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Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
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Discussion Starter #1
Just thought I'd make a post documenting the attempts of a total 2stroke amature to modify one of these lovely little engines.
I've assembled quite a few and with each one gone further with the mods and with information gleaned from this forum hopefully more precise with the installation.
The last engine I thought I'd take the next step, split the case and try and flow everything. I'm not sure on the correct terminology. But I removed material to allow better flow into the transfer ports and boost ports. Below is my attempt. Very open to suggestions and criticism, im in this to learn so am expecting failure and lessons learnt
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Anyway, I chamfered all the edges in the head widened the exhasut port and matched it to the exhaust. Took some material off the top of the cylinder on a granite slab with wet and dry. Installed with headgasket and this was the squish. Am I correct in reading this as 0.6? I took it on the other side as well and this was 0.5 so I've got a bit of room to drop it but would assume at temp this would shrink slightly?
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Anyway. This engine has been broken in and running on a 15mm pumper carb it is incredible the difference over the stock engine that was there before. Feels more than twice as powerful. So off this success I've now begun building a new engine.
Old case. Split. Have new crank seals. Probably buy new Japanese bearings or reuse old ones seem OK.
Using this head. Found it on ebay. Two boost ports but a none ported piston.
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Questions on the above.
Is it worth removing the devider on the transfer ports? All my other heads have just 2 large ports.
Plan on making boost ports deeper, any issue with this?

The piston unlike the BBK wasn't ported. So I read a load of threads found some old pics from boosted and had a go. I'm well aware its not that pretty I just want to know.
Will it work or have I made a paperweight?
I started to clean up the inside of the piston as well. Also flat topped the piston very slightly and Will polish as well.
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Just want to get rid of all the casting marks. The added weight saving can't be a bad thing either i guess. The other engine had a FCC fitted. Are they really worth it? I've read about the turbo crank mod and thought I'd try that on this build instead?
Anyway. If this all goes well I'll be dropping it into my lucky 7. Currently running 44mm head with widen exhaust port and matched to exhaust. Random performance exhaust. Ali clutch with HD springs. 15mmpumper carb. Dominoe 1/4turn throttle.
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All advice and constructive criticism welcome.

Max
 

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when you do flow work you want to remove as little as possible from the inside of the crankcase you do not want to diminish the crankcase volume there is a trade off between better flow versus diminished crankcase volume

I do not believe in removing the divider in the transfer ports The increased volume of having the divider in place helps send more fuel flow up the boost port channels which is what you want

I think your window will work I would have went with two smaller holes just a little bit farther away from the rings to prevent blow by from getting past the rings and down into your boost Port channels.

Here are some pictures of how I do mine
 

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Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
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Discussion Starter #3
Thanks mrK. Good news, I went a bit higher than I'd planned, the cutting bit slipped so I had to go higher to smooth the scuff out. Still getting used to using the dremel, which speed works with which bit etc.
The flow work on the engine I showed had the FCC crank fitted, I had read what you mentioned regarding volume but assumed, maybe incorrectly that as the FCC would stuff the case id have a bit more scope for removal, ill be more reserved on this one which has the stock crank.
So I can enlarge the transfer ports a little. Ill work out heights later, will remove headgasket so know I have to extend them that much plus possibly the same again.
I'll post some more pics tomorrow when I get another chance to get into the workshop.

Max
 

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It's coming along nicely. The case probably was done a little bit extra. But try it out.
Say what you want about the dividers but the Sanren 44mm heads we're one of the best cylinder heads made and they don't use dividers. Out of the box flowed way better than the stock heads on these bikes. Here are some pics
 

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Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
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Discussion Starter #5
Thanks for the replies guys.

My only other concern with the transfers was that the little ridge in the middle may be bad for the rings, its about 6-7mm wide.
What would be the likely result if I removed them, increased flow but an increase in volume so a slight drop in velocity?

Is it worth installing another FCC to decease volume, ive read so many conflicting opinions on the FCC are they a net improvement for these engines?

Thanks again guys. Ill update this post later today when I get back into the shop.

Max
 

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Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
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Discussion Starter #6 (Edited)
Just a quick video showing the first engine. The one with the 2piece head that the flow work was done for starting and running. Bare in mind its only just run in so Is still running rich. I think it sounds pretty good and throttle response even rich is really snappy.
The other one is me riding it for the first time. These mini quads are a whole heap of fun but you really do have to committ and ride the things. If your not hanging off it at any sort of speed your going straight on into an accident, lol. Turns out getting up on two wheels is a doddle.

https://flic.kr/p/2jXF1Sc https://flic.kr/p/2jXEe4C
 

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Wow, that little quad looks like a trip! We'll have to be on the lookout for one of them in the near future..
 

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Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
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Discussion Starter #8
Wow, that little quad looks like a trip! We'll have to be on the lookout for one of them in the near future..
There awesome mate, if you ever see one of the blata ones come up grab it, much better quality than the chinese ones but the chinese ones are great as well.
I'm going to remove the front brakes and front suspension on the chinese ones as it isn't needed, doesn't really work and just adds weight. The next engine im building will be going into the blue quad so I'll take pictures and show you lot the end result.

Max
 

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Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
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Discussion Starter #9
Didn't do anything on the engine but stripped the other quad down. Plan on building it up for the kids. Want to fit the reduction gearbox so the revs can stay high hopefully helping the clutch. Need to weld a plate to allow me to shift the motor over to get the sprockets to line up. Shouldn't be too hard. Going to weld the front rigid and look at sorting the rear suspension. Get it all sprayed with a decent engine hot a farm nearby they can run it but its like horse paddocks so it needs to have plenty of torque.
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She's a little ruff but a clean and paint new plastics done up in paw patrol livery should do the job, lol.
 

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Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
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Discussion Starter #10
A mixed day of results.
Who would of thought precisely altering the dimensions of a engines cylinder head would be tricky. I'm not ashamed to admit I underestimated the skill required to do competent porting work. I'd read a ton of info, watched a heap of YouTube videos, bought a decent dremel and assumed I was going to be the next 2stroke guru. Not so. I had read the term 'hogging out' the transfer ports and took to them with gusto.
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Barbarian. Anyway. After a cigarette and a talking to I grabbed one of the decent spare heads I had and set about attempting a boost port to go with the piston that was now going to waste. Nothing like blind optimism to see you though.
This was again much harder than I expected. If anyone csn be bothered to briefly describe their method im all ears.
After much faffing I had something that looked alright. I've got limited bits and figuring out the correct application the correct speeds etc is a learning curve.
Its not pretty, the sandpaper bit skirted off a few times, you can't feel it but it shows, thinking about 1000grit wet and dry to sort it or might leave it. Also the top is slightly on the piss. Very slightly. Height wise its just under 1mm higher than transfer ports at its highest height so appears alright. We will see.
I've cleaned the flow work in the case a bit since the pics and happy with the results, only focused on feed side this time to preserve case volume;).
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I think next time just slowing down and not rushing would of avoided a lot of the mistakes above. Either way. Bearings are cleaned and fitted with new oil seals. Crank spins nicely with no lateral play. Get the head fitted next day or two, check squish, most likely loose base gasket. I will lighten flywheel. Git new Ali clutch to chuck in. Never bothered balancing one before, might do that, likely just chuck hd springs on and get at it, lol.
As always all comments and critisisms welcome. Even if the boost port is a bit funky and the rings might not love it. Ill get it tother and run it. I'm sure it'll be at least as good as a stock lump with a 15mm pumper on it even if I have slightly goosed the head. Hey ho, we live and learn.
 

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Ooops on head one. Head 2 looks great. I am not very experienced on the porting either. But looking good and practice makes perfect.
 

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A mixed day of results.
Who would of thought precisely altering the dimensions of a engines cylinder head would be tricky. I'm not ashamed to admit I underestimated the skill required to do competent porting work. I'd read a ton of info, watched a heap of YouTube videos, bought a decent dremel and assumed I was going to be the next 2stroke guru. Not so. I had read the term 'hogging out' the transfer ports and took to them with gusto. View attachment 158112
View attachment 158113

Barbarian. Anyway. After a cigarette and a talking to I grabbed one of the decent spare heads I had and set about attempting a boost port to go with the piston that was now going to waste. Nothing like blind optimism to see you though.
This was again much harder than I expected. If anyone csn be bothered to briefly describe their method im all ears.
After much faffing I had something that looked alright. I've got limited bits and figuring out the correct application the correct speeds etc is a learning curve.
Its not pretty, the sandpaper bit skirted off a few times, you can't feel it but it shows, thinking about 1000grit wet and dry to sort it or might leave it. Also the top is slightly on the piss. Very slightly. Height wise its just under 1mm higher than transfer ports at its highest height so appears alright. We will see.
I've cleaned the flow work in the case a bit since the pics and happy with the results, only focused on feed side this time to preserve case volume;).
View attachment 158114

View attachment 158115

View attachment 158117

View attachment 158118

I think next time just slowing down and not rushing would of avoided a lot of the mistakes above. Either way. Bearings are cleaned and fitted with new oil seals. Crank spins nicely with no lateral play. Get the head fitted next day or two, check squish, most likely loose base gasket. I will lighten flywheel. Git new Ali clutch to chuck in. Never bothered balancing one before, might do that, likely just chuck hd springs on and get at it, lol.
As always all comments and critisisms welcome. Even if the boost port is a bit funky and the rings might not love it. Ill get it tother and run it. I'm sure it'll be at least as good as a stock lump with a 15mm pumper on it even if I have slightly goosed the head. Hey ho, we live and learn.
Man, looking good. Its not easy. It takes time.
For more practice, I would use JB weld to fill the hole on the first cylinder. Then just clean it up. Polishing after some sanding does wonders for flow. Even if there is some uneven surfaces.
 

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Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
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Discussion Starter #13
Glad to hear attempt 2 is looking like it might work. Its very hard to keep everything straight and true, finding out how much material to remove etc. Like anything worth doing its going to take time.
Blata, my initial impulse is to smooth it all out and polish it but I've read and been told that a slightly ruff or mottled finish is in fact better. Apparently fuel droplets like to form on a polished surface, look at the stock finish on the inside of the crank case its ruff, although that could just be chinese cheapness im assured its done for a reason.
The piston im lead to belive is wise to polish, as well as the wrist pin. Im yet to find a definitive guide on which surface finish is best for each part of the engine. Ill do some reading and maybe put one together.
Im very tempted to open up the polini engine I bought and compare them stock to stock with the chinese engine just to see why one costs what it does, leaving materials aside and just focusing on the machining, design etc.
That could be a good learning excersise and I've been dying to open it up and have a look.
Maybe later today....
 

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Blata quadard. 2 xhinese copy quads. 3 lucky 7's. 1 lucky 7 trike. 1 cag.
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Discussion Starter #14
I was also debating getting some jb weld to repair that head, ive had good success with it repairing my cracked sump on the corrado thats lasted 6years so far with no issue.
Now I've read you can't use it to fill in the decompression notch, im assuming as its too close to the combustion itself but in the transfer ports it would be removed from direct heat as such. Hey, its goosed anyway so can't hurt to stick it on an old case with a some new rings and piston and see what happens. Its all good knowledge whatever the outcome I guess.
 

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You should try to get the 3rd port to the middle of the bore. A port wide of 16mm is no problem.
All so you should create a angel with a direction to the sparkplug, not a 90° to the cylinder wall, because you blow the load into the exhaustport.
 

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Discussion Starter #16
I've spotted what you mean chrisi, it needs to go a few mm to the left to square it up. Its currently 13mmish wide so could extend it. Is it just not optimal to have it off-centre?
Are you referencing the top of the piston? I'd read a few places flattopping was desirable to force the blast toward the cylinder walls rather than directly at the rings?
Do you mean shape the piston to force the mixture toward the spark plug? Cheers

Max
 

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I've spotted what you mean chrisi, it needs to go a few mm to the left to square it up. Its currently 13mmish wide so could extend it. Is it just not optimal to have it off-centre?
Are you referencing the top of the piston? I'd read a few places flattopping was desirable to force the blast toward the cylinder walls rather than directly at the rings?
Do you mean shape the piston to force the mixture toward the spark plug? Cheers

Max
The Piston needs to match the shape of the squish band inside the cylinder dome this is a very important part of controlling detonation

 

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I've spotted what you mean chrisi, it needs to go a few mm to the left to square it up. Its currently 13mmish wide so could extend it. Is it just not optimal to have it off-centre?
Are you referencing the top of the piston? I'd read a few places flattopping was desirable to force the blast toward the cylinder walls rather than directly at the rings?
Do you mean shape the piston to force the mixture toward the spark plug? Cheers

Max
It's better when the ports are symmetrical to the middle line of the cylinder. The cylinder is filled more evenly. Your 3rd ports end with a flat area in 90°to the cylinder wall. If you imagine how the mixture flushes through the port and then hits this edge, you only get swirled and your mixture shoots towards the exhaust port. The end of the channel should point towards the spark plug, or at least a few degrees above the piston. It is the same with the main ports, these should also be directed a few degrees above the piston crown.
 

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Discussion Starter #20 (Edited)
Managed to grab a couple of hours in the shed so attempted to improve the port taking on board advice given. Its a little better, its hard to make out but the top is chamfered im scared I may of pushed the port slightly too high so I'm going to leave it. Its about.1.5mm higher than the top of the transfer ports. I will be removing the base gasket so I guess that buys me a little more room. We Will see. It looks cleaner, is more central and has a better top. I'm happy.
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Also had a go at the exhaust port. Found this handy diagram in another thread, think it was cam2 who did it originally but using this I set to work. Pretty happy with the results. I measured everything before, set the gauges and then slowing took the material off until it all tallied up.
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Not perfect again, took a small amount out of the bottom right looking at the pick so not sure what the result of that will be, its a tiny amount but I know it all matters, hey ho.
Now I had a polini engine and exhaust sat in a box which realistically I won't be doing anything with for a while, I can always get another exhaust. I took the header off, cut another off an old cag exhaust. I had 3 spare and this one is an older one but had slightly thicker diameter pipe. Ground it down ever so slightly and fitted perfectly into the polini.
Probably have to piss about with it but I've got enough bits to make it work, should do the job.
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And that was that for the night, going for a blast in the morning down the yard so will try and remember to get a video. Cheers

Max
 
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