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Post by Schlappy on Mar 25, 2019 17:30:53 GMT -5
Recently replaced the cylinder, piston and head on my Genuine Roughhouse 50 (49.7 cc 2 stroke) with stock replacement parts and for a couple months things seemed fine, but now lately strangeness has reared its all too frequent head. Around or above 6200 rpm, an aggressive vibration and sound emits from somewhere underneath and the bike loses most acceleration, sounding like a louder muffler is on it. Upon inspection there were no loose cooling cowl or fender rub, nice and snug exhaust through and through but it persists. I removed the head, cylinder and gave the connecting rod a jostling - solid as the rock of Gibraltar. Then gave the piston a wiggle. Should there be absolutely NO play in the piston horizontally and/or vertically in or around the bearing pin / casing cage ? I haven't closely inspected the reed valve yet as I'm awaiting gaskets for it and i'm fairly certain it's not cvt related, at least not the the best of my knowledge.
I need to be figured out any insight is appreciated.
Again the symptoms are at higher rpm (6200 rpm / 22-24 mph) the whole bike vibrates and the muffler sounds louder, struggling to accelerate.
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Post by 2stroked on Mar 25, 2019 18:51:13 GMT -5
There will be a small amount of play when wiggling the con rod. Not a ton.
The exhaust note changing is odd, how did the plug look when you pulled it out? The only time I have had a scoot change exhaust notes was because I blew a head gasket. But that was a constant sound.
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Post by oldgeek on Mar 25, 2019 19:32:58 GMT -5
Sounds like a CVT problem to me. Have you inspected it yet?
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Post by Schlappy on Mar 26, 2019 15:16:53 GMT -5
Not a cvt issue I checked it all and everything seems fine. The spark is a nice tan color.
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Post by geoffh on Mar 26, 2019 16:15:23 GMT -5
I,d spend a while browsing the tech sec 6200rpm = 24mph that's just slow unless your oversize and your tires are flat,strip and check the CVT again,look at belt,rollers etc recheck the exhaust is sealing,the engine is probably fine they go wrong in a spectacular fashion very quickly if not OK.keep us posted we will help but you need to show us what you,he done.
Geoff
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Post by 2stroked on Mar 26, 2019 19:58:30 GMT -5
I would really closely at the rear half. If its possible, start the bike, put it on the center stand and rev it out. Watch to be sure the belt is moving up in front and down in back as you rev, and vise versa as it slows down.
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Post by Schlappy on Apr 5, 2019 13:25:34 GMT -5
I think I've found it out finally,
Piston slap and too much play in the big end.
Simple crank case separating, right? new bearings, why not do all bearings whilst it's open, swap some crankshaft and small parts, check this and that - stitch her back together and have the wedding.
wish me luck
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Post by aeroxbud on Apr 5, 2019 13:56:30 GMT -5
At least you found the problem.
Good luck with the rebuild.
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Post by harleyracer59 on Apr 8, 2019 21:03:59 GMT -5
weigh old and new pistons and the wrist pins. bet they weigh different. that's whats causing your vibration. and the change in exhaust note, is probably perceived by rider. and really a combination of everything shaking from motor to plastics. have someone else ride it and take it to the problem rpm. keep rpm around there and ride past you and down the street, turn around 100-150 yards and come back. off the bike I bet you wont hear the change in tone. maybe when it gets closer youll hear the added noise of vibrating parts. but it will be in addition to the exhaust. please report back with what you find.. good luck.  |
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Post by Schlappy on Apr 25, 2019 21:45:25 GMT -5
Well I really screwed myself.
I removed the engine, stripped it completely down to just the case in hopes of separating the case halves for a crankshaft & bearings swap (stock parts(wasn't bothering with the transmission end)). All that was left was the center stand pin but it wouldn't budge. Took it to a garage and they pounded on it for 5 minutes before giving up. They squirted the pin up with PB Blaster and told me:
"The pin is aluminum and the stand iron so something was welded. Let it soak for a day and try again."
Next day I tried again but it moved maybe a couple millimeters tops, no separation of case halves whatsoever. Frustrated I decided to re-assemble when I snapped a bolt! (I don't have access to a torque wrench, and wasn't paying attention.
Wasn't a bolt behind the stator but above that assembly closest to the reed valve opening, but a case bolt none the less).
To add further injury, when re-inserting the oil pump a tiny washer slipped off the end of it and fell into the crank case. So now not only can I not separate my case halves, there's a washer in there too. Furthermore the crankshaft doesn't exactly spin freely. At near top dead center it sticks hard. Motor doesn't turn over.
If anyone knows where to get a case separator tool and flywheel comp puller for the Genuine Roughhouse 50 (Minaerelli Horizontal 50cc) on the cheap please holler at me. my strict budget doesn't allow for mechanics, garages or new engines.
Until then, wish me luck staving off suicide.
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Post by rancevas on Apr 26, 2019 5:24:22 GMT -5
Don't worry, there is nothing that you can't fix. A broken bolt is always frustrating to hell. Recently I was disassembling a 4 stroke 125cc V shaped Honda Varadero motor. The main reason for disassembling it was that the owner wasn't too bright - he unplugged the carbs, removed the side covers and let the sand get into all of the smallest creases. Ugh. So, when I was putting it back together, a bolt snapped and fell into the crankcase. Cold sweat and anger settled in. I needed to drive that damn engine to a mechanic so that he could wield something to it and take it out. And he did. What a relief that was!
So, coming back to your engine. The metal parts got wielded together, right? That might mean a lack of lubrication, which means a faulty oil pump. I still have the very same engine in my garage - Minarelli horizontal 50cc. The oil pump on those things are unreliable as hell! I suggest you stick to premix next time. I had to rebuild mine 2 times because of that highly sophisticated oil pumping technology.
Take a picture of the bolt that snapped and the bolt that is stuck. We need to know the exact situation to give you tips.
And I'm pretty sure you must rebuild the engine to get it working normally again. Stiff crankshaft might mean that bearings went to hell.
I separated my minarelli crankcase without any special tools. I did it by tapping with a rubber mullet on the protruding crankshaft from the transmission side. If you have a metal hammer, place a piece of wood in between. And if you are not planning on reusing that same crankshaft - just beat it until it falls out. (Be careful not to damage anything else, alright?)
(You must remove stator before separating the crankcase. Under it there are about 9 bolts that hold it tightly together)
I removed stator without special tools as well. But the way I did it was so embarrassingly stupid, I can't share it with you all. All I can say - don't involve any hammers and screwdrivers, though.. But hey, trial and error gets it right.
And finally, when you feel frustrated, step away from that engine for a couple of hours. It's mind boggling how much nerves a small engine can eat up. It requires a really cold outlook. I'm sure you will fix it, all you need is a strong positive mindset and a bit of motivation (It's a very hard thing to keep when everything's going to hell). Once again, there is nothing that you can't fix!
Good luck.
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Post by aeroxbud on Apr 27, 2019 19:52:22 GMT -5
I'm not sure about your engine. But I know my Yamaha vertical Minarelli has the stand moulded into the case on one side. Done two, and they were both the same. Could still split the engine. Just the stand on the spring side stays attached to that case half.
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Post by Schlappy on May 9, 2019 0:39:46 GMT -5
Update: By some miracle I got the case separated finally and even managed to get the snapped bolt thread out without drilling, PLUS the tiny washer that fell inside off the oil pump was located. The center stand pin took an ocean of lube. Was I ever ecstatic. rancevas - Here's hoping my oil pump will behave. My fuel oil lines have since bled dry so going to prime like there's no tomorrow. Heheh, how attached to that 50cc engine are ya ? aeroxbud - Mine too is molded on one side, which I concluded all the pounding on the end of it by that garage and myself did nothing more than deform the ends. I'm beginning to think that garage is typical. Know what I mean? Inspection of the crankshaft and it's bearings showed they are in perfect condition, no play whatsoever, contrary to what that garage told me. Side to side and up and down nice and tight. Just going to replace rubber oil seal bearings, fresh gaskets, grease and reassemble and cross my fingers. Been watching 1000's of hours of vids on case assembly and I'm not a huge fan of the hammering in method. Gonna try the fire and ice method, with the help of dad's lucky rubber mallet. Hunted through two towns for a HEXAGON FLANGE BOLT(M6*60L) and no soap, so have to wait the week for online delivery. For a bolt. If after everything I can't get it to start or worse, has the same mysterious issue(s) Ill have no other alternative than to tie a chain to it, the other end around my neck and push it off the bridge crossing a river. I fear I've used up the only favor god granted me on this endeavor. |
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Post by aeroxbud on May 9, 2019 0:47:15 GMT -5
That's good news. Things are looking up. 👍
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Post by ThaiGyro on May 9, 2019 2:45:10 GMT -5
If at first you don't succeed...Check all bearings and tolerances in both crank connections and CVT bearings. Make a list, record side play/end play/fore play. Then, do it all again. If your check two or three times, in methodical fashion...forward, backward, sideways and the numbers change? You are getting closer. The diagnosis given above seems correct to me regarding bearings or CVT issues, as they are very dynamically connected and you are getting consistently bad vibration feedback. (RPM) Could be one or a combo. Since you have it shredded like the Scarecrow in OZ..go through everything in meticulous detail. Your answer could show up on a flying monkey. Even simple stuff. Wheels bearings? Floorboard screws? Muffler solenoid? When you refer to tying pieces to humans and jumping from bridges, please take note: I despise the thought. Not funny. What is funny is tying that to that lame ass garage mechanic who gave you no help...and pushing. Gene pool control.
In fact...pack them up and send them to Spain, in care of Lionel Messi. Liverpool did, problem solved.
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