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Post by Schlappy on May 29, 2022 19:26:52 GMT -5
Lately the ol' Roughhouse has been chewing up pistons like there's no tomorrow! The culprit 100% of the time is a broken wrist pin bearing causing bits to crush piston rings resulting in compression loss. What could cause these weakest links to keep crumbling ? The crank arm has zero up & down play with just a little side to side, like it always has. Each rebuild get a new piston with new bearing, wrist pin, and cir clips that comes with the piston kit that matches the cylinder and it's manufacturer, flushing out the crankcase with brake cleaner and thoroughly inspecting. The hole that the bearing sits in is smooth and damage free. Engine oil is used to lube it all during assembly. I need answers money is gotten too tight to keep buying pistons.
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Post by Zino on May 29, 2022 19:47:19 GMT -5
Can you post some pictures of the pistons Are you using g circlips c circlips or horse shoe type
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Post by Schlappy on May 29, 2022 21:12:59 GMT -5
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pili
Scoot Enthusiast
Posts: 209
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Post by pili on May 29, 2022 22:25:52 GMT -5
Possible oil delivery problem? Weak pump or pinched line? So odd I've never had that particular problem.
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Post by Zino on May 30, 2022 9:53:56 GMT -5
Ouch That walked out of the grooves they dont look beat up just the side of the piston . Is this a polini quality control issue ?
I usually use the g clips (I can never get the c clips to Install confidently) The Horseshoe clips that polini sends are the easiest to put in . Some guys say put the hardest ones in you can find so they are hard to get out .
I turn them so that the opening is up like this "u" so the open end is up towards the top of the piston . Others install it so the open end is down When I feel they are in in rotate them 360 degrees with a pick to make sure they are in the groove and then turn them to position .
If you are done with Polini And your Polini head is okay . Athena Sports Alumunim cylinders work really well with the Polini Head . It tightens the squish right up . It improves the cylinder and makes it a copy of the Stage 6 MK1 that was very popular.
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Post by Schlappy on May 31, 2022 7:55:05 GMT -5
pili I hope it's not a delivery problem. The way I go thru oil from the reserve would indicate it's getting oil and I add a teaspoons worth to the tank at fill up. @ Zino I too have the clips' openings up or down. The Jug wasn't too badly scored and have really no choice but to reuse it with a new piston. Waiting on a reinforced wrist pin cage to be delivered. Ive been following your Roughhouse build and have been keeping a closer watch on my temps. Is it normal to peak around 330F (wot) in the summer ? would jetting up or down help lower temps ?
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Post by Zino on May 31, 2022 11:50:04 GMT -5
With the stock carb is was hitting 330 with a street pipe stock bore stock carb That would be the upper limit for my scoot based on sound feel and plug color With a 17.5 carb I run a little cooler I have a extra Athena jug and piston I pulled off a zuma with a few hundred miles on it that you could swap too
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Post by Zino on May 31, 2022 12:01:59 GMT -5
With the stock carb is was hitting 330 with a street pipe stock bore stock carb That would be the upper limit for my scoot based on sound feel and plug color With a 17.5 carb I run a little cooler I have a extra Athena jug and piston I pulled off a zuma with a few hundred miles on it that you could swap too
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Post by Schlappy on May 31, 2022 13:57:15 GMT -5
Update: Another one bites the dust: Another thing I noticed just now, My case halves are "off center" by around 4mm or so, as if the cases were moved at some point. The mating surface of the jug to it is perfectly flat, and the crank spins free &smoothly, but on the inside the don't quite line up exactly. I've never disassembled the halves, but I did a low speed tip over once on the exhaust side last winter. Can definitely feel it with fingertip rub. I'm considering loosening the case halves bolts and see if I can re-align but I'm lack of any case splitting tools. You'd really let me have that Athena kit That'd be awesome I'll pay for shipping.
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Post by Zino on May 31, 2022 18:17:13 GMT -5
That cylinder is toast from top to bottom. Something is a miss here is a picture of my extra roughouse engine from same angle so you can compare.
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Post by Schlappy on May 31, 2022 20:27:11 GMT -5
Looking at yours tells me mine is normal. Does your piston arm have any side to side play like maybe 2-4mm like mine ? I was told a very little was normal. I have a case splitter & bearing / seal puller on its way and am going to practice on my original RH50 which has all new bearings and crankshaft in it that have Zero miles on 'em for the current build, when and If it needs it. Getting a 2nd RH was a good idea i've used a lot of parts from the 1st to rescue the current, like a mirror, rear light bulb, airbox, even swapped a rear tire as well as various other extra parts. As for now I've got the original 50cc jug back on. What size jets (main and Idle) did you have when yours was 50cc, aftermarket pipe ? If you're serious about that Athena Jug & Piston I'd be grateful!
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Post by Zino on May 31, 2022 22:58:00 GMT -5
My side to side play is less than 2 mm . You have a hotter pipe than the street pipes I was running primarily I was running a 85-88 main 38/35 pilot worked real well. I was turning low 8 rpms . If I had the yasuni z the rpms would run a little higher . I would expect to up the main to a 90 and above with the pilot being a 38 or a 40 So I was richer through the full throttle range . Let me grab the athena and send you some pics . Do you have a good polini head or are they all trashed ? The Athena stock heads are OK the polini head works real well at tightening up the squish. here is kenho and i talking about the polini head paired with his athena cylinder in his thread 49ccscoot.proboards.com/thread/25916/kens-08-zumba?q=polini+headin this thread He returned his polini kit because of quality control issues and kept the head . The polini cylinder head is the same on the corsa and the contessa 49ccscoot.proboards.com/thread/25916/kens-08-zumba
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Post by snowmeiser on Jun 1, 2022 4:01:41 GMT -5
It seems to me as your motor is detonating either from gas quality , to much timing and or to much compression sending shockwaves to do the damage in the pictures.
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Post by aeroxbud on Jun 1, 2022 4:04:14 GMT -5
That mismatch between the case halves looks similar to what you find on a lot of other scooters. After so many problems I would be looking at replacement of the crank. Perhaps the eye is slightly off after the first seize. This would put uneven pressure on the wrist pin bearing. The Yamaha aerox cranks have been know to do this.
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Post by Schlappy on Jun 3, 2022 19:30:01 GMT -5
@ Zino Here's the head: You tell me would this be useable again? This would go right to the cylinder no copper / aluminum gasket, riight ? I'm hoping so because that's what I had done.. I found the crankshaft that came out of my 2016 RH, my first RH50, from the bottom end rebuild that went foul. The bike garage I took it to machine pressed the new crank and bearings in, and it spun freely but after the halves were back together and piston and jug were on, it stuck very hard except near bottom dead center, at which point it was abandoned. Anyway this original crank assembly has over 14k miles but it's arm is much much tighter side to side less than 2mm, also with zero up & down than my current, plus all the seals and bearings in the 1st bike have Zero miles on them because they're new, and my case splitter, seals/bearing pullers arrived today. I'll be tearing down the 1st and try to find out why it sticks checking specs on everything. I'm apprehensive about separating the current bike because it runs and of my inexperience and disaster the 1st time around with the 1st bike. I have 3 crankshafts to my name. The current which I think has too much play in the arm, the oldest, which seems to not have needed to be replaced, and the brand new unrun one in the old scoot, all of them are stock parts.
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