Is there any other piston that will work with this engine?
- Thread starter mrfubs
- Start date
I think you're talking about stroke. Eye-to-eye, the conrods are 85mm for the grubees, and 80mm for everything else (with a grain of salt, apparently there's 4 different kinds of motors that we know of, the grubee (Type B) and dax (Type D) are the most common)
38mm stroke is standard 65.8cc iirc, 40mm stroke is a newer/stroked crank thats about 69cc. Conrod lengths will be the same though, but that extra 2mm could be an issue. That means that the piston will come 2mm closer to the crank, and 2mm closer to the head, a properly sized jug may be required...
As for the piston, looks gorgeous, just dont cut the piston till you test fit it with the shorter conrod. How much skirt is there between the bottom of the reed window and the bottom of the piston? That's great that we got a better measurement (guy told me 4.7oz which is 133 grams, I figured it wouldnt be THAT heavy). then again that already has the reed port so it's probably a better alloy. My piston assembly will weigh about 87g after the titanium wrist pin. Is the whole piston a snug fit, or is it comparable to our stock pistons? And absolutely dont forget about us if you find it performs well!
I will definitely keep everyone in tuned on how it goes. Iv been trying my best on how to figure out how to make this engine the most reliable while making the most power it can at the same time. I feel pretty confident if i can get a hold of a crank with a shorter con rod. S*** now that its getting harder to find them i might just buy two cranks to have them.
As far as the skirt goes i think i have to trim 2 mm off the skirt, and mew ill let you know asap on how much meat is left on the skirt. Ill have 2-3 mm left before it hits the reed openings which i think will still be fine for this engine.
As far as the skirt goes i think i have to trim 2 mm off the skirt, and mew ill let you know asap on how much meat is left on the skirt. Ill have 2-3 mm left before it hits the reed openings which i think will still be fine for this engine.
alright so i bought one of dax's bottom ends today, BTW anyone else interested hes got less than 12 left and i waited 12 weeks to buy one, so before hes out id buy one if i where you. $68 shipped and it is equipped with the shorter connecting rod so that means i will be able to use this Hoca piston i bought in about a week.
cool Im rdy to hear the results if you get it together and going before I get my motor in and put together and on the bike I may be ordering on. Im not looking forword to all the work I have planed to the stock piston lol
haaha nice, the only thing im not looking forward to is the amount of time i had into my current cylinder grinding ports and adding ports to get where im at. Im going to buy a new cylinder this way ill have a whole complete engine just about, besides the head and reed cage. If this all works ill be able to turn even higher rpm than i am now and not wear the cylinder out no where near as fast as the stock piston and rings.
If you fail to find a new cylinder, the GT5-a piston is good, but your reeds wont work with it, you'd need a new set, but it's pre-ported
I shouldnt have any problems getting a cylinder for 20-30$ hopfuly. I went a head buying the necessary pieces to make the engine i had in mind and i am 93.64% sure i can get this to work no problems lol
NEW VIDEO.
http://www.youtube.com/watch?v=1_kAkipr1jM
NEW VIDEO.
http://www.youtube.com/watch?v=1_kAkipr1jM
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The cylinder foureasy used to achieve 45mph on a 41T sprocket, 24" wheels
http://www.treatland.tv/puch-athena-kit-p/puch-athena-70cc-kit.htm
He also claims this one will work. https://www.treatland.tv/puch-gilardoni-74cc-cylinder-reed-kit-p/puch-gilardoni-kit-no-head.htm
He used a custom made 7mm spacer.
Using the long con rod (Grubee GT5? he says he has a 40mm stroke, mine's measured at 38mm) he says you need to press a brass bushing into the small rod end, then ream it out to 12mm to fit the new piston (no need for a bearings, the bushing replaces it, and withstands high RPM's better).
http://www.treatland.tv/puch-athena-kit-p/puch-athena-70cc-kit.htm
He also claims this one will work. https://www.treatland.tv/puch-gilardoni-74cc-cylinder-reed-kit-p/puch-gilardoni-kit-no-head.htm
He used a custom made 7mm spacer.
Using the long con rod (Grubee GT5? he says he has a 40mm stroke, mine's measured at 38mm) he says you need to press a brass bushing into the small rod end, then ream it out to 12mm to fit the new piston (no need for a bearings, the bushing replaces it, and withstands high RPM's better).
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i would buy that cylinder but the only thing holding me back is $190 lol i can get 8 Ht Cylinders for that price. i think im going to try a new boost port with my new engine built ina week. im going to try 2 more transfers instead of 1. and drill a lot more out of my crank if i get this hoca piston to work because if it does ill be able to turn 11,000 give or take with the same amount of wear the original rings do to the cyl wall. 55mph +
yeah it aint cheap, but it IS performance tuned to ridiculous proportions. Foureasy said he was getting around 5hp out of it, and I think it's torque tuned. However for that price you could also try an Arrow cylinder for $60, apparently they're "perfect ported" as well. As for the balance, I wouldn't advise it. I have a crank here that's been drilled quite a bit for balance and it didn't work, it shook less than stock but had no power and was prone to "shock stalls" (where our cranks can keep momentum for a second if we come to a sudden stop, mine didn't, its own vibrations killed it) Going with it's pre-balanced tune will suffice, especially being that the Hoca piston is almost the same weight total as our stock ones
so i got dax's lower end and am happy with the quality. The crank lower con rod bearing is copper in color and has copper washers on each side to eliminate any play. Also 3 oil holes on the upper con rod hole as well with notches and 3 holes on the bottom! Thats not even the best news! the best news is the Hoca piston is a direct bolt on piston (in a way) the first thing i did was slap the hoca on and see if it would rotate with out the bottom of the skirt hitting on the crank, it doesnt hit but is like 10 thousands away from. Im going to trim 1-2 mm off and be in buisness! Also with this longer stroke crank the transfers are opened more.
Check out my crazy ported cylinder .
Check out my crazy ported cylinder .
thats some great looking ports there! how are the transfer angles? and thats awesome, yeah I'd shave off 1-2mm then, thermal expansion may cause it to smash and lock so 1-2mm will save it. Hows the deck height? does the piston sit further up? Cant wait to hear how it runs too!
yep! it comes almost flush to the top of the cyl! Its going to breath so well. I have each port so wide there only milimeters away from going into the main bolt journals lol. Have you seen daves new reed block design? its meant for a 18mm carb.
http://arrowmotorizedcycles.com/shop-now---high-performance-ported-cylinders.html
http://arrowmotorizedcycles.com/shop-now---high-performance-ported-cylinders.html
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Yeah I saw those, I'm actually really thinking about it because I just got a 19mm carb. Their 9hp motors use 25mm carbs (persoanlly I think its unneccesarily huge for these motors) but the extra size of the reeds/manifold would definitely help! For sure, if you can spare the money, I think it'd be well worth it.
How did you port those so big though? how long did it take? I've got my exhaust ported to 178 degrees, but I would like to reshape the transfers and widen the exhaust and my 1/4" dremel cutter would take hours upon hours to do that.
How did you port those so big though? how long did it take? I've got my exhaust ported to 178 degrees, but I would like to reshape the transfers and widen the exhaust and my 1/4" dremel cutter would take hours upon hours to do that.
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i used a carbide double cutter sphere bit 6$ ea. on ebay and removes materiel in a hurry! I also bought a set assortment of dremel high speed cutters on ebay for like $15 there small and can get in the tight places with no problem, keep in mind the highspeed cutters need a smaller chuck in your dremel than the double cutters.
All together took me a couple hrs taking my sweet time.
How did you measure the degrees? i advanced the exhaust a little, but would be interesting to know what degrees.
All together took me a couple hrs taking my sweet time.
How did you measure the degrees? i advanced the exhaust a little, but would be interesting to know what degrees.
It's based on stroke, rod length, and deck height, as well as how far down your ports are (the more accurate the better, I measured to 0.01mm), but here is where I measured it http://lambretta-images.com/archive/porttiming.php#.Ue3Gldw0jDo