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Post by midlifecrisisrd on Apr 11, 2010 13:44:50 GMT 1
Hi, have been away from two strokes for a few decades so not sure if I have just been spoiled with modern stuff but how noisy should a ypvs be.
Bought motor that had been rebuilt, only done 200miles since rebore and crank.
Motor runs fine but has metalic noise that seems to be coming from bottom end, sounds like from gearbox but hard to tell. Does not go away when clutch in and doesn't go away or get worse when revved.
Any ideas?
Steve.
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Post by midlifecrisisrd on Apr 11, 2010 15:59:17 GMT 1
Mine does exactly the same and i have never got to the bottom of it and i have done about 1500 miles since I had an unrelated duff crank and when i changed that ,i also fitted all new gearbox bearings and looked at everything. So when i put it back together,i expected the noise to go but was still there !!!! Will keep running it and see how it goes. Building a second one so will see how that sounds when I get it running. Steve.
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Post by bare on Apr 11, 2010 18:02:03 GMT 1
Could be the Rotor rubbing the Stator, but that's on the other side of the engine. Primary gears not of correct backlash? Only an issue if theyt have been 'changed' since manufacture. Bearings? Crank and or Clutch. Missasembled bits? Regardless...strange noises in machinery ...Do Not.. self heal, they invariably cost more to 'fix' with each passing moment of use.
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Post by midlifecrisisrd on Apr 12, 2010 13:16:12 GMT 1
Could be the Rotor rubbing the Stator, but that's on the other side of the engine. Primary gears not of correct backlash? Only an issue if theyt have been 'changed' since manufacture. Bearings? Crank and or Clutch. Missasembled bits? Regardless...strange noises in machinery ...Do Not.. self heal, they invariably cost more to 'fix' with each passing moment of use. Can hear it from both sides, I changed the rotor and stator from 31K to R but will be changing back soon, will see if it makes any difference. Have heard of rotor not seated on crank properly so will have to check that as well. Could it be the clutch basket bush, does seem to be some lateral movement through the clear clutch case although very slight, may just be the centre bolt not sitting central. One thing I did notice is that if you turn the gearbox sprocket you can feel resistance but on my R motor it spins freely but it is high mileage. The noise sounds to light to be primary drive almost like the kick start mechanism or something. On other bikes I've had if you move the kickstart down a bit while running you hear the ratchet all the time. The YPVS only makes the ratchet noise when you are rotating it, if you hold it down half way the ratchet noise goes away when you hold it still. Is this right? Steve.
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Post by bare on Apr 17, 2010 18:02:37 GMT 1
Dunno "noises' frighten me as well but no answer. Do suggest GL4 Gear oil (it's cluctch safe) in the trans 75/85 is ...Very good ...in my experiences (it's equivalent to 10/40 'approx' engine oil viscosity as GL is a different weighting system) solving a progressively dissapearing Neutral problem as the engine warmed.. when it was using Yamalube 10/40.
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Post by midlifecrisisrd on Apr 20, 2010 20:24:27 GMT 1
This noise is very similar to mine I'd say mine sounds the same, not a knock or rattle, just seems like general mechanical noise that you notice more at idle. Steve.
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cooler
Thrash Merchant
Posts: 490
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Post by cooler on Apr 20, 2010 20:51:46 GMT 1
Had a similar noise when i first rebuilt mine, after replacing the clutch and crank still had no joy,eventually found it to be mismatched crank cases, hope it's not the case for you but was for me ...... that's sommat else to worry about now...
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Post by midlifecrisisrd on Apr 21, 2010 8:28:04 GMT 1
Had a similar noise when i first rebuilt mine, after replacing the clutch and crank still had no joy,eventually found it to be mismatched crank cases, hope it's not the case for you but was for me ...... that's sommat else to worry about now... Thankfully mine are marked with same number so no worries there. Steve.
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cooler
Thrash Merchant
Posts: 490
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Post by cooler on Apr 21, 2010 19:00:36 GMT 1
got to hold me hands up and say that i don't know but i do know it solved my problem,,, if i was to take a punt at your question i did notice some scoring in the bottom case on the flywheel side possibly caused by the crank webbs but don't hold me to that although i believe that the tolerances of the cases are individual at the casting/production stage so the prognosis does seem to fit the symptom...... but i am happy to stand corrected......
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Post by alfella01 on Jun 14, 2021 15:11:20 GMT 1
Hi Steve did you get to the bottom of this noise ?
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Post by midlifecrisisrd on Jun 14, 2021 16:04:59 GMT 1
Hi Steve did you get to the bottom of this noise ? Lol, good old forum search function. This was 11 years ago 🤣 I ended up stripping the whole engine and started again Rebuilt doesn't mean everything was replaced 🙄 Steve
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Post by alfella01 on Jun 14, 2021 16:49:41 GMT 1
What did you find ? If you can remember 😁
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Post by midlifecrisisrd on Jun 14, 2021 17:32:11 GMT 1
It was on 1.5 over and bore was a bit loose from memory
Steve
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