Still on the first tank and it's already pulling hard past my old top speed with a stock engine...
Maniac57's ported 66cc
- Thread starter maniac57
- Start date
Ported and polished monster.
Nice! Dang, when that thing gets broke in good, you're gonna have to join the 40mph club.
Nice! Dang, when that thing gets broke in good, you're gonna have to join the 40mph club.
Is the engine on that bike one of the song-top engines?Still on the first tank and it's already pulling hard past my old top speed with a stock engine...
sounds purdy good
Nope. Just a generic Rose motor as far as I know...
Nothing special inside.....except the porting!
All I know is I love the nice wide fat mid range and it has substantially less four stroking with the piston ramped for better transfer flow...made a HUGE difference.
Nothing special inside.....except the porting!
All I know is I love the nice wide fat mid range and it has substantially less four stroking with the piston ramped for better transfer flow...made a HUGE difference.
Yeah I know your not the one with th song-top engine so again sorry about that question in the previous post...my bad brother.
But, I do want to comment on the piston ramping if you dont mind.
I have put several of these 66cc engines together over the last 5 years, not nearly as many as you have or several others on here, but what I have found is that every single time I have ramped the piston a little on the transfers and exhaust side, Iend up with a better running engine, all of my fastest engines have had pistons with a little ramping to get the air fuel mix in a bit quicker and get the exhaust out a bit quicker.
I know there are members who are very knowledgable about these engines who caution against piston ramps, but along with good clean ports the piston ramping has been one of the most noticeable performance improvements I have seen on an6 of my engines.
I do think if the jug itself offer ideal port timing the ramping can be more harmful to lower end performance, but if the jug has really low transfers and the piston lacks a lot opening the exhaust port @ BDC, I think ramps to help open the transfers a little quicker and just more overall @ BDC and doing the same on the exhaust is a big improvement on those low port jugs.
I have some jugs that basically just rack the transfers open when piston is a@BDC, no way that engine can rev much with that set up.
Raising the jug with an extra base gaske5 cqn help this issue but when you do that yourslowing the intake timing down some also.
Y3s piston ramps do affect final compression, but all the compression that is possible is useless if timing is off and you cant get an ideal charge of fuel/air into the combustion chamber.
I think the trick on these poorly designed engines is to find that sweet spot where you get good fuel charge at the right time and then have a good enough compression ratio to take advantage of the mix in combustion.
I dont claim to have to formula and some that due will not share it, but I do know what has worked best for me on my engines and ramping the piston when using a jug that only opens the tranfers about 50% at BDC seems to be a good performance boost for more rpm potential if all else is done right, well tuned carb, good flowing exhaust etc.
The GT5 engine I just got running a couple weeks ago is a prime example, the Fred piston I put in it is allowing it to rev to about 9000rpm running a standard NT carb, slighly modified kit pipe and a Pedal Chopper head that isnt giving me n3arly the compression I can get from a Puch, Fred Head or the Jakes Diamond head I have.
That engine only has about 60-70 miles on it and I've done 42mph with a 41T sprocket.
I do think the jug needs to be milled to its optimal height especially when a ramped piston is being used, which I did on my GT5, I checked the squish to be @ .025 this isnt as tight as it can be but I decided to leave it there since I will likely change the head and Im not sure where it will be then and I didnt want to go to far with it if possible since initially I just wanted to get this engine running to see what the balance of it would be, it just happens to be very good so I'll do some building up from here to find out what I can get it to do.
By the way maniac, the GT5 Im running that Im so impressed with came from rose326a according to what I was told by the member here I got it from, the magneto that went out n it was stamped 2012 so its a ouple year old model but it has a very smooth running crank, every bit as smooth as any of my 40mm stroke dax lowers.
But, I do want to comment on the piston ramping if you dont mind.
I have put several of these 66cc engines together over the last 5 years, not nearly as many as you have or several others on here, but what I have found is that every single time I have ramped the piston a little on the transfers and exhaust side, Iend up with a better running engine, all of my fastest engines have had pistons with a little ramping to get the air fuel mix in a bit quicker and get the exhaust out a bit quicker.
I know there are members who are very knowledgable about these engines who caution against piston ramps, but along with good clean ports the piston ramping has been one of the most noticeable performance improvements I have seen on an6 of my engines.
I do think if the jug itself offer ideal port timing the ramping can be more harmful to lower end performance, but if the jug has really low transfers and the piston lacks a lot opening the exhaust port @ BDC, I think ramps to help open the transfers a little quicker and just more overall @ BDC and doing the same on the exhaust is a big improvement on those low port jugs.
I have some jugs that basically just rack the transfers open when piston is a@BDC, no way that engine can rev much with that set up.
Raising the jug with an extra base gaske5 cqn help this issue but when you do that yourslowing the intake timing down some also.
Y3s piston ramps do affect final compression, but all the compression that is possible is useless if timing is off and you cant get an ideal charge of fuel/air into the combustion chamber.
I think the trick on these poorly designed engines is to find that sweet spot where you get good fuel charge at the right time and then have a good enough compression ratio to take advantage of the mix in combustion.
I dont claim to have to formula and some that due will not share it, but I do know what has worked best for me on my engines and ramping the piston when using a jug that only opens the tranfers about 50% at BDC seems to be a good performance boost for more rpm potential if all else is done right, well tuned carb, good flowing exhaust etc.
The GT5 engine I just got running a couple weeks ago is a prime example, the Fred piston I put in it is allowing it to rev to about 9000rpm running a standard NT carb, slighly modified kit pipe and a Pedal Chopper head that isnt giving me n3arly the compression I can get from a Puch, Fred Head or the Jakes Diamond head I have.
That engine only has about 60-70 miles on it and I've done 42mph with a 41T sprocket.
I do think the jug needs to be milled to its optimal height especially when a ramped piston is being used, which I did on my GT5, I checked the squish to be @ .025 this isnt as tight as it can be but I decided to leave it there since I will likely change the head and Im not sure where it will be then and I didnt want to go to far with it if possible since initially I just wanted to get this engine running to see what the balance of it would be, it just happens to be very good so I'll do some building up from here to find out what I can get it to do.
By the way maniac, the GT5 Im running that Im so impressed with came from rose326a according to what I was told by the member here I got it from, the magneto that went out n it was stamped 2012 so its a ouple year old model but it has a very smooth running crank, every bit as smooth as any of my 40mm stroke dax lowers.
All I know is I have been ramping pistons for decades and I have always liked the effect it has on the chinadolls. All the material removed should have a beneficial effect on balance as well as improving flow, ESPECIALLY with "eyebrow" transfers.It's about the ONLY way to really get those tiny jacked up things to flow on a stock block and jug. I really don't think the lost comp matters.
I simply do not have the tools needed to set port timing correctly with deck height by milling or spacing the jugs. It's a good way to work with what you have.
So far, I have not felt any loss of overall performance due to lower compression. The better flow MORE than makes up for any losses.
And so far, even this radically ramped piston is doing fine.
Honestly I think the help aiming the transfer flow is actually having as much effect as the larger & earlier opening ports if the incredible improvement in four-stroking is any guide. It's almost a bigger improvement in how my bike feels than the gained power!
This engine literally almost feels like a Japanese reed valved motor, it's THAT much smoother running and happy feeling. Clearly there is a large improvement in filling the chamber with fresh charge as probably 85% of chinadoll four stroking is due to intake contamination and poor scavenging. Think I'm wrong and that it all in the jetting? Well mine had a PERFECTLY jetted sha flatslide BEFORE the transfer mods and still four stroked like a china motor. Especially at steady cruise.
ALL the improvement was due to porting rather than the better carb.
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those are some huge ramps maniac, much larger than I have done to mine but if it works, it works...
I haven't done the 60mph top speed like a hand full of others have accomplished and honestly have no desire to go that fast on one of my bikes, but I took dax lower, put a jug on it that wasnt one that has the larger ports, I enlarger the intake and exhaust some, I cleaned up the transfers and polished the inside of them best I could with the tools I had to work with, only other mod was done to piston, 12 holes drilled in it and ramps at transfers and exhaust port area.
That was the engine I set my personal goal to hit or break 50mph with, since I built my first bike that was something I had in the back of my mind as a potential goal and the better balanced dax lower along with the mild port work and piston moods such as ramping is what allowed me to achieve my goal.
I know for a fact if I hadn't ramped that piston for quicker port timing I would not have achieved my goal with that engine.
I haven't done the 60mph top speed like a hand full of others have accomplished and honestly have no desire to go that fast on one of my bikes, but I took dax lower, put a jug on it that wasnt one that has the larger ports, I enlarger the intake and exhaust some, I cleaned up the transfers and polished the inside of them best I could with the tools I had to work with, only other mod was done to piston, 12 holes drilled in it and ramps at transfers and exhaust port area.
That was the engine I set my personal goal to hit or break 50mph with, since I built my first bike that was something I had in the back of my mind as a potential goal and the better balanced dax lower along with the mild port work and piston moods such as ramping is what allowed me to achieve my goal.
I know for a fact if I hadn't ramped that piston for quicker port timing I would not have achieved my goal with that engine.
I mostly did it this radically intentionally to show that the naysayers claiming piston failures would result from thinning the crown were wrong.
Also goes to show the loss of compression is minor and easily overcome by the better flow.
The main thing I have found to making this work reliably is to not get too close to the ring groove. Weakening the piston land above the ring too much can lead to it collapsing and pinning the ring, which WILL lead to failure. I always leave at least 1/16th or so above top ring for safety.
And be careful how far from the edge you go ramping, as the piston crown is thicker near the edges.
Also goes to show the loss of compression is minor and easily overcome by the better flow.
The main thing I have found to making this work reliably is to not get too close to the ring groove. Weakening the piston land above the ring too much can lead to it collapsing and pinning the ring, which WILL lead to failure. I always leave at least 1/16th or so above top ring for safety.
And be careful how far from the edge you go ramping, as the piston crown is thicker near the edges.
only issue i have had with one piston was drilling holes a little to close to the thinner part of the skirt and piston cracked between two holes, wont make that mistake again.
never any trouble with ramping top edge of my piston only consequence I've experienced so far has been better performance.
never any trouble with ramping top edge of my piston only consequence I've experienced so far has been better performance.
Still running great after break in! Speedo battery died but last observed top speed was well about 38 which is by FAR the fastest I have pushed ANY of my chinadolls.
If those ramps were going to cause problems, they would have failed when I was holding it wide open for three blocks I'm thinking....
So far I'm calling this proof ramping works without reliability issues.
If those ramps were going to cause problems, they would have failed when I was holding it wide open for three blocks I'm thinking....
So far I'm calling this proof ramping works without reliability issues.
Oh yeah, the piston ramping works just fine, my ole Kulalna moon dog bike has a dax engine that has piston ramped and serious port enlargement, cruises for miles and miles at WOT mid 40s MPH.
It only has about 500miles on it now but most of them are at really high rpms for multiple mile trips and much of it in really Hot Texas summer conditions, it has good power for pulling me up all the local hills and good top speed power with a 34T sprocket.
Ramping is especially helpful when the jug being used has lower than idea tranfers, just use two base gaskets, ramp piston a bit and lower intake port and 1mm and the engine will run so much better in the medium to upper rpm capability of that engine.
It only has about 500miles on it now but most of them are at really high rpms for multiple mile trips and much of it in really Hot Texas summer conditions, it has good power for pulling me up all the local hills and good top speed power with a 34T sprocket.
Ramping is especially helpful when the jug being used has lower than idea tranfers, just use two base gaskets, ramp piston a bit and lower intake port and 1mm and the engine will run so much better in the medium to upper rpm capability of that engine.
Mine wants to rev out farther than I can stand the buzzing, so considering it would top out before I did prior to the mods Ima call this one a big ol win.
I don't really care how fast it will go. I love the nice fat midrange and good low end pull.
I don't really care how fast it will go. I love the nice fat midrange and good low end pull.
The main problem I am having is the fact that I have another engine with more aggressively ported jug waiting for testing, and I seem to be wringing this one out MUCH harder than I normally run a doll.
I think my subconscious WANTS to blow it up so I'll have a good excuse to slap in the next one!
Also have that sweet little NanTong JaiLi with the same type of midrange porting job waiting for some loving.
After all, it's NOT like this is the first two smoker I have ported....just the first CHINADOLL.
I've been porting since the late 70's when I ported my very first engine, a Honda FL250 Odyssy. A good friend walked me through it and MAN did that motor wake up! Went from a tame bounce around tiddler to a rip snorting, tire spinning MONSTER with nothing but some time and a top end gasket set.
Been hooked ever since!
I think my subconscious WANTS to blow it up so I'll have a good excuse to slap in the next one!
Also have that sweet little NanTong JaiLi with the same type of midrange porting job waiting for some loving.
After all, it's NOT like this is the first two smoker I have ported....just the first CHINADOLL.
I've been porting since the late 70's when I ported my very first engine, a Honda FL250 Odyssy. A good friend walked me through it and MAN did that motor wake up! Went from a tame bounce around tiddler to a rip snorting, tire spinning MONSTER with nothing but some time and a top end gasket set.
Been hooked ever since!
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