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Coolant or Jetting or both cr125 fouling plugs instantly

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So I have an 07 cr 125 fouling plugs before the bike even has a chance to warm up, plugs come out wet and oily on the tip. had both crank seals replaced last season because my main drive side seal blew. While it was split I had a new crank put in, we noticed my cylinder plating was pooched so I sent my cylinder off to be re-plated, put a new piston in the shiny new looking cylinder put the old warped head back on and called it a day. then rode it all season  having absolutely no idea about the warped head because I overlooked it when I was excited to put my bike back together and ride. Its now winter, snows on the ground. I recently went to go for a put and fouled a plug before I could get to the end of the street and back. I was also smelling coolant so checked the rad while running the bike, lots of movement and tiny bubbes. Pulled the head off and sure enough it was warped to the point where I could rock it back amd fourth on the mirror and see a small gap... so NOW after I replaced the head my problems persisted and I can still see little bubbles swirling around vigorously in the rad if I rev it with the cap off, I've had boiled it down to my cylinder probably being warped then I found a leaky hose by the exhaust that was dripping coolant onto the outside of the exhaust port. Which brings me to what I think may be an incredibly stupid question, could it just be the loose hose sucking in air that is causing my rad fluid to have small bubbles in it? And maybe im just experiencing increadibly rich jetting now that my head is actually sealed properly?   :lame:   :banghead:    :smashpc:  over and out.

Edited by Mikkel Flewwelling

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On top of your coolant leak issue,

cold weather, cold engine, rich jetting and high flash point 'racing' premix oil will all combine to foul plugs.

 

Once the mating surfaces trued and engine back together, perform a crank case leakdown test just to rule out a bad RH crank seal.

(damaged during installation, defective seal etc.) and closely inspect the reeds for any gaps or damaged petals.

Edited by mlatour

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Thanks alot for the reply's! I'll definitely do a leak down test before I start messing with jetting to rule out the crank seal. As for the cooling issue, does anyone know for sure if a loose rad hose would cause the cooling system to suck in air or would it only cause the system to loose fluid? Just curious. gonna pull the head and studs and check flatness when its warm but if its as easy as tightening a couple hoses to fix that issue that would be nice :ride:

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No a loose hose clamp would not suck in air while the engine is running (the bubbles you're seeing in the coolant)

You are probably seeing combustion gasses escaping from the warped head/cylinder mating surfaces.

 

Don't put off correcting that issue, if severe enough an internal coolant leaks can

wash away the oil film on the cylinder leading to a seizure.

 

My YZ125 service manual says any warpage must be under 0.03mm / 0.0012", guessing your CR is somewhat similar.

While you have the parts in hand, true the surfaces on both the cylinder head and cylinder.

 

Thick plate glass can be used for lapping the surfaces (with 400 grit sandpaper)

but if you have a local machine shop, ask to use their granite surface plate for 30 minutes in exchange for a dozen donuts.

Edited by mlatour

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Figured that would probably be my answer thanks for the advice, definitely wouldn't risk riding without fixing that issue. I guess I'm gonna have to pull off the head and cylinder, any tips for checking the cylinder for warpage? Tools/techniques? And could I have possisly warped my brand new head by torquing it onto the warped cylinder? That would be a bummer :facepalm:

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Usually a straight edge is layed across the surface and you insert a feeler gauge to measure gaps.

Say the specs are close to the 0.0012" suggested, you need very precise tools to measure this!

 

In your case, since you already suspect the mating surfaces to be warped, 

just go ahead and lap them on the flattest surface available

using a 'figure-8' movement until the 'sanding pattern' is even across the entire surface.

 

If you observe closely, until the surface is true there will be areas (center or edges) 

that don't shine or reflect light the same when tilted at an angle.

 

To prevent damage, always torque the head nuts in a criss-cross pattern and in gradual steps to the final required value.

Say the spec is 20lb/ft,

run them finger tight, then to 10lb/ft, then 15lb/ft and then the final step to 20lb/ft.

 

 

Any chance the cooling system froze up recently due to improper anti-freeze concentration ?

 

 

Edited by mlatour

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I wish I had taken some before and after pics of what I mentioned earlier:

19 hours ago, mlatour said:

if you observe closely, until the surface is true there will be areas (center or edges) 

that don't shine or reflect light the same when tilted at an angle.

 

I had lapped my cylinder head on a a piece of glass and by looking at the sanding pattern suspected

the glass plate wasn't 100% flat and true or, well enough supported from underneath and allowed some flexing.

 

Local machine shop let me use their granite surface plate and observing the sanding pattern or 'shine'

become even across the surface confirmed this was indeed the preferred 'true' tool to lap with.

Edited by mlatour

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Hmm, you make solid point there, I found a relatively thick sheet of glass but thinking I may take the old head and lap that one first to see what kind of result I'm getting before lapping the cinder and head on what might not be a 100% true surface. Heard of some people using permanent marker to cover the entire surface before sanding, the low spots are supposed to show better that way. What do you think? 

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