Map I didn't have a vibration problem I had a slow engine, the piston skirt covered almost 1/3 of the intake port. The bonus was less vibration and more power. I haven't had both crankshafts side by side but would like to compare a 48 and 66 .
wristpin needle bearing question
- Thread starter Thunderhead289
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I've always been under the impression that both engines used the same crank or at least I think thats what I've always thought, honestly I've never given the smaller engine much thought and if I've ever seen a crankshaft listed as being only for the 48/49/50cc I dont remember, I was thinking that the case was different to accommodate the smaller jug/cylinder and that the other difference was bore size with all else being the same,, I guess there could be a difference in rod lengths like with PK style engines vs Grube engines, not sure about that one either, if you can fill any of these gaps in for me here please do.....
Another thing that just came to mind is that since this thread is actually about the upper bearing, I cant remember ever reading a post about someone running the smaller 49cc engine and having an upper bearing failure......????? Again I could have missed that or just dont remember but with the lighter piston and the fact that almost eveyone has had what is said to be less vibration maybe the pper bearing have been less of an issue with 49cc engines.....shrug...?????
Just thinking about all of it and figure someone may have some good answers on the matter, all this talk about this is making me want to get one just to see what my experience with it will be, I've just always been concerned with it being way under powered but maybe not so much. ..
Map
This is interesting..
http://juicemotoparts.com/experimental-aluminum-wrist-pin-bushing.html
Map,do I mark the piston thru the ports before pulling jug in order to cutem?
http://juicemotoparts.com/experimental-aluminum-wrist-pin-bushing.html
Map,do I mark the piston thru the ports before pulling jug in order to cutem?
Yes, with intake removed and piston all the way up also known as TDC/ top dead center you will see how much of the piston skirt is actually blocking the port you can either scratch it with a pointed something like an icepic or just use a sharpie magic marker or pencil, I always just scratch mine with a scratch awl which is like an icepic, no way for the mark to get rubbed off that way, I use my bench grinder to grind thematerial off but a dremel witha coarse drum sander will work good also, ever a round file can be used.
Hope this answers your question ok
Map
Post edited.... the aluminum bushing is a bad idea.... dont do it, tried it on titanium pin and major failure after 50 miles....!
That aluminum bushing may be a winner for reducing weight up top, I know that ever automotive conrod bearings and main bearings have aluminum as the second layer just under the babit material and after a few miles as the babit wears down the engine is actually running with some of the aluminum bearing surface against the crankshaft, as long as the aluminum bushing isn't to soft and it get planty of oil it might actually work good, aluminum expands a good bitwhen it gets hotand that might tighten up the tolerances between the conrod and wrist pin to a quieter running topend as long as the bushing is machined to not be to tight when it heats up, also seems that a precise machined titanium bushing running on the titanium wrist pin might be another possble option that might be a good one.....hmmmmm wheels turning now....
I may have to order the combo and give it a try in one of my engines just to see if I notice and improvement in the balance....
Thanks for sharing the link 60weight
Map
That aluminum bushing may be a winner for reducing weight up top, I know that ever automotive conrod bearings and main bearings have aluminum as the second layer just under the babit material and after a few miles as the babit wears down the engine is actually running with some of the aluminum bearing surface against the crankshaft, as long as the aluminum bushing isn't to soft and it get planty of oil it might actually work good, aluminum expands a good bitwhen it gets hotand that might tighten up the tolerances between the conrod and wrist pin to a quieter running topend as long as the bushing is machined to not be to tight when it heats up, also seems that a precise machined titanium bushing running on the titanium wrist pin might be another possble option that might be a good one.....hmmmmm wheels turning now....
I may have to order the combo and give it a try in one of my engines just to see if I notice and improvement in the balance....
Thanks for sharing the link 60weight
Map
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Please enlighten us on what you mean by 60 degrees Theon
Manu of us notch the piston to clear the intake port better for a less restricted flow past piston, that is what I was recommending, I'm assuming you are talking about raising the port opening to change port timing a little but I could be wrong.
map
Edited: Aluminum bushing is bad idea.. tried it and it failed quickly....
I just ordered the Aluminum bushing and a titanium wrist pin a few minutes ago, I'm curious about how it will perform in an old BGF engine that actually runs good but has pretty severe vibes about 32mph with a 36T rear sprocket, I think this is the engine I'll try it in to see how it does.
Map
I just ordered the Aluminum bushing and a titanium wrist pin a few minutes ago, I'm curious about how it will perform in an old BGF engine that actually runs good but has pretty severe vibes about 32mph with a 36T rear sprocket, I think this is the engine I'll try it in to see how it does.
Map
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Lol..... when I seen your forum name 60weight I had a good idea you were a Harley man, I dont have an old one but I love my Harley and when I compare it to my old *** bike it makes me want to throw rocks at the old Yamaha....lol no comparison..... old Yamaer Hammer is an OK bike for town riding but the comfort power or balance just aint there compared to the Harley softail custom.I did to Map...and a brass one,and a roller one
Reading here about porting and piston work.
Just used to the oil pumps on my old Harleys I suppose,gitting used to the way these 2 strokes oil
Now back to the 2 smokers...., I also have a couple of the brass bushings I ordered from juice last year, im gonna give the aluminum bushing with titanium pin first and see if it helps one of my engines that Im very familiar with, the vibes are pretty bad above 32mph on this bike so Ill use speed as my test and will not change anything else just to see if I notice a reduction in vibes at that speed or above, biggest question right now in my mind is will the aluminum bushing hold up to to long high speeds rides I do when I ride I to town, to my job its a 16 miletrip one way and this bike has made that trip more than once without a single issue and I ride at a good clip the entire way, Im actually feeling pretty confident that my Opti2 will give plenty good lubrication but Im wondering if the aluminum will take the beating the bushing will take at the high rpms.......shrug
Only time will tell.....!
Map
Still waiting on the titanium wrist pin, Juicemotoparts has been behind getting things shipped, I ordered the parts back on 3/15/2014 and still waiting, hopefully they will get it out to me next week and then when I have a chance Ill put it in the old BGF engine and see what the results are.
Map
I got a titanium wrist pin from Juice Moto & tried it. Right away I noticed how much smoother it ran in my Super Rat! But it didn't last. Within 5 miles the vibes started coming back. Within 10 miles, it was knocking the piston against the head. I killed it & pedaled home, yanking the head. Witness marks on the piston, but the head is okay. I pulled the jug & pin to discover a damaged pin. Old stainless pin is going back in. Maybe I can drill holes in my piston to lighten it, or save up my pennies to send my motor off to someone skilled to have it balanced properly.
My advice for those considering a titanium pin, DONT! It may have nearly the same tensile strength of steel but it doesn't hold a candle to case hardened stainless steel. It's too soft to use in an unbalanced two stroke. I lucked out & caught it in time before serious damage resulted. If I had been running flat out full throttle, my motor might be roadside shrapnel now. It did not last ten miles of easy cruising (20 mph).
My advice for those considering a titanium pin, DONT! It may have nearly the same tensile strength of steel but it doesn't hold a candle to case hardened stainless steel. It's too soft to use in an unbalanced two stroke. I lucked out & caught it in time before serious damage resulted. If I had been running flat out full throttle, my motor might be roadside shrapnel now. It did not last ten miles of easy cruising (20 mph).
Attachments
No, that's to show scale.
Not everyone sees it for what it is. Quarter gives perspective.
Edited: Aluminum bushing is bad idea.. tried it and it failed quickly....
I plan to use a bushing instead of a needle bearing, which did you use?
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Needle bearing. Bushing is heavier & defeats the purpose of using lightweight titanium.
I have thought about this also, I plan to weigh everything out and if it's as far off I think it may be then the titanium pin will not go in the engine, I can remove a few grams by notching and drilling the piston in areas that wont compromise strength are uncover a port, just doing that to a piston alone may remove just as much weight as would be lost with the titanium wrist pin, but by doing this to the piston it is possible that the mod will allow the titanium pin and brass bushing to still have less weight than the steel pin and needle bearing alone, oh well, when and if I ever get the titanium pin I can mess around with it and see whats what, I am just getting more and more skeptical about using it at all, the idea of a lighter pin is great but if it wont hold up then its just a waist of time and may only cause people to destroy an otherwise good running engine.
Map
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