going case inducted!!!

[mech_engineer]

The engine have sfk bearings rated for 40k rpm, titanium wrist pin and a lot more... got every thing you can buy or create to tjese engines...built this engine cost me a lot... the problem i use the same piston from my last engine blow up maybe the piston rings sufer some damage, also the engime was runing lean and a high performance engine with a 54 tooth keep the engine at high rpm all the time ... i know is my fault but was fun ... tomorrow i will rebuilt the engine again... almost i forgot the rings and piston melted on one side from runing lean and without i know it ..i ajust the carb needle for more gas the engine gain a lot of power but due to the melt the rings broke into many pieces giving the piston, jug and the :, ( fred head 5.3 a moon like looking... a friend of mine told me that he never saw a engine blow up like that in his 5 years of experince in china girls

 

[electron]

I may be wrong, but the carby needle does nothing at WOT: That's up to the main jet.
2nd hand piston and rings & "keep the engine at high rpm all the time" hmm.. sounds like a recipe I've heard of.
...coming from a newb.
Keep up the entertainment!

 

[mech_engineer]

the crank needle bearing is broken apart thats why the engine damage it keep trowing particles the next day i rebuilt the engine it only last about 10 minutes and damage the engine again. for now the project is on hold. need money to buy a new stroker crank from a friend but is a little expensive almost 3 times the cost of an single engine. note this crank in made from 0 no china crank will be use.

 

[mech_engineer]

new updates... i designed a 73cc engine i am waiting for the machine shop call to pick up the crank... and have designs for a 80cc stroker (only need a some money and time to send it to the machine shop) and h-beam aluminum rod (need to select a new bearing due to the power of the engine the bearings can wear to fast). ; )
also i change the rear wheel to a 29er lets see if i can do the 65mph i need some luck (puchased a full face helmet for down hill) . sorry for this late update but i am in my last semester of aerospace and also working 35 hour a week.

 

[Davezilla]

better late than never... but definitely glad to hear you're still working on this... Can't wait to see what you come up with.
With my crazy schedule there's not as much time to invest into some of my ideas, or if I do get the time it's always when funding is low... Mine does run really good the way I got it set up but I pretty much haven't even touched the cases on my old engine since like June or early July. Just got a reed valve adapter made up to install onto an inlet port sometime last week, but didn't install it to try it out yet since my time can be so limited. It's compact and it fits a 19mm Tilly carb so I'm really itching to try it out... But at the same time a bit gun shy about taking anything apart in case it has to sit that way for several days. Mainly I like to keep it running since I keep it at the shop now and it's great for doing a quick run to the convenience store or for a quick shot down the street for breakfast... Not to mention it looks better in one piece when customers want to see it or hear it run.
I'm definitely interested in how you're making an aluminm rod for your setup too, let me know what you come up with when you're ready to do it.

 

[mech_engineer]

Well thanks, rigth now the machine shop guy is dont anwers my call i think he doing it on purpose; for the aluminum rod... is a long story i design a project for a aerospace company if it get the company approval i am going to get a lot of equipment like cnc milling, water jet... and a lot more to make a good and modern machine shop.

 

[mech_engineer]

ok here is the vid of the new engine the 73cc stroker a friend of mine told to me that the engine in running lean on gas. the engine only have the 3er tranfer, matched case to head tranfer ports and ported exhaust port the timing is stock for now.

https://www.youtube.com/watch?v=GI9HPFXU4IY

 

[Davezilla]

Looks and sounds great... Do you plan on changine the port timing as you work this one? And are you planning on boring out the jug or adding more stroke to bring it up to 80cc in the future? Really Nice work so far

 

[mech_engineer]

my math formulas got a boost from last time... now i have computer programs that i made with a friend of mine he also is a engineer. the program give me the exact port area and timing using the Yamaha parameters and different stroker cranks. For this engine is in prototype phase now i need to wait some time before to change the timing to see how it perform with out mayor mod. for now is running 32 mph without tuning the carb or check the compression, stock timing on a 32 sprocket and 26" wheel. the only bad thing is that it needs a lot of fuel to start. it only start with almost an ounce of gas at the case and 1/4 ounce at the chamber once it start it keep starting every time but if i let the engine cool down i need to add more gas to the case and the cylinder. the carb choke is on back order at ebay. if any one can help me with the starting problem will be helpful. to obtain 80cc only a spacer at the cylinder deck and piston skirt trimming is needed then we have plans to make a 100cc with a 50mm piston but that one is on the drawing board (CAD). well from the only ride i took with this engine the torque difference is really big. the engine only do a little bit of work max rev are like 6k rpm, the engine need a lot more fuel at lower rpm and need more rpm at top because it is 4stroking a lot at full throttle. the 32 mph can be maintained at 1/2 throttle. i am planing to drill the 50 idle jet to obtain more fuel at lower rpm

 

[Davezilla]

Larger idle jet and smaller main jet should get you in the ballpark... Your idle jet needs to be big enough that when you screw the idle mix out past 2 1/2 turns it should get a rich stumble, but when you screw it in it should lean stumble before the mix screw is all the way in as well. You should try for the right idle mix at around 1 to 1 1/2 turns out from soft bottom.
The idle jet plays a part in the full working range of the carb so going bigger with the idle jet can flood the top end out so going for a smaller main will clean up that ares, start rich and work your way smaller until the 4 stroking goes away for the most part at WOT. Once both these are set, then you can set the needle for a clean run at cruise speeds. I use small 4mm washers that are 1/2mm thick if it feels too lean going up a notch but too rich going down a notch since each notch is 1mm thick you can fine tune by using a 1/2mm thick washer under the needle clip.
If you got a good adjustment range at idle and low speed, fine tuning the mid range should be doable without using the 1/2mm washer under the clip, but in some cases you may need to get in between needle settings to get it to run at it's best in the mid range.
Does the carb you're using use an actual choke or does it use a fuel enrichment circuit where there's no physical choke but a small valve and an extra jet that's opened up to add more fuel during startup? if it uses the fuel enrichment circuit like big motorcycles you can play with the enrichment jet if all else is working good when the engine is at operating temp. If it uses the more simple choke that just blocks off the air inlet you'll need to find the right parts to fix your carb, but you can also solder the hole in the choke plate and drill a smaller hole if it needs a richer mix at startup than it can get just by putting the choke on.

 

[mech_engineer]

thanks i drill the idle from 60 to 65 and start every time... like you said i need to lower the main to 85 and give a try.. but there is a problem the new trued, welded and stroker crank... have a lot of torque only at 20 miles of testing the lower pin shear due to shear stresses they pass 50000psi now i need to make a chromoly (steel 4130) lower pin that can handle almost 80000psi. with a 36 and half cleared ports the engine develop a huge torque almost compared to the time i use the 54 tooth sprocket. now that the crank split it self in two i need to change the long rod to a short rod to make the full ports clearance. it make 38mph in my home town with a lot of hills because i live in the center of the island. with the short rod and full port clearance i think it can make the 50 like nothing. thanks for your interest in my development, lest see if the 2015 brings a 70mph in the gps with a 32 tooth and 29 rear wheel. the funny thing is everyone here in the island ride their bikes without helmet. and i am using a downhill full face helmet because i what to protect my ideas...

 

[Davezilla]

So you snapped the crank pin already? Bummer... was it a weld that failed or was it the actual metal it's self? pics please, if you can... I'd like to see what went wrong.

True, if you make a new one out of 4130 or go overkill and use 4340 it shouldn't break, but I wouldn't think a steel crank pin would be that fragile since many are made of cast steel or even cast iron and last forever. A 4130 cran would be really nice tho for the weight savings and definitely shouldn't break.

 

[Ron344]

I have been thinking of building a case inducted motor for sometime now so yesterday I started. I milled the the cylinder on the intake side and made a cover for it. I'm going to make it a piston port I did some work on it to day I will send pictures later.

 

[Ron344]

Here a couple of pictures of the work I've done so far. I will have to order a reed set next. I was thinking about your crank pin It might have broke because of the heat from welding. it could have weaken the metal.

 

[mech_engineer]

in some part is possible due to the heat may change the metal structure but almost all cranks in the racing application are welded to keep the trued... the pins are weak to shear stresses in this case the pin work on shear forces and a more harder material is needed this is the same as racing solid clutches the pins that hold the pads in place tends to fail due to shear. the stroker crank make more torque due the nature of the phisics torque=force*distance... more distance due to the stroker and more force because of the 73cc is not a 66cc anymore... is the same as cars more performance parts are needed to prevent failure. the best would be a heat treated titanium pin but are expensive

 

[mech_engineer]

rock solid engine 70cc stroker crank is a solid pin

 

[Ron344]

I would think if it was due to torque the wrist pin would have broke first. It has to be another reason it broke. If you have a 50cc crank pin it's the same size as 66cc crank why doesn't it break because it has more torque. Why would you think your motor with only 7cc bigger would make it break. It doesn't make sense it has to be another reason. This is just what I think.

 

[Davezilla]

Nice work Ron!!
I got a similar idea and made a reed block out of 1/2" thick 6061 T6 sheet stock, didn't mill down the cylinder tho as the reed protrudes into the port, mine uses a DLE 80cc RC engine reed and bolts to a 19mm Tillotson carb. I put the project on hold back in June or July but I got all the pieces at my shop. Decided the reed block I made needs to be remade to accomodate a few improvements and to correct teh bolt spacing between the block to cylinder and block to carb bolts since it tilts the carb about 30 degrees. The Tilly is a floatless carb so tilting it's not a big deal, but I'm leaning more towards a Mikuni VM18 or Dellorto PHBG 19mm so I'll need to remake the reed block, then make a plate with a tube welded in at an offset for carb clearance. It's still early in the works and may get ditched all together if I decide to just plug up the intake port and go case inducted.
Right now I got a really strong engine I made up from a Dax lower end and one of my older jugs with less than 5 hours run time on it, changed the port timing considerably adding to the intake and exhaust duration and adding another 12 degrees to the transfer duration, bored out the stock intake to match the carb, and made an expansion chamber out of a KTM 50 pipe with a 4" long section of a pocketbkie's expansion chamber welded in to add more length to the chamber. the end result was a 40mph bike that still has excellent low end torque... Part of the reason I put the reed valve engine project on the back shelf, the temporary engine turned out so well it became more of a permanent engine and the reed valve engine more of an experimental engine until I get something that performs better than the one I got installed right now...

 

[mech_engineer]

The wrist pin is made of titanium

 

[mech_engineer]

I am back... Long time... I have been working and now i am going back with two stroker engines one 73cc and other 80cc have a new approach because last stroker only last for 2 hours of pure torque. New crank design ; )