yosh motor with carbs and close ratio trans....ect,ect very cool stuff

73 mm is bigger than 1015 yes?.....its late, but i thought 1075 was 72 mm .....73 would be 11oo something...no?

1105

903cc = 66mm
1015cc = 70mm
1045cc = 71mm
1075cc = 72mm
1105cc = 73mm
1135cc = 74mm
1197cc = 76mm


Ben... Whoa! :woohoo: Ya Freaking Aye Cool!....

I had boose bumps reading that totally awesome old literature... At the time of this writing I'm grinning extensively... :woohoo:

Kudoo's...

OMR

Interestingly enough, the increase HP% in my build came out about the same as depicted in the Yosh stage kits... Interesting how this all works huh... :laugh:

Example in my build: Similar to the stage 2!
.365 cam at 105 lobe centers...
29mm Carbs...
1015cc kit...
Head port and polished...

OEM Rear HP ~ 65hp
First Dyno 86hp
Soon 2nd Dyno expect ~95hp thus 47% increase in HP overall....

Other variables all add no doubt but that's a huge jump in HP...

OMR

Old Man Rock wrote:

903cc = 66mm
1015cc = 70mm
1045cc = 71mm
1075cc = 72mm
1105cc = 73mm
1135cc = 74mm
1197cc = 76mm


Ben... Whoa! :woohoo: Ya Freaking Aye Cool!....

I had boose bumps reading that totally awesome old literature... At the time of this writing I'm grinning extensively... :woohoo:

Kudoo's...

OMR



Interestingly enough, the increase HP% in my build came out about the same as depicted in the Yosh stage kits... Interesting how this all works huh... :laugh:

Example in my build: Similar to the stage 2!
.365 cam at 105 lobe centers...
29mm Carbs...
1015cc kit...
Head port and polished...

OEM Rear HP ~ 65hp
First Dyno 86hp
Soon 2nd Dyno expect ~95hp thus 47% increase in HP overall....

Other variables all add no doubt but that's a huge jump in HP...

OMR

what have you done different to get more ponies OMR...?
that is more or less what Im gonna get larry to do for Pens bike....but I will go to 1075 (just cause I have the piston kit already) with the ported head cams and a set of smoothbores 29's all dumpng through a yosh pipe...or maybe a mori pipe...either way I think it should make 105 hp more or less.
Im gonna sent larry the whole motor soon as im done school

As written...

.365 cam at 105 lobe centers...
29mm Keihin Cr Special Carbs...
Wiseco 1015cc kit...
Head port and polished Stage 1 Larry C...

Ok, should have added Kerker w/1.5" comp baffle...
Dyna S coils and EI...
15/37 sprocket combo...

OMR

haha...I get that OMR...but you are expecting more from your second dyno session....Im wondering what more you have done to expect the additional increase in HP

DOh!...:laugh:

First session, only about 20 miles on the new build thus no jetting/sync other than what was sent from SUDCO stock adjustments.... First valve clearances in spec but will change during break in period, piston rings not fully seated in sleeves yet, torques will loosen slightly, cam lobes not even broken in, re-CAM degree for tighter accuracies @ 105 lobe centering etc...

Since then, sent the head back to Larry for I didn't listen carefully enough the first time I spoke to him :blush: so new 1 over size exhaust valves installed... OEM valve seals vs 3rd party... CFM, valve seating etc all re-checked.... My bad for not listening correctly Larry... thanks mi amigo!

Jetting & sync dialed in, running synthetic oil thus less friction/heat, piston rings properly seated, valve clearances dialed in, engine is broken in @ 3K miles etc....

This is where the additional 10% will come from...

OMR

well you've definately been thinking about this!...haha
thats awesome....I am very curious to see what the actual numbers are....

The one thing that may reduce the HP numbers for me are that I am in Edmonton where the elevation is around 2000 feet above sea level....
but until I get the work done I wont know....her bike doesnt need to be a rocket...but you just know Im gonna wring that thing out every now and then....so it has to be fun!!

Im trying to organise a "can-am" run with a bunch of the boys from the old days....wont be till next summer though....maybe make it to arizona...if we can handle the heat haha

"well you've definately been thinking about this"...

Oh that's an understatement... Ask Plum and Larry about how anal retentive I get :huh: , drives them freaking crazy...
Deep down, I think they dig it (research) though....

Phoenix is @ 1400 above sea level so that's close to Edmonton Elevations... Dial in your jetting for elevations, temps, humidity etc... shouldnt matter...

"maybe make it to arizona...if we can handle the heat"...
Yeah sure, come in August! :evil: Your tires will be sticky here no doubt....:whistle: 115*F!!! :pinch:

Just getting ready for the 4K mile adjustments... Valve clearances, oil/filter change, carb sync etc... Then Dyno!
Should eb another week or so...

OMR

More HP will come from leaning out the waayyyyyyy tooo fat jetting Sudco sets up the CRS carbs with. It was FAT CITY and nowhere near broken in on the first go 'round.

My estimate is Dave's bike should pull about 93-96 HP at the rear wheel if done on the same dyno.


Funny stuff how what was once considered racing setup got to become relatively mild street motor setups as the years went by and the new bikes go so much faster

"leaning out the waayyyyyyy tooo fat jetting Sudco sets up the CRS carbs with."... Yup!!!

2 Sizes down on the Mains and Slow Jets (pilots)...
1 Size leaner on the Needle itself.

As discussed with Larry and Plum, SUDCO sells them out the door way rich... They don't want any pistons to fry on their customers and have to deal with that BS... Not to mention they get to sell more jets as well...:huh:

Seriously though, there's no way they could pre jet 100% accurately, would be impossible for as mentioned, every engine is different even if same components (pistons, cams and carbs) where used... Sure could be close to start but not 100%, no freaking way...

Head work, CFM air flow and porting, exhaust RPM band range, primary lengths, primary size, pods, timing, camshafts, baffles etc... all play part in this madness...

Have to love it though for once you do get them dialed in...
Freaking madness, instant WOOD, who needs Viagra... :blush:

OMR