Pocketbike Forum banner

41 - 60 of 60 Posts

Super Moderator
Joined
2,456 Posts
Don't get me wrong you want to get the exhaust gases out but it's more important to worry about the pressure waves that keep the fuel charge from going out the exhaust

That's what you're paying for when you buy a high-end exhaust is the time it took somebody to calculate it all out so that it controls the pressure waves extremely well

If you open up the exhaust port too far and the pressure wave is not strong enough to hold the fuel charge in while the Piston is coming back up you're only losing power...
 

Super Moderator
Joined
2,456 Posts
Not small port or giant wide mouth port but the proper size ports is the key to making 馃

what you do as you grab an old cylinder port the transfers out exactly the same as a cylinder you're going to use

Start opening up the exhaust Port until it loses RPMs!

I'm pretty sure you guys will end up with the same thing slightly wider and raised just a tiny bit

I'm pretty sure a giant wide mouth Port is going to be more for alcohol based race fuel where it takes double the amount of fuel...
 

Banned
Joined
406 Posts
At what point did anybody talk about giant mouth exhaust ports? Most of the talk is mild porting of the exhaust port and a couple around here seem to think that that is a lot of porting. And what do you know about pressure waves Mr moderator?
 

Super Moderator
Joined
2,456 Posts
If you want your engine to turn 9,000 to 10,000 rpms you need a bigger canted exhaust port or and plenty of porting. I put ramps on top of my piston for exhaust and 2 side ports it push the mixture up. This cyld works very well. you need to lighten everything.
This is excessively large the picture on cams profile is more like what you want...

This one was probably built for race fuel
 

Attachments

Banned
Joined
21,744 Posts
This is excessively large the picture on cams profile is more like what you want...

This one was probably built for race fuel

IMHO you sound excessively deficient in knowing how everything works as far as exhaust port shapes n sizes and whats quite sad is you have no clue which raises the question of if this is a pocketbike forum and your a mod maybe you should just do the job you wanted instead of throwing blanket statements as you judge the size of the area of the size of the end of the port and not where it really matters which is at the cylinder where the piston and port meet and do you know how thats calculated...?

Its called using a degree wheel then you take those calculations and you put the lil numbers in whats called an exhaust port duration calculator but without real numbers you'll get whats called fairytail statistics which coincide with blanket statements which coincides with fictional facts which are not cool coming from a mod of a forum designed to educate IMHO..LOL....LOL...

After youve successfully modified as many engines as me which you will never ever do not even in a thousand years nor will you ever sucessfully ever setup and use a degree wheel in your life IMHO can you make statements as per the type of porting the cylinder has without knowing the #'s I s........LOL

Oh and Im quite impressed[not]you can tell by that picture how much compression that cylinder was built for and the squishband its gonna be set at...I dont think you do but I know who will know those facts quite soon as it hasnt even been built yet but that pic you posted doesnt look all too much different than a stock oldschool cylinder...LOL.....

Whats funny is you look at the shape and say thats for race gas meanwhile if you actually knew how to build performance 2 strokers youd know what a port shaped for a flared header looks like and the benefits to a flared headder but you dont and that compression dictates fuel type also power level when tuned and porting dictates the timing events of the power...You mock what you cannot understand and thats not what a mod is all about.........
 

Registered
Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
Joined
50 Posts
Discussion Starter #46
158685
New bearings arrived today, not sure if they are ideal but checked the specs and they are rated to like 40k rpm metal.shielded. should be fine. They feel so good compared to the chinese ones, buttery smooth.
Hope to get the engine assembled and installed into the blue quad this weekend. We will see the outcome of all my enthusiastic dremel work. I'm excited. Will be running off a stock carb for breaking in until the new 15mm pumper arrives next week.
Seriously thinking about welding the front rigid as the suspension is just horrible and doesn't work to any sort of usable degree. Just get a new slightly longer rear shock, and keep that. I plan on running it in short grass fields so thinking a bit of suspension on the rear might not go amiss. Thoughts?

158687
 

Registered
Joined
35 Posts
New bearings arrived today, not sure if they are ideal but checked the specs and they are rated to like 40k rpm metal.shielded. should be fine. They feel so good compared to the chinese ones, buttery smooth.
I hope you are going to remove the metal shields, engine crank bearings should not use those..:D


Exhaust port size seems a very personal question for some.
Is there a formula for calculating an exhaust port pipe side area for a given piston side port area for TOOLBASED engines?
 

Registered
Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
Joined
50 Posts
Discussion Starter #50
I hope you are going to remove the metal shields, engine crank bearings should not use those..:D


Exhaust port size seems a very personal question for some.
Is there a formula for calculating an exhaust port pipe side area for a given piston side port area for TOOLBASED engines?
I was not, thanks for the heads up, after reading the spec I assumed they would be fine as is. Is it due to lack of lubrication? Couldn't I just open up the inner shield? Are they easy to remove, cant say ive ever had to do it before? Just flatblade screwdriver and pop them out, they seem very tight.
 

Super Moderator
Joined
2,456 Posts
SKF is what they use for NASCAR very good bearings definitely remove the bearing shield from both sides.

Back to the exhaust Port size... This one came out ok not excessively large.
 

Attachments

Registered
Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
Joined
50 Posts
Discussion Starter #53 (Edited)
Right, been doing some more fettling.
I remembered i had never done any mods to the reed block or stoppers on any of my builds so thought it was about time I did. I've just run fibre glass reeds on one. And then stock reeds on the others.
Always had trouble getting either the fibreglass or carbon reeds to seal nicely. I ordered 3 fibreglass reeds and only 1 actually sealed. I had a spare carbon 1 piece set and after reading others had done it set about cutting out the centre bar etc.
158747


Obviously still got to clean it up but again the bloody reeds will not seal. There is a thin gap along the top.

158754


I tried a different stopper in case that was squiffy. Tried putting a set of stock reeds ontop to see if that would close it. Nope.
I've got spare plates so will just keep the central bar and just open it up like I've seen in other threads.
Here's my modded reed stoppers, nothing too severe.
158749

158750


Think I will use them with stock reeds and a opened plate.

Also want to try a modded stock carb as ive read alot about the pumper failing due to ethanol and we have it in nearly all our fuels. So want to see what performance I can get with the stock ones.
I've got 3 pumpers now and don't want to be replacing them every 6months. We will see how they last.
Ive had a go at opening the stock manifold, have I gone too far? I went a tiny bit squif on the carb side but it measures just over 16mm on the gauges. The reed end I think looks good. Will tackle carb next.

158752
158753


Got the new bearings in. Bakes the cases and chucked bearings in freezer, they literally dropped it. I removed shields from both sides and cleaned all the grease out. God they feel better than the old stock ones. Just going to order some decent seals and I can put it together, never seem to get as much time as I need, lol.
Quick question.
Can you remove the crank case seal and use yamabond type gear, would this not give you back some of the case volume you loose when blueprinting? Or is the gasket required for clearance for the crank, just didn't know if it was done or not?
Thanks again in advance.

Max
 

Super Moderator
Joined
2,456 Posts
It depends on your case's if you can put the two halves together without the gasket if it squeezes the bearings then you need the gasket what I do is put the two halves together and give the crank a spin without the crank case seals if it spins free then you're golden and then go ahead and and use a fuel resistant silicone and put the crankcase together if it spins tight then you're going to need the gasket.

Like I say never be afraid to learn from multiple sources and try new things that's what makes this hobby fun. especially on an engine that costs less than taking your family out to dinner 馃榿
 

Banned
Joined
21,744 Posts
View attachment 158685 New bearings arrived today, not sure if they are ideal but checked the specs and they are rated to like 40k rpm metal.shielded. should be fine. They feel so good compared to the chinese ones, buttery smooth.
Hope to get the engine assembled and installed into the blue quad this weekend. We will see the outcome of all my enthusiastic dremel work. I'm excited. Will be running off a stock carb for breaking in until the new 15mm pumper arrives next week.
Seriously thinking about welding the front rigid as the suspension is just horrible and doesn't work to any sort of usable degree. Just get a new slightly longer rear shock, and keep that. I plan on running it in short grass fields so thinking a bit of suspension on the rear might not go amiss. Thoughts?

View attachment 158687
Depending on rider weight and the speeds n such it may turn into something a lil on the harsh n crazy side..Kinda like a gocart

If you modify the front a-arms by making them 1.5-2" wider each and modifying the steering rods longer also mounting longer shocks from a jap brand quad more outwards towards the tires it should give ya a much better ride as the shocks on there have no real travel and are more like pogostick springs...LOL.......

I took my old 200cc Cobra quad and turned it into a reverse trike and widened the frontend 3" on each side and used a frontend from a Suzuki 250cc quad

IMG_20180113_194300.jpg

IMG_20180503_122825867.jpg

20180928_145717.jpg
 

Banned
Joined
21,744 Posts
Right, been doing some more fettling.
I remembered i had never done any mods to the reed block or stoppers on any of my builds so thought it was about time I did. I've just run fibre glass reeds on one. And then stock reeds on the others.
Always had trouble getting either the fibreglass or carbon reeds to seal nicely. I ordered 3 fibreglass reeds and only 1 actually sealed. I had a spare carbon 1 piece set and after reading others had done it set about cutting out the centre bar etc. View attachment 158747

Obviously still got to clean it up but again the bloody reeds will not seal. There is a thin gap along the top.

View attachment 158754

I tried a different stopper in case that was squiffy. Tried putting a set of stock reeds ontop to see if that would close it. Nope.
I've got spare plates so will just keep the central bar and just open it up like I've seen in other threads.
Here's my modded reed stoppers, nothing too severe. View attachment 158749
View attachment 158750

Think I will use them with stock reeds and a opened plate.

Also want to try a modded stock carb as ive read alot about the pumper failing due to ethanol and we have it in nearly all our fuels. So want to see what performance I can get with the stock ones.
I've got 3 pumpers now and don't want to be replacing them every 6months. We will see how they last.
Ive had a go at opening the stock manifold, have I gone too far? I went a tiny bit squif on the carb side but it measures just over 16mm on the gauges. The reed end I think looks good. Will tackle carb next.

View attachment 158752 View attachment 158753

Got the new bearings in. Bakes the cases and chucked bearings in freezer, they literally dropped it. I removed shields from both sides and cleaned all the grease out. God they feel better than the old stock ones. Just going to order some decent seals and I can put it together, never seem to get as much time as I need, lol.
Quick question.
Can you remove the crank case seal and use yamabond type gear, would this not give you back some of the case volume you loose when blueprinting? Or is the gasket required for clearance for the crank, just didn't know if it was done or not?
Thanks again in advance.

Max
The give n take on blueprinting has the most advantages with zero take as the mod is all a plus..

If you dont stick with the basics and remove more than whats pertinent[barest minimal yet still being effective] you can subtract from the mod but thats pretty hard to do as you already know how forgiving these engines are unlike an IAME or Parilla engine...

When you increase the velocity your strengthening the intake charge and when you bump up compression you strengthen the engines power and when you port it right it times the events perfectly from the dip zone all the way to the end of the powerband...

Strengthening the intake charge diminishes the heavier resonance waves that can come back like an exhaust with alot of back pressure and no expansion chamber diameter to cause alot of spent gasses to overpower and replace the fresh mix by pushing the fresh mix back into the crankcase which diminishes performance.....

When you do the blueprinting right you rarely have the need for a tuned pipe especially if you get a lil speed bump in the exhaust port at bdc...................

Pound for pound if you take a bone stock engine and just blueprint the whole thing and raise the compression without widening or raising any ports it will still run like a scalded dog with the right tune...LOL
 

Banned
Joined
21,744 Posts
Getting the air through the reedplate and the reedstopper with the most force and volume and the least turbulence you will gain hugely.........

The way I get the stopper to open wider is I change the mounting angle of the stopper where it mounts to the reedplate and adjust the angle of where the screwheads rest..

Most would simply say just cut the center bar out and use a polini reed....The tin reeds work the best and why would you go from 6 sides flowing fuel down to only 3 ?
011-3.jpg
011-3e.jpg
015-7.jpg
015-7e.jpg
IMG_20170317_161252927_zpsmoi1sont.JPG
IMG_20170317_161549656_zps4ng5yiuz.JPG
 

Registered
Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
Joined
50 Posts
Discussion Starter #58
I tried they both ways, tried refacing the reed block adding the tin reeds ontop etc, nothing worked.
I'm going to modify a standard reed plate, slightly opening the duel inlet holes and run stock tin reeds. Like Cam showed above. From what I understand the stock reeds struggle at high rpm when they begin to flutter, where we race its all about low to mid range power, we only just touch top end on the biggest straight for about half a second so I'm not worried about hindering max rpm it means a hood strong seal at lower engine speeds.
Been a really busy week but hoping to get the engine assembled today so might have some more pics later.
 

Banned
Joined
406 Posts
I tried they both ways, tried refacing the reed block adding the tin reeds ontop etc, nothing worked.
I'm going to modify a standard reed plate, slightly opening the duel inlet holes and run stock tin reeds. Like Cam showed above. From what I understand the stock reeds struggle at high rpm when they begin to flutter, where we race its all about low to mid range power, we only just touch top end on the biggest straight for about half a second so I'm not worried about hindering max rpm it means a hood strong seal at lower engine speeds.
Been a really busy week but hoping to get the engine assembled today so might have some more pics later.
Generally on a stock motor you can go with carbon fiber or fiberglass Reed, a modified medium or heavily modified engine you need to run tin reeds. Anything can flutter at high RPM. The tins are definitely stronger.
 

Registered
Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
Joined
50 Posts
Discussion Starter #60
Right then, been a bit quite lately, work has been frantic, luckily and been working away so been hard to grab time in the workshop.
Had a disaster on Friday night. Got the entire engine assembled, was just about to install the flywheel and couldn't see the keyway to set timing. Then it dawned on me. I'd installed the crank back to front.
Had to strip the entire engine to bits, flip piston and reassemble, so that blew any chance I had of getting it fired up. Amature move, lol.
Anyway. Got it sorted, ive posted a few pics below.


First attempt at modifying the reed plate and stoppers. Also installed trimmed stock reeds over a stock set, sealed really well so hopefully that'll work.
159133

159134

159135


Also modified the ignition system with new better quality 7mm ht wire.
159136


Lightened stock flywheel, not the neatest job but will work. Took a bit of material off the centre lugs but it all feels fine once the pullstarts on so I'm just going to consider it extra weight reduction.
159137


Need to tweak the new exhaust as it doesn't quite fit but that's an easy fix.
It looks good, compression feels great. Ill get the squish results this weekend and get her fired up and see how she runs. I'm hoping for good things as the last one was a real success. This is a stock head but same diameter as the supposed BBK so will see how they compare.
159138
159139


Thanks again for all the feedback and hope someone even greener than me will find some use out of the thread.

Max
 
41 - 60 of 60 Posts
Top