Need help with piston bearing

did you consider running the bronze bushing???
they are much more durable than a roller bearing, I think.
rc

I just noticed on 1 page its listed as being 10x14x16.5. IKO Torrington also do a 10x14x16.5. Just check the spec sheets to make sure they're suitable. FWIW, Tony from Rock Solid Engines told me that a bushed small end would not stand up to the rigors of their Hi Comp Billet head & would fail, so they cant have the same load bearing ability as a roller bearing, he seems to know his stuff. Cheers

Check old Briggs and Stratton engines they are bushed and have been ran at go cart tracks pushing over 20 H.P. My first H.T. had a bushed bearing and at over 6000 miles it looked cherry.

Yeah, I've seen plenty of sintered brass & sintered bronze alloy type bushing in ll manner of applications tht with proper lubrication last very well & handle great loadings, like in king & link pins etc, & plenty of bushed small ends, I was simply passing on wot I was told. I do have a chinagirl bush here (not fitted). It appears to be some kind of bronze alloy, not brass. Whether or not its sintered (heaps of microscopic holes to hold lube) I couldnt say. Cheers

re bushed small ends. Ok, a 4 stroke crankcase is an oil rich enviroment, a 2 stroke is scavenged. Small end loadings in a 4 stroke r bi-directional, uni- directional in a 2 stroke. Heat from firing that soaks 2 the small end occurs every 2nd stroke as opposed 2 every 4th, causing the sparse, highly loaded lubricant 2 lose viscosity so while bushed small ends r fine in low power 2 strokes, they become less able 2 handle it the more u try extract more performance from the motor. Thank you Mr Jennings. Cheers

ivan H said:

re bushed small ends. Ok, a 4 stroke crankcase is an oil rich enviroment, a 2 stroke is scavenged. Small end loadings in a 4 stroke r bi-directional, uni- directional in a 2 stroke. Heat from firing that soaks 2 the small end occurs every 2nd stroke as opposed 2 every 4th, causing the sparse, highly loaded lubricant 2 lose viscosity so while bushed small ends r fine in low power 2 strokes, they become less able 2 handle it the more u try extract more performance from the motor. Thank you Mr Jennings. Cheers

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That must be why it worked fine on my H.T. Flawlessly I mean that bushing looks brand new. ''seriously''. I mic'ed it out and it is cherry. I have plans to reuse it as the machine tolerances are better than any of the roller bearings I have come across in a HT in that spot of the motor.

I weigh in at 250 plus, carried all manner of cargo while I used that motor and red lined it routinely . Sorry just not totally sold on that conception explanation. Today's engine oil that we have is far superior that what we had years ago too. Also just what kind of heat do you get from a little ol Briggs motor on alcohol and 20 some ought H.P.

Hi GH, I'm not familiar with the Briggs & Straton motor ur talking of, & I'm not saying they dont produce 2 strokes, just all I've seen r 4 strokes. Jennings did testing 2 get his published findings, wot I wrote came from them, just as I wrote wot Tony from RSE told me (FWIW). I know RSE dont release products until they have been thoroughly researched & developed so I imagine he had good reason 4 telling me wot he did. If u want 2 argue about take it up with him, I simply posted wot I had been told & Jennings findings. Cheers

Hi GH, sorry mate, I shouldnt have said "argue", thats a bit harsh & I didnt mean 2 b rude 2 u. I appologise 4 that, I should'a said "if u want 2 discuss it further", ok. Keep on ridin. Cheers

I have a problem with what your are saying for a fair reason i think. These china's have such a piss poor sloppy roller bearing at the piston for one among other things. Even if you get a good bearing the the odds are like one in four that the rod end opening was even machined right. IMO from reading and seeing ..

So now everyone will blindly think that for some reason a china with a roller bearing at their piston is the good thing and it is not. For 4 longs years now everybody I know and hear from has blown a motor up.. The forum has a long history of this as well.

If the H.t . was built right that would be another story. I have seen countless motors blown up here where I live with my own two eyes in person. The small engine shop I work in has nothing good to say about them they show up blown up here too and told me of this before we even got to know each other....

Here is the deal I got a good motor once from the right sweat shop in China. It had a wrist pin brass mixed alloy bushing. I am flat out saying there is no way to wear it out. Mine is cherry. @ 6000 miles. The Cylinder being of inferior materials wore smooth out at the exhaust port. This bushing is not wore out and good for another 10,000 miles as far as I am concerned , with beating the bike hard. Nothing beats hands on personal experience and I will stand by it..

The china does not in no way posses this imaginary Uber kewl H.P. or have the rev's to back up the Gordon Jennings ditty point of view in my opinion the way it is being worded by you or I would have a wore out bearing.. Pretty simple

The clutch wont make it past 4 H.P.

What is actually comical is that I am arguing about a China Motor .

But folks should know the truth.. A upgraded piston bearing of any kind is better than the cheesy roller bearing these motors come with.

I also doubt that Gordon Jennings was messing with a pyle of broken China Motors when he wrote that book.

The real reason behind the not using the brass mixed alloy bushing any more was to keep the cost down on production and make more Dorito's . That cost them more money to do with out a doubt....

So when a follow figures out the sloppy tolerances into his equation where are you going to source the perfect slightly over sized roller bearing???? They are made in standard sizes last I checked.

So, I picked up a couple of Teflon 9/16" teflon faucet washers.
Is the exact measurement between the piston bosses 17mm?
If so, I will have to shave .7mm off each washer as my vernier caliper measures 2.7mm thickness.
I am thinking this may be difficult to sand down teflon,... OK, I tried it, elbow grease, some coarse sandpaper, some time, it's doable.

So yeah, teflon, good to 260 C, (500F)

Hi Toadmund, 17.3 on the 1 I measured, but there's a lotta manufacturers over there so expect as much variation. If ur gunna try extracting more grunt u should upgrade while ur in there, not that costly. A really good bearing is around $30. Cheers

Hi Goatherder, I dont at all disagree with u regarding the bearings in these, as u've no doubt seen me post its the weekest link in them. I upgraded them soon as I had 2 have the cases apart due 2 a crankcase gasket leak from the factory, as uno. I do like the bit about the dorito's, that gotta laugh outta me, good 1. They gotta lotta other week links as well, as uno, including the cdi which kinda pull em up on the rpm side of things. Anyway, cheers

and having a 10mm wide floating bearing in a 17.3mm space is just rediculous. Thats is definitely the weekest link. Its simply got no chance, & its crap quality 2. Cheers

I think I will order the Stihl chainsaw bearing at a garden store locally.
Part #9512 535 2340
http://thebookshq.com/download/illustrated-parts-list-stihl-ms-341-5.html

Yeah, its a good proven bearing, at least uno it'll handle any rpm these'll ever b capable of shimmed up. Not good 4 any bearing 2 b half outta the rod at times. Uno u can get good small CHT guages 2, the stock head aint got great cooling ability. They're a thermocouple setup with a copper ring that fits under the spark plug. Ultralights use em so if u have trouble finding 1, uno. Cheers

With regard 2 shimming the small end, the TD2 Yamaha's rod was centeralized on the big end by shimming the small end as they found thrust washers on the big end caused big end failures as it limited lubrication supply to the big end, so if it was good enough for race Yamaha's,,,,. Cheers

Does any one know what the numbers on the top of the piston mean?? I have 2-PK80's and I'm changing out the wrist pin bearings for better quality but the #'s are 4 and 5 seem to be the same size and dome just different #'s

even though i'm bumping this thread a bit, thought i'd share my $.02 for using a bearing.

http://www.vxb.com/page/bearings/PROD/NEEDEL_ROLLER/Kit9375

this is the one i had in both my grubee and my daemon motor engines before i switched to a 4 stroke.

it actually worked beautifully, had the pressed in nature of a bushing, while giving the friction reduction of the needle bearing.

only 1mm -ish of space between the sides of the bearing, and thats if it'll even move after it's been pressed in.

Thanks! for the info, since this thread is maturing I bought another brand awhile back that was recommended by some others on this thread and this is what it went into,a 1911 Indian BTR tribute, the engine is Highly Highly! modified and really is no longer a Chinese engine with all the top qaulity parts from around the world.
I did book mark this for future use Thanks! again