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Post by Bozzy on May 2, 2017 8:51:19 GMT 1
Sorry guys will delete this like after as I know it's just for LC's but is something that I am sure someone will have advice to and I know the post will be missed in the other section rdlccrazy.proboards.com/thread/39839/ar125-bad-noiseWill delete this link after cheers Bossy |
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Post by muttsnuts on May 2, 2017 9:05:20 GMT 1
is the piston hitting the head gasket? - has it recently been rebored or is it nickasil bores ?
if not, could be a broken ring
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Post by headcoats on May 2, 2017 9:14:40 GMT 1
You will have to bite the bullet and get the top end off for inspection
Wouldn't run it anymore
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Post by davey on May 2, 2017 13:25:37 GMT 1
Head and barrel off , i wouldnt run it again
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Post by Bozzy on May 2, 2017 15:06:36 GMT 1
Head and barrel off , i wouldnt run it again had barrel off twice and no signs of any damage. head has been skimmed but did put two base gaskets to check clearance even put old head on and it still does this. the piston does move in the bore you can wiggle the piston from the top but then again my old one did this. |
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Post by stusco on May 2, 2017 15:14:24 GMT 1
Is there play in the small end bearing,had a similar sound on a tdr250 before it ate its self
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Post by Bozzy on May 2, 2017 16:13:15 GMT 1
Is there play in the small end bearing,had a similar sound on a tdr250 before it ate its self Now that's a great question and something I have been discussing with someone earlier. I have used a new original small end but I noticed last night that just putting the little end into the conrod my old one was actually a better fit than the new one. I know they are not a snug fit but you can rock the new one a lot more in the rod than old The sound is defiantly worst on overdrive or no load and goes when reved up is this signs of the little end? I also just not sure also what piston slap sounds like as well as there is clearance in the bore Andy you can move the top of the piston said de to side but would this not knock or tap all the time |
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Post by bare on May 2, 2017 18:24:09 GMT 1
Best to disassemble it Try the suspect small end needle cage for slop when the wrist pin is fitted.
Fair chance that if it wasn't buggered previously.. It is Now.
Meaning fresh rod and bearings required.
Machinery has small margin for errors.
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Post by Bozzy on May 2, 2017 20:19:29 GMT 1
Best to disassemble it Try the suspect small end needle cage for slop when the wrist pin is fitted. Fair chance that if it wasn't buggered previously.. It is Now. Meaning fresh rod and bearings required. Machinery has small margin for errors. thank will do it was new piston and pin. When you say rod you do mean (and I hope) the pin not the actual conrod meaning engine strip down? Checked the piston bore clearance. Book say 0.045 to 0.055..... my original barrel and piston I could get 0.10mm but tight then again its done 18k however the new MA tuned barrel I could start to get 0.15mm and 0.1mm was a friction fit..... BUT as its a tuned barrel/head I am not sure if clearances have to be greater and would not the sound change or get a little less when heating up as it stayed the same if not louder.. ok when revs are high but tick over or run down its bad as vid.. I expect it can only be either Little end or piston slap. |
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chippy348
Drag-strip hero
Posts: 277 
Member is Online
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Post by chippy348 on May 2, 2017 21:17:58 GMT 1
Daft question, is the piston in the correct way around ? I may be wrong but i think the AR125 has its ring pegs at the front of the piston, so if you fit the piston as per 99% of 2 stroke engines to the rear then they will be crossing over the ports. Just a thought it may be wrong though.
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Post by Bozzy on May 2, 2017 23:23:11 GMT 1
Daft question, is the piston in the correct way around ? I may be wrong but i think the AR125 has its ring pegs at the front of the piston, so if you fit the piston as per 99% of 2 stroke engines to the rear then they will be crossing over the ports. Just a thought it may be wrong though. Not a daft question its all appreciated. Made me actually check Looking from the top of the bike from front to rear the top ring has the peg at 11 oclock and the bottom ring about 1 oclock at the rear of the piston. The piston did have an arrow on the top facing forwards but that does put the rings as noted ie to the rear. I checked my original piston and tit appears all matches with the new one. However I noticed the rings are slightly thinner and I have marks up the barrel where they are nothing to catch or feel and the ports having been opened up makes the solid bit between where the rings run a little bit tighter. However I would expect if they were catching high revs they would catch and not just on the run down but I might be wrong. |
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Post by JonW on May 3, 2017 8:29:40 GMT 1
Is the PV properly setup? If these are like the KMX they have some kind of sliding bar that moves scroll PVs, if its set wrong it can tick.
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Post by stusco on May 3, 2017 10:27:27 GMT 1
No powervalves rotary and reed valve intake system
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Post by Bozzy on May 3, 2017 23:09:19 GMT 1
I really have concern that there is too much clearance in the piston bore... being able to get 0.15mm into the gap (ok wont slide down but 0.1mm does)book says 0.055 max its not looking good.I just don't know if tuned barrels are made with greater clearance than standard been trying to get Mick A but not sure if he is on hols or something
Bits are getting so expensive set of rings £16+. Was thinking ok getting a new piston gudgeon pin but they are £20 quid and I don't know if the one I have is ok its only ran for 10 mins
Starting to regret messing with trying to tune now.
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Post by arrow on May 4, 2017 7:30:21 GMT 1
I really have concern that there is too much clearance in the piston bore... being able to get 0.15mm into the gap (ok wont slide down but 0.1mm does)book says 0.055 max its not looking good.I just don't know if tuned barrels are made with greater clearance than standard been trying to get Mick A but not sure if he is on hols or something Bits are getting so expensive set of rings £16+. Was thinking ok getting a new piston gudgeon pin but they are £20 quid and I don't know if the one I have is ok its only ran for 10 mins Starting to regret messing with trying to tune now. The clearance at the top of the piston is way more due to the taper. The place to measure like that is around the bottom of the skirt. |
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Dave B
Drag-strip hero
Posts: 240
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Post by Dave B on May 4, 2017 8:28:58 GMT 1
Both piston slap, caused by too much piston to bore clearance, and clatter from a loose small end bearing are most noticeable as the engine slows when you close the throttle. While the engine is accelerating, there is enough gas pressure on the piston crown to hold the piston hard against the front cylinder wall, and to hold the small end bearing down. As you close the throttle, the gas pressure falls, and the piston can rattle from the front of the cylinder to the back, and the momentum of the rising piston as it stops at TDC will lift the gudgeon pin in the bearing, making a clattering noise.
I've only listened on computer speakers, but I'm pretty sure I can hear both noises from your AR.
Incidentally, pistons are tapered, on purpose, but the standard place to measure is just below the rings, not at the skirt. They are often oval too, but let's not bother about that!
Personally, I think you need a rebore and a new piston kit complete with small end bearing and pin. Changing parts piecemeal will be money down the drain.
Most people will have a rebore done after port work anyway.
Cheers
Dave
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Post by jon on May 4, 2017 10:12:51 GMT 1
Most people will have a rebore done after port work anyway. Cheers Dave Dave, that's not what Bob Farnham said to me, 'having a rebore after port work'. He said the opposite, that if a rebore was needed it was done before port work. The reason for this is to ensure port heights remain the same. Jon |
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Post by mattybeckett on May 4, 2017 10:38:49 GMT 1
Sounds like little end to me.
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reggit
Drag-strip hero
Posts: 230
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Post by reggit on May 4, 2017 17:36:13 GMT 1
Does sound little end-ish, is it doing it on throttle, off throttle, or all the time?
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Post by Bozzy on May 5, 2017 0:44:22 GMT 1
Its doing it more off throttle but does make the noise ticking over however appears to go at higher revs ie say 5k and above but will make the sound again when closing the throttle on run down. It is a new piston, dudgeon pin and original bearing just bought another off ebay but its copper case and I pushed one of the roller down out of the cage so not sure if I should try this replacement.
Tryed the little end with pin through in the rod the new one did actually appear to be a more snug fit that the original pin etc before changing which was ok. Thinking if I should try the old pin and bearing..
I will check the bores again but the new one you can start to get the 0.15mm down where as the old one (16k+ mils) .01mm and nothing else.
With the head skimmed I tried the old head to make sure its not clearance and noise still there
I am using 2nr base gaskets but sure this would not cause this?. one gasket put the squich around .5 to .6 which I though was too tight.
Bike was great before and after all that work and money I end up with an engine that sounds like a diesel!.
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