Separate names with a comma.
Discussion in 'Motorized Bicycle General Discussion' started by BamaJNJ, Aug 18, 2013.
is or has anyone done this successfully? and with what material?
This is a sore subject around here because the person who first posted the idea told people to use JB-Weld. The problem is he failed to inform people that proper surface prepeartion was critical.
Any epoxy based filler material can and will fail unless the base material is properly cleaned and degreased prior to trying this questionable idea. Yes, I'm sure people have tried and used it but you can be sure they knew the hazards and were prepared for them and knew how to use the product.
Do a lot of research before you attempt it and be sure to read the label of any material you plan to use and follow the manufacturer's advice on surface prep.
The big problem with using JB Weld is that it turns soft if exposed to the ethanol used in most brands of gasoline.
thanks tom well ive been looking thru the old posts and seen quite a bit and yes sir i completly understand about proper preparation...just curious about what the current thought on the subject is...i understand you are against jb weld (from older posts ive seen)...one question i have is what is the approx operating temp of the crankcase under load.. would a laser temp pointer give a accurate enough reading?
good to know VMB...non ethanol gas...check
I've been asking this a while myself, can never seem to get an answer, but I've used JB weld in the transfer ports which would get considerably hotter than the case due to the direct exposure to exhaust gases. so whatever JB welds melting point is, it's less than that. I have stuffed my case though, but using Permetex copper gasket maker probably not advisable, but hey, it works for me. Only reason I used it is because I ran out of JB. Aluminum's failing point in an engine is around 450*F if I remember correctly (I remember seeing a chart but I cant remember what site), not including other factors (proper torquing, good mix, proper timing, etc.).
good info mew thanks! that puts my mind at ease a bit...im going to try and get some temp readings with one of those laser temp readers tomorrow if the dang rain will let up any
What this boils down to for me is the fact that stuffing the case will make VERY LITTLE difference in anything less than a full-bore race motor.
99.999% of humans don't need to try this esoteric stuff because they don't have the knowledge or experience to get anything but disappointed.
By the time you could actually benefit from stuffing the cases, you should know all you need to know to try it.
If you have to ask, you don't need to be fooling with it. It's nothing but a problem waiting to happen without the experience and skill level to make it happen.
There's a REASON race engine builders have huge piles of destroyed engine parts...
and they KNOW what they are doing!
Just get a pipe and a bigger gear and ride it like it was meant to be ridden.
Buy a Morini or KTM if you want a full bore screamer.
Unless you have serious cash and like spending it in big batches, a full race china girl is probably not for you. The cost and level of modification required to get the HT even close to the Morini's power make building the HT a waste of time.
The only way you will ever get the ht to run with the Morini/KTM would be to build one from scratch from all billet.
And even then it would need to be totally redesigned with ignition, porting and balancing upgrades.
Don't waste your time stuffing cases unless you are bored and have lots of spare parts.
Nothing very exciting will ever come of it.
There are other products you can explore. Devcon makes something they call 'Liquid Titanium" and is good for up to 600 degrees F. Even there you'll need to properly clean and prep the surface.
The hazards of this far outweigh any performance gains so be advised that failure of the material to adhere to the casting inside the crankcase can cause fatal damage to an engine. Be careful.
Your idea of using a temperature sensing device is valid as long as the device is a quality tool that will assure accuracy. The inexpensive thermometers I've seen offered might not be give you the accuracy you'll need to determine casting surface temperature. Good thermal sensing equipment is very expensive. Those $20.00 items from some discount tool suppliers won't do the job.
thanks for the words of encouragement Maniac...i will take heed your advisement...however i am bored and do have a multitude of spare junk and maybe even a lil skill as well...thanks
Reason I stuffed my crank was to get primary compression back from drilling the crank. I decided to run it without stuffing and melted the JB weld and blew out my crank seals. You NEED the pressure to overcome the exhaust gases. However just as maniac said, spare parts. I happened to have a whole spare motor that wouldnt run for spare parts, so I only modify what I know I can replace should something go wrong. Getting arrow reeds? probably should stuff the case, RSE reeds arent too bad for compression loss so they're nearly a bolt-on (aside from reed porting). With the extra transfer from reed porting, you'll want the extra case pressure to prevent exhaust gases from blowing into the case and melting your reeds, seals, or just all-out grenading (because before the reed port, your pressure was concentrated in two transfers. With the extra port, that same pressure is now divided by 3 transfers, lowering transfer pressure). The motor, stock, runs fine. Too much compression and you'll blow all your air/fuel mix straight out the exhaust and waste alot of power and gas, too little, and as stated above, bad things happen. So unless you've modified how your motor is fed it's air/fuel mix, modified parts that dropped your pressure, or increased cylinder compression via a new or modified head, you dont need to stuff it, it's harder on the bearings and seals if you do, so do it out of need, not out of boredom.
I agree with you on most everything maniac - but I totally disagree with you here. I have a 66cc china with a 35$ puch head, ported cylinder, massive moped pipe (used $25), 21mm dellorto carb ($35) and hours and hours of tuning and I can totally outrun a friend of mine who has a moroni (not even a clone!) His tops out at like 35-40mph. I know this may be a rare situation but what im trying to say is that it doesnt take a whole lot of money (sub $150) and a little knowledge / reading of graham bell's two stroke performance tuning handbook to get a 66cc china really screaming
Where did you find a dellorto that cheap? I'm looking for a 19-21mm as well and cheapest I can find is $75
He has all different versions of the phbg carbs. Good seller. Shipping is a bit of a pain if your impatient like me. It took around 15 days total.
By all means, if you want to play with ht's, have at it!
I only meant to express my opinion on stuffing cases.
With a nickname like Maniac, I fully understand doing things just because nobody thinks you can.
As long as you don't expect a wheelie popping 50hp monster to appear, there is HUGE fun and knowledge waiting in these lovely china girls.
This engine can teach a newcomer ALL the basics of piston port two strokes.
I wish they had been available when I was a kid learning how to run with the big dogs...learning would have been a whole lot cheaper!
Remember no matter what you use to stuff cases, unless it bolts in, surface prep is critical! Clean, clean, clean and then clean it again!
Rougher is better as well. The more tooth the surface has, the better epoxy will grip.
Also remember, pump gas has lots of stuff in it these days to make most common epoxies fail sooner or later. Ethanol is only one of the issues.
Stuff that used to work may not with modern gas blends.
Flush area very good with methylene chloride this will remove all oil from aluminum.
Years agomy dad did a lot of aluminum tig welding and I remember him using the methylene chloride and a stainless steel brush to clean and prepare the surface for welding.