Is there any other piston that will work with this engine?

[mrfubs]

Hello all!

Im just ceriouse if anyone has seen or had experience with any other pistons that will work in these engines. The reason i ask is because the thickness and the materiel the piston rings are made reduce the engines cylinder wall life by far as apposed to skinnier nickasil plated rings like a dirtbike.

 

[mrfubs]

if anyone has the engine with the lower piston wrist pin hole you might want to look into this piston. Thinner piston rings that are coated, that alone will improve the longevity of the engine.

http://www.partsforscooters.com/169-188_Piston_Ring_Set

 

[mew905]

EDIT: I just saw the dimensions I needed on the page for the piston

The 49cc has a replacement piston available from the Honda Hobbit scooter.

those pistons would work, but it would set the piston 1mm lower than normal, so you'd have to use a thin base gasket (stock ones are around 1mm thick, getting some gasket paper from Part Source you can get some really thin stuff for $5) so as to not upset your timings (HOWEVER from what I've seen, you should really just lathe 1mm off the head mating surface, as the transfers are 1-2mm too LOW for the stock piston). You could also trim 2mm from the skirt so it clears the crank or to reduce weight (because it sits 1mm lower and the skirt is 1mm longer)

 

[mrfubs]

I didn't even think of the fact that if the piston is ran in a non reed engine that on the combustion stroke a lot of the intake charge will be blown through the intake with out reeds to stop it, other wise seems like a good idea to me.

Unfortunately that is the only piston iv been able to find with a similar wrist pin diameter and overall dimensions with piston rings that are made for a plated cylinder unlike the steel ones we have.

 

[mrfubs]

heres another piston to be looked into

http://www.scooterpartsexpress.com/piston-ring-set-47mm-big-bore-jog-minarelli-50cc

 

[mew905]

Minarelli is the same people who made the first piston you listed, however there's no information on how far down the wrist pin hole is. Otherwise it would fit. The first one you posted, however, is perfect for our application, we'd have to cut 1mm off the skirt (no big deal) and shave the head mating surface of the jug slightly to gain back compression, but it should work wonderfully with any type D motor (essentially anything but the Grubees)

 

[mrfubs]

I believe the crank from bike berry the one with removable weights uses the piston with the lower wrist pin hole. I might go that route if I can't find a piston with the wrist pin hole Twords the middle. I believe those plated rings will extend the life of the cylinder and rings by double.
My yz250 piston rings are half the thickness as ours

 

[mew905]

yeah, each ring on ours is 2mm, they *should* be 1mm and be just as effective (and smaller ring gap). so 2x 1mm rings should act like running a single ring on our motors, reducing wear and such. I'm definitely interested and may try that first piston you listed.

 

[mrfubs]

If you do try out let me know your results like if you had to cut a bunch off the top or so. The wrist pin hole is labeled 25mm from the top of the piston that's 1 inch, my wrist pin hole is like .8 of a inch from the top of the piston.

 

[mrfubs]

yeah, each ring on ours is 2mm, they *should* be 1mm and be just as effective (and smaller ring gap). so 2x 1mm rings should act like running a single ring on our motors, reducing wear and such. I'm definitely interested and may try that first piston you listed.

i just noticed the second piston i linked uses a 12mm wrist pin so X that one out.

 

[mew905]

i just noticed the first piston i linked uses a 12mm wrist pin so X that one out.

It says you can order it in a 10mm flavor, so it's not impossible yet The question is if that 25mm distance is of the 12mm variety or not. who knows, the 10mm could be 26mm from the crown (to wrist pin center, which will match the Type D motor exactly)

 

[mrfubs]

Awesome! And I think your right about it being probably being 26mm from the crown looks like I might be buying a different crank to make this setup work! I have to much time into my cylinder to let it wear out so quickly.

Or it would be awesome to have a custom piston made but I have no idea what that will cost

 

[mew905]

Awesome! And I think your right about it being probably being 26mm from the crown looks like I might be buying a different crank to make this setup work! I have to much time into my cylinder to let it wear out so quickly.

Or it would be awesome to have a custom piston made but I have no idea what that will cost

I think the closest people have come to custom pistons is the coated pistons someone offered here a while back. I would have got one myself but Paypal and I have issues haha, apparently they ran pretty slick. I have measured and weighed our pistons for jag so he can give recommendations as per the 66cc (his whole site was about the 49-60cc previously). The "Type D" motor (to my knowledge, every motor except the grubees) has a wrist pin 26mm crown to center, which should work perfectly. The grubees wrist pin is 21mm crown to center, so if you have one of them (like myself) then you'll need to replace the crank. However if you check out my piston, its so cut up it may as well be custom

 

[mrfubs]

holy big window hahah my window is like 1/4 that size, i noticed you drilled a hole next to the wrist pin is that for weight reduction? i was thinking about drilling 2 holes right above the wrist pin hole so when the piston is going into the compression stroke the transfers will blow a little mixture through the holes and help lube that wrist pin.

what did you notice off doing that big of a window as well?

Iv been searching for just 47mm piston rings to see if maybe i can rig some better rings on it instead of buying a new crank just to use a piston for the rings it uses. A iron crank from bikeberry is $17 now and the weights are like $4.80 a peice so all said and done $36 shipped.

i wonder if theres some sort of spacer that can be rigged where the rings sit to take up 1mm of space so that if i go with normal 1mm thickness rings they wont be flopping around to much

 

[mew905]

holy big window hahah my window is like 1/4 that size, i noticed you drilled a hole next to the wrist pin is that for weight reduction? i was thinking about drilling 2 holes right above the wrist pin hole so when the piston is going into the compression stroke the transfers will blow a little mixture through the holes and help lube that wrist pin.

what did you notice off doing that big of a window as well?

yeah I know its a huge window haha, I marked out the width of the intake port and made the window to match, I added an extra window above it (as you can tell, its more of a slot) because at BDC my window was still completely closed. Those holes in the side are for weight reduction as well. Most of the rings you'll find will be 1mm, ours uses 2mm, so you're better off just buying the new piston. I've been looking for compatible cranks and cylinders as well but thusfar no luck. It's a great find on the piston though, however I'm a bit wary on the weight, Amazon.com has them listed as well, and while it doesnt list the weight, the other 47mm piston kits seem to have a consensus of 4.8 oz (about 140 grams), which is 30 grams heavier than ours (silicon and other additives to make the piston stronger and more slippery, also make it heavier) I'll have to weigh this other one but apparently Hoca is a chinese copy of the Minarelli motor, at least from what I gather on other sites (they keep mentioning chinese companies on it), which means that it *may* be no better than our little pistons.

My piston assembly now weighs 97.3g, just shy of 13g lighter than a stock 66cc piston. I'm getting a titanium wrist pin as well from here for a further reduction of 8.5g, for a total weight of 88.8g

As for what I've noticed? performance wise, nothing, my motor doesnt produce the bang I need to go past 7200 RPM (~61kph) on its own yet. However the vibrations... oh god the vibrations, so smooth. Normally when you put a mirror on your bike with long arms like mine (the $5 mirrors from Canadian Tire) it vibrates so much you cant even make out shapes, just colors and lights. Mine runs so smooth I can make out what kind of car is behind me.

 

[mrfubs]

nice nice thats awesome you have no vibs at that rpm, What are you using to determine the rpm? the meter i have i dont think is exactly right because the highest it got was 4180rpm and it sure sounded at least 7-8000.

Theres a few more pros on using that hoca piston over ours, 1st it is casted and iv always been a fan and ran casted pistons in my dirtbike, its the best for the cyl wall and ect.. although yes the silicon makes the alloy less frictional at the same time will brittle the alloy so it would more likey shatter than bend on a major failure 2nd a casted piston with thinner/plated rings will agree more with the chrome based cylinder plating, i believe our rings are best suited for a cast iron sleeve.

I dont believe the weight will be a big issue there may be torque gains from the extra weight and or more vibs but all you gotta do is drill more materiel off the crank That and the lenght of the Hoca piston from the skirt to crown is 48mm ours is i believe 45ish?

so at the end of the day $36 for new crank assy. $35.53 for piston $71.53 said and done for a improved longevity engine that may run cooler from less ring/piston friction and may run/rev higher easier.

iv got $570+ into my whole deal lol so it might take a couple weeks before i talk my self into doing this.

Heres a Hoca looking piston on ebay for quite a bit cheaper i just emailed for specs

 

[mrfubs]

so right off the bat you have to cut like 3mm off the skirt so it doesn't smash against the crank on the combustion stroke that will trim some weight off the whole deal right there.

 

[mrfubs]

. Delete .

 

[mew905]

so right off the bat you have to cut like 3mm off the skirt so it doesn't smash against the crank on the combustion stroke that will trim some weight off the whole deal right there.

if its the first piston you linked to, if either 10mm or 12mm are both 25mm from the crown (I have a feeling thats the 12mm version, the 10mm *could* be in a different spot). Assuming its 25mm from the crown for the 10mm version, then you only need to cut off 1mm of the skirt... maybe.

 

[mrfubs]

what do you think about just running 1 piston ring?