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Discussion Starter #21
Budget builds are most likely on everybody's mind. The real question is what did you buy this engine for originally?
You can blow most of your budget just on the purchase. I understand that you're basically just cleaning up and balancing the motor. With just labor and time and no other parys incolved.
You could buy one of these motors for $100 not put any money into it or sometimes you can pick these motors up for $40 and you're in the golden Zone for anything you want to do, no other parts or replace some very important items.
You 100% correct the total budget on this engine is 60$ I picked mine up on ebay it was 39.95 including shipping I'm pretty sure there is a method to their madness and the engines I find on eBay for under $60 are ones that failed the quality control inspection which I will be getting into soon none the less with 20$ you can definitely get some key crucial parts to make these little motors scream maybe a rocket key ( I will be making my own) a velocity stack and air filter and a premium spark plug will see how things go as my build progresses.
 

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Discussion Starter #22
Yes it seems like that.
It would be a fun comparison.
My 40mm engine got a balance factor of 45 but I haven't lighten the piston yet.
But if I take of 2 grams it would just get a balance factor of 46%.
How bad are the full circle cranks? 10mm wrist pin.
Drilling some holes and fill with epoxy would make the fcc better. But if it's to much off it won't be good anyways
You can definitely build a screamer with the full circle crank you definitely want to drill two large holes next to the rod pin throw both sides and then epoxy fill them then you have the option of drilling two small holes next to where the crank bearings are or option two is to drill straight down through the crankcase where the feed ramps are into the void where the seal and the bearings are at so that they can get lubrication the clutch side being the most important due to the heat the third option would be to put a metal ceramic bearing in the clutch side but be warned if you put a metal ceramic bearing on both sides you will lose spark.
 

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Discussion Starter #23
I started to rework the cylinder base where the ports go up so that the jug can feed fuel properly into the transfer ports. I'm still deciding whether or not to add a boost port more than likely I probably will ;)
 

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Discussion Starter #24
I decided to go with a single boost port when I make my boost port I use 3 layers of ducttape near the grinding grinding area then I ducttape all the way around the cylinder this is so in case I slip well grinding my cylinder has a chance then I put the blue painters tape over the top so I can see what I'm doing
 

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Discussion Starter #25
Dang it the website has not saving my postings today :( I will repost later today
 

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Discussion Starter #26
After grinding in my boost port I leave the tape on and go in with some sand paper and smooth everything out then I check to make sure I didn't go higher then my exhaust port and create a ash tray just slightly higher then the transfer ports is what you want about 1mm
 

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Discussion Starter #27
Piston time so here is what happened to my engine...
The factory did not deflash or debur the skirt of my piston the assembler just shoved it in there and yanked the pull cord until the grinding noise stoped and called it good that's why some of the engines don't run very long and why they think breaking an engine in at 25:1 is key to the success of a good engine???

So it happened and now I have to fix the damage or get a new piston this is a budget build so I have to play the hand that was delt to me it will be ok because the engine was never run I can dig out the chunk of flashing out of the piston and carefully buff and polish the damaged spot with my Dremel!
20200926_214917.jpg

No problem I spent some time fixing it up streamlining the inside of the piston polishing the top and drilling out the window
I allso changed the shape of the piston around the wrist pin so it can feed the transfer ports properly

As for the rings they where allso damaged I looked at them through a jewelers loop and they have a flat spot on them so I might have to use some of the budget to get new ones :mad:
 

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Discussion Starter #28
Started work on case matching my cylinder to my crankcase I also relieved the channel in the crankcase for my boost port.
 

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Discussion Starter #29
I went ahead and did the turbo crank mod then recalculated my balance factor after the mods my balance factor actually improved and is now 31.52 meaning I need to add 11.5 g what I will be doing later by drilling and tapping and adding to the flywheel in a strategic location...
 

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Discussion Starter #31
I am out of town right now I'll be getting it finished up this weekend
 

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Discussion Starter #32
Not like I have a set schedule to finish the build you know I have other things going on as well in my life and other projects that I'm working on and it's winter time might as well take my time you know but I did get the bottom end assembled.

I don't see why you wouldn't want to balance the engine 😉

Mother's aluminum mag wheel polishes is grit free and you're going to want to do something to try to get the grittiness out of the cheap Chinese trash bearings. 💪

I think you may have confused my build with another build thread my crankcase has never been arrow marked in the spin direction ???

even though mine is not arrow marked I see nothing wrong with drawing an arrow with a sharpie on the crankcase not like it will hurt anything.

I also don't really see anything wrong with building an engine on a budget I mean they're just pocket bike engines right I mean weed eater engine I mean nb411 Robin Subaru weed eater clone engines
 

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Discussion Starter #33
The N2O works and it is awesome I ended up just putting everything in a back pack instead of trying to attach everything to the bike I did make an Arduino with progressive duration timing but unfortunately the amount of time that you can run the N2O on a pocket bike is too short to really use it properly so to conclude lol it works it's awesome you can feal the power increase and all that until the wrist pin bearing goes LOL it doesn't take long to start getting really really clickey...
I ended up repurposing the Arduino for a 3D lithographical printer.
 

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Discussion Starter #36 (Edited)
Did you dry-spin the bestings to test them??
Yes I blow them out with air and brake clean and if they spin ok on my finger then I use them if they still feal like gritty and have spots where they want to stick I give them the treatment again most of the time after three times the treatment the bearings aren't going to get any better and you just have to throw them away and get new ones

the other thing that you have to think about with the bearings is they might feel okay when you spin them on your finger but when they're inside the engine spinning at whatever RPMs you're pushing them at they're really not okay and if you're building an all-out race motor then you definitely would be replacing the bearings on a budget build you're really just going for the hand that was dealt you...
 

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Discussion Starter #37
I just buy SKF bearings. Budget or not, I don't waste my time on a rebuild with stock bearings. If the engine is new, run them as is. They don't feel gritty. And you don't use a wheel polish on bearings. At least I would not.
It's just a life hack to get new china bearings to feel halfway decent.
 
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