3rd transfer is done, same height as others, although I have herd of opening it a fraction earlier, this is not my ideal jug, as it is the smaller port variety, but I think I've managed to get the exhaust port big enough, just.
Building a Ht Motorized Bicycle or Three.
- Thread starter Theon
- Start date
That setup looks great!!
The longer petals will give you a little more on the low end but may become unstable and flutter at higher rpms... You can beat that problem by cutting a second set of petals and extending them about half the way to the end of your reed block. I've seen this work, then fine tune by narrowing the top reed petal if it's too stiff... You can also run it with a hole in the first petal so it'll only use the top petal at lower rpm but both layers will open at higher rpm... There's a lot of room to experiment here with thicker or thinner petals, one layer or 2, hole in the bottom petal, or tapering the top petal etc, etc, etc... You can also try fiberglass or carbon fiber, or a combination of both, and sometimes metal reed petals work good, but they can ruin your engine if one ever breaks off.
The longer petals will give you a little more on the low end but may become unstable and flutter at higher rpms... You can beat that problem by cutting a second set of petals and extending them about half the way to the end of your reed block. I've seen this work, then fine tune by narrowing the top reed petal if it's too stiff... You can also run it with a hole in the first petal so it'll only use the top petal at lower rpm but both layers will open at higher rpm... There's a lot of room to experiment here with thicker or thinner petals, one layer or 2, hole in the bottom petal, or tapering the top petal etc, etc, etc... You can also try fiberglass or carbon fiber, or a combination of both, and sometimes metal reed petals work good, but they can ruin your engine if one ever breaks off.
Nice job on the third transfer, it's hard to see in the pic but is it angled steeper to help direct the fuel/air up to the top of the chamber or does it shoot it more straight out?
Dave even with the limited milling ability of your lathe, wouldn't be hard to do that way,
I did a lot of filing!
but it is a lot easier to take too much with the mill.
This RSE reed block does come up nice, but I think your GT60 block will also work.
If I had a mill I would have recessed the block mounting flange into the cases a little, but you would need to make a jig to hold the cases.
I'm going to RSE tomorrow to get another block, if anyone wants one?
Didn't ask the price, but prepared to pay $40. As I have modified this one and need another now for the Goat.
I did a lot of filing!
but it is a lot easier to take too much with the mill.
This RSE reed block does come up nice, but I think your GT60 block will also work.
If I had a mill I would have recessed the block mounting flange into the cases a little, but you would need to make a jig to hold the cases.
I'm going to RSE tomorrow to get another block, if anyone wants one?
Didn't ask the price, but prepared to pay $40. As I have modified this one and need another now for the Goat.
I usually don't measure my milimeters when setting up port timing, but I do use a degree wheel with a dial indicator to ensure TDC is right at my zero mark on the wheel. The way I do it is by bringing the piston to TDC, then setting my pointer to the zero mark on the wheel, then I rock the crank in both directions and see where the pointer is pointing when the piston goes down .001", with these small engines it'll usually move about 3 degrees in each direction by the time the piston drops .001" so once it's fine tuned I can read where I just start to see the port and record my degrees.way to goru planning on turning the now deleted inlet to a transfer somehow?
i went 1mm higher .95" from atdc. a little narrower than last time by about .1"
that will give me a new muse. i guess its at around 170- 180 degrees off the top of my head. gt5a block w gt5 cyl again. its not much wider than stock the way it sits now.
This is just the opening event and not the actual duration, there's a simple formula for the duration which is to subtract your reading from 180, then multiply that number by 2 and that's your duration.
With the engine I just set up, the port timings are as follows...
Intake duration is 128
Exhaust is 168
Transfers are 130
This is a piston port engine and that's why the short intake duration, with a reed valve, the intake can be much higher, or you could even set it to 180 and it would still run great. This is pretty much as high in duration you would want for a piston port engine before it becomes too peaky with the powerband.
Here's a simple port timing calculator that can give you your timings with milimeters, this method works great when doing port maps or using a dial indicator
Have a 'Black widow' kit for a pocket dike, easy to copy, have a 110mm x 110mm sheet of carbon .35mm Polini reed. Will do a little experimenting.
The third transfer is rather flat on the roof, roof angle is an interesting subject, I think it probably does need a little more angle,
I've read flatter transfer roof for higher compression.
I do plan to run high compression.
what angle do you suggest for the transfers?
The third transfer is rather flat on the roof, roof angle is an interesting subject, I think it probably does need a little more angle,
I've read flatter transfer roof for higher compression.
I do plan to run high compression.
what angle do you suggest for the transfers?
I can mill some smaller parts on the lathe, but setup time takes forever, I guess I could mil that area with the lathe but it would literally take hours to do each side because of the setup time. I'd use a die grinder and some carbide rotary files to get it cut to the basic shape, then switch to smaller finer rotary files, and maybe even switch to a pencil grinder with the diamond burrs for the really critical or fragile stuff.
That must be nice to be able to go to RSE's shop and pick up parts like that, over here we have to buy the whole reed kit just to get the block, stuff like that I'll get some aluminum bar stock and spend the time to cut my own, I could easily make that reed block with the lathe in a few hours... IF I ever get a small mill i could cut that time way down, but I'm still working out a deal to buy this auto shop so I can't spend any big money right now...
That must be nice to be able to go to RSE's shop and pick up parts like that, over here we have to buy the whole reed kit just to get the block, stuff like that I'll get some aluminum bar stock and spend the time to cut my own, I could easily make that reed block with the lathe in a few hours... IF I ever get a small mill i could cut that time way down, but I'm still working out a deal to buy this auto shop so I can't spend any big money right now...
The inlet timing on piston port is very important, very few kits have this right, the transfer and exhaust are often reasonable.
But simply trimming the piston skirt to the opening will unlikely to be correct. This aimed at any noobs that might be reading, but there is no real reason to short cut.
A squish test using solder with a little patience will find you TDC.
A degree wheel only needs to be a $1 protractor from the news agent.
Despite others 'luck' in getting 45MPH from there engine without checking port timing and squish, it aint that hard!
And is going to guarantee results.
And yes Dave is right 128 is the most you would want, For most HT motors closer to 120 is better, or so I've read.
It's good to see professionals like Dave here offering advice, most are to busy.
Cheers Dave.
But simply trimming the piston skirt to the opening will unlikely to be correct. This aimed at any noobs that might be reading, but there is no real reason to short cut.
A squish test using solder with a little patience will find you TDC.
A degree wheel only needs to be a $1 protractor from the news agent.
Despite others 'luck' in getting 45MPH from there engine without checking port timing and squish, it aint that hard!
And is going to guarantee results.
And yes Dave is right 128 is the most you would want, For most HT motors closer to 120 is better, or so I've read.
It's good to see professionals like Dave here offering advice, most are to busy.
Cheers Dave.
I'm thinking you'll be ok with your third port aimed flat into the cylinder since you're running an expansion chamber that'll push any air/fuel charge that may escape out the exhaust port back in. Without an expansion chamber it would probably be better to point that port up toward the center of the combustion chamber to help prevent short circuiting and initiate the air fuel mix into the loop pattern.
Thanks Theon,
Actually I'm really pushing my luck with 128 intake duration on a piston port engine, I was going to leave it a lot closer to 120 but it seemed to work ok with my last build, it would take off from a dead stop without needing to pedal but had no power going up a mild hill at low speed, but once it got over about 3000 rpm it started to come on strong enough to work ok, and over 4000 rpm it came on really strong.
And my degree wheel... it's printed off an internet picture, then glued to a plastic disc that I cut out... the pointer is a piece of scrap aluminum I cut to shape and put a bolt thru... nothing fancy, fancy is definitely not needed here...
Actually I'm really pushing my luck with 128 intake duration on a piston port engine, I was going to leave it a lot closer to 120 but it seemed to work ok with my last build, it would take off from a dead stop without needing to pedal but had no power going up a mild hill at low speed, but once it got over about 3000 rpm it started to come on strong enough to work ok, and over 4000 rpm it came on really strong.
And my degree wheel... it's printed off an internet picture, then glued to a plastic disc that I cut out... the pointer is a piece of scrap aluminum I cut to shape and put a bolt thru... nothing fancy, fancy is definitely not needed here...
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Similar boat Dave,
And would love to be opening a shop with the money I have for a Shed.
I don't want to be bringing work home, it has it's advantages but also it's problems.
Also easier to justify charging properly.
But my carpenter mate has not shown.
I need to put some time to this my self.
It's so much easier to get motivated when you have someone else with a similar goal.
And would love to be opening a shop with the money I have for a Shed.
I don't want to be bringing work home, it has it's advantages but also it's problems.
Also easier to justify charging properly.
But my carpenter mate has not shown.
I need to put some time to this my self.
It's so much easier to get motivated when you have someone else with a similar goal.
I know how that goes, I've had a few freinds ask if they could go in with me but I really didn't want 2 sets of opinions trying to run a business so I decided to go in at it alone. i had a deal set up and would have been opening up last week, but the guy I was going to rent the shop from ended up selling it to another person who paid cash for the whole shop. Right now I got a really good chance to buy this other business that's already established and the guy just simply wants out because he lives about 300 miles away and can't run it from there.
I'll find out, hopefully this week if they are going to go for my offer.
it's just not fun right now having the money in the bank but can't touch it because it's going to be needed to open up a shop, especially when I'm pretty much used to buying what I want when I want etc... lol
I'll find out, hopefully this week if they are going to go for my offer.
it's just not fun right now having the money in the bank but can't touch it because it's going to be needed to open up a shop, especially when I'm pretty much used to buying what I want when I want etc... lol
my measuring calipers are a familly heirloom to me. people get really silly thinking that they know whats best in porting. getting all specific gets you NOWHERE when the next engine has a different exhaust etc/ like i own 5 pipes going on 6 and they each have there own merrit.
my degree wheel is for every other engine. besides i prefer calipers accurate to .001 not graham bells monkey wheel. i save the monkey wheel for real engine work
besides i dont have to be specific about singular degrees if it cannot compute widthes.
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theon if that is still apart and the blowdown is good then please consider .05" or 1+mm raised 3rd. mine was great.
my degree wheel is for every other engine. besides i prefer calipers accurate to .001 not graham bells monkey wheel. i save the monkey wheel for real engine work
besides i dont have to be specific about singular degrees if it cannot compute widthes.
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theon if that is still apart and the blowdown is good then please consider .05" or 1+mm raised 3rd. mine was great.
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3rd even w t trans equals midrange and drive up rpm. top end will be flatter and be doing more duty as in be rougher at max rpm.
if u raise 3rd the top end will be smoother by removing the double duty such as less transfer pushing at once w ex opened. go 3mm if u want to
perhaps this is more directed at boost port but you can fill in the blanks.
if u raise 3rd the top end will be smoother by removing the double duty such as less transfer pushing at once w ex opened. go 3mm if u want to
perhaps this is more directed at boost port but you can fill in the blanks.
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it is reasonable to think that any port depending on equal psi/ that each port has its own blowdown. stacking more in th same place will only put the power there leaving more deficiency below and above as the jetting gets worse still to manage.
zero off that info is in degrees or w a degree wheel people lol
degree wheel is just a tool. im not building stroked motors from scratchnor do i have to do any valve timing. please explain to me how a degree wheel is going to give u answers like i just offered??????? did u need a d.wheel? no.
most cant get past the starting line of understanding one anyway. .95 inches is .95 inches. do u get accuracy of .001 w a dwheel. no
anyway coffee time.
zero off that info is in degrees or w a degree wheel people lol
degree wheel is just a tool. im not building stroked motors from scratchnor do i have to do any valve timing. please explain to me how a degree wheel is going to give u answers like i just offered??????? did u need a d.wheel? no.
most cant get past the starting line of understanding one anyway. .95 inches is .95 inches. do u get accuracy of .001 w a dwheel. no
anyway coffee time.
Exhaust flow should be good, KTM pipe is suppose to give 9HP on a KTM 50?
I agree on lifting 3rd Transfer port a little, and also giving a little more angle to the roof,
I like the degree wheel, as I find it easier to think in Deg than linear measurements in a non linear stroke.
I was thinking to start with reasonably conservative port timings, and slowly raise ports as I test what works for this motor as everything about this motor is new to me, and I'm not sure what to expect.
Will be upgrading the barrel once I find what works best.
This motor will take only a few minutes to swap barrels, with case mounted carb, slip joint exhaust and plenty of room in the frame.
Getting primary compression up will be my next step, was considering getting another RSE crank for it today, but Tony said he's out till his order comes and will likely be 4 weeks.
A bit of a hassel, as I like the RSE crank, and it will need different case stuffers than the crank I have, still plenty to go on with here.
And will be getting the final pieces to the Goat today, which I would like to strip the bike and paint the frame now that the weather is starting to improve here.
Once the Goat is done, I'll start playing with my trikes again.
I agree on lifting 3rd Transfer port a little, and also giving a little more angle to the roof,
I like the degree wheel, as I find it easier to think in Deg than linear measurements in a non linear stroke.
I was thinking to start with reasonably conservative port timings, and slowly raise ports as I test what works for this motor as everything about this motor is new to me, and I'm not sure what to expect.
Will be upgrading the barrel once I find what works best.
This motor will take only a few minutes to swap barrels, with case mounted carb, slip joint exhaust and plenty of room in the frame.
Getting primary compression up will be my next step, was considering getting another RSE crank for it today, but Tony said he's out till his order comes and will likely be 4 weeks.
A bit of a hassel, as I like the RSE crank, and it will need different case stuffers than the crank I have, still plenty to go on with here.
And will be getting the final pieces to the Goat today, which I would like to strip the bike and paint the frame now that the weather is starting to improve here.
Once the Goat is done, I'll start playing with my trikes again.