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Discussion Starter · #1 ·
Found the piston I am using in the F1, a Husqvarna 44mm one ring piston w/ 10mm pin. Going on a 10mm FC Cag crank. The ring stop pin is in the middle so perfect for one of my 4 port extra cylinders I have here.
Also in the 5 piston photo, a bunch of other modded pistons I have waiting for an engine.
 

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re pictures 1 & 3

did you measured the distance between middle of the wrist pin and the top

It seemed to be , after installing to short - in relation of the stock piston ... or it just seems so / optical on the pictures ( if you put them on the same high / hole to hole ) .
The cuttings are also bigger as the stock ones ...

and the 2 extra canals / ports maybe not the best then with the case because there is only one in the middle position ( like all brands engines ( also as the C 1 case )
 

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Discussion Starter · #3 · (Edited)
Yes, I have measured, the Cag pistons top has been ground down and beveled on top to clear the head on a custom engine I had before.
The stock Cag 10mm pin piston is from the top of the pin hole 12mm to the edge and 16mm to the top of the crown. The 44 Husqv. is 11mm to the flat top. First I wanted a one ring piston. I can mod the 17:1 compression cap, or grind down the edge on top the piston to clear the top if needed. The ring split is in the middle, so I want 2 extra ports, and a strip in the middle for the split to ride on. I have other cylinders and boxes of new pistons & rings and 10 & 12mm rod end bearings, and 10 and 12mm FC cranks and all,lol.
I already had the piston on a rod in new stock cases and a different cyld than in the photo.
 

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Discussion Starter · #5 ·
Here are 3 photos from my new Thread. Cases have not been modded yet, so no crank or piston. When I get the piston on the crank then I can look at the Clyd height, squish and port timing. I will post what I had to do to make it work. If I had a lathe & Bridgeport mill, I could really have some fun,lol. I was looking at a China lathe, $500, perfect for this junk.
 

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Yes, I have measured, the Cag pistons top has been ground down and beveled on top to clear the head on a custom engine I had before.
The stock Cag 10mm pin piston is from the top of the pin hole 12mm to the edge and 16mm to the top of the crown. The 44 Husqv. is 11mm to the flat top. First I wanted a one ring piston. I can mod the 17:1 compression cap, or grind down the edge on top the piston to clear the top if needed. The ring split is in the middle, so I want 2 extra ports, and a strip in the middle for the split to ride on. I have other cylinders and boxes of new pistons & rings and 10 & 12mm rod end bearings, and 10 and 12mm FC cranks and all,lol.
I already had the piston on a rod in new stock cases and a different cyld than in the photo.

You can lock the two pistons together side by side on the wristpin to gauge the piston height similarities/differences by eye and to calculate those differences simultaneously........






EPR If you look in craigslist under tools theres people selling lathes and mills cheap,,,harbor frieght has some pretty nice ones too.....
 

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Discussion Starter · #7 · (Edited)
Yeah, I did that in the 2 pistons together in the photos at the top w/ 6 pistons, you just can't see from the angle its at. The top of the 10mm pin hole to the flat top Husqv piston is 14mm the Cag is 12mm and 16 to the top of the crown. So, its 2mm to high on the outside edge. The top of the ring groove to the to top of piston is .146". Only have to clear the compression cap and can grind .080", 2mm off the top of the piston enough to clear and maybe alittle on the outer edge of the cap near where the piston comes up. The caps 17:1 so I might grind a full hemi head cap, and relief to clear the piston. Think the 44mm black cylinder is to short, will probably use the silver one. I have a jar full of 40mm and 44mm 15 and 17:1 caps to choose from.
 

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Discussion Starter · #9 ·
Not yet, but it's back together, if you read the other post about taking it apart and what for, you will under stand better. The billet case Cag engine has a Blata-Polini style intake, mine has a banshee 19mm intake manifold, and I don't have intake gaskets for it yet. Putting a Dell copy 19mm PHBG carb sleeved to 17mm in the rear bore to reduce the volume but increase the speed of it thru the manifold thru the Polini reeds.
Still working on my engine stand, have 4 different new engines waiting to be heat cycled.
 

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Discussion Starter · #12 ·
It's a lot of work, and about $170 w/ SKF bearings and seals, and you need a FC crank. The big problem with the Husqvarna is they all have a 10mm pin pistons, and I have a lot 12mm stock and FC cranks and piston here,lol. I just bought an HP cag engine from a member here w/ 10mm FC crank and alloy head/cylinder 2 pc. Taking the crank from it an putting it in my ADA 40mm head/cyld eng w/ a 40mm one ring Husqvarna piston.
Then put a 12mm FC crank & piston back into the engine I bought. Years ago I saw some rod sleeves you press into a 12mm rod end and then you can put a 10mm bearing & piston.
 

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flat top pistons need combustion domes that are flatter that pop up domes...
Bingo.......Its not impossible to get the combustion dome reworked by an aluminum head specialist but it isnt cheap either.....The cap can be milled down too....:cool:....

Now most will know why I dont use flattop pistons in my builds.......An indexed dome piston works just as well if not better because the dome helps cut down upward resistance flattops suffer from.....:D
 

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Discussion Starter · #15 · (Edited)
I don't even know if the one ring piston will work. This is a 30mm stroke my C1 has a 37mm stroke, and maybe more time to build compression. Haven't had a degree wheel on it, all I did was grind the top of the piston down to clear the 17:1 dome shelf on the ADA alloy head, plus took some off the bottom to clear the crank & to open the feed to the main transfer ports. I did not want 17:1 so I ground the first angle change in the cap to a more hemi shape, to get down to about 16:1. I have all kinds of 44mm Cag pistons I have modded already if the Husqvarna piston don't work right. I have a 40mm 2pc cyld kit with a 10mm FC crank & stock Cag cases with NaChi bearings and SKF seals w/ a 40mm one ring Husqvarna piston and a modded V reed block w/ a WT-668 walbro I am working on too. The 10mm FC crank is in the mail, I hope.
I bought a 180cc 61mm big bore kit & high angle cam today for my GY6 BMS 150cc scooter. Confused on the rollers and variator plate I have w/ 14g rollers, that says high performance, and they sell, 9, 10, 11, 12 and 13g ones too, and some are not round??? The have 3 racing clutch springs $25, and a whole hp clutch assembly for $66, and then there is the belt to, there cheap ones and good ones, was thinking about Kevlar belts, but I will deal with that part later. The thing is fun to ride, but don't like the idling when the gas is off your coasting, can,t wait for more power,lol.
 

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one ring pistons will work fine no mater the stroke, the variables are the thickness of the ring, materiel, ring gap location, and how much actual ring gap there is once broken in.

a thin ring reduces drag and allows for more rpm safely as it wont get as hot as a thick ring at high rpms, cons: it wears faster, creates less ring to bore seal, and less low rpm torque. there is always a hair of blowby at a ring gap, as there has to be a gap sp the ring wants to spread out into the bore walls, now here is a part of ring physics that most dont understand,...

the actual explosion of aif/fuel creates a positive pressure wave that leaks past the piston crown into the ring channel and presses the ring harder against the walls making more tighter seal. as a ring wears out the gap between the back of the ring and the piston ring channel increases and pressure is lost, making less power over time/wear.

on a two ring piston the top ring gets the most pressure, a hair is leaked past the ring gap by nature and some pressure is in the bottom ring. this is why some will see massive blowby and crown caramelizing on the sides by the top ring but the bottom ring is fine and the motor still runs decently. thats the reliability benefit of a two ring piston motor.

the gap IMO should always be 180 opposite from the widest port, wich is usually the exhaust port. most designs keep the gaps on the cooler intake side of the motor, and usually centered or offset to ride a port bridge/rib and avoid gap expanding in a open port. it can be safe to have a ring gap in a open port as long as the campher is perfect and the port spread is symmetrical

the physics of flat top pistons vs pop up pistons for starts at the combustion stage. lets all assume that every flat top piston is a properly spark plug gap index-ed hemi domed strait plug. so the inital point of explosion starts at the direct center of the piston. the burning spreads out faster along the flat surface and once hitting the bore walls pushes more evenly across the entire piston crown surface area, and THAT is what makes flat tops moar powa...

a pop up has a slower burn rate as there is now more surface area than a flat top, and the downforce power to the piston is dispersed less evenly.

the 45mm bore husky cylinder i have is flat top and angle plug. the squish band and the dome are really flat and tight. so there are vairations. ive also put the 40mm polini flat top single ring pistons in small bore stroked head kit long rod cags, and they raped ape, super sleepers
 

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Discussion Starter · #17 · (Edited)
Thanks for all the info., I have seen your work, and your way beyond what I know about hopping up & timing these engines. One thing that's weird is when I ground the top of the piston down to clear head, at BDC the top of the piston was right at the bottom of the exhaust port. Another thing I noticed the Husqvarna rod has no bearing the pin goes thru the piston and thru the rod. I looked for a rod bearing for their 44mm chainsaw, there is none in the piston kits.
 

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Thanks for all the info., I have seen your work, and your way beyond what I know about hopping up & timing these engines. One thing that's weird is when I ground the top of the piston down to clear head, at BDC the top of the piston was right at the bottom of the exhaust port. Another thing I noticed the Husqvarna rod has no bearing the pin goes thru the piston and thru the rod. I looked for a rod bearing for their 44mm chainsaw, there is none in the piston kits.
i cant imagine a upper con rod not using a pin bearing. thats weird:confused:
 

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The one I got in that madness of parts had a pin bearing in its box.. Without it the piston would slap up and down on the pin no? Need me to measure the bearing?

I'm was going to be trying the same piston in the 50 build also, I was thinking chop the top and use the compression dome but now I got more thinking to do.. Any Chance of the piston working good in Non Chopped stock style head with an angle plug? Or is that to Dome also? Can I mill the Dome of a compression set a little flatter?
 
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