Honda CR125R piston slap?

[Stusmoke]

The hole where the coolent is draining from is supposed to be there.
You have leaking water pump seals.
Check your gearbox oil for water as well.
Rule of thumb with any bike I buy is do not trust the previous owner.
Put fresh fuel in straight away, check all fluids and then fire it up.

By the sounds of it stu I would pull the barrel of as a bare minimum and go from there.
You are going to need a water pump seal kit as well.
Best you fix everything now before it turns to custard.

My thoughts too. I don't trust previous owners either. But the jokes on him for selling me a dodgey bike, cos I kept the left crank case and silencer from the wreck. hopefully that'll pay for the damages

Im gonna go pull the top off her now. The spark plug seemed to be in decent nick besides some carbon fouling so its hopefully a top end job. and the water pump seals aswell.

[Stusmoke]

Never reuse base and head gaskets. Honda cr 125,s have 2 diff. sized cylinders a and b. Even if you put a honda a size piston in a a size cylinder, the honda piston is too small, causing piston slap. The alum. frame resinates it further. A forged piston is also much louder than a cast piston. Do a google search, some riders are using Husky pistons, in there 2000-03 cr125,s. I think the Vortex piston for a cr125 is the same size as a Husky piston. There is a performance increase when you get the correct size piston. Your prob. asking your self, why did honda put the wrong size piston in, part of the reason is it,s more diff. to seize the motor, from the wrong jetting. More or less the stock piston is for break in purposes only. A play rider that never jetts his bike should stick with the stocker.

I pulled the cylinder head and barrel just now. Getting the barrel off was a nightmare though. Anyway all is good in there, piston looks brand new. I'd be willing to bet you're on the money with the incorrectly sized pistons. When I was looking at new piston kits it said the stock bore was 54 mil. When I looked on the engine, it informed me it was 54.5 mil. So I'm pretty sure you nailed it thanks. And TMKIWI the tranny oil is a sickly grey color so you were on the money with the water pump seals too. I'll drain the tranny oil tomorrow but do I need to do anything do the tranny other than replace those water pump seals? Also, will riding this bike with that .5 mil space destroy the cylinder? I would've thought it would. I'm gonna be screaming it till the cows come home too it will be shown absolutely no mercy.

Thanks guys

[Jeram]

yeah will destroy your entire motor if you ride it any more.

all it'l  is the skirt or crown to catch one of the ports and it'll be all over, im suprised its still in good condition!

[Stusmoke]

yeah will destroy your entire motor if you ride it any more.

all it'l  is the skirt or crown to catch one of the ports and it'll be all over, im suprised its still in good condition!

Thats what I thought 

Thanks again honda, you guys always come through on good ideas

http://www.motosport.com/dirtbike/WISECO-PROLITE-2STROKE-PISTON-080-OVERSIZE
will that do for a piston replacement?

Or perhaps: http://www.wiseco.com/ProductDetail.aspx?ItemID=676M05450&ModelID=121&ModelYear=2001&AppID=4187
Are they the same thing? It definitely says 54.5 mil bore just under the left hand side crank case cover. Thanks guys

[SachsGS]

Measure the cylinder,piston and ring end gap so that you know for certain the condition of the top end.

Coolant leaking into Japanese transmissions is a HUGE problem.The Japanese trans. are typically cast,machined and case hardened and when you loose the lubricity of tranny oil the case hardening is then pounded off and you are left with a mess. Seen it many times.

[Stusmoke]

Measure the cylinder,piston and ring end gap so that you know for certain the condition of the top end.

Coolant leaking into Japanese transmissions is a HUGE problem.The Japanese trans. are typically cast,machined and case hardened and when you loose the lubricity of tranny oil the case hardening is then pounded off and you are left with a mess. Seen it many times.

A good idea, I'm not runnning it at the moment so I'm gonna drain the tranny oil today. I should also add that the cylinder looks likes its sleeved, heres some pictures. Sorry if its a bit difficult to see




Its hard to see the piston there but it looks fine.
It looks like its sleeved, whats the verdict? in the event it is sleeved, wouldn't that make the piston the CORRECT size?

[Stusmoke]

Hahahahahaa okay so theres one mil at bare minimum of side to side play on the crank end of the conrod, and the same thing with the piston end. I guess we know where the cronic rattling noise is coming from right?

How in the name of christ this engine hasn't shredded itself to pieces is beyond both me and what one could consider to be logical. I stuck that mother to its rev limiter several times when I was checking it out and rode it pretty hard. Its unbelievably unlucky that it didn't blow. Yeah, I definitely said unlucky. If it had blown I would've told him to gtfo my property would've saved me alot of trouble.

So I guess its time to split the cases huh? What am I looking at fellas? Would I just be able to tighten the shit out of everything or will it all need to be replaced? Also, all the tools I will need to pull off this repair.

I will have a video up next post. Thanks guys I appreciate you taking the time to help me out.

[Stusmoke]

http://www.youtube.com/watch?v=WuqTb2DivXM&feature=youtu.be

Worlds worst rebuild.

[Recovered]

when I did the top end on my 2002 Honda CR125 this past November I ordered the "A" piston for mine to go with the "A" cylinder when the parts arrived I had a "B" piston and a note from the factory stating that you can NOW use the "B" piston in the A cylinder Honda discovered that the tolerances were much closer and could use the B piston with A cylinder without any problems as far as any other years useing those two together I couldn't tell you. Honda pistons are for break in purposes only OOOMMMGGG thats a good one super trucker who told you that BS your pro racing buddies and there mechanics and team managers??

[2T Institute]

Hahahahahaa okay so theres one mil at bare minimum of side to side play on the crank end of the conrod, and the same thing with the piston end. I guess we know where the cronic rattling noise is coming from right?

How in the name of christ this engine hasn't shredded itself to pieces is beyond both me and what one could consider to be logical. I stuck that mother to its rev limiter several times when I was checking it out and rode it pretty hard. Its unbelievably unlucky that it didn't blow. Yeah, I definitely said unlucky. If it had blown I would've told him to gtfo my property would've saved me alot of trouble.

So I guess its time to split the cases huh? What am I looking at fellas? Would I just be able to tighten the shit out of everything or will it all need to be replaced? Also, all the tools I will need to pull off this repair.

I will have a video up next post. Thanks guys I appreciate you taking the time to help me out.

Side play in the rod  and piston is correct. Piston to bore clearence is what needs to be checked.

[Jeram]

check vertical wear on big end

ANY up/down movement in big end of rod is a no-no and will need to be rebuild.

[Stusmoke]

http://freestylemtx.com/forum/showthread.php?t=12534

Heaps of guys on there are reporting similar problems and saying its normal. the piston can't move around in the cylinder at all either so I'd be willing to bet the rattling noise is coming from the loose conrod. Theres no up or down movement but that massive side to side play has me worried. Also I should add for a piston that was small enough to cause piston slap? It was nigh on impossible to get it back into the cylinder. I don't think the pistons the problem anymore, I think that conrod's side to side play is causing the noise now. I really don't think its meant to be that loose. But I've been wrong before. Also, I'm going to check over the entire bike and make sure theres nothing on there that could be loose and causing the rattle.

[Jeram]

check the piston size, and then check the manufacturers clearance specs... then compare this to the bore size. its the only way to do it properly.

0.5mm movement of either side of rid is OK

have you considered that the noise, if not coming from the piston/bore is more likely comming from the crank bearings or the powervalve flutter? RC valves are known to flutter on some bikes and it sounds just like piston slap

[Stusmoke]

The conrod says B on it, and the piston is a vertex with the numbers 1001 on it. Not sure of the significance of that but it didn't seem to have a letter on it anywhere. Besides the letters in vertex of course. The previous owner rebuilt the whole bike so he says and from the condition of the crank, conrod and piston, I'm inclined to believe him. I'll get some new gaskets and see how I go. But from what I can see theres nothing wrong with it. Numb nuts had obviously neglected to warm it up whenever he rode it and it shows, but thats about it. Nothing major. RC valves you say? How would I go about inspecting them and will I need specific tools?

[Super Trucker]

when I did the top end on my 2002 Honda CR125 this past November I ordered the "A" piston for mine to go with the "A" cylinder when the parts arrived I had a "B" piston and a note from the factory stating that you can NOW use the "B" piston in the A cylinder Honda discovered that the tolerances were much closer and could use the B piston with A cylinder without any problems as far as any other years useing those two together I couldn't tell you. Honda pistons are for break in purposes only OOOMMMGGG thats a good one super trucker who told you that BS your pro racing buddies and there mechanics and team managers??

  That,s the word right from DGY, on some cr125 another year cr piston works better, other manufacters pistons also, especially for expert level mod engines. Yeah honda just figured it out, that you can use the wrong size piston, whatever man. Let,s just try to help Stu out, or you can throw more insults my way, I don,t care.